Engine/Transmission (1994 - 1998) transmission problem

[SGehrke]

I know this topic has been addressed before, I have a 96 2500 with an intermittent shifting problem. It shifts in an out of O/D at all speeds even when slowing down. This happens about every other day. I have replaced the TPS, installed the DTT noise filter, cleaned all the grounds I could find, and the batteries and cables are brand new. I haven't pulled the orange and blue wire out of the wire loom yet, that was my next step. Does anyone have the exact location of all the ground wires that might effect this or any other ideas? Thanks.

 

[DJWyckoff]

I would take it to a shop with a scanner and have them cheak the gov and transducer press to see if they are correct. what prompted this was it a fluid and filter change? that could cause a gov or ducer to stick mine did it once.

 

[tp0d]

First, Welcome to the TDR!!



A quick check would be to unplug the brake light switch from the brake pedal. If the switch is out of calibration/etc, it can activate momentarily when going over a bump/etc, and thats all it takes to unlock the TC.



I installed a lockup switch on mine, but that wouldnt help for on-highway driving. As for the TC unlocking when slowing down, if you hit the brake or let off the go pedal, it will unlock every time.



Someone here has added a potentiometer to bypass the TPS, and from what I can see it has made a big difference. You may want to check out that route for the long term.



heres a link



https://www.turbodieselregister.com/forums/showthread.php?t=155114&highlight=tps+potentiometer



good luck



-j

 

[DJWyckoff]

tp0d did I read right when locked up your torque unlocks wile braking and no throttle?

mine is locked all the time and will almost stall the truck if forgot about and stoping and mine will lock in all forward gears. trannsbuddy more info here:

http://dunriteconverters.com/

 

[SGehrke]

Thanks for the replies. I tried unplugging the brake switch plug, still doing the same thing. Any other suggestions?

 

[tp0d]

DJWyckoff:



The TC will unlock when the brake is depressed (brake light switch activated), or the throttle is released. This is the standard function of the PCM. I have installed a mystery switch on a remote cable to get around this. .



Your transbuddy will almost stall the truck? that cant be good for the converter, gears, or your rear end. I have stalled mine with my switch once or twice, but I am very careful with it. I still like my $5 switch compared to a 500-1000$ trans controller...



SGehrke:



Hmm... quite a problem you have there. . You could possibly have a problem with either the Trans Temp sensor, or the Trans Speed sensor. . Might be worth it to drop by Autozone or the like, they have a ODB-II scanner they can hook up and possibly check the status of those sensors. If the temp sensor reads high, it will stop the transmission from using 4th i think and possibly lockup. The TSS can do the same. .



good luck



-j

 

[SGehrke]

It dosen't seem to change if I'm on the throtle, letting off or on the brakes you can feel it locking and unlocking. Where do find info. on this mystery swich and do you think this would cure my problem? I'm pretty sure its electrical because the problem is not there all the time.

 

[Jschafer]

The TST web site has the wire diagram for the mystery switch or you can do a search on here for "MYstery Switch". The mystery switch will help get around your problem but will not fix the problem and forgetting to turn it off is not good. The trans temp sensor is in the cooler line next to the trans pan on the drivers side if it is faulty it can make the trans shift out of OD. You can unplug it and install a 1k 1/2 watt resister into the plug (less than 1 dollar) this will fool the PCM if this fixes your problem the trans temp sensor is bad, however you can run the resister all the time if you want. ther is a post going on at this time about this problem "Random kick down and temp Lite"

Joe

 

[Joe G.]

The truck is a '96 so no temp sensor in the cooler line if no one has installed 47RH cooler lines. From what I've read on the forums, the '96 had more problems with the TPS than other years. If the truck has an early build date then the PCM has to be reflashed for the mystery switch to work. If you need it the part number for the reflash is 04886926. You can get around the TPS problems by installing a potentiometer in the ground wire to the TPS connector. If you do that you can adjust the OD and lockup points.

 

[SGehrke]

I tried the potentionmeter with my old tps and couldn't get it to work right. Will this cause the O/D to stay locked in if it is adjusted up? Will it take care of the electrical noise? Thanks

 

[Joe G.]

It won't take care of the electrical noise. It will change the OD and TC lockup points. There has been some experimentation with just doing away with the TPS and installing a pot in the cab so you can adjust the voltage to the PCM. I don't know how that has worked out. You might PM Howard Durand and ask him.

 

[Howard Durand]

I think Ridesamule is the one that replaced the TPS with a potentiometer.

I am using a pot. in the ground wire of the TPS for my adjustments but if the TPS is bad that won't be much help.

It would be fairly simple to remove the TPS completely and wire in a potentometer that can be mounted anywhere.

I have found that when I set the at rest voltage on the TPS above 1. 4 volts, the OD won't engage until about 55 mph.