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 The TH400 or Turbo 400 is a good transmission that was supplied in numerous cars years ago. This renowned transmission was uncovered in GM’s cars, too as, Rolls-Royces, Jeeps, Jaguars, Ferraris, etc. The TH400’s high-level of fostering could it is in tied come its exceptional features, and also it verified that civilization can when again count on GM transmissions.

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But what were these functions sported by this durable and also legendary transmission, and also generally, what set it personally from other transmissions from this manufacturer? an overview of the TH400 transmission will offer you a better idea. Review on to discover out!

The GM TH400 Transmission

The GM TH400 infection is a three-speed automatic infection that was longitudinally positioned behind the engine. This placement is aimed at giving the best power ratio and durability because that rear-wheel drive. The TH400 has actually been rated in ~ 450 ft. Lbs. Of input torque, nonetheless, aftermarket design that have been modified might go past that rating.

History that the TH400 Transmission

The TH400 was launched by basic Motors in 1964, as a replacement to the ST300 2-speed automatically transmission. The was supplied in a wide variety of vehicles, hence, it to be not just exclusive come GM cars.

Upon the launch, the TH400 was noticeable in Buicks and also Cadillacs, and also a year later, that was used in Chevrolet and also Oldsmobile cars. Buick, Olds, and Cadillacs that were later launched in between 1965-1967 likewise featured the transmission however with creative variable-pitch stator. This stator helped to differ the talk converter’s characteristics, and also you can tell a auto has this stator by the two-prong plug top top the case.

In the 1970s, the TH400 was offered in heavier-duty GM trucks and it was accessible in 2wd and 4wd configurations. The specify name of the TH400 was readjusted to 3L80 (3-speeds, Longitudinally positioned, 8000 lbs. GVW or Gross vehicle Weight) in 1990 to do it simpler for buyers to recognize the transmission.

The change in naming does no come as surprise because some GM transmissions were likewise renamed (for example the 700R4 come 4L60). Around the same time once the TH400’s name was changed, one overdrive version dubbed the 4L80-E was launched.

This is an electronically regulated transmission the is still being produced and used in a range of heavy-duty GM and also military cars/trucks. Generally, here’s a perform of cars that used the TH400 transmission:

1965-1967, 327 V8 (Rambler/AMC)1968-1971, 350 V8 (Buick)1969-1972, 225 V6 (Buick)1972-1975, 232 I6 (AMC)1975-1979, 258 I6 (AMC)1972-1979, 304 V8 (AMC)1972-1979, 360 V8 (AMC)1974-1975, 401 V8 (AMC)GMJaguarFerrariRolls-Royce

Features the the TH400 Transmission

The features of the TH400 Transmission enabled it to carry out improved power over previous transmissions. The was likewise durable, and these features can be tied come the following:

Aluminum and also iron construction.Weighs 135 pounds there is no fluid.Bell housing incorporated into the transmission.First gear: 2.48:1, reverse gear: 2.08:1, and 3rd gear is an also 1 to 1.Came with 3 tail pillar lengths.

Turbo 400 transmission Identification

The Turbo 400 transmission can be identified in the adhering to ways:

1. Outside Build

The TH400 transmission comes through a instance made of cast aluminum alloy to provide it strength and durability. The case is really smooth and also its length sits at size of 24-3/8″ long. This TH400 is the biggest of the usual GM automatically transmissions, however, the infection still maintains a compact design.

There is a hex bolt sample on the rear mounting challenge of the transmission and also the ribs run forward longitudinally. In line with that, the liquid pan has actually an irregular shape.

2. Variants of the TH400

There are two variants of the TH400, and also these room the TH375 and also TH475. The TH375 was provided in smaller displacement cars in between 1972-1976. In contrast, the TH475 was used in bigger trucks native 1971 since it is one extra-heavy-duty version. One have the right to easily various either these variants personally by looking the end for the “375-THM” designation cast on the bottom of the tail housing.

TH350 vs. TH400

A simple method to identify them is to check the kick-down mechanism. The TH400 transmission takes benefit of an electric slide switch regulated by the accelerator linkage. Top top the various other hand, the TH350 supplies a mechanical cable kick-down the is connected to the accelerator linkage. Despite the difference, the TH400 is taken into consideration the heavy-duty variation of the Turbo-Hydramatic 350.

Transfer situation of the TH400 Transmission

The TH400 can easily be adapted for use in most Jeeps longer than CJ5s, and also as such, that is great conversion transmission. Whether it’s the 2wd and also 4wd execution of the Turbo 400, one of two people of these deserve to be used. Nonetheless, the 1976-1979 AMC situation is comparable to that of the TH400’s, from the collar of the case and also back, however, that is tilted around four degrees.

Engine Compatibility and also Adaptability

The engine compatibility and also adaptability that the TH400 infection include:

1. AMC/Mopar Jeep

The faster Turbo 400s in Jeeps featured a manufacturing facility adapter plate, whereas older AMC versions came v a devoted AMC layout case. That is entirely feasible to do the Chevy 400 compatible in the AMC I6 & V8 engines. As an update of this nature can result in a an ext enhanced Jeep powertrain over 727, 999.

2. Chevrolet

The front challenge of the TH400 is compatible with the Chevy 90 degree “Small Block” or the “Big Block” patterned engines.

3. Buick / Olsmobile / Pontiac / Cadillac

The TH400 is compatible in Buick engines especially when you use a Buick V8 or V6 version of the transmission.

Common TH400 Problems

The TH400 may have offered improved power over its predecessor, the ST300, yet it tho came through its own problems. Notable amongst this is an early shift and less efficiency when the engine revs high. The latter occurs once the kick-down switch, responsible for shifting in between gears and maintaining maximum RPMs, stops working. The move would’ve helped in, effective power usage.

On the other hand, the cause of this trouble can it is in tied to the wrong placement of the vacuum hard-line, relocating from the input manifold through a pliable rubber line. The heat produced by the engine and also transmission leader to the deformity the the rubber, in order to failing to host the press properly. One more problem of the TH400 is the possibility for that transmission fluid to leak slowly into the hose if the seal is not solved properly.

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The Bottom Line

An synopsis of the TH400 transmission mirrors it is a long lasting transmission the can provide a good performance. The TH400 was provided in a wide variety of cars indigenous GM and also other manufacturers. Interestingly, the transmission have the right to be adapted for usage in numerous engines today. In the end, even if it is it’s a new or aftermarket TH400 you resolve for, you space bound to gain the complete benefits offered by this transmission.