Resto-Mod Restorations — Part 15: Drive Train
Transmission swaps are common in Resto-Mods. Muncie four-speed gearboxes are a popular choice of builders who want to keep a Resto-Mod "all Chevy." Muncies can easily be adapted to a wide range of GM and non-GM cars.
Jeff Noll's Muncie M-21 close-ratio four-speed manual transmission is supported by a sturdy cross member at the rear of the tailshaft.
There are three basic types of Muncies: M20, M21 and M22. Jeff Noll's '67 Camaro uses an M-21 close-ratio four-speed with a Hurst Competition Plus shifter. Jim Mokwa used a Tremec six-speed in his GTO. This is a very popular Resto-Mod transmission. Some builders prefer the convenience of an automatic.
Jim Mokwa's high-tech Tremec six-speed manual transmission looks small bolted up behind the big 400-cid Pontiac V-8.
Jeff Noll's Camaro has an 11-inch Centerforce diaphragm clutch. Jeff's third member is a 10-bolt Positraction rear end dressed up with a billet aluminum cover. Inside the axle you'll find a Motive Gear 3.73:1 ring and pinion gear set.
Jeff used a 10-bolt Positraction rear axle with a billet aluminum cover and a Motive Gear 3.73:1 ring and pinion gear set inside.
Muncies came in many GM models of the '60s and '70s. They were used in muscle cars and Corvettes. Milder GM cars had Saginaw or Borg-Warner four-speeds. A Muncie differs from a Saginaw in that its reverse lever is in the tail housing, not the side cover. One difference between a Muncie and a Borg-Warner is the Muncie has a 7-bolt side cover (two less than a Borg-Warner).
Muncie serial numbers have nine symbols that tell the GM division, year, model, assembly plant and car they were used in. The first symbol indicates division, the second matches the last digit of he model year and the third tells what assembly plant the car was built in. The last six match up with the car's VIN.
Hopefully Jeff checked the numbers on his Muncie before he started this install. Some models are more valuable to a purist than to a Resto-Mod project.
Before installing a Muncie four-speed in a Resto-Mod, check the serial number and other codes. You may have a tranny that is worth a lot of money to a purist. You could probably swap it for a better unit and get cash to boot. Finding the right box in a junkyard could even be turn out to be like winning the lottery.
David West of Milwaukee, Wisconsin, actually "restores" Muncie transmissions and harvests the rarer cases for collectors.
According to transmission guru David W. West of Davids 4 Speeds LLC, all Muncies work on the same basic principle. The input shaft goes to the cluster gear. The cluster is mated to all the speed gears, first, second third and fourth. The speed gears are independent of the main shaft. The magic is in the synchro assemblies. The synchro hub is splined on the main shaft. The slider and the synchro ring grabbing on the cone of the gear allows the slider to engage the engagement teeth. That's the shift process. Downshifts go into the next gear.
Cutaway transmission illustrates how gears on the main shaft mesh with the cluster gears below them.
Think of a transmission in terms of levers. The lever is engine power. It creates leverage like extending the length of a wrench. (David West illustration)
Think of a transmission in terms of levers. The lever is engine power. It creates leverage like extending the length of a wrench. If you lengthen a wrench it will break a tighter bolt loose. A transmission does the same. With the leverage and the gears combined with a lever action, you increase the engine's power.
The Muncie M20 is basically a wide-ratio transmission and was intended for normal street driving use. The early ones had a 2.56:1 first gear. The later 1966-1974 units had a 2.52:1 first gear. They are compatible with a GM 3 Series differential. They are for economy and street drivability and just cruising.
The Muncie M21 is a close-ratio unit originally designed to be matched with 4.11:1 or 4.56:1 GM 4 Series differentials. The M21 was designed for higher performance cars. A close-ratio gearbox keeps shift points closer together, which keeps rpms up. With a close-ratio box, a driver can run through the gears and keep the engine in its power band so it performs in street racing or drag racing.
The Muncie M22 has straight-cut, high-nickel-content gears. It uses much the same ratios as the M-21, but it can handle much more abuse. An M22 retains less heat due to the straight-cut gear design and the lack of thrust that helical-cut gears create. An M-22 holds up well. The downside is that it is noisy. It will rattle at low rpms and whine at higher rpms. The M22 is called the Rock Crusher.
The M20 and M21 came out about the same time in 1963, but the M22 didn't come out until 1965. It was developed for the Corvette Grand Sport racing program. Only about 50 early units were made. There were very few M22s until 1969 and a lot of the later M22s were service replacement units sold over the parts counter and installed by dealers. They have stamped coding on them.
Nowadays there are custom gear ratios and other aftermarket set ups, including M21 wide-ratio and M22 wide-ratio units. You can pretty much get what you want. Beefed up boxes for are popular among Resto-Mod builders.
With the reproduction parts available today you can rebuild a stock Muncie four-speed or you can make a number of hidden upgrades to up performance.
When rebuilding a Muncie gearbox, you can often compensate for OEM problems that were more pronounced in the earlier units. The '63 Muncie had issues. The '64 and '65 versions are better and popular with Corvette builders. You can take a '65 case and put in later model stuff. You can bore the cluster pin and put in a one-inch pin. Installing a later synchro assembly to give the functionality of a later model transmission and the looks and aesthetics of a '65.
Synthetic oils shouldn't be used in Muncies. The synthetics are not "synchro friendly." They are so slippery they don't allow synchro rings to grab. This leads to grinding gears. Synthetics also have a different consistency than a natural fluid. Early Muncie cases, especially, tend to be more porous and don't hold up well with a synthetic. They leak out more easily than natural gear lubes.
A GL4 gear lube works. GL5 is supposed to superceed GL4 and there's concern about this. Experts feel GL5 has enough sulfur to be corrosive to brass. It's also like a synthetic in not allowing the synchro rings to grab the gear cones.
Don't put an exotic shifter in your Resto-Mod and top it off with a beer tap. Shifter design counts. People forget about shifter geometry. Each gear shifter has a specific application. A shifter handle has a specific bend. This can be important, especially up top, if a gearshift has to clear a console or custom dash. Impeded movement can keep a shifter from going in and going as far as it has to. Grit getting into the grease in the shifter mechanism can also cause problems.
Shifters also have three selector plates that come out the bottom that have a unique bend to them and unique length that corresponds with the arm that's attached to the shift shaft. The rods are also unique to each application. If you mix and match randomly, the length and shape of the bends will changes and affect the shifting geometry. Having the proper geometry is a necessity.
If there are sloppy arms or arms too long in length, it can allow shifting into one gear, say third, very positively, but not allow the same shifter to go all the way into fourth. Many times a Resto-Mod owner will say his transmission is grinding when it goes into fourth, but in reality, shifter geometry is the problem.
A quality rebuilt M20 is worth about $1,000-$1,200. Rebuilding one in your home shop is a complex process. Books are available to provide detailed illustrations and parts breakdowns. Go slow and take your time. Work in a clean environment and use lint-free rags. Keep all parts and your hands free of dirt and dust. Clean your workbench before you begin assembly on it. If you walk away from the job for long periods, cover all parts on the bench with clean, clear plastic sheets.
Tremec five- and six-speed manual transmissions are used as original equipment in a number of popular vehicles including Mustangs, Corvettes and the Ford GT. Transmission Technologies Corporation develops and builds them. Each OEM model is designed to fit a specific vehicle and deliver a certain level of power or torque, so Resto-Mod builders must consider horsepower and torque.
Jim Mokwa used a fabric belt sling on the end of his engine hoist to support his Tremec transmission while moving it into place behind the engine.
Once the main shaft was slid into the belhousing using a guide tool, the Tremec was bolted up securely to the big V-8.
Tremec offers three aftermarket five-speed transmissions that will fit most performance-oriented Resto-Mods. The T-45 of 1996-1999 is still available as an aftermarket replacement unit. It was first engineered for the Mustang and was also used in light-duty trucks. If you are looking for a high-performance transmission to back up a high-torque engine, the T-45 is not your best choice, since Tremec now offers TKO transmissions for higher torque applications.
The TKO-500 and TKO-600 transmissions are super-strong five-speeds that are very well suited for retro-fitting to vintage muscle cars or Resto-Mods with GM LS1 small-block V-8s, Chevy big blocks or 5.0-liter Mustang engines.
Tremec's T56 six-speed is a durable, smooth shifting and quiet transmission that can handle 330 lb.-ft. to 550 lb.-ft. of torque This six-speed overdrive transmission was developed for a wide range of vehicle requirements. More currently, It is used in the Z06 'Vette, Viper, SVT Mustang Cobra, Aston-Martin DB7 Vantage and V12 Vanquish, and Holden Commodore and Monaro models.
The T56 features an 85-mm center distance and its double overdrive provides extended ratio coverage and allows for closer ratio steps. The aluminum die-cast housings reduce its weight. Tapered roller bearings are used on the main shaft and countershafts to reduce noise and improve durability
The use of needle bearings under all speed gears improves high-speed performance and reduces shift effort. Advanced synchronizer technology, powdered steel core blocker rings and engineered friction materials that improve its durability are other T56 selling points. A multiple cone synchronizer design provides for lower shift effort and increased capacity and a patented strut-type synchronizer design also contributes to the T56's improved durability.
Other T56 bennies include a constant-mesh, synchronized reverse gear, an internal, single-rail shift system, an integral clutch adaptor with front cover end-loading design for increased driveline bending strength and greater application adaptability and the ability to accommodate multiple shifter locations.
As you can well imagine, some Resto-Mod builders want the self-shifting ease of a beefed-up automatic transmission in their high-tech performance machines. Bowler Performance Transmissions (www.bowlertransmissions.com) of Lawrenceville, Illinois, builds such units and owner Mark Bowler put on a seminar about his favorite subject at the 2011 Hot Rod & Restoration Show.
Mark feels that the Resto-Mod movement inspired people to drive again. Thanks to the confidence that technology updates inspire, we have cars that look like trailer queens, but drive like 'Vettes. For car owners, overdrive automatics provide improved engine life, better fuel efficiency, lower cruising rpms and reduced heat. The most popular overdrives are the GM 700-R4, GM 200-4R, GM 4L60, 4L65E and 4L70E, the GM 4L80E and 4L85E, the GM 6L80E, the Ford 4R70W, the Ford 4R100 and a Gear Vendors aftermarket overdrive unit.
The 700-R4 and 200-R4 GM units are still very popular non-electronic overdrive automatics. The 700-R4 offers 3.06, 1.63, 1.00 and .70 ratios and a lock-up torque converter. The case is 30-3./4-inch long for all models except Corvettes and the Chevy-only bolt pattern means that adaptors will be needed for other cars. Although it earned a bad rep when new, Mark likes the 200-R4 with its 2.74, 1.57, 1.00 and .67 gear ratio spread and the fact that its 27-11/16-inch long case is the same length as older Powerglides and TH350s with a six-inch tail housing. That means you can put it in an older car-even a '60s model-without reworking the tunnel or drive shaft. And bolt patterns for Chevys, Buicks, Oldsmobiles and Pontiacs are available. 200-R4s also use a lock-up converter.
These trannies did have issues such as with throttle valve cable adjustments, which control line pressure and could cause damage if not set properly. Also, aftermarket carburetor systems are not designed for overdrive automatics and have improper linkage geometry that can result in poor shift quality and transmission failure. Another issue involves the lock-up converters. If the lock-up wiring is not installed or connected, your converter will slip continuously, creating excess heat. All of these problems can be overcome with three things: 1) Throttle correction systems; 2) Constant pressure valve bodies and 3) Lock-up control systems. Bowler sells kits for the first and third fixes.
The electronic overdrive automatics give car builders customized shift timing and feel, plus diagnostics abilities. These transmissions are known for their dependability. Resto-Mod builders especially like having the ability to change from automatic to full manual control shifts with the flip of a switch, as well as the ability to get optional paddle shift or tap-shift control systems.
Stand-alone aftermarket transmission controllers can be used to enhance the performance of electronic overdrive automatics for as little as $600. The PCS 2000 contoller requires use of a laptop and offers more versatility for custom calibrations. The PCS Simple Shift is an affordable option that requires no laptop and provides simple dials for calibrations. The Compushift CSII controller requires no laptop and uses a handheld display for redoing calibrations. Othe popular controllers used by Resto-Mod builders are the Holloey Dominator EFI model, the Big Stuff II contoller or a factory ECM with custom tuning done to it.
Those who want a paddle shifter can look into three models that Mark Bowler has tested. The Twist Machine features wireless paddles that control up/down shifts while in D or OD ranges. It works only with electronic automatics and still requires aftermarket controllers and gear shifters. The PCS Paddle Shift has similar features but requires the use of a PCS 2000 or Simple Shift controller and includes an LED indicator on the paddles. MasterShift paddles can be used with most automatic and manual transmissions. The paddles select P, R, N, D, 2, 1 ranges so no gear shifter is required. MasterShift paddles can be used with factory or aftermarket controllers and a dash-mount gear indicator is optional.
The 6L80E six-speed transmission has 4.03, 2.36, 1.53, 1.15, 0.85 and 0.67 gear ratios. Many Resto-Mod builders get turned on by six speeds, without realizing that the stock 6L80E is only rated for 630 lbs.-ft. of torque. It can be used in hotter cars if you add upgrades such as a hardened steel internediate shaft, upgraded clutches and seals, welded clutch hubs and a billet 10 x 11-inch converter. The 6L80E (as well as the 6L90E) is a high transmission with a higher output shaft than a 4L80. This can create ground clearance and tunnel clearance problems. Other issues with these units are electronic controls and programming.
Smaller and easier to fit, the 4L80E can be built in four-, five- and six-speed versions. The four-speed ratios are 2,48, 1.46, 1.00 and .75. The five-speed ratios are 2.75 or 2.97, 2.23, 1.57, 1.00 and 0.75. The six-speed ratios are 2.75 or 2.97, 2.23, 1.57, 1.18, 1.00 and 0.75.
Ford's overdrive automatics are the AOD, the 4R70W and the E40D. Of the three, Bowler recommends only the 4R70W—which is not as physically huge as the E40D and gets rid of the temperamental cable that the AOD uses—or the electronically-controlled AODE—that can be used behind Ford FE engines without an adaptor plate. The 4R70W has 2.84, 1.55, 1.00 and .70 ratios with a case that measures either 31-3/16 or 32-7/16 inches. It bolts up to Ford engines in both the small-block 302 and 4.6-liter modular families and has a lock-up torque converter. Compared to the AOD, the 4R70W and AODE have no cables to adjust, more reliable valve bodies, stronger internal parts, true lock-up converters and the ability to tune shift points, shift feel and lock-up timing.
Resto-Mod builders interested in using the Gear Vendors overdrive will get four big benefits: 1) A 22 percent overdrive; 2) the option of splitting each gear; 3) The possibility of having six to eight speeds (depending on transmission type) and 4) A very simple installation procedure. These units also look fantastic.
Mopar fans have at least four overdrive options available. They can add the Gear Vendor overdrive to a Mopar 727 automatic. They can opt for a 48RE box with custom valve body and PCS controller. Or if they do not have an "all-Mopar" hang up, they can use either the 4L60E or 4L80E GM electronic overdrive automatic with a custom adapter plate.
To keep any transmission cool, Mark Bowler suggests staying away completely from the use of a tube style cooler on the frame rail. Plate design coolers are the better choice and are much more efficient. They run $550 and up, but are worth it if they save your tranny from overheating. In extreme conditions, when cooling really matters, Mark suggests adding an extra fan or two. Deep aluminum transmission pans also keep things cool. And you should only use the correct, specified brand name transmission fluids. Synthetic transmission fluids are especially good and do a much better job than regular fluids dissipating heat
Clutch Bullet Points
Manually-shifted Resto-Mods with extra-horsepower high-torque engines need a performance clutch. Rich Barsamian of Advanced Clutch Technology (www.advancedclutch.com) hit the high points of clutch selection in a seminar he presented at the 2011 Hot Rod and Restoration Show. Using the wrong clutch can result in a stiff clutch, poor engagement, chatter or bad engagement timing.
High-performance Resto-Mods need a quicker-engaging clutch with high heat capacity. Materials, strong springs, design and a choice of hole sizes count.
This ACT clutch uses stronger springs, rather than trick geometry, to increase the amount of engine torque it can handle.
Cars with a modified engine need a clutch with quicker engagement and higher heat capacity that can handle more power. Different materials, stronger springs, parts design and a choice of hole sizes count. Avoid the use of clutches that use geometry—rather than stronger springs—to increase torque capacity.
Rear Axle Bullet Points
Jim used POR-15 to refinish his GTO rear axle. The GM 12-bolt posi rear was fitted with Mosser 30-spline axles.
Jim Mokwa installed the rear axle on stock GTO rear coil springs. Rear control arms and sway bar are also black. The car has a 3.73:1 final gear ratio.
Thanks to Resto-Mod builders, rear axles are getting a lot more attention today than they used to years ago. Since your Resto motor has more ponies than the stock engine the car left the factory with, the factory differential may blow up with the increase in power. The favorite choice of builders is a Ford heavy-duty nine-inch axle. If you're lucky, you'll turn one up in an old Ford truck sitting in your favorite salvage yard. Or check with companies such as John's Industries (www.9inchfactory.com), Strange Engineering (www.strangeeng.net), Currie Enterprises (www.currieenterprises.com) or DTS Custom Services (www.dtscustom.com) that make or rebuild axles with new internals.
Jeff's Camaro has monoleaf rear springs finished in black to match the axle. Competition Engineering Slide-A-Link traction bars were added.
Jeff Noll fitted Energy Suspension polyurethane frame and control arm bushings at all four corners and used Edelbrock Performer IAS rear shocks.