1989 Pontiac Bonneville Recurring Transmission Problem


To Car Talk,

I own a 89 Bonneville SSE since 7/1992, had 33000 miles.

Jan. 96, there was a funny sound coming from the trani. Diagnostic: torque converter was worked on. Mileage was 64540

Sept. 99, experienced slippage, whole trani was rebuilt. Mileage was 107974.

May 92, trani overheated going uphill, causing gear slippage, fluid bubbled up and poured out from the stick shaft causing smoke and all. Cooled down, on flat road it would shift gears and continue to overheat uphill. Trani was rebuilt. Mileage was 135303.

June 2, 2007, trani overheated again going uphill with the same scenario as in May 92, causing gear slippage, heavy smoke, would not go past 2nd gear. Car was towed home. Trani was rebuilt and an additional small radiator was added to help keep the trani cool. Mileage was 167337.

June 30, 2008, trani overheated again going uphill with the same scenario as in May 92, and June 07 but not as bad a 6/2/07 because I stopped immediately. Smelt the fluid on the stick and it did not smell burnt. I waited for the engine to cool down and see if it would shift gears, it did. So I drove home some 100 miles away going uphill at between 35 and 45 RPM with flashers on and 60 on flat roads. On 7/1/08, I drive the car and it would not shift past 1st gear. Tested manual shift from 1st to 2nd to Drive and ODrive, nothing. It’s stuck in 1st gear. Tested it again on 7/2/07 and got the same result. Checked the fluid and it’s at the proper level but this time it smelt burnt.

Called the Pontiac dealer I deal with to see if there was any recalls on this trani due to it overheating. None was found.

Something is overheating this trani and now my husband and I are wondering if it might be engine related.

I love my car and babied it. It’s serviced regularly and all. Although I am not so willing to pour any more money in a rebuilt trani due to it’s resell value I still would like to know if you would have any idea what could be the cause of this trani failing this many times.

I hope to hear from you soon.

Thank you.

Theres a couple of things going through my mind. First of all, Is the engine overheating or running hotter than it should?? Above 200 degrees?? Where do you live?? What kind of climate?? Are you towing anything?? I would check 1: Cooler flow. If the cooler or coolers are restricted in any way this would cause the transmission to overheat. Its possible there is some restriction which is only affecting it when going up hill. You did say in Jan of 96 the trans was making noises and the torque converter was worked on (Probably replaced) Its possible the old converter had started to come apart and sent trash through the trans into the cooler causing some restriction. With restriction in the main cooler, the trans will still run hot even with an external cooler attached. Have the cooler/s flow tested And, 2: Has anyone checked the operation of the torque converter clutch to see if lockup is ocurring?? If the TCC is not locking up, the transmission will run hotter than it is supposed to.