Also known as: TH-250, THM-250C

When I bought the Caprice, I thought that it had a Turbo-Hydramatic 350 transmission, the bread-and-butter three speed automatic fitted into all kinds of GM cars from days gone by. What I didn't know is that the TH-350 has a twin, the TH-250.

The TH-250 is a transmission for the sake of having a transmission. The name follows the old convention for Hydramatic transmissions, where the numeric part is the torque rating. A 305 or any other engine from the late 70s and early 80s would have only made around 250ft-lb of torque anyways, so a TH-250 was good enough to get the job done. Compared to a TH-350, the TH-250 is made of lower strength parts, has some differences in how second gear is selected, and was probably cheaper to manufacture.

A TH-250 looks identical to a TH-350 in almost every way, except for one key component. The case is mostly the same and the pan shape is the same. Below is an image showing what to look for to make the distinction between the two.

The TH-250 can be identified by an external adjustment nut behind the cooling lines. A TH-350 has a blank spot on the case instead.

The pan on a TH-250 looks the exact same as the pan fitted to a TH-350.

According to my good friends at Chevy Talk, the TH-250 is not capable of taking much more torque than it was rated for, and with the high availability of TH-350 transmissions at low cost, swapping the TH-250 out is the easiest, cheapest, and therefore best way of sending a lot of torque to the rear of the car.

Problems

I have had a fair number of problems with the transmission, the worst one being that the lockup clutch sometimes will not disengage, which causes the engine to stall when stopping the car. Normally, putting it in neutral was enough for it to clear itself, but one time, it had to be put in reverse and driven backwards for a moment for it to disengage. The lockup clutch would also spontaneously engage and disengage while driving on the freeway.

Another less serious problem is with manual gear selection. If I put the shifter into 1, the transmission will select 1st gear, as it should. Engaging D also does what it's supposed to. What I could never do is engage 2nd gear. If I moved the shifter from D to 2, the transmission would stay in 3rd gear. If I came from the other way by putting it from 1 to 2, the transmission would stay in 1st gear. Even after a few linkage adjustments, the problem remained. No matter what, 2nd gear could not be selected with the column shifter.

Another problem, which cost me $65 to deal with, was when the transmission got stuck in reverse. No matter what I did with the shift lever, the transmission was jammed. I ended up calling a tow truck to move the car off the road and back onto the driveway. I left town for about two weeks, and when I came back, the transmission worked just fine again. I adjusted the linkage again anyways, and the problem never came back. I'm still not sure what caused it, although it can't be a coincidence that the problem happened right after I had left the transmission hanging by the shift linkage without a jack stand supporting the weight.

Rate This Page

Page last modified on December 29, 2009 23:24:07. (ID=46)