Choosing the Right Gearbox

By: Paul Tuzson

Date: 30.09.2017

Toyota Four-Speed

Toyota Four-Speed

Toyota Five-Speed

Toyota Supra

Toyota Supra

Muncie gearbox

Muncie gearbox

Saginaw gearbox

Saginaw gearbox

Top Loader Gearbox

Top Loader Gearbox

BorgWarner Single-Rail Gearbox

BorgWarner Single-Rail Gearbox

Aussie Four-Speed Gearbox

Aussie Four-Speed Gearbox

BorgWarner/Tremec T5 Gearbox

Tremec TR-3350/TKO Gearbox

Tremec TR-3350/TKO Gearbox

Tremec T-56 Gearbox

Tremec T-56 Gearbox

Jerico Five-Speed Gearbox

Doug Nash/Richmond Gear

Holinger RD6-H

Holinger RD6-H

Holinger input gear and dog

Holinger sequential off gearbox

Toyota Four-Speed

Toyota Four-Speed

Toyota Five-Speed

Toyota Supra

Toyota Supra

Muncie gearbox

Muncie gearbox

Saginaw gearbox

Saginaw gearbox

Top Loader Gearbox

Top Loader Gearbox

BorgWarner Single-Rail Gearbox

BorgWarner Single-Rail Gearbox

Aussie Four-Speed Gearbox

Aussie Four-Speed Gearbox

BorgWarner/Tremec T5 Gearbox

Tremec TR-3350/TKO Gearbox

Tremec TR-3350/TKO Gearbox

Tremec T-56 Gearbox

Tremec T-56 Gearbox

Jerico Five-Speed Gearbox

Doug Nash/Richmond Gear

Holinger RD6-H

Holinger RD6-H

Holinger input gear and dog

Holinger sequential off gearbox

Get into gear with the right gearbox for your ride

From Unique Cars issue #310, April/May 2010

Gearboxes 

Choosing a gearbox can be fairly straight-forward if you're going to use the standard OE units that were available for your car. However, there are and were many other options available, like Japanese gearboxes adapted to bigger engines.

Then there's the complete opposite approach offered by high-output, specialised competition gearboxes like Jerico, Holinger and the like.

Some adapted otpions aren't as popular as they used to be because parts for the'boxes ae either not available or very hard to find, even though the bellhousings and kits can still be had. However, you may still find any of these gearboxes bolted in behind a car you're going to purchase so we've included them here in our fairly comprehenseive round-up of gearboxes past and present.

For lower power applications

The reason some Japanese 'boxes were so popular was because they were built much stronger than they needed to be for the cars in which they were standard equipment.

Toyota 'boxes are the most commonly adapted and they can be fitted to just about anything by means of custom bellhousings or adaptor plates.

Toyota Four-Speed

Toyota four-speed 'boxes were used on four and six-cylinder engines in 18R Coronas, Mark 2 Coronas, six-cylinder Cressidas and Crowns. They are available with two different shifter positions and are strong enough for use behind normally-aspirated sixes. Sometimes, they've even been used behind mild V8s successfully, although decent power out of a V8 and enthusiastic driving will break them.

Toyota Five-speed

This 'box looks the same as the four-speed RT10 Corona transmission but it has a bulkier rear housing. The five-speed was made in three first-gear ratio versions - 3.0:1, 3.25:1 and 3.5:1. It's commonly referred to as a steel-case Toyota and models used with six-cylinder engines were fitted with a heavier duty needle-roller bearing in the front cluster.

Toyota Supra

These 'boxes were fitted to Coronas, Celicas and, obviously, Supras. They're popular as replacements for four-speed Holden 'boxes because they're much stronger than steel-case of our-speed Toyota 'boxes. The four, first-gear ratios we know of are 4.0:1, 3.7, 3.5 and 3.28:1. Twin-turboed 3.0-litre Supras were fitted with an even stronger version but it's always been rare; it's about half-as-wide again as a normal Supra 'box and will easily take 550hp. Supra 'boxes can have the shift-lever fitted in four different locations.

Gearboxes for higher power

Classic high-output iron engines will always be a good fit with the OE heavy-duty gearboxes that were originally designed to be coupled with them. These are the main ones.

Muncie

The Muncie was used from about 1963 to '74 and all versions had aluminium cases. The Muncie came in a close-ratio 2.2, a 2.52 version, the famous 'rock crusher' and a 'big Muncie', which was available for about a year on HQ Monaros fitted with 350 Chev engines.

Early versions had a 7/8-inch layshaft but this was later increased to 1-inch. Later versions also had heavier rear housings. Everyone wanted a rock crusher and some Muncies were sold as that  type when they weren't really.

Super T10

The Super T10 was developed for racing. We don't have a shot of one but they look virtually the same as the Muncie. Annular grooves indicate the ratios; the more grooves, the lower the ratio. Features of this high-performance 'box are a fine, 26-spline input shaft, double-row needle-roller bearings at either end of the main cluster, larger diameter mainshaft, gears designed for better lubrication and cooling, biggger bore gears, a 32-spline output shaft, which lines up with a Turbo 400 yoke, and a choice of aluminium or cast-iron cases. The Super T10 is now manufactured by Richmond Gear in road and race versions.

Saginaw

The Saginaw was used behind 253 and 308 Holden engines from 1968 to '70. Annular grooves machined around the splines on input shafts indicate the first gear ratio.

Information from Castlemaine Rod Shop indicates that a Saginaw with no grooves has a ratio of 2.85:1, one groove 2.54, two grooves 3.11, and three grooves indicated 3.5. Spare parts are fairly expensive but this was quite a good four-speed 'box.

Top Loader

The Top Loader takes its name from the fact that its components are loaded through the top during re-assemly. It's so famous for its toughness that adaptors are available to fit it to just about anyting, although you'll probably have trouble finding one. People who have them tend to want to hang on to them and you're ceertainly not getting mine. It came in wide and close-ratio versions and had a 1 1/16-inch. 10-spline input shaft. There was a bull-nose version fitted to the Phase III HO that had a 10-spline input shaft with a larger diameter of 1 3/8-inch and a 31-spline output that was the same as an FMX auto.

BorgWarner Single-Rail

From XB onwards, the Single-Rail was used behind V8 and six-cylinder Falcons, V8 and six-cylinder Chryslers, Cortinas, and V8 Leylands. Holden also used a light version for a while and it's a good idea to buy the correct tailshaft with the 'box, particlularly if it's from a Leyland or a Chrysler, because no other yokes fit.

The 302 V8 version had a lower first gear than the 351 due to the latter engine's greater torque. Single-Rails can be toughened up and adaptors are available to fit them to most engines.

Aussie Four-Speed

The Aussie four-speed isn't all that strong but fitting uprated ball bearings with extra balls helps it cope. There's an M20 version with a first gear ratio of 3.05:1, which was fitted to 253 V8 engines and an M21 version used with the 308. This had a first gear ratio of 2.54:1.

BorgWarner/Tremec T5

In Australia, Brock Commodores had the first T5s and these had fine, 26-spline input shafts. There's a large variety of input shafts available for these 'boxes. The T5 is a current 'box with very fine tolerances and parts from one 'box shouldn't really be used as replacements in another because wear patterns should match. If they don't, a noisy 'box will almost certainly be the result.

Because of the fine tolerances, it's vital to use the correct oil in these 'boxes. When fitting a second-hand 'box, it's important to know where it came from for conversion purposes, but it's often difficult to identify the various versions and there are BorgWarner and Tremec versions. The main difference between them is the shift rposition, which can be important in a conversion.

Higher power OE and aftermarket gearboxes

The best gearboxes for high-performance V8s are the dedicated aftermarket types designed to handle major pwoer and torque. Newer OE performance units will also handle decent power.

Tremec TR-3350/TKO

The Tremec TR-3350/TKO gearbox is actually, believe it or not, an evolution of the Top Loader and has the same bolt pattern. It's smooth and easy to use on the street but tough enough for track use at the drags or around a circuit. The addition of the fifth speed overdrive is a real advantage in a performance car fitted with a low-ratio differential but there are even more good points. The shift lever can be located in up to eight different positions and, depending on the verion, this gearbox will take up to 813Nm.

Originally, the 3350 and TKO were different models. The 3350 has been discontinued and supplanted by the more highly rated TKO. Really, if you're building a project and you want a modern performance gearbox it's hard to go past the Tremec TKO. Ratios are 2.87:1 in first, 1.89 in second, 1.28 in third, 1.00 and 0.64 or 0.82 in sixth. The TKO has both electric and mechanical speedometer pickups, a number of cross member mounting options and, parts should be readily available.

Tremec T-56

The T-56 six-speed gearbox was introduced in 1992 behind the Dodge Viper. The version for that application is rated at 745Nm. There are versions for Ford, Chrysler and GM or it can be adapted to other installations. The T-56 can be found behind LS1 engines in Commodores but this local version has a reduced rating of 475Nm. Locally, Mal Wood has had replacemtn gears cut the the T-56 and these boost the amount of torque the 'box will take by a considerable amount.

Jerico Five-Speed

The five-speed Jerico unit shown is different to other gearboxes. The layshaft is set off to the side rather than directly underneath, giving the 'box a flatter profile and making it extremely useful in lowered, performance cars. Unfortunately, Jerico units don't have synchros but they will handle up to 1355Nm of torque and 970kW. There are about 900 different ratios available.

Jerico also makes four-speed, three-speed and two-speed 'boxes that have underslung layshafts, so these models look more conventional than the five-speed. I must say, I've never seen one of these other types.

Doug Nash/Richmond Gear

The Doug Nash is no longer made under the original name but it's a classic performance gearbox and parts are still available. In fact, Richmond Gear makes both road and street examples in five-speed and six-speed versions. The interesting thing about this gearbox is that fifth gear isn't overdriven, it's the 1.00:1 ratio. There is a street version availble that has synchros and first gear in that 'box is 3.27:1. Ford, Muncie and Chrysler patterns were originally available.

Holinger RD6-H

This Australian product is designed for rear-drive racing cars, and the RD6 is locally-designed and manufactured. Unfortunately, Peter Holinger, the man responsible for it, has passed away but the company is still going strong. The range of ratios available for this 'box is absolutely huge and it'll handle 881Nm of torque.

It's a six-speed but it's not synchronised so it's only suited to track use. That said, I've heard there are a few being used on the street, It's safe to say, though, that because of the space between the engagement dogs you won't see them in peak hour queues or in the supermarket carpark.

There's provision of oil cooling and, in some models, even an oil pump. The earlier version of this 'box is the H6S and is identifiable by its ribbed, rather than smooth, front case. It would be brilliant to see a street verion of this 'box. 

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