Ok here's the deal... Took it to my uncles transmission shop today and got a good honest opinion on it. He tested the TPS and it seemed to be pretty much shot, so luckily they had a somewhat, USED one that worked ideal. It was registering 1V, at idle, the whole time. Anyhow that was great once we got that in and tested. So the next thing we did was the Vehicle Speed Sensor which proved to be A-OK. Then we tested the current from the TPS to the computer and it also seemed fine. We had it up on the hoist and wire seemed to be remoltly fine from what we could see. With all that done, not a thing seemed cured. The only solution we could come to was grounds which we checked and again, nothing. After 2 hours of that we called it a day and I was told to come back tomorrow and give it another ground wire check and then we'll be checkin the computer to see if it's working right. And if it is, I guess it's some wiring somewhere. But this all brings me to ask you fellas... could we be missing something thats fairly common on these trucks? Any input would help here... I miss my O/D

Mike

 

The crank sensor is common, but the alternator wouldn't be charging. If somebody bypassed the regulator in the computer at some point, and now the crank signal isn't making it to the computer that could be the problem. Have you tried hot-wiring the OD to see if it actually goes into OD?

 

If this doesn't sound like a stupid question... but how exactly do you go about hot-wiring the O/D?

 

You can hot wire it by grounding the control wire (orange/light green stripe) coming out of the solenoid on the trans.

Take a length of wire and ground one end, put a switch in it somewhere convenient. Take the free end and strip it back about 1.5 inches, and cut off all but about 4 or 5 strands. Unplug the solenoid and stuff the wire in the appropriate cavity, then plug it back in. If you can't get it to plug back in, cut another strand off.

While you have the solenoid unplugged, check to see that there are 12 volts on the blue wire when the key is on. Also use an ohmmeter to make sure the solenoid isn't an open circuit.

 

Alrighty then... I'll take that into consideration and I'll get back to ya same time tomorrow. Thanks Wanna

 

I fought with my OD off and on since last Aug. Finally pulled on one of the wires going into the TPS connector, and it came out of the plug. Mopar used to sell a repair plug, but it has been discontinued. I bought 1 of the last 2 that were listed in dealer stock in NY. It was about $40, but that is now up to what the dealer who has the part wants to charge. Long story short, it fixed my OD and cruise problems. Several years back, I had another harness short across from the input to the output, replaced the plug and it fixed that, so I knew Mopar used to sell a repair harness so it gave me a place to start. I will try to post the part number tomorrow so you may be able to cross reference it or find a harness if you need it.

 

I forgot, I also have a toggle switch for emergency use, which I used while I fought with this. I just grounded a wire, ran it thru the switch and then used a 3M Scotchlok wire tap on the orange wire ahead of the trans connector. This way you can leave it and let it shift automatically or throw the switch and do it manually. Just be sure to disengage below 35 mph or so.

 

The part number for the now discontinued repair harness is: 4728883 Description: Wire PKG-Thro. Hope this helps someone. Since Cummins sells the TPS I wonder if they have a pigtail harness to fit?

 

I guess this took some time to reply too... considering I've been busy. BUT I did get the temperature gauge or whatever, on the tranny, tested to see if it was throwing off the O/D... again though, nothing. So after checking the VSS, TPS, ECM and the temp gauge... All that's left is some wiring I'm guessing. He pointed out one of the connectors from the tranny that hooks to the engine and possibly that could be bad but we'll have to see what happens next time they check it.

 

So when you 'hotwire' the OD in the tranny, it won't disengage until you turn off the switch? It won't downshift at all?

 

this sounds like fun. with pods, flip the switch and hold overdrive to smoke out tailgaters!!! perfect for dyno too. but, for example, if you are going 60mph and the switch is on to engage the OD, what if you turn it off? will it remain in OD or will it jump around until the tranny knows to keep it in OD? is it smart enough to remain in OD or does it become a pain?


thanks, Pat

 

I don't think mike has tried hotwiring it yet , to see if it works, but i think that may be the next step , it's orange wire to ground right?

 

I gave up completly on my TPS. I now have a floor mounted dimmer swt wired to ground out the orange wire. I simply tap it with my left foot to engage OD and tap again disengage.

I did have to put a light on the dash to remind when it was in OD. Lost a couple races cause I took off from the light in OD. First and second are fine as OD doesn't kick in till 3rd. So if you leave it engaged you get 1 then 2 but miss 3rd and go straight to OD.