Engine/Transmission (1994 - 1998) auto trans hunting

[bill threlkel]

I have been having a problem with the auto trans, after runing for 150 miles the trans sound like it is shifting up to over drive when the over drive is locked out. When going up sharp turns on steep grades where the trans was lock out of over drive. seams like its in between gears and then will shift up to over drive. With a load on the truck or towing i have to drop the trans to second to stop the up down shift. If you put your foot in it the trans will kick down and feel like it is between gear on freeway i don't have any problems. Its driving me crazy.

Bill

 

[ndurbin]

it's your TPS that causes this. There are acouple fixs you can try to get it to stop; 1 take the TPS off and use some electrical cleaner to clean it off or 2 rewire it by running the wires in their own loom or buying the kit from TDR member shendren thru his ad in the TDR classified ads .



I rewired and replaced the TPS earlier this year and I haven't had any problems so far. I'd try cleaning it and rewiring it first before I dropped 200-300 bucks for a new TPS.



Nathan

 

[DBrickel]

Yup. It sounds like the TPS

 

[DBrickel]

I should also say Use the electrical contact cleaner (do not use wd40)

 

[biggy238]

Just curious as I have a new TPS (thank you dealership) but what happens if you fill it full of WD-40? Sounds like someone might have had a bad run in with this.

 

[Howard Durand]

If you have OD locked out, the shifting you are seeing is between 3rd and TC lockup.

The 47RH is a good transmission but the PCM is missing a few brain cells. Your TPS may be dirty but the real problem is probably the PCM.

To be able to tow with it you could use a "Mystery Switch" to enable you to control the torque converter. The switch should be able to do three things, lock the TC, unlock the TC or leave it normal.



Does your transmission shift into OD too early? Such as at 35 or 40 mph? If so, check with a dealer to see if your PCM can be re-programmed. Some can and some cannot. Mine is one that can't so I am working on a scheme that will take control away from the PCM. I have reasonably good control of the TC now but still have to be able to keep the OD from engaging too soon.

 

[Dfuruness]

Electrical Contact Cleaner worked for me. I did not take it off I just soaked it with the cleaner. It works fine now and will for a long time.



Don

 

[nball]

I tried everyone of the things mentioned. Replacing the TPS helped but did not completely cure the problem. I now have to believe that it is a combination of bad wiring and a dirty TPS. I am now going to try the wiring kit mentioned by ndurbin above.

 

[bill threlkel]

Thanks to everybody for the replys. I will clean the tsp and do the wire thing.

Also i have a BD lock for the tc and when locked and when the overdrive is lock out it will do the same thing shift to over drive. Drives me nuts spent 3500 on a rebuild 3 years ago. Put in BD shift valves ,BD shift logic, BD tc and rebuilt clutch packs.

thanks bill

 

[dseabaugh]

I drilled 2 small holes in mine and flushed it out with contact cleaner and it has been perfect for 30,000 miles now.

 

[Howard Durand]

Manual control of the OD is through pin #10 of the PCM. Pushing the manual switch momentarily grounds this pin to lock out OD.

OD should not unlock unless the button is pushed again or the ignition switch is turned off.

I have had several occasions where the OD locked out on it's own for no reason but never had it unlock that way.



Did this start after installing something else, like the BD TC control, valve body or shift logic? If so, you may want to contact BD about the problem.



Try removing the ground cables from both batteries for a few minutes so everything will be de-energized. Then re-connect them and take it for a drive. Sometimes the PCM gets confused and this may force it to reset to it's default program.

 

[bill threlkel]

The trucks is shifting better now,I took off the tsp and cleaned it good with contact cleaner and reinstalled then redid the wireing. Hope this lasts a while.

Thanks again to all that helped.

Bill

 

[tp0d]

I tried everyone of the things mentioned. Replacing the TPS helped but did not completely cure the problem. I now have to believe that it is a combination of bad wiring and a dirty TPS. I am now going to try the wiring kit mentioned by ndurbin above.

nball::: Have you tried rotating the TPS counterclockwise about 1/2hr? (very little rotation, about 1/8" on the studs). I did this when I took my TPS apart and cleaned it, and man did it make a difference. I pull a lot of hills here in Pittsburgh, and I like it to lock in 3rd at lower speeds. With that adjustment, I get lockup at 41mph (with od off) and it holds to around 30... Od on is much smoother also. . I took a 3/16" drywall rasp to the plastic lug holes and egg shaped em about 1/8". . Rotated the tps counterclockwise about 1/8" and thats all it took. . night and day difference. .



good luck



-j