Our Community is 940,000 Strong. Join Us.


94 Bonneville Overdrive problem


rossi1369
10-31-2005, 02:46 PM
1994 Bonneville that we have owned since new, has 120,000 miles and was very well maintained. Since approximately 90,000 miles the car will drop out of overdrive after driving for a while. It may be 10 minutes, it may be 40 minutes but every trip the car will just use 3 gears after its been driven for a while. Brought it to a dealer and they replaced the TPS but that didnt fix it, I also swapped to a cooler 180 degree thermostat. The SES light is not on, and the Cruise control works fine at all times.......With 30k + miles i know it cant be anything mechanical, and replacing the trans is not an option. The only thing I can think of is that the 4th gear shift selenoid is bad - and after it heats up it will stop working. Any ideas would be appreciated. Thanks!

maxwedge
10-31-2005, 03:57 PM
Have it scanned on a bi directional trans scann,er it can command 4th, confirm the shifting and generally in the hands of an experienced tech, diagnose the problem. I don't know why anyone would put any parts in relative to this without a proper diagnosis.

rossi1369
11-01-2005, 11:28 AM
Have it scanned on a bi directional trans scann,er it can command 4th, confirm the shifting and generally in the hands of an experienced tech, diagnose the problem. I don't know why anyone would put any parts in relative to this without a proper diagnosis.

When the dealer (Star Pontiac in PA--->They suck) scanned the car the only code that popped up was a stored code for the TPS. They said this could be the OD problem so they fixed it. No more codes showed up. The OD problem was still there and they recommeded trans replacement (like they do for every tranny problem) and wanted to look further into. I didnt want them to have any more of my money so i said no thanks.

maxwedge
11-01-2005, 12:45 PM
The scan with a trans specific scanner, as I said, doesn't care about codes necessarily, the operator looks at solenoid commands, gear ratio errors rpm/slippage errors and command and confirm trans shifts, a good trans shop should ready and able to diagnose this. It still could be an internal mechanical problem though.

dkinmn45
01-24-2006, 02:37 PM
Do you have an update on the overdrive problem? ...I have a 1995 Bonnie which does exactly the same thing - after it warms up with about 10-15 minutes of driving it down shifts out of overdrive. I suspect the A or B solenoid in the transmission.

maxwedge
01-24-2006, 03:25 PM
A scan with a trans function scanner will tell you if the solenoids are working and confirm o/d slippage or engagement, anything else is guess work.

Lakehead6
02-01-2006, 11:33 AM
I have a 1994 Bonneville with the same problem. When it drops out of OD, I can stop, shut off the engine and restart and it works fine. This is intermittent, but is more frequent. 134K miles.

hamyers
02-20-2006, 01:27 PM
I have a 1994 Bonneville with the same problem. When it drops out of OD, I can stop, shut off the engine and restart and it works fine. This is intermittent, but is more frequent. 134K miles.

I have a 95 ssei with the same problem. Tranny had other issues such as hard shifting but certainly when it warmed up the same problem occured. I could put it in neutral, switch the key off & on quickly and the problem would go away temporarily.

Got a decent price on a tranny overhaul last April and problem went away for a few months. However it has happened two times since during warm weather. I expect the problem to resurface with warm weather.

I expected it was a stuck relay or solinoid but what ever it is it got better for a while, lasted all summer, but....

Good luck. GM must know about this but is no help as far as I can see.

Howard

Add your comment to this topic!