help diagnose tranny problem

[95_Eddie_4.0]

Below are the symptoms:
1) Will not shift out of first all the way to redline if you stay in the gas.
2) Will shift into second at around 3k rpm only if you let out of the gas.
3) Shifts to 3rd and overdrive ok
4) If running 45-55 mph and step on the gas it downshifts from 3rd to 1st

OBD tests have been run and also shifts monitored by ODB going down the road, no codes or problems noted.

Fresh fluid and filter today(has been changed at about 40-50k intervals)

Seems to me to be pressure related as when under no load(going down hill) you don't have to let out of the gas as far to get it to shift. Under heavy load you have togo to higher RPM and let off further to get it to shift.

Any suggestions would be appreciated.

Also, it's not temperature sensitive. It does the same hot or cold.

 

[95_Eddie_4.0]

Come on guys, someone has to have some ideas...

 

[Alec]

Hmmm, you say the OBD stuff has been monitored, but it sounds like it may be the TPS (throttle position sensor) or a problem in the vacuum line to the tranny.

 

[95_Eddie_4.0]

I would think vacuum too if it were not shifting well in all gears. Do you have any suggestions for troubleshooting TPS?

Thanks!

 

[Alec]

there are certain voltage parameters for the TPS, but if you're not throwing any codes, you're probably within those limits. The sensor might just not be fast enough anymore or is starting to die. A new OBD I TPS is about $30 at a parts store.

 

[MSP]

I have the identical symptoms on my '94. I changed the vaccum diaphram last week and saw no improvement. My next step will be the throttle position sensor. Have you tried it on yours?

 

[95_Eddie_4.0]

Next mine started a whine(pump) and started slipping. Ended up with a total rebuild of the tran$mi$$ion. But hey with close to 200k miles that's the first major repair.

 

[DennisB]

tranny problems

Had to have my tranny rebuilt at 98,000 miles. Have not had any prolblems since and now have 248,000 miles on my 92' XLT. Strongly suggest yearly trans service...I learned my lession the hard way.

 

[tcbarney]

If you had said it only did it when cold, I'd have suggested checking the governor. (Dead Link Removed)