Hello to all of you. I have been reading and benefitting from this forum for over a year, but I am up against something that so far has eluded a lasting soution. I am hoping some of you may be able to help out.

First a little background. I have a 1997 2500 ext cab long bed 2wd. It currently has about 191,000 mi. I bought it from my Dad a year and a half ago when it had 175,000 on it. The truck is completely stock. No mods to speak of. My Dad had the transmission rebuilt at AAMCO at around 160,000mi. Unfortunatey he lost his paperwork so I do not know exactly what they did.

About six months ago I was experiencing a few erratic transmission shift issues so after reading on this forum I bought and installed an APPS Noise Isolator and cleaned all the grounds. It seemed better for a couple months.

OK fast forward to a few months ago. Sometimes when I would take off, the truck would not shift out of first gear. I would stop, put it in reverse, then drive a couple of times and it would then take off in second gear and proceed normaly (after a sluggish start), but the check engine light would come on and record a code 37. Reading lots of threads on the forum led me to believe I needed to replace the govenor pressure sensor and the solenoid with the round 8 pin connector.

I did all this, adjusted the bands, changed the filter, and added an auxilliary ground strap to the transmission case just for insurance.

Just BEFORE I did the above work, I started to have an additional problem where the truck would seem to "downshift" itself, even going downhill without touching the accellerator. It would erratically go up and down in RPM by itself. I could tell that it was evidently going in and out of torque converter lock and OD. Reading here I found that this pointed to the TPS. More on that in a moment.

After I did the transmission work mentioned above, the transmission has been very solid on take off, always starts in first gear, and always upshifts well. But I still often had the wierd shifting. So I checked the TPS voltage. With key on connector off, I had 5vdc at the connector. Stripping back a bit of the insulation I measure the TPS voltage with the key on, truck not running, accellerator at idle position. My reading was 1.58 Vdc which I read here can set a check engine light (it often does - code 37) but it seems like it should have been enough voltage to prevent the torque converter ock-up / OD problem which it seems is usually caused by too low voltage. I did adjust the TPS to 1.4 Vdc (the lowest reading I coud attain). The problem did not go away.

Last night I replaced the TPS with a new one. I tried to adjust for the lowest reading I could, however the lowest reading I can get is higher than my old TPS. My current best is still over 1.5 Vdc (about 1.58 actually). I still have the problem.

This is discouraging to say the least.

Sort of feel like I'm "out of ammo" on this. I have lots of expience with 727 transmissions, but diesels and electronic controls are new to me.

Any help would be appreciated, especially tips that have proven results.

Thank you all, this is a truly wonderful forum.

70charger500

 

Charger500 to DTR!
Looks like you've done your homework on this one. Pretty much covered the common bases anyways.
Try swapping out your Auto Shut Down relay in the power distribution box with your horn relay and see if that makes any difference.
Otherwise, it's sounding like you may have a wiring problem or a PCM problem. If the relay swap doesn't help, start at the transmission case and check the plugs, pins and wiring. Get an ATSG manual if you don't have one - it tells you the pin-outs for the transmission plug and how to test each circuit. I don't know of any good links with that info or I'd post 'em up for ya...