You have a universe of transmission options for swapping an LS into an early F-Body, and like other components of your equipment package, the transmission you select should be based on application. Most owners stick to a transmission that has a compatible bolt pattern for the LS because it’s convenient and many superb transmissions simply bolt up to the LS bellhousing. You can opt for a classic GM automatic or manual transmission, but for a pro-touring or track car, most owners choose a latemodel 5- or 6-speed transmission.
This Tech Tip is From the Full Book, SWAP LS ENGINES INTO CAMAROS & FIREBIRDS: 1967-1981. For a comprehensive guide on this entire subject you can visit this link:
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General Motors designed the LS platform with much platform commonality. Similar to the common engine mount bosses on all LS engines, every LS engine uses the same transmission bolt pattern. The bolt pattern layout allows for a direct bolt up of all LS-compatible transmissions, so 4L60E, 4L80E automatics bolt up and so does the Tremec T56 and other similar manual transmissions. However, you don’t need to use a current transmission. You can use a classic transmission, such as the Muncie M20, M21, and M22, or Turbo-Hydramatic 350 and 400. These were industry-leading transmissions for their time and while you may be able to find a more efficient modern transmission with an overdrive gear or ones with the particular ratios you are looking for, these still remain capable transmissions. Mating a classic transmission originally made for the Gen I Chevy small-block is not difficult. The classic Chevy transmission bolt pattern has one less bolt than the modern LS transmissions. So when installing the transmission on the LS, you leave out the passengerside center bolt, which would enter the water jacket of the LS block.
Many new transmissions are available to harness the power of the LS-series engines and direct this power to the rear axle. A myriad of automatic and transmission options are available for LS engines and F-Body swaps. After all, transmissions play just as much of a vital role in a build as the engine does. Also, in defense of the mostly unseen transmission, it is probably one of the major factors in how much fun a car is to drive. It’s amazing how easily a manual transmission suddenly turns a pretty average driving car into a race car.
In this chapter I cover the basics and some subtle nuances for putting just about any transmission in the GM lineup behind an LS engine into a first- or second-generation F-Body. In all the transmissions I’ve seen swapped behind LS engines in these cars, I have yet to see a stock location engine/transmission combo that needed the transmission tunnel cut. There are those who have had to cut and modify the transmission tunnel, but typically these are for very specific reasons, such as having the engine raised higher than the stock location, lowered, or broken body mounts.
In the following case, Mary Pozzi’s car needed a new tunnel because she wanted to shove the engine farther back for better weight distribution. In such a situation, you certainly have to cut the floor and tunnel; otherwise feel confident that the stock tunnel can remain intact.
I suspect that this transmission is the most likely candidate for hot rodders building an F-Body, and for good reason! Most variants of the T56 can withstand at least 450 hp and 450 ft-lbs of torque, which can usually fit most builds. The T56 is also a killer road-race transmission. With a choice of close and wide ranges of the first four gears, you have a great selection of how aggressive you want to be.
In addition, the T56 is an excellent cruising transmission that has two overdrive gears. Not one, but two! With fourth gear being a 1:1 ratio, the two extra gears are just a bonus. Chances are that you probably won’t ever need sixth gear as most people running this setup have to be running 75 to 85 mph to ever see the benefit of it, but it’s nice to know that you can run 75 mph down the highway at close to idle speeds.
The only downside that I see with the transmission, and my only gripe, is that this bugger is big and heavy. The T56 weighs around 125 pounds where a typical T5 runs a mere 85 to 90 pounds. Still, the extra weight is worth it.
Tremec T56 Transmission Installation
I like Tranzilla transmission fluid because major race teams use it. If it’s good enough for them, it’s good enough for me. It’s a fully synthetic oil that protects greater than stock OEM fluid.
The ATS T56 crossmember fits as well in a stock frame as it does in a modified one. It has lots of adjustability and cutouts to fit the exhaust snugly to the floorboard. Use Grade-8 hardware to bolt it into the same location as the stock crossmember.
The clutch slave cylinder has been installed; two bolts on either side that go into the transmission. The top port is used for bleeding the system while the lower port is used as the quick connect for the master cylinder.
This crossmember came with the Speed Tech frame. It’s fully adjustable forward and backward to accept virtually any transmission I can throw at it. Grade-8 hardware fastens it to the frame.
The correct bolts were not included with the slave cylinder so I had to source them from the local hardware store. They are M6 x 1 x 16 mm. Torque them to 25 inch-pounds.
Use a dab of red or blue Loctite. Slowly guide the transmission into place, being careful to seat the input shaft snugly into the pilot bearing. You should have a buddy help in the process because the transmission is heavy and difficult to move into position. You could use a floor jack to slide the transmission into the proper position in the transmission tunnel.
Whether it’s behind a small-block Chevy or an LS engine, the ATS crossmember works well. The ATS piece reuses a stock TH400 transmission mount to secure it to the transmission and crossmember. It mounts and bolts in just as the stock transmission does. Tolerances on these pieces are tight so be prepared to do a fair amount of maneuvering.
The Speed Tech frame uses the same transmission mount as the ATS piece. It’s secured with two bolts. I left the bracket bolts loose to make up for any slack the transmission needed to take up.
This is a good close-up of the transmission crossmember that comes with the Speed Tech front subframe. It has a lot of front-toback movement that allows me to place the engine and transmission virtually anywhere I choose. Using Grade-8 bolts, the crossmember just sits in place on top of the frame and is bolted in.
The T56 is fully mounted. The two openings in the front transmission plate are for the hydraulic clutch. The top one is the bleeder screw and the bottom one is the quick-disconnect port.
I pulled out the ATS T56 crossmember for a good look at this three-piece unit.
The clutch master cylinder from General Motors (PN 12570277) has an input shaft that needs to be shortened. I purchased a Speed Tech conversion kit and went to work cutting off the old sleeve. I used a cut-off wheel and pliers to remove the old arm. Be careful not to go too deep when cutting it off the sleeve or you could ruin a very pricey item.
After removing the old sleeved shaft, you are ready to install the new joint. You use a vise to compress these two together and a chisel to dimple the shaft. The threaded piece is for the pivot arm. The tube must be pressed on; it’s not threaded on the inside.
After your master cylinder is mounted, you have to find a safe passage to the transmission so that the braided line isn’t kinked and is far away from any heat from the headers.
Mount the master cylinder reservoir close to the pedal and make sure it’s at the highest point possible to prevent any air from entering the system. This helps in gravity-bleeding the system. I used sheetmetal screws to secure it to the firewall.
Here’s how it should look when you are finished. Two bolts hold the master cylinder onto the booster and four bolts hold the booster to the brackets. Using sheet-metal screws the reservoir should be mounted high so that it is the highest point of the system and out of the way.
I had to make a significant modification at the arm coming out of the firewall to the clutch pedal. I removed the clutch pedal and drilled and tapped a hole for the clutch. The original holes are not in the correct location nor are they the correct size. You have to take the pedal out of the car.
The engine and transmission are mated up and ready for the initial install. You usually have to install the engine and transmission assembly several times to ensure the steering linkage doesn’t interfere with engine parts. Moving the engine back also presents issues; the headers may not clear the upper control arms and cross-shaft bolts. (Photo Courtesy Mary Pozzi)
Because Mary wanted to move the engine and transmission farther back than the stock location, the transmission tunnel most likely required modification to allow proper fit for the transmission. (Photo Courtesy Mary Pozzi)
Here’s the position of the tunnel after the initial trial fit. Additional metal is cut and welded to strengthen and reposition the original sheet metal so the transmission fits. (Photo Courtesy Mary Pozzi)
The transmission tunnel was enlarged. It was spot-welded and fabricated with a little more room for the transmission. (Photo Courtesy Mary Pozzi)
Bleeding the Clutch
One of the jobs that people seem to complain the most about is bleeding the clutch. There’s no secret here that General Motors didn’t necessarily make this the easiest job in the world, but it also isn’t impossible.
Note that all T56s use a 7/16- inch wrench to open the bleeder. Do not let the reservoir become dry and always keep it topped off with DOT 3 fluid.
Here are three easy ways to bleed the clutch slave cylinder:
Gravity Bleed: This method is straightforward. Just open the reservoir cap, crack the bleeder with your wrench, and crack open a beer. It helps with the mess if you choose to use a catch can and to put a clear hose on the end of the bleeder to view the fluid. Wait for the fluid to start leaking out and you are good to go. This method is the slowest and often time doesn’t always work. You can jump start the gravity bleed by lightly pushing the clutch pedal, but don’t go crazy with it.
Hand Pump Bleed: This method is for the one-person show. The best way to complete this task is to use a hand pump just like the one you use for bleeding brakes. Open the reservoir and twist-open the bleeder. Use the vacuum pump just like you would a typical brake system. Make sure to keep an eye on the reservoir, letting that go dry makes your job much, much worse.
Traditional Bleed: The traditional way to bleed the clutch is just like a two-person brake bleeding operation. One person is in charge of the pedal and the other is in charge of the bleeder. The idea is exactly the same as a brake bleed, one person pushes the pedal down and barks out, “ON!” and the other person opens the bleeder to allow fluid to travel through the system. After the pressure is moved along, the bleeder operator informs the pedal person, and the process is repeated until all the air is out of the system.
The T56 has a number of connections on each side of the transmission. The three that you’ll be using are the vehicle speed sensor (VSS), backup lights, and reverse lockout solenoid. Depending on which speedometer you have, the VSS does or does not directly plug into the transmission. Most electronic speedometers are compatible with the transmission but need to be calibrated to it. Some may require an additional converter if your speedo is mechanical. ShiftWorks has a comprehensive kit that allows you to run a mechanical speedometer, but this requires replacing the tailshaft and slightly modifying the existing shaft. This is a really good option if you want a clean install.
The other option that is fairly popular is the Cable-X system. It’s a small electric box that converts the pulse signal from the VSS into a mechanical feed. They claim that this box works with virtually any speedometer on the market, and for the amount of work it takes, it’s a good price at around $300.
Flywheel and Clutch Installation
This is a good comparison of two master cylinders: a fully hydraulic LS version (top) and a hydraulic master and mechanical fork version for LT-style transmissions (bottom).
To convert your vehicle to a fully hydraulic system, a fi rewall clutch master cylinder adapter is necessary. This one is from ATS (PN 080002) and is a simple bolt-on.
The LS3 crankshaft has the standard six-bolt pattern for the flywheel. Use new bolts when installing the fl ywheel. You don’t want to risk a bolt failure by using old bolts.
This flywheel-holding tool replaces the starter and holds the flywheel in place while you tighten or loosen the bolts. It also works great on the crank bolt. It’s a lot better than a screwdriver jammed against the block, isn’t it?
The RAM Clutches fl ywheel (PN 98931HD) is aluminum and allows higher horsepower levels on the street without exploding on you. The guys at RAM didn’t give exact power capability numbers but they did say it would help with throttle response. It’s bolted on the back of the crankshaft with a dab of Loctite.
When installing any clutch bolt it helps to use a dab of Loctite on the threads. Again, insurance is cheap.
My QuickTime bellhousing (PN 8020) is SFI approved for almost every racing series and is a serious piece if you have a lot of horsepower. If a transmission fails, it can literally explode and send shrapnel at high velocity through the transmission tunnel. If your LS produces more than 500 hp, a heavy-duty bellhousing is a wise investment in safety equipment. You get the bellhousing, adapter plate, and all the hardware needed.
Install the adapter plate before the flywheel so that the bellhousing has a place to bolt onto on the bottom. The adapter has two alignment holes on either side that slide over the transmission bellhousing dowels. This is a good time to clean off the surface of your flywheel; most are shipped with a protective coating. Tighten these bolts to 75 ft-lbs with a torque wrench.
A cheap plastic clutch alignment tool is handy for aligning the clutch plate without it. Make sure this doesn’t wiggle around when installing the rest of the system. Once the pressure plate is in place the alignment tool can be removed and put back into the toolbox.
Don’t forget the pilot bearing. It’s essential that you install it. The GM PN 12557583 is the pilot bearing. I was able to get one at the local NAPA auto parts store for $20 (PN BRG B657). Pound this in until it is flush with the rear of the crankshaft.
At this stage, you need to install the pressure plate. Again, use some Loctite on each bolt and tighten to 75 ft-lbs.
The bottom bolts for the QuickTime bellhousing need to be installed in reverse with the bolt facing backward, otherwise you run into interference with the oil pan.
Here are all the locations for the plug-ins and ports for the T56. The transmission works just fine without anything plugged into it; you just may not have a working speedo. (Illustration Courtesy Alldata Illustration)
Reverse Lockout Solenoid
A quick word about the reverse lockout solenoid: You can wire this up, but I frankly feel it is almost not worth the effort. With the reverse lockout solenoid hooked up, you have to shift hard into fifth gear and slam the shifter into reverse. It’s virtually impossible. The T56 shifts into reverse in conditions under 5 mph or basically stand-still. All that you need to do is just give it a little tap and the transmission shifts into reverse. For this very reason, most people I’ve seen just leave this alone and don’t plug it in. It’s your call.
Adding a speedometer to a T56 is fairly easy to do if you have the correct speedo. Options are available for those who want to use the stock speedo or one that is mechanically driven, which just takes a bit more work.
Right off the bat, almost any electric speedo works with the T56 output in the tail shaft. One wire is the exciter wire and the other is the ground. More times than not, getting the wires right doesn’t really matter as long as you have both hooked up. However, you have to make sure that you calibrate the speedo. This usually involves driving a certain distance and hitting a couple of buttons. This is a requirement of most mainstream gauges, such as Auto Meter speedos.
My Stack unit is a bit on the odd side and requires a pulse amplifier and a little math. I had to push the car forward one full revolution of the tires and measure the number of pulses. Then using the length of one tire rotation I was able to calculate the number of pulses per mile and enter that into the Stack unit; a bit more lengthy, but equally effective.
Now, for you interior purists who just can’t live without your factory speedometer, you are in luck. You have two options. The first is to replace the tail shaft with one that allows for a mechanical input such as the ones from ShiftWorks. The other option is to run a Cable-X system. This converts the pulses from the transmission into mechanical movement. It’s a simple three-wire setup that can be hidden under the dash.
Throwout Bearing Spacing
I had difficulty setting the correct throwout bearing clearance when mating the T56 to my LS3 combo. The clutch and the bearing must have 0.200 inch of clearance between them. If the clearance is too great, the throwout bearing extends too far and causes premature wear. On the other hand, if the clearance is less than this spec, the clutch disengages. This causes slippage in the clutch and effectively makes it seem as if you’re riding the clutch, even when your foot is off the pedal.
Aftermarket spacers can be used to attain the correct clearance. Most speed catalogs, such as Jegs and Summit Racing, sell spacers and shims in various packs starting around $20. This is typically a bigger deal when purchasing an aftermarket bearing or a rebuilt one, as the tolerances are most likely not the same as factory stock.
The Tremec T56 Magnum variant of the standard T56 is able to handle upward of 700 ft-lbs of torque while the stock T56 is typically rated at 450 hp and 450 ft-lbs of torque. The Magnum has a very short shifter throw with a very sharp engagement in the syncros when the shifter is maneuvered. The Magnum is roughly the same size as the T56 and looks very similar; it is a bit longer, almost 2 inches in overall length, so you have to shorten your driveshaft. The Magnum has two different gear sets: 2.66 or 2.97 first gear. I decided that the 2.97 first gear was more optimal for this application and for auto-crossing where the courses seem to be tighter and it allows me to dig out of the hole just that much more quickly. The two overdrives are another bonus (just as the stock T56 provides), so in my world it’s the best of both.
The Magnum is a versatile transmission and it has three important design features to note. First is the reversible shifter. It allows for more varied placement of the shifter, which may allow you to reuse the stock shifter location with minimal cutting and prodding. Due to loose tolerances in the manufacturing of F-Bodies in the 1960s and 1970s, you may have to dimple the floorpan with a ballpeen hammer in a couple of places to make sure it fits properly. With my T56 I didn’t have to do this, which is the norm; others may not be so lucky.
Second, the Magnum can use either a mechanical or electric speedo attachment, and this is great news for anyone who wants to run stockstyle mechanical gauges.
Third, the Magnum has provisions for a Ford-style mount or the traditional TH400 GM mount.
If it’s good enough for the ZR1 Corvette and the Dodge ACR Viper, it is suitable for the LS3 in my car. The shifting actuation, or shifting feel, is quite different than the typical clutch-bang-gas type of driving; rather, the Magnum is shifted with a light touch for optimal performance. The transmission I chose is the Tranzilla from Rockland Standard Gear (RSG). RSG first takes a Tremec Magnum T56 transmission, then adds a Viper tail shaft, and reworks some of the rings to make them handle roughly 1,000 ft-lbs of torque and abuse. With this transmission, you cannot reverse the shifter and it does not have a mechanical speedometer output. Instead, it only has an electrical speedometer output. But it has so many advantages. Regardless, I know that the RSG Tranzilla is able to keep up with me even if I upgrade engines or decide to add a power adder such as a supercharger.
One option for your transmission is to buy an engine and tranny combo all in one. You should also buy the main ECU and transmission controller as a single unit. If you have a manual transmission you can skip this section because you don’t need it. If you don’t, I cover the basics of installing a modern transmission with the LS beast.
The newer and more modern upgrades of timeless classics such as the 700 R4 and TH400 are great ways to get out on the road quickly and reliably. These bolt directly to your LS engine with no worries about modifications. The only catch is that these transmissions require a computer-assisted controller to make sure everything works properly. The 4L80E is a bit more robust and can be built for high-horsepower applications. The 4L80E case is larger than the 4L60E but neither should require transmission tunnel modifications. The only decision left is really what shifter you want to use!
If you choose to go with a modern automatic transmission, you have to find some way to control it. If you have created your own harness, you probably already have the proper connector and a built-in transmission controller. You can also specify to the maker of wiring harness that they include the proper wiring for your specific transmission; it just helps keep things clean and less complicated.
Of course there are aftermarket options for almost everyone. The obvious one is the standalone computer and harness from General Motors (PN 12497316). They come as a kit and can be used to control the 4L60E, 4L65E, 4L80E, and 4L85E line of transmissions. The kit comes with the computer connector and the ability to program virtually any parameter. A lot of other controllers may be on the market that do a swell job just like the GM controller, but for the vast majority of people, this controller does the trick quite well.
For those of you who need a more programmable option, OptiShift has a slick controller unit that costs around $600 depending on application. This option can be fully programmed with a laptop and even has a cool-looking readout for temperature, sensor values, and fault codes. I’ve seen them in action and I am fairly impressed with how this unit functions. This might be a good option if you have a highhorsepower application and want a bit more control over your transmission functionality.
When it comes to the installation of older-style transmissions into first- and second-generation F-Body vehicles, there’s good news and bad news. The bad news is that things become a little more complex than the standard bolt-it-up way I am used to doing things.
First, you have to make sure that your wiring harness is correct. Whether you order one or make your own, you want to be sure the harness matches your transmission style. Most companies make sure it’s the correct harness, but it never hurts to triple-check. For example, in the case of the T56 or other manual transmissions, you don’t need an external controller like the newer-style automatics require. This makes life a lot simpler.
In addition, it’s worth noting that when in doubt, give the manufacturer a call to verify the parts list you plan to use. I cannot stress this enough. The more you plan out your build, the easier it is in the long run.
PACE Performance (PN PAC- 1680-TK5) offers a good kit that includes virtually everything you need. While they say this kit is good up to 500 hp, a kit is available for horsepower up to the 600 range (PN PAC-1680-TK6). PACE requires that you specify what spline shaft you have, but that’s a given, right? The kits typically include a QuickTime SFI LS 4-speed bellhousing, Ram LS steel SFI flywheel, Ram 12-inch clutch disk, ARP bolts, pilot bearing, Clutch fork pivot ball, and fork boot. For $1,260, it might be the best option for you. You have to provide the mechanical clutch linkage from the pedal to the throwout bearing, but that’s pretty standard.
If you have all the necessary parts but just need a bellhousing to convert your Muncie to an LS engine, QuickTime sells them (PN RM-6036) through various vendors.
Refer to the above-mentioned throwout bearing measurement procedure if you choose to run a hydraulic throwout bearing with your manual transmission.
You can certainly install/mate a classic transmission to your LS engine. There are many reasons to do it. Maybe you have half a dozen lying around your front yard or maybe because TH400s are stout and fairly plentiful. Whatever the reason, you certainly can make it happen with the appropriate spacer, bolts, and a few extra steps.
The major difference is that the LS engine is .400 inch shorter than a typical small-block. The other difference is that the upper right bolthole for the bellhousing is missing. Thankfully, the bolt pattern is the same so you are able to use the same transmission case.
The solution to the shorter length is to use a spacer that can be purchased at places such as ScogginDickey (GM PN 12563532) and Chevrolet Performance. Jeg’s and Summit (Hughes PN HP3795) carry their own proprietary brands. You then need to purchase longer bolts to match the spacer (GM PN 11569956). The spacer is bolted to the crankshaft first, between the crankshaft and the flexplate; do it the other way around and you have problems. You also need a flat-faced GM flexplate (PN 12551367). This allows the starter to be engaged in the correct spot by moving it rearward that extra .400 inch (Hughes HP4004X).
Beware that not all flexplates and flywheels are the same. The 1955– 1986 crankshafts with a two-piece rear seal has a 3.58-inch bolt circle while the 1987 to present crankshafts with one-piece rear seals have a 3.00- inch bolt circle. The LS crankshafts that have one-piece rear seals have a 3.11-inch bolt circle.
I have heard that you can use the curved or beveled 4.8/5.3 and LS1-style flexplates. This requires ovaling out the torque converter mating holes to make it fit properly. I’m not too keen on this idea as it tampers with something that takes a lot of abuse. Nor can I verify that this is accurate, so it may be worth investigating more fully before diving in. In this setup, you have to use a spacer, but it goes between the flexplate and torque converter to fill that cavity.
The final option may be the easiest, but also the most costly. You can purchase an LS-specific torque converter for your older-style automatic transmission that eliminates the need for a spacer. Currently several companies make a version for your transmission; expect to pay $450 or more.
A number of crossmembers are on the market, and any of them does just fine. There are different crossmembers for each style of transmission; the most popular is the T56 crossmember. It must be said that it helps to plan ahead and make sure that the headers and engine mounts work with the crossmember. Ask first, purchase second.
The most popular name in crossmember swaps is ATS. It’s a threepiece unit. This piece works well with the stock subframe as well as aftermarket ones. Of course, Speed Tech acquired ATS a number of years ago, so it’s only fitting that their subframe comes with a transmission crossmember flexible enough to fit just about every transmission.
G-Force is a specialty company that makes a wide range of crossmembers for the first- and secondgeneration F-Bodies. They have a solid reputation and make crossmembers for almost any transmission. They offer units for older transmissions such as the T10, TH400, TH350, 700R4, and even newer ones such as the T56, 4L60E, and 4L80E.
Hurst Drive Lines
Hurst Drive Lines has a wide variety of parts and price ranges for making the T56 or TKO-5-speed swap or addition. They sell entire kits that take care of everything you need such as the clutch, clutch hydraulics, tubular crossmember, electrical connectors, shifter knob, transmission, driveshaft, flywheel, bellhousing, and speedo-meter cables or wires. These kits can be had for the first- or secondgeneration F-Body as well as a wide variety of others applications.
The only downside I could find is that each component is not available individually; they only come as a kit. Still, when you purchase a complete kit such as this one, you know that it’s designed to work in concert with all the other pieces.
Reusing the stock crossmember is entirely possible; the trick is to modify it to make it fit your swap. I’ve seen a few reworked stock crossmembers that work perfectly well. The center part of the crossmember needs to be cut out, then careful measurements need to be taken to see how far the drop should be. The driveline angle here is extremely important. A good rule is that the engine needs to be tipped back roughly 3 to 4 degrees and the rear end should be tipped upward about the same amount with no more than a 2-degree difference for typical street driving.
I recommend a thicker plate steel (between 1/8 and 1/4 inch) if you choose to modify your stock crossmember. As with everything the compromise is time versus money. Crossmembers are readily available so you may have to consider which is a better choice: your time or a couple of extra dollars and less effort.
Regardless of what transmission you want to put behind your LS engine, chances are someone sells a bellhousing for it. QuickTime offers an SFI-certified bellhousing to bolt just about any trans behind an LS engine, including Tremecs, Richmonds, and all the popular GM automatics. Other companies offering transmission solutions are McLeod and Lakewood. If you’re stuffing a T56 six-speed behind your LS mill, the low-buck route is to just run an aluminum GM housing, and of course, newer GM automatics have the bell integrated into the transmission case.
Written by Eric McClellan and Posted with Permission of CarTechBooks