92 Cummins Overdrive problem

I know this is a subject that has probably been beaten to death here, I am new so please forgive me.

I have a 92 2500 4X4 with a receintly rebuilt (3 years ago Jasper) trans. About a year ago we had the OD stop working on the highway, I pulled over and replaced the throttle position switch, had lunch.. and I had OD again, for about 1/2 hour and it went away again.

The transmission to date works fine when cold, or till I drive a few miles then I loose the OD till she gets cold again. The engine temp gauge never shows hot, and I have also just changed the fan clutch.

I called Jasper who told me it was either a speed sensor, or tempature sensor. Since I had previously changed the speed sensor and my speedometer is working fine, I ruled that out. I have to assume the tempature sensor he refers to is the one attached to the cooling line under the transmission. How can I prove a bad tempature switch ? I am open to other ideas or tests.

Guys, I would love some help Thanks Doug Crall snipped-for-privacy@ccjax.com

The thermal switch in the coolant line provides a ground to the SBEC when the fluid temperature reaches 275°F. I wouldn't automatically assume that a faulty switch is the problem, there might be a problem that is actually elevating the fluid to cutoff temperature.

Thanks for the reply John,

I have smelled the fluid, and does not have a burnt smell, and still looks like red table wine. On the cooling switch, I could monitor to see if it switches to ground, and then check the trans for over tempature. Dosen't the sensor have 2 wires? If so I can place a volt meter across the switch. If it is the switch, is it available? I believe it is part of the cooling line.

If it is not the trans oil temp switch, what else can it be? Does it also monitor the engine tempature, Is that where it senses too cold for Overdrive? if so, does it use the same engine temp sensor as the dash temp meter?=20

Doug Crall

Try removing the thermal switch from the transmission line, re-attached electrical connector, plug hole in line. I tried a variety of resistors in that circuit that I think Bill Kondolay ( from Diesel Transmission Technology ) suggested & I ended up removing sender, installing pick-up for temp gauge & zip-tying sender/wire to frame. That damn computer wanted to see that switch, nothing else worked!

So when you removed the sensor, was it a hole or a screw thread? I would imagine the computer wants to see something out there, I don't mind replacing the sensor if it's bad, or questionable, I am just not sure you can get parts for a 14 year old Dodge truck that they didn't make too many of to start with.

Thanks for the suggestion

Doug Crall

I know this don't have anything to do with the trans problem, but I love the 91'-93' body style, got a 92' myself, and a diesel, ya don't see many of them anymore! I have replace parts on my 92' and never had a problem with getting a part.

Scott

I like the 92 body style a lot better than the 2 newer body styles too,and the access to the engine, in particular the fuel filter is far better . I can change the fuel filter and be back on the road in under

5 minutes. However you can't beat the improvements that Dodge made in the newer truck cabs.....much more comfortable, quieter, and I bet the AC & Heater have better capacity. I know my 92, I freeze in the winter and sweat in the summer.

Doug

Doug

Sorry for the slow response, just getting over a hard drive crash. I removed sensor, which is threaded ( pipe threads maybe?? ) , installed temp sensor for trans temp gauge in empty hole & zip tied theremoved sensor with connector to sebc still attached to cross member by tranny. Hope that helps. If not, email me!