THM125c Automatic Transaxle

Fluid Fill

"Where is the automatic transaxle fluid dipstick?"

Open the trunk. Look right in front of you. You should see the valve covers. Look back a little. Look back by the trunk wall. Now look all the way down. Do you see the tranny yet? Now look for the tube that is sticking out of the tranny. There should be a dipstick in that tube. The tranny dipstick is amazingly hard to see, so you will have to look for a little bit, but I ensure you that it is there somewhere. It is just not on the same level as the oil dipstick. It's not marked either.

From: Jeff Claunch


  • Slips in 2nd gear
  • Low shift point under full throttle
  • My automatic slips in 2nd gear

    You mentioned that your automatic was slipping in 2nd gear. This is often caused by a bad O ring seal on the intermediate band servo piston. If caught early enough, you can prevent, or at least minimize burning of the intermediate band. If ignored, the band burns up (from slipping) and a reman. is is order. The O ring can be replaced by dropping the pan to gain access to the servo.

    From: Tin Man

    My automatic shifts too low in the RPM range under full throttle

    "No matter what, the trans won't shift past 4500 RPM full throttle. I've tried adjusting the TV cable every which way, and can get the light throttle shift points to change, but it refuses to rev past 4500 to the proper 5500, always forcing an early shift. Also, it won't kick down from third to first (when I know it should) under full throttle at 30 MPH or so. It will kick down correctly at lower speeds, but will still only rev to 4500. I'm thinking now that a line or govenor pressure is off a bit, fooling the trans into thinking it should shift."

    You may have a weakoned/fractured governor spring. For some expert advice, try Tony Garcin (He was the developer of the TransGo shift kit for the Fiero when at TransGo). He also has various springs to alter the shift points of the 125 trans. He's at (I think; if that's wrong, try (818)442-5817). Another source for springs is the B&M Shift Point Kit Part #20236. I've no experience with that one, but it's advertised to "Fit most GM Automatics" and the picture I have looks as if the springs are the same.

    From: Robert Yorke

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