auto transmission shifting problems

[Glaze]

I have a 1997 4x4 with a stock (so far) Cummins. It has 84000mi. Lately the automatic transmission has a hard time deciding when to shift into overdrive. From a stop I will excelerate to 50mph holding 2000rpm. When the transmission trys to shift into overdrive (about 47mph) the engine rpm fluctuates until I reach 55mph, then everythings fine. Problem is really bad when towing. I have already tried changing fluid and filter along with band adjustments to spec. Any suggestions before I go to the dealership?

 

[DavidGardner]

Probably heard this before but here it is again. Call Bill Kondolay at DTT. Nice guy and can probably tell you what your problem is. If you need work I would recomend him over the dealer.

 

[Joe G.]

This one sounds like a throttle position sensor problem. These things get ratty so the connection is bad on intermitten. Try hoseing it down with contact cleaner and working the throttle back and forth. If the symptoms change then it's the TPS. Also remove and clean the connector.

 

[azgearpro]

sounds like tps, or kick down cable out of adjustment, or may need to replace

 

[Glaze]

auto transmission problems

Thanks for all the responses! Here is what we found...

The throttle position sensor was out of adjustment. At idle the voltage should read 1. 0v +/- 0. 2. At wide open throttle voltage should read 2. 2 to 2. 9 volts higher than at idle. This spec is for a 1997 CTB with 47RE transmission.

As I posted before when I first noticed the shifting problem I had the transmission fluid and filter changed. The bands were checked and found to be only slighty out of spec. The mechanic told me band adjustment would not affect overdrive since that is "electrically" controlled. The mechanic also informed me that the transmission fluid was two quarts low. After changing fluid the truck must be driven enough to allow any trapped air to escape from the TC in order to get a correct fluid reading. Check fluid while warm with transmission in neutral.

I know most of this is preaching to the choir. This is my first diesel and I'm still learning. Your website has been a tremendous resource. Thanks again.