How to Install a T56 Transmission in an LS-Swapped Chevelle

The 6-speed T56 manual is the most popular transmission used in LS engine swaps. Formerly offered on the 1998–2002 F-Body and GTO, the T56 bellhousing, flywheel, and clutch pack are readily available. The T56 transmission fits into most GM muscle cars, requiring only minor modifications to the transmission tunnel, if you set the engine for­ward 1.5 inches. When using the rear “stock” bellhousing position, exten­sive tunnel mods are required. Swap kits are available to help make the install easier. American Powertrain offers a complete T56 swap kit for GM A-Body platforms, simplifying the entire process.

The clutch mechanism, however, requires modifications. The hydrau­lic clutch is required for T56 swaps, and unless you use a kit such as the American Powertrain Hydramax sys­tem, it can become messy fast. You need a hydraulic release bearing and a clutch master cylinder, and then you need to adapt the pedal to the master.

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This Tech Tip is From the Full Book, SWAP LS ENGINES INTO CHEVELLES & GM A-BODIES: 1964-1972. For a comprehensive guide on this entire subject you can visit this link:

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The 1993–1997 T56s use an external clutch slave cylinder; later 1998– up units use an internal slave cylinder. The 1998–up T56 transmission is better suited for the Gen III/IV engines with the correct bolt pattern and input shaft, but McLeod offers components that adapt older T56 transmissions to the Gen III/IV engines.

Early T56 transmissions (1993– 1999 LT1-compatible units) can be converted to mate to an LS or 2014– up Gen V LT-series engine with a different input shaft. The input shaft is quite simple to change (see the special section, “Fitting an Early T56 to an LS Engine” for more on the conversion).

Although the T56 has traditionally been the favored 6-speed manual gearbox, Tremec has replaced it with an updated version. Actually, two versions: the Super Magnum T56, which is the best option (available in the aftermarket and from Chevrolet Performance, and the TR6060.

The Super Magnum T56 is one stout transmission that’s capable of transmitting 700 ft-lbs of torque. The gearing is set at 2.66, 1.78, 1.3, 1.00, .80, and .63 dual overdrive. This will hit your wallet pretty hard at more than $4,500. It is, however, the stron- gest 6-speed manual.

The T5606 is essentially an original T56 case with beefier internals. Those larger guts take up a lot of room. Because the case had to stay the same size, the extra room had to be taken from somewhere. The result leaves a little to be desired from the TR6060. Tremec’s solution was to use smaller synchronizers. They are very fragile, and grinding the gears even once can wreck the synchro for that gear.

If the synchro is damaged, it will eventually fail and you will start burning up the gears themselves. Because of this, the TR6060 is not the best candidate for an LS swap. It will certainly function, but be aware that these transmissions are prone to failure. Should you choose to use a TR6060 in your swap, make sure you use Redline D4 ATF transmission fluid or Royal Purple SynchroMax. These oils have been reported to reduce cold-shift grinding and provide a better overall shifting feel for the TR6060.

When it comes to mounting the hydraulic clutch master cylinder, you can build a piecemeal kit yourself, fabricate the mount, or purchase a kit through American Powertrain, Detroit Speed, and others. The first component is the firewall master cylinder mount. Street & Performance offers brackets for use with a GM clutch master cylinder (GM PN 12570277) designed for GM cars 1958–1964 and separate parts for 1967–up models. Once the cylinder is in place, a line is run to the hydraulic clutch bearing. A fluid reservoir gets mounted on the firewall.

On the Chevelle build featured in this book, a hydraulic system from American Powertrain was used. This greatly simplified installation of the M21 Muncie 4-speed. The Hydramax hydraulic bearing uses a stack of shims to set the depth of the bearing. This allows for a perfect mesh for the clutch diaphragm. The hydraulics are relatively simple to install. The kit comes with a Wilwood master cylinder and can be bolted directly to the firewall where the stock pushrod comes through. The supplied bracket for the master cylinder is adjustable for angle.

An adapter tab may be required to bolt the original clutch pedal to the master cylinder pushrod. This tab must be fabricated and welded to the clutch pedal. The placement of this tab is critical. If the tab is too high, the pushrod does not fully engage. If it is placed too low, the pedal is hard to push.

 

 

 

 

 

 

Using a piece of 3/16-inch-thick mild plate steel cut to 1 x 31⁄18 inches, the tab should be spaced .300 inch, starting at the 1.712-inch mark. Once bent, drill the tab with a 3/8-inch hole, measured from the long side of the tab at 2.629 inches on cen­ter. The placement of the tab on the pedal is 1.769 inches from the center of the square hole at the top of the pedal, and it sits at 114 degrees from the pedal side to the top of the tab. The tab should then be fully welded to the pedal arm. Trim off the small triangular-shaped section of the tab that overhangs the pedal on the underside. The clutch pushrod bolts to the tab via a 3/8-inch bolt and locknut.

Using the stock pushrod linkage hole increases the pedal effort on the clutch. By raising the pick-up point on the pedal, the effort needed to dis­engage the clutch is greatly reduced. This pedal ratio is the difference in length between the pivot (fulcrum) of the pedal to the pushrod hole (Y) and the fulcrum to the center of the brake pedal (X). A hydraulic master system should be between 5:1 and 7:1.

Consider this: A master cylinder with a 1-inch bore and a pedal ratio of 6:1 with 100 pounds of pedal pres­sure yields 600 pounds of pressure at the master cylinder. Reduce the pedal ratio to 4:1 and the pressure at the master drops to just 400 pounds. That is a significant difference and increases your effort by 33 percent. You can use the stock hole in the stock A-Body pedals, but it absolutely will be more difficult to operate.

It is possible to adapt an LS engine to use a manual clutch link­age. If you are installing an LS and manual transmission in a GM vehi­cle originally available with a man­ual clutch setup, you need linkage, clutch, Z-bar, and related compo­nents. The Gen III/IV blocks are not drilled for the Z-bar, which makes it difficult to adapt the LS engine to a manual linkage. Fabricating a simple bracket that locates off the bellhous­ing bolts and attaches to the Z-bar is the best solution.

The T56 has a top-mounted shifter at the rear of the transmission that creates a small compatibility issue for the stock console or shifter location in GM vehicles. An S&P shifter relocator kit easily resolves the problem. This piece from Driveline Components is built for your specific placement needs. Because engine and transmission mounts differ, each shifter must be ordered individually. The T56 relocator shifter can move the shifter 1 to 4.1 inches forward. In addition, the shifter can be centered or offset to the left or right. If you choose to use the stock T56 shifter, place it 4 to 5 inches rearward from the stock location. The Viper T56 uses the forward-mounted shifter position, but this requires adapter plates for LS swaps.

Another popular manual swap is the Tremec TKO 500 or TKO 600. These 5-speed manual transmissions are very popular among GM muscle builders and offer excellent perfor­mance. American Powertrain offers complete kits for installing the TKO (and T56) for the GM A-Body plat­form. These kits feature hydraulic clutches, bellhousing, and all the components to make the installation simple and easy. TKO transmissions use a top-mounted shifter as well. To adapt these shifters to the stock location, a Hurst Blackjack shifter can reposition the shifter to the ideal location.
The TKO transmission does not fit quite as neatly under the body as the T56 does. The transmission fits some GM vehicles without modifica­tion, but the 1964–1972 GM A-Body platform requires a large section of the transmission tunnel be removed and replaced with a reshaped panel. The American Powertrain kits come with the requisite patch panel, cut

 

 

 

 

 

titanium-aluminum alloy construc­tion, CNC machining including spot-faced mounting holes, pre­cision dowel pin holes, and bores that yield a precise fit. This bell­housing bolts to all GM Gen III/IV V-8 engines for installation of the Muncie, T-10, Saginaw, Richmond, Tremec TKO, Tremec T56-011, and other specially built transmissions. This bellhousing works with stock clutch linkage and hydraulic clutch actuators. It includes a steel inspec­tion cover and mounting hardware, and it’s designed to use a 168-tooth flywheel and standard GM starter. This bellhousing is lightweight at only 15 pounds, and uses all fac­tory linkage parts, including clutch forks, Z-bar, rubber dust boot, etc. According to Chevy Performance, you must use the LS truck flywheel (PN 12561680), a 12-inch clutch and pressure plate (PN RAM88744), and six metric pressure plate bolts (PN 12561465).

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This Tech Tip is From the Full Book, SWAP LS ENGINES INTO CHEVELLES & GM A-BODIES: 1964-1972. For a comprehensive guide on this entire subject you can visit this link:

LEARN MORE ABOUT THIS BOOK HERE

SHARE THIS ARTICLE: Please feel free to share this post on Facebook Groups or Forums/Blogs you read. You can use the social sharing buttons to the left, or copy and paste the website link: https:// lsenginediy.com/ how-to-install-a-t56-transmission-on-a-chevelle/

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You can also use an original Chevy big-block manual transmis­sion bellhousing instead of buying a new one. The specific part you need is the 621 Chevy big-block bellhous­ing. This fits the Chevelle chassis and the LS engine without issue. The Chevy small-block and truck bellhousings have clearance issues. The flywheel needs to fit the LS and have a standard Chevy small-block clutch bolt pattern. I used a PRW conversion flywheel (PN 1634680) on the 1969 Chevelle shown in this book. For the pilot bearing, the LS7 bearing (PN 12557583) fits the LS flywheel and costs less than the extended conversion bearings and works just as well.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The clutch depends on the transmission you are using. There are 10- and 26-spline input shafts. Make sure you have the right clutch for your transmission; beyond that, any Chevy small-block clutch works, provided your flywheel has the Chevy small-block clutch pattern. A 26-spline transmission can use a stock truck LS manual flywheel with a matching LS clutch.

If you use the conversion fly­wheel, the stock-length (1.25 inches) throwout bearing works great. For stock flywheel and clutch com­binations, an extended throwout bearing is required. General Motors offers a 1.75-inch-length bearing (PN PT614037) for these applica­tions. This requires using the stock mechanical pushrod clutch linkage.
Aftermarket versions of these parts in complete kit form are avail­able from sources such as McLeod and Advance Adapters. These clutch kits are designed to adapt the Gen III/ IV engines to early-style GM manual transmissions such as the M21/M22, SM420, SM465, and NV4500. Also, these kits allow the installation of Richmond Gear manual transmissions such as the ROD 6-speed. The Advance Adapter clutch kits typically include a custom flywheel, 11-mm flywheel bolts, 11-inch Centerforce pressure plate and disc, pilot bushing spacer, throwout bearing, collector gasket, 10-mm bellhousing bolts, 10-mm lock washers, and XRP dowel bolts.

If you want to assemble your own parts kit, you need to match the flywheel and clutch to the out­put of the engine and make sure the splines on the clutch disc match the transmission. GM transmissions use 10- and 26-spline input shafts, the early manuals (before 1971) typi­cally have 10 splines, and the later units have 26 splines. That said, other aftermarket manual transmis­sions have either 10 or 26 splines. The 26-spline shaft is more durable than a 10-spline shaft because it dis­tributes the input load better.

In the engine bay, the clutch master cylinder mounts to the firewall. You can use the stock clutch rod location with a slight modification. The adjust­able bracket that comes with the Hydramax kit needs a little trimming to clear the opening in the firewall. I marked it with a pencil.

 

 

 

 

 

 

 

 

The other option is to use an extended bearing, so you can use the original old-style bellhousing. Match the clutch to the engine and use a longer bearing to make up the dif­ference for the shorter crank flange. Several manufacturers offer extended bearings including McLeod, PN 8617, and GM, PN 12557583. By using the old-style bellhousing, you should have a provision for the Z-bar and be able to run a manual clutch set-up.

Clutch Basics

A typical manual-shift car almost always comes with the standard, basic single-disc clutch from the fac­tory. They are durable, have a good pedal feel, and work great for low to medium performance. The clutch’s job is to transfer the power of the engine to the transmission and to sever that link when required. That doesn’t sound like much, but consid­ering the massive power output we are seeing on the street, holding that con­nection without slipping is a tough job. The two main types of clutch are: disc-sprung hub and solid hub.

Most street clutches have a sprung hub. A set of six to eight springs absorb a small amount of the impact from the spinning flywheel as it grabs the stationary clutch, and it reduces the chatter and noise from the clutch. In addition, clutches have a set of limit pins; think of them as bumpstops that set the maximum rotational limits for the hub-to-disc connection. If your hub springs are too light, the engine bounces off the limit pins, which results in chatter.
The Marcel spring is a device often used in clutch discs; it reduces chatter as well. Thin washer-type springs sit between the disc and the clutch facing.

Solid hubs are more race-oriented; they do not chatter and help enable smooth shifting. Solid-hub clutches do not last long on the street due to the vibrational fatigue on the splines.
The torque capacity can be deter­mined using simple multiplication. For example, if you have 650 ft-lbs of torque as a maximum flywheel load, you can work backward using known variables. The coefficient of friction is one of the items that you might find listed in the specifications table for a clutch. Rough numbers are .25 for organic, .36 for ceramic, and .40 for sintered iron. These general guideline numbers are not product-specific, but a good place to start. As a rule, the higher the coefficient number, the better the grip at a cost of wear life and chatter.

Disc Options

The number of friction surfaces is the same as the number of clutch sides. A single-disc has two friction surfaces; a dual disc has four. The size of the clutch disc determines the radius. Clamping force is determined by the pressure plate and how the springs leverage the disc. Increasing the fulcrum length does not affect the pedal pressure, but the spring force does. However, increasing the fulcrum length does reduce the life of the clutch.

Many compromises must be made in clutch system design because certain changes affect the holding power. Increasing the spring rate of the pressure plate increases clamp­ing force, which also increases pedal effort, especially with a nonhydrau­lic pedal. You can increase the diame­ter of the clutch; this also means you need a larger flywheel, which soaks up more power and slows the rev time. Clutch design is a fine balance of criteria.

Adding a second disc to the clutch pack significantly increases the torque capacity. Dual-disc clutches don’t require high static clamp pressures, so the lighter pedal requires less effort to engage and dis­engage. A dual-disc clutch has dou­ble the friction surface, so they can use organic friction materials, which provide a smoother engagement (less chatter) and longer life. This is the reason dual-disc design has become so popular in street and street/strip applications. Although a single-disc system may transmit 600 ft-lbs, a similar dual-disc system can hold 1,200 with less pedal pressure.

Two types of twin-disc systems are available: strap driven and stand driven. The distinction refers to the style in which the center floating plate is driven. Strap-driven floater plates are attached to the flywheel with a set of straps. This adds a little weight to the flywheel, but it makes for very quiet operation. Most street applications are better off with a strap-driven floater.

The stand-driven floater plates float between a set of posts between the pressure plate and the flywheel. When idling, the floater tends to rattle, which could be annoying in a street car. The stand-driven unit allows for faster shifting, which is good for completion.

Multi-disc clutches do come with a few drawbacks. The distance between the flywheel and the trans­mission is a finite area, so there is limited space for adding clutch discs. This can be an issue with some fac­tory hydraulic slave cylinders as they have a limited length of travel. The disc height must be tuned to the car as well, so you want a multi-disc kit that has everything, including the flywheel. Otherwise you will be learning how to set disc height.

Pressure Plates

The clutch does the hard work; the pressure plate is the mechanism that releases and engages the disc. The three types of pressure plates are: diaphragm, long, and Borg & Beck. Each design has benefits in their use­ful areas.
Diaphragm pressure plates are the most common in street applica­tions. This is what you think of when someone says “pressure plate”; the diaphragm is a series of long spring bars that fan out around the release bearing. These are effective for street and high-performance street appli­cations because they have excellent spring pressures, load the clutch disc evenly throughout the entire diam­eter, and have a break-over point. This means that the clutch pressure reduces significantly at the point where the springs are over center. When you are stuck at a traffic light, your thigh will thank you.

Long-style plates are more often seen in strictly drag racing applica­tions. The Long style uses three nar­row fingers that couple the release bearing to a group of nine springs around the pressure plate. To release the clutch, the nine springs must be compressed. This design is very popu­lar for the quick shifts of drag racing. The long style is very tunable through spring rates, stand height, and centrif­ugal weights. The centrifugal weights add additional force on the clutch because the engine spins faster.

Borg & Beck is a version of the long style that uses three fingers to compress springs for disc release. This style uses rollers that swing out as the engine revs to increase disc pressure. McLeod’s version provides consistent action for fast shifting.

Friction Material

The friction material is just as important as the rest of the design. Organic, Kevlar/carbon, ceramic, and metallic are the four types of friction materials used in clutches, with countless variations including hybrids. As discussed earlier, the higher the friction coefficient, the more grab the material has at a cost of wear life. Other factors to consider when choosing friction material include engagement, holding power, and glaze resistance.

Organic friction materials consist of metal fibers woven into an organic fiber, the most common being fiber­glass, carbon fiber, brass wire, and a few proprietary binders to keep it all together. The binding resins cre­ate some durability and performance problems with organic clutches. As with brake pads, overheating causes them to glaze. That nose-hair singe­ing smell you get when you roast the clutch (or brake pads) is the resin burning. When it cools, both surfaces are left with a thin layer of slippery crystallized resin. Although organic clutches are susceptible to overheating, they are very capable for most street cars. Organic materi­als are the softest of all the friction materials, which means low chatter, smooth engagement, and good hold­ing power.

Kevlar/carbon discs are a good alternative to organic clutches on street/strip cars. Made in a similar manner to organics, the Kevlar fibers are weaved and compressed with a resin. They are harder than organ­ics, so they chatter more. One of the issues with these types of clutches is that although they have excellent heat resistance in the clutch, they also retain heat. That means that the flywheel becomes hotter and stays hot. Once you overheat a Kevlar clutch, it does not recover quickly. These materials are excellent for street/strip applications that don’t see a lot of stop-and-go traffic.

Ceramic clutches are very good at absorbing heat and wicking it away from the mating surfaces of the pres­sure plate and flywheel. They have better holding power than organic materials. Ceramic materials suffer, however, in durability and chat­ter. The hardness of the materials makes them chatter much more than organics with their abrupt engage­ment. This also wears out the mating surfaces faster than with organics. Ceramics wear faster than Kelvar/car­bon clutches, but have higher heat tolerance. Stop-and-go traffic can be an issue for ceramic clutches.

Metallic clutches are made of sintered iron and sometimes bronze; they are extremely hard. The sin­tering process heats the particles to red hot and then compresses them together, leaving a rough block. Although not quite melted, they are heated to the point that they stick together, so there is no resin to overheat and glaze. These bad boys chatter a lot, but they also have the highest holding power. They are not street friendly because the engage­ment is very abrupt. This means they wear out the mating surfaces quickly. Metallic clutches are capable of handling more than 750 hp in a single-disc system.

Hybrid clutches use one mate­rial type on one side and a different material on the other. This allows the clutch maker to blend char­acteristics of both materials. For example, a McLeod 500 clutch has organic pads on the flywheel side with segmented ceramic on the pressure plate side. This provides longer wear life for the flywheel and smoother engagement but better hold through the pressure plate.

Written by Jefferson Bryant and republished with permission of CarTech Inc

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