Got a 95 Dodge 2500 4x4 extended cab 8' bed with cummins and automatic trans

About 5 years ago it started to turn the OD/OFF switch on even though the button wasn't pushed. And occasionally the converter would unlock.

I was thinking the the TPS was the problem with converter. Took it in for service before making 2 long trips pulling my 24' enclosed trailer. He recommended rebuild and thought the TPS was ok.

@ 97,000 had trans rebuilt and billet converter installed.

After having it rebuilt the converter was still unlocking some. Trans guy changed TPS and all was good for a while.

Then on trip to Florida it was ok going down and almost back home it started again. Running 72 MPH it unlocked and locked, thought might be the brake switch, held foot under pedal no help. Slowed down to 68 MPH stayed locked in. Next trip to Florida ended up being only able to run 65 mph and stay locked in.

Trans guy then gave me a paper showing torque converter cycling and what they did to solve the problem.

So for the last 5 years I have been chasing this problem. It only does it when running on the interstate above 70 MPH. So since I don't drive it much find out when on vacation that what I didn't work.

2 new batteries, 2 new negative cables, rebuilt alternator, TPS bypass switch and my last attempt to be able to run over 70, installed a toggle switch to orange wire with black stripe to pin 54 on module to ground it as instructed from TST site.

Thought that would be the last attempt, but the trans temp light then came on after having it locked in for a while.

It does this without pulling a trailer, pulling my 24' and 12' enclosed trailer, so load on the truck makes no difference, speed is determining factor.

WHAT SHOULD I TRY NEXT?

Any chance it could be an issue with the VSS sensor, or its plug in? Possibly the solenoid in the valve body?

I am just tossing some ideas out, I haven't had any first hand experience with anything newer than a 93.

did you take the checkball hose out that runs to tranny cooler?

Explain more please, don't know of check valve.

Had to change the trans cooler a few years back due to rust, trans temp light came on only after manually locking converter

Not sure if it applies to your year, but on my 99 the converter was rapidly locking/unlocking on the highway like that and I had to replace all 4 battery terminals and add in a noise filter to the tps wire.

So it seems like the lock/unlock is doing what it is supposed to be doing, meaning it's unlocking when the trans temp is getting to hot, and kicking back in when it cools. My guess? That should also kick it to 3rd gear when it's getting too hot too sometimes. My reasoning is, since once you put that switch in and kept it in lockup then your tranny lite comes in when hot. If your trans temp lite is coming on, the sensor lite kicks in a 285degrees, now that's hot and not something to ignore.
I know there some weird electrical interference etc in those years which makes it hard to diagnose. You could change out that temp sender just to see if that is faulty. I have the specs for testing it out if needed. A laser temp gun on the tranny line near the sender will give a good accurate reading also. THen you'll know for sure what you are running temp is.
Having it kick in/out like that a lot is not good either, creates heat and not good for trans.

-J

there is a hose going to tranny cooler that has a checkball valve .those get clogged up over time and could be messing with the pressure. when you are driving over 70 that is when your pressure will be highest.

Jimbob,

So could I install a trans temp gauge and know what the actual temp is? What should the temp be?

It is something my buddy and I thought it could be but the trans temp light never came on before the switch was installed.

Checked fluid and there was no discoloration or burnt smell and it was in the safe zone.

As far as battery cables will have to check positive cables but think they looked ok, but that doesn't mean anything. Since I have bypassed the TPS and have a potentiometer in place doubt that is it, but What wire did you install noise suppressor?

You sure can! I actually took the factory trans temp sensor out which is inline just coming out of the front tranny line going to the oil cooler, and put the aftermarket sensor (Napa, VDO). I run an electronic temp gauge, and running at highway speeds is about 155degrees. Temporarily, you have to jumper the trans temp sensor plug (paperclip etc) or just let it hang but plugged in. Otherwise, it wont kick into 4th. This spot is THE best place for the sensor, that fluid will be the hottest (and most accurate) coming out of that line, those aftermarket tranny pan sensor locations will not even show up on a gauge.

Mine is in a '92 cummins auto OD nonlockup but yours is pretty similar, but with lockup. Towing 7K up a hill just to see what heat I could make in OD, I got up to 180degrees and didnt get past that.

So what I did with the factory sensor is I teed it in right before it goes into the front trans cooler line. There is actually factory rubber hose for a stretch which makes it perfect spot to put it with barbed fittings. You'll have to extend your 2wires up to that spot from the tranny. I don't recommend cutting up your nice factory bent steel tranny lines, they are not cheap from Dodge if you can get them.

Here's a pic of the tee before I installed it. The '93older don't have a "hot trans temp" lite in the cab, when it gets too hot, it just kicks it out of 4th gear, and that lets ya know.. So the factory sensor is my "backup" and I just watch the gauge.. The way I see it, if you see that trans temp lite comes on, sometimes it may be too late. ATF thermal breakdown probably starts at 230degree up, if you'r running that high anyways, you are shortening your lifespan of that tranny a great deal. I wouldnt run over 200degrees if I could.

Make sense?

-Jimbo

Post deleted by jimbob101

JimBob

thanks for the info

best I have gotten so far

I have seen the brake pedal switch unlock the converter at highway speeds as well. Took me forever to figure that one out...


Josh

Well finally got truck back with trans serviced, temp sensor changed and replaced cooler line that had slight crack and leaking

Trip from Indy to Louisville last night hauling my daily driver in 24' hauler

Tried to stay on cruise @75 mph but even when off was over 60 for most of trip

Crossed my fingers and converter stayed lock unless I tapped the brakes.

So a 27.50 part might have been the problem

Thanks guys for the suggestions and hope my next trip is uneventful.