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93 Cummins trans slips in and out of overdrive

Posted By: Rhinodart

93 Cummins trans slips in and out of overdrive - 06/06/13 10:46 PM

I am in the middle of a banzai run from Chicago to Fort Lauderdale, FL and somewhere in Kentucky the overdrive started to shift in and out. Sometimes it will stay in for 15 or so miles then start shifting again over and over. I am driving it with overdrive off and can only manage about 65 mph and am using too much fuel of course. What caused it and how to fix, any adjustments that can be made on the road? The truck also started idling very low too and will die when coming to a stop but not all the time too.
Posted By: dusturbd340W5

Re: 93 Cummins trans slips in and out of overdrive - 06/06/13 11:56 PM

could be a TPS problem or a OD sol problem VSS problem or internal pressure problem. Would have to put it on a scanner and look at data to see what's going on.
Posted By: pinkduster

Re: 93 Cummins trans slips in and out of overdrive - 06/07/13 12:04 AM

Simply unplug it and plug it back in again. This might be a quick "on the road" fix for you and has worked for me MANY times. I assume the slightest bit of green stuff type corrosion can mess up the signal. Sometimes just striking a new connection can clear it up. Sometimes you have to use spray electric parts cleaner and dielectric grease to get it working properly again.
Posted By: pinkduster

Re: 93 Cummins trans slips in and out of overdrive - 06/07/13 12:18 AM

My 93 idles just under 1000 rpm on the factory tach. But a couple years ago it would just randomly fall to about 300 rpm. Never stalled out though. It was the beginning of the end for my injection pump though. Drove it over a year like that. Still ran when I took it in for diagnosis and never did quit on me.
Posted By: pinkduster

Re: 93 Cummins trans slips in and out of overdrive - 06/07/13 12:19 AM

Quote:

Simply unplug it and plug it back in again. This might be a quick "on the road" fix for you and has worked for me MANY times. I assume the slightest bit of green stuff type corrosion can mess up the signal. Sometimes just striking a new connection can clear it up. Sometimes you have to use spray electric parts cleaner and dielectric grease to get it working properly again.



By "it" I mean the TPS.
Posted By: Rhinodart

Re: 93 Cummins trans slips in and out of overdrive - 06/07/13 12:28 AM

I just googled tps and will disconnect it at the next stop and clean the connectors, thanks! I have a Chivvy electric pump now and it works flawlessly and only cost $90 and you can get one at any parts store, so no more Dodge pumps for me...
Posted By: jimbob101

Re: 93 Cummins trans slips in and out of overdrive - 06/07/13 02:27 AM

Does your speedo work? Sometimes unplugging and checking out the two wire connector on the trans or transfer case has a bad connection. THe speedo is part of the OD shift, and also the trans temp sending unit on the front trans line coming out of the trans. Could be a worn out TPS unit that sits on the top of the injector pump. All the auto trucks I've had, have had to replace them sooner or later. But kinda weird that it happened in a middle of a trip!
Posted By: Rhinodart

Re: 93 Cummins trans slips in and out of overdrive - 06/07/13 10:55 PM

Stopped for dinner at the Crackhead Barrel and unhooked the connector to the TPS three times. Just got back from the last 1,000 miles and the overdrive worked flawlessly! If only I would have checked here for the first 2,000 miles... My right foot was cramped-up good trying to get 65 MPH out of the truck with no OD.
Posted By: pinkduster

Re: 93 Cummins trans slips in and out of overdrive - 06/08/13 01:03 AM

Quote:

Stopped for dinner at the Crackhead Barrel and unhooked the connector to the TPS three times. Just got back from the last 1,000 miles and the overdrive worked flawlessly! If only I would have checked here for the first 2,000 miles... My right foot was cramped-up good trying to get 65 MPH out of the truck with no OD.



Nice! 65 mph out of one of these trucks without OD is nuts! It must have been screamin'. Your nerves must be shot! I can't stand driving mine without OD. If it starts to act up, I pull over IMMEDIATELY and unplug it and plug it back in.
Posted By: superwrench

Re: 93 Cummins trans slips in and out of overdrive - 06/08/13 01:34 AM

Yep...I got 4.10's in my 92....55 MPH is MAX without OD.....changed that TPS a few times along with the speed sensor on the trans. I keep spares now if on a long trip. Only bad thing is that the TPS is STUPID expensive (500.00) up here.I've tried the connection thing at the plug, but it was only a bandaid fix...screwed up a week later.My vote is put a NEW TPS in there...and NOT one from an auto parts store....get the Chrysler one.
Posted By: pinkduster

Re: 93 Cummins trans slips in and out of overdrive - 06/08/13 01:52 AM

I had my TPS replaced back in 2002. It wasn't anywhere near $500 (from the Dodge dealer). For the past 11 years, I've had to do the unplug thing maybe twice a year. The last time it happened, I sprayed both connections out with electric cleaner and I absolutely loaded the inside and outside of the plug with dielectric grease and it has not happened since. I think , for me, it has all been about keeping moisture out of the connection. Last summer, the speed sensor did crap-out again. I've replaced that twice in the 12 years I've owned the truck. Keeping a spare in the glove box is probably a good idea.
Posted By: Rhinodart

Re: 93 Cummins trans slips in and out of overdrive - 06/08/13 02:32 AM

I read all about replacing the TPS with a potentiometer, but there are equal yes's and no's, what have you guys heard?
Posted By: hp383

Re: 93 Cummins trans slips in and out of overdrive - 06/08/13 06:01 AM

My 93 had the potentiometer conversion done.

I liked it, never had any trouble with it. I also liked having the ability to sdjust when the OD would engage.

If you do the swap, just remember a tiny adjustment on the know is all you need to move the OD engage speed. No need to do any real cranking of the dial.

Also as mentioned keep an eye on the VSS, and the plug in connector. These too will cause you to lose OD, but usually the speedo will either not register, or will bounce around if this is the problem.

My 93 went through 2 new VSS units in as many years.
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