TH400 Rebuild Kit

In a car, regardless of its type (passenger, cargo) it means a system of units and mechanisms that transmit the rotational, progressive motion from the engine to the wheels.

On the correct operation of each component of the system depend:

  • safety of the driver, passenger;
  • fuel consumption;
  • wear and tear on rubbing, touching parts;
  • the conformity of the specifications with the information declared by the manufacturer.

Its parts, assemblies and mechanisms are made of wear-resistant materials capable of withstanding high mechanical loads, exposure to temperature fluctuations, chemical agents. To reduce friction and cool the unit special engine oils are used, which must be regularly changed according to the instructions of the car manufacturer.

The standard set of transmission consists of several components: clutches, gearboxes, cardan gear, main gear, differential gears, axle halves.

Depending on the layout (front, rear, all-wheel drive) transmission can include other units: CV joints (joints of equal angular speeds), transfer gearboxes, friction, viscous clutches.

How much does it cost to rebuild a TH400?

3L80 (TH400) is a 4-speed automatic unit. It was presented in 1964 in Buick and Cadillac cars, as well as in Chevrolet and Oldsmobile. The innovative variable speed stator was developed and launched in 1965-1967 in vehiclesthat were able to significantly change the characteristics of the torque converter.

3L80 (TH400) in 1970 made its way into the segment of heavier General Motors trucks, in configurations of rear-wheel drive and all-wheel drive SUVs and pickups. It is a very popular automatic unit in the automotive industry as well as in the aftermarket. They are found in General Motors, Jaguar, Rolls-Royce, Ferrari and others.

As in other automatic units, in 1990 General Motors changed the naming scheme TH400 (Turbo-Hydramatic), and then it became the model 3L80 (3 – 3speeds, L – longitudinally located, 8000 lbs. – GVW.) The updated version 3L80 was produced since 1990, as a 4-speed automatic transmission 4L80. Many details are interchangeable.

The complete rebuild kits are $300-$700 depending on the quality and components. Most shops usually put about $300-$400 materials, and about $200-$400 labor. The best rebuild kits are transgo, B&M, Raybestos th400 rebuild kits.

How do I upgrade my th400?

The gearbox plays a major role in the transmission. Even with a relatively weak engine, the car can be fast thanks to the right gear ratios. Sports cars differ from serial ones, first of all, by gearboxes, and then by motors, bodies and suspension. You can upgrade your TH400 by making anew original shafts and gears having kept the case of the gearbox (its redesign is too expensive). This work is extremely labor-intensive, and therefore not cheap.

Do you need special tools to rebuild a transmission?

When carrying out repair work on the gearbox, you should strictly adhere to the principle: all removable elements are placed in the order in which they were removed, do not rely on their visual or mathematical memory. It is advisable to replace the entire gearbox main shaft and bearing. In addition, the glands and washers at the sealing points should be replaced on new parts, because as a result of disassembly and then assembly, the gaps and spaces are increased.

Specialized tools are used for repair of suspension and transmission of cars, such as removers of springs for suspension shock absorbers, removers of springs for assembly of shock absorbers in a lightweight version. You will also need a Jack, a set of heads, wrenches and horns, amplifier (pipe), crowbar, WD40 (deoxidizer), couplers, hammer depending on the type of work.

How much is a transmission rebuild kit?

First of all, a computerized diagnostics must be performed to detect the fault. The result will show whether there is a fault in the electronics and, and if so, which one. In the vast majority of cases, the above-mentioned diagnosis well detects an electronics malfunction if, of course, there is one. The errors detected should be corrected as soon as possible since they can lead to even more serious problems in the future.

If this computer test does not detect a malfunction, then the automatic transmission must be checked for mechanical damage. The oil state can also tell you a lot. The ATF oil must be sufficiently transparent, free of foreign impurities and odours.

If this is not the case, then most likely there will be a mechanical breakdown. Here, in the overwhelming majority of cases, one cannot do without disassembling. It will also be necessary to have at least a set of gaskets, oil and automatic transmission filter. In the future, when disassembling the box, if you decide to do so, and the detection of malfunctions will need to buy parts that are out of order. Or you can buy a complete rebuild kit. Most kits will usually cost from under $100 to over $300 – definitely a massive saving over the cost of a new transmission.

Editorial Staff

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