Overdrive question

[RedD250]

My overdrive has been acting up the last couple days. Sometimes it won't shift in until later than normal, like 40 mph. Sometimes it won't engage at all for miles and miles, then just start working. Sometimes it'll go in and out. Cruise control does not work until it finally holds overdrive. I have the genos TPS delete, which has been working to fix this problem for several months now. But not anymore. What else could cause this?

 

[brucejohnson]

Here is a thread from another site with some suggestions to try.

https://www.cumminsforum.com/threads/1993-no-overdrive.326491/

 

[RedD250]

Thank you for the link. I have a couple questions, if anybody might know. That thread on the other forum is very old, and I'm sure none of the original parties involved are still around.

"check the coolant thermal switch by unplugging it and jumping it with a wire."
Not sure what that means, jumping it with a wire? Can somebody explain?

"check the trans overheat switch on the hot port out of the transmission, cant miss it, 2 orange wires... jumper that also"
Same, not sure what they mean by "jumper".

I'm pretty sure it's not the TPS, as I have the TPS delete from Geno's, but is there any way to test that?

Today, my speedometer started going haywire too, bouncing all over the place, then it just went to 0 and stayed there. Odometer stopped working too. The speedo did start working for a few minutes after a few miles, but the trans did not go into o/d. I parked the truck, and started it back up after a couple minutes, and everything was fine. Shifted right into o/d, and speedo was working. After about 5 miles of driving, it popped out of o/d, then right back in when the speedo started acting up. The speedo has never done that before, so I'm not sure if it's related to the o/d issue or not. Thanks for the help!

 

[BigPapa]

The sensors are two-wire. “Jumping” it means to unplug it, take a wire that’s stripped on both ends (called a jumper wire), and stick an end into each of the terminals of the connector.

 

[RedD250]

Ah, gotcha. Hell, if that makes it work, I may just leave it be to save money on a new sensor that will probably be broken the day I get it like everything else these days lol. If I can even get a new one. The trans overheat switch is pretty much useless anyway. It doesn't activate until the trans temp is well past the "you've toasted your transmission" stage anyway. I'm beginning to think there is another problem though because of the speedo going haywire. Anybody have any thoughts on that?

 

[BigPapa]

 

[RedD250]

Thanks for that, saves me having to dig through the FSM for the locations of everything. I'm gonna start with jumping the 2 sensors, then I guess I'll move on to the VSS and the gear ratio reducer. I found a thread on how to rebuild the gear ratio reducer if it's bad. Well, not really rebuild but repair it. https://www.dieseltruckresource.com...93/speedometer-gear-ratio-reducer-fix-198605/.

I found a new computer for the truck, too: https://www.fs1inc.com/1993-dodge-ram-250-5-9l-pcm-engine-computer-ecm-ecu-programmed-plug-play.html

I'm fully expecting a reply from them saying "sorry, that's no longer available" which has happened twice so far for other parts. I'm thinking if it's not too expensive I may just go ahead and buy it to have on hand for when the original one dies, which I'm sure will happen sooner than later.

 

[BigPapa]

I’d stay away from Flag Ship 1. They’ll tell you they have it, take your money, then tell you they don’t and you’ll have to fight to get your money back. I went through that trying to get an ECM for my son’s Mustang. I fought with them for
six weeks.

 

[RedD250]

Thanks for the heads-up. I'll go elsewhere. Seems that they are still readily available from several different sources, and there are ebay companies that'll rebuild your original one too, so that shouldn't be a problem when/if the time comes.

 

[brucejohnson]

Thank you for the link. I have a couple questions, if anybody might know. That thread on the other forum is very old, and I'm sure none of the original parties involved are still around.

"check the coolant thermal switch by unplugging it and jumping it with a wire."
Not sure what that means, jumping it with a wire? Can somebody explain?

"check the trans overheat switch on the hot port out of the transmission, cant miss it, 2 orange wires... jumper that also"
Same, not sure what they mean by "jumper".

I'm pretty sure it's not the TPS, as I have the TPS delete from Geno's, but is there any way to test that?

Today, my speedometer started going haywire too, bouncing all over the place, then it just went to 0 and stayed there. Odometer stopped working too. The speedo did start working for a few minutes after a few miles, but the trans did not go into o/d. I parked the truck, and started it back up after a couple minutes, and everything was fine. Shifted right into o/d, and speedo was working. After about 5 miles of driving, it popped out of o/d, then right back in when the speedo started acting up. The speedo has never done that before, so I'm not sure if it's related to the o/d issue or not. Thanks for the help!

Sounds like the speedometer cable has broken.

 

[RedD250]

The '93 uses a vehicle speed sensor, there is no cable, just electronic wizardry, unfortunately.

 

[brucejohnson]

The '93 uses a vehicle speed sensor, there is no cable, just electronic wizardry, unfortunately.

I was just looking at the sensors and wondering if you had an electric speedometer. I'm not too familiar with the 1993 system, when they converted from mechanical to electric. I found listings for the cable. Then at the bottom of the listing was a "related items" link to the sensors. Either way the signal may be causing issues with the related systems like cruise control and transmission shifting. Should be an easy fix. I see BigPapa's trans picture shows the sensor.

 

[RedD250]

Yeah, I'm thinking I have a combination of problems, because even when the speedometer is reading accurately, I still have the intermittent o/d problem. On the plus side, I was able to find both of the temperature sensors still available for sale. I had previously looked for the transmission high temp sensor and was not able to find it, but here they both are, if anybody is interested:

Thermal switch: https://puredieselpower.com/dodge-p...e-5.9l-cummins-replacement-thermo-switch.html

Coolant temp sensor: https://puredieselpower.com/dodge-p...ummins-diesel-coolant-temperature-sensor.html

VSS is still available from NAPA, they have 3 different ones, and all 3 of them come with the pigtail.

 

[RedD250]

That thermal switch in the link may not be what they claim it is on the website. I did some digging, and it looks like it's for the KSB, whatever that is. It is also a 3 wire switch, and the one on my trans cooler line is 2 wires. I found a NOS part (56026720) on ebay, so I know that one will work. I'm not sure if that's what I need yet or not, but I figured I better snap it up since it was the only one the guy had, and I can't find that part number or any cross reference anywhere else. Hopefully it'll last another 30 years. If not, does anybody know of an alternative and currently available sensor that will work for the trans cooler line?

 

[RedD250]

Well, it seems that the VSS was the culprit for all of the problems. Which is odd, since it was working fine when the overdrive and cruise control were not. I put a new VSS on today and drove it for about 20 miles, and everything is working as it should now.

On another note, I have learned my lesson with replacement parts. Always buy 2 if not 3 or more of anything you need. That way when the first one or 2 are broken right out of the box, you can keep on with the project and not have to clean up and drive to the parts store and possibly have to wait several more days for a replacement to come. This is the 3rd time that a brand new part has been DOA or defective in some way. Sorry state this world is in indeed. Everything is just garbage.