How to Identify a 200-4R Transmissionby Floyd Drake III
The General Motors THM-200-4R automatic overdrive transmission was introduced in the early 1980s as the overdrive version of the earlier THM-200. The THM-200-R4 is one of the last of GM's venerable turbo Hydramatic automatic transmission line, which has been in use since the 1960s. The THM-200-4R is essentially a hydraulically-controlled transmission that has an electrically-controlled torque converter clutch solenoid. Identification of the 200-4R can be accomplished visually, and relies on access to the transmission pan located on the bottom of the THM-200-4R.
View the transmission pan by going under the vehicle, if still installed, or by turning the transmission over, to view the bottom. The transmission is in the middle of the vehicle and the best access is to go under the vehicle from either the driver's or passenger's side door.
Notice the shape of the transmission pan. According to 442.com, the THM-200-4R has an unusually-shaped pan that almost looks like two separate pans, with a main pan and a smaller pan towards the rear. The shape is essentially rectangular with an angle on the passenger's side rear of the pan. This shape is different from all other GM automatic transmissions.
Look at the bottom of the transmission pan. According to 442.com, the bottom of all THM-200-4R transmission pans are stamped on the bottom with the word "M E T R I C."
A native of New Haven, Conn., Floyd Drake III began writing in 1984. His work has appeared in the "New Haven Register," Medford's "Mail-Tribune" and the "Ashland Daily Tidings." Drake studied journalism at Southern Connecticut State University. After working as a reporter in Oregon, he is now based back home in New Haven.