Longevity of GM Automatic Transmissions

My 1990 Pontiac Grand Prix's 4T60 has 200k+ miles on it. The engine and suspension (strut tower braces, Addco swaybar, Koni adjustable struts) are modified. I drive it very hard. The tranny is all original minus the side gasket.

I drop the pan/filter every 50k miles and only use Amsoil synthetic ATF.

Between 1989 and 1993 GM was trying to prove they could compete with Japanese cars and built them pretty well. In 1994, GM came out with cheaper/thinner plastic panels and other *high tech* cost saving features.

GMs 4T60E (E for electric) is weaker than the older 4T60 (vacuum controlled).

Your mileage WILL vary!

-- Kevin Heider

The TH-125 in my Phoenix has 213k miles, one fluid and filter replacement at 144k when I overhauled the motor. The only problems it has are delayed shifting into reverse after a long trip and occasional delay into second when hot. Both problems existed when I got the car at 125k miles. Currently the car is on backup status until I replace the cat and do a general emissions systems tuneup.

JazzMan

Eric Fraser wrote: Who has the most miles on a

328000km on a 1992 Chevy Beretta GT 3.1L with the 3T40 in it. Saw red line daily. Had the occasional slipping in reverse, only when hot, when it met its demise to a red light runner. Never changed the fluid or filter.

Dennis

I've owned three GM TH350's. All had over 100k miles. Car died before the tranny did. Blew up a TH375 on a 26 year old Buick... the case cracked and it leaked to death. Wife's 90 Beretta made it to 125k miles - lockup solenoid went, causing grief - didn't replace it in time... ended up smoking the tranny.

The champion: Friend's 85 Celebrity. 200k miles. Don't know the last time the tranny fluid was changed. It's starting to rust bad and the oil pressure light starts to blink when idling hot, but tranny is fine. He's going to drive it another winter or two...

Ray

210k miles, 86 Caprice 5L V8, never changed fluid or filter since I bought it with 62k miles in 1989. Doesn't leak. Never had a single problem.

- Bill