: Transmission shifting problems and acceleration thumping issue on incline/uphill

07-05-09, 05:26 AM
Hello all,

I have a 1986 Cadillac Fleetwood Brougham (Olds 307 Y with 152,000 miles) with the same problem now ever since I purchased it roughly 6 years ago. The car runs and shifts fine in the beginning and when outside temperature is cool.

The problem I have almost seldom happens or very unnoticeable when its cold outside, such as at night or on a cold day in the low 50 degree's.......it happens when the engine/transmission gets up to normal operating temperature....after driving it for about 15-35 minutes, and the hotter it is outside the sooner the problem starts.....

It starts out when shifting from 1st-2nd gear, there's a loss in power and as the car tries to get up to speed it vibrates/jerks a bit....and same thing when downshifting from 2nd-1st, the car (im assuming the transmission) vibrates/jerks in a back and forth motion....

...I've read other posts of this exact problem, to which they have found out the problem was the TCC Solenoid needing to be replaced......but I also have another problem that usually follows a few minutes after this, and this new issue has started recently........after the initial problem of the late shifting issue, when accelerating after a stop or slow speed up, the car starts vibrating badly and a thumping sound comes....you can feel it like something from the engine or transmission is spinning and hitting something somewhere.....(this only happens on slight inclines/uphills) while pressing the acceleration.....this sound/thumping only happens on slight inclines/uphills, it doesnt happen on flat level roads or downhills when accelerating....

...When pressing the gas down all you hear and feel is a thump thump thump sound (the more you press the gas the faster and harder the banging sound), so I let off of the gas and the sound goes away, but when I try and press the gas again the sound and feeling comes again....the only way I've found to overcome this is to step down on the gas to put the car into a high gear (kicks into overdrive), which only then you dont feel and hear the thump thump noise...

I have had transmission services a couple times within the past 3 years, but these issues have always been there, with the latter happening more recently...

I'm hoping that a TCC Solenoid replacement will fix both these problems, especially the banging thump issue..

Anyone else have this same problem??

Any thoughts on what could be the issue and possible fixes??...would be greatly appreciated, thanks.

07-06-09, 12:30 PM
I have the same problem with my 88. When you go from 2 down to 1, its more noticable. The car seems like it shifts rough, but its almost like the engine is surges/loses power for a split second. Its not that bad, and I really dont drive the car that much.... (not even 200 miles this year yet) but would love to get it fixed. Let me know how much the solenoid is, just so I have an idea.

07-06-09, 04:46 PM
The tcc solenoid is around $45-50. I'm also going to get the 4th gear pressure switch replaced since the tranny's gonna be opened up...its positioned right there next to the TCC Solenoid.

Hopefully I can get it done within the next 2-3 weeks, I'll keep you updated as to if it resolves the issue.

07-08-09, 09:58 AM
Thanks, I take it you are doing it yourself? I dont have too much experience on transmission... Ive never messed with them. This might be one I'll have to take to the shop.

07-08-09, 07:35 PM
The TCC does not activate until the car speed is above approx 45 to 50 MPH. It does not control up or downshifts. Thats done thru a TV cable thats adjusted at the carb on its bracket. I presume you drive this car in the D closest to N on the shift indicator? If you are in the habit of upshifting manually to overdrive on the freeway, the lower gear shift points will be delayed because the line pressure is higher. The car was designed to be driven in overdrive 90% of the time. If, while on a slight incline or hill, the trans upshifts and quickly downshifts, then you pull it from overdrive down one notch to direct drive to lessen wear on the overdrive unit in the trans. The rotating clunk noise could be something, muffler? that contacts the driveshaft when the engine torques over to one side on accelleration, only a guess. So, a TCC solenoid I think is a waste of time and money. I would have a trans shop verify the TV cable is adjusted by the book and is not binding up when hot 1st. then report back.

07-29-09, 03:18 PM
I got my car back from the shop that installed my new replacement TCC Solenoid roughly 1.5 weeks ago and and as of yet I have not had the problem happen.

So as of right now I believe my issue has been fixed!! WHOOHOO!!! The TCC Solenoid was around $50 at my local pepboys store. I have yet to test it on a longer trip duration, preferably at least 40 minutes to an hour worth of driving,... but I have driven it up on the freeway for 20-30 minutes with no problems yet. :)

We'll see if it affects the mpg, as I have read in other posts that it has increased theirs after the replacement was made. I get roughly 15mpg with 50/50 driving....but I've heard of others getting 23 on the highway, which I have never been able to achieve with my 307, my highest on a trip was 18.3mpg.

I will report back after I take a longer trip.