What You Need To Know Before You Buy A GM With A 700R4 Transmission
Posted by Regis F. on Friday, December 14th, 2012
The 700R4 transmission was first introduced by General Motors in 1982 and used up through 1992. It is sometimes also referred to as the 4L60. The 700R4 was one of General Motors first over drive automatic transmission and was used in everything from Corvettes to pickup trucks. The first 700R4 had their share of issues. Here is a list of things to look for when considering buying a car with this transmission.
The first 700R4 had an input shaft with 27 splines. This design was subject to failure because it really need more spline to handle the load properly. In 1984 they introduced a 30 spline input shaft which was much stronger. Steer clearing of the early models with the 27 spline input shafts.
Because the 700R4 was put behind cars that were abused like the Corvette and Camaro, and pushed to their limits while serving duty in pickup trucks, the 700R4 can easily be overheated. Overheating is the number one cause of transmission failure, making an aftermarket cooler highly recommended.
The 700R4 used a Throatall Valve cable, or TV cable for short. This cable must be adjusted properly or the transmission will fail. If anyone has messed with the TV cable, it is highly recommended that it be reset, and properly adjusted.
The 700R4 often suffers from the loss of the 3-4 clutch pack. The only fix is to rebuild the transmission or replace it with a re-manufactured unit. I recommend using performance 3-4 clutches and a shift kit to modify the holding pressure of the clutch pack.
The governor has a tendency to stick. When this happens it takes a lot more rpms to make the transmission shift. Common failure points on the governor are the gears, the springs coming loose or debris preventing the valve that the governor is connected to from moving.
The valve body on the 700R4 can easily warp. Many times this is caused by overheating the transmission. To fix this problem, the valve body needs to be removed from the transmission and sanded on a perfectly flat surface. All of the valves should be removed and a fine grade emery cloth should be used to clean up the bores and the valves.
Due to the age of the 700R4, a common problem is leaking from seals and gaskets. Especially prone to leakage is the front and rear seals. The rear seal can easily be replaced by just removing the driveshaft. The front seal is a whole different story. To replace the front seal the transmission needs to be removed from the vehicle. I highly recommend you take a good look at the front of the transmission for fluid leaks. Transmission oil is usually red (or green) while engine oil is a golden color. Cars with low mileage are more prone to leaks than high mileage cares. Why? Because if a car sits, the seals dry up and leak. A car used on a daily basis usually does not have this problem
Do your homework before buying a car with a 700R4. Sometimes a low price will justify the cost of replacing the transmission. If the transmission does need to be replaced I highly recommend replacing it with a re-manufactured unit.