1996 Volvo 850, mileage 155K, ATF recently flushed. I recently noticed that lock-up hasn't been engaging consistently after A/T shifts into 4th gear. That little tiny final "shift" is missing, and RPM's hover higher than normal when cruising down highway and accelerating. Lock-up only seems to work for the first 10-15 minutes of highway driving when it usually disengages and won't engage again until the car is being driven cold. The A/T light has not come on.

Is this fixable without removing or replacing the tranny? I think I read there was a solenoid that controlled the torque converter lock-up? NOTE: I can't tell if lock-up works in 2nd & 3rd gear, not as obvious as in 4th gear.

Any help would be appreciated! Thanks...

there is a lock up solenoid. you need to drop the subframe to pull the pan the replace the solenoid. it may just be trash from the flush. keep driving it and maybe that'll clear it. usually, the lockup solenoid will post a trans code. good luck, chuck.

Thanks for the info! What is involved in dropping the subframe and pulling the pan, and how labor intensive is this? Does this mean removing the transmission? Is this a job any transmission shop could accomplish, or would it need to be a Volvo dealer? Thanks in advance...

because the subframme supports the engine, you have to hold it from the top, loosen the motor mounts and drop the subframe about 1 foot. the pan is on the front of the trans. there's no gasket, a special sealer is used on the pan. can't tell you WHICH solenoid it is, there's 4.

i'd give the car some time, if that doesn't clear it up, then find a place with an autodiagnos. that tool can talk to the trans and activate each solenoid. if it fails that test, then i'd replace it. good luck, chuck.

I'm not sure what you mean about tranny lock up. Do you mean when the gears engage? And final shift? what tranny light? Arrow up?

Anyways pull your tranny codes off the computer and if you do find out what they are and clear them - Since you have a 96 a shop will have to do that for you unless you have the reader itself.

But before doing that, since you had a tranny flush, I would check your tranny fluid. Even though its flushed doesnt mean (that whoever did it) put the proper amount back. If doing the 12-14 liter flush doesnt mean the same amount came out in the bucket. Check your fluid with the dip stick.
Hope for you thats all it is. Good luck.