Help! No overdrive

[Pipevine]

My truck quit going into overdrive. Only code is p0500. Have replaced both speed sensors, the tcc/od solenoid, checked the 3-4 accumulator spring, cleaned the wire harness plug on top of trans, cleaned plugs at ecm. Can anybody point me in the right direction here. Even tried wiring a switch with resistor into thd number 6 or 7 pin on the transmission harness to force 3-4 up shift to no avail. Other than no OD it shifts flawlessly.

 

[cerberusiam]

Assuming this a 48RE transmission, if you cannot force an OD shift by grounding pin #7 on the trans control harness the problem is likely internal. Put a gauge on the OD circuit and see if you get any bump in pressure when you manually engage OD.

 

[Pipevine]

I think ive slightly narrowed the problem a little. I have no power going to the number 6 pin. Isnt 6 OD and 7 lockup? Im getting nothing through the dk green with tan stripe wire as i believe i should until the ecm commands OD at which point it should ground it, correct? Question is, where is the next spot to check for voltage in that wire upstream from where it goes into the plug at the case?

 

[cerberusiam]

Those pins are a ground circuit terminated in the ECU, you will not see voltage until you ground them with the key on and maybe even rolling. The larger wire in the bundle will be the 12V source and when you ground 6 and 7 they will activate the OD or LU then throw a code.

 

[Pipevine]

ok now i'm getting codes: p0500 (no vss signal), p1740 (tcc/od solenoid performance), p0713 (trans temp sensor volts too high), and p0868 (gov pressure sensor volts too high). As far as what i was trying to do with the test light , Bob at Goerands told me to tie into the number 7 wire with a jumper into the cab and hook the test light to the jumper and then the other end to ground to see if the light went out when i should be commanding od to show whether or not the computer was sending the signal for od.

 

[cerberusiam]

Now it looks like a shorted wire problem. I would replace the VB harness next, it has the tendency to do things like this.

 

[Pipevine]

Just replaced the tcc/od solenoid and harness. Is that what youre talking about?

 

[cerberusiam]

Yes, that whole harness. Have you tried clearing the codes and seeing if they stay gone or come back? All of those will lockout OD and probably lockup in certain cases.

 

[Pipevine]

Yes replaced it last week. Will try clearing codes again and see what happens.

 

[Pipevine]

cleared codes. truck seems a lot "peppier". Still no od. Only code that has showed back up so far is p0500. this deal is really kicking my ***.

 

[BigPapa]

Sounds like you're in limp mode.

 

[cerberusiam]

P0500 Vehicle Speed Sensor Malfunction

Have you replaced the sensor on the rear diff?

 

[Pipevine]

Yes sir replaced the one in the transfer case too

 

[cerberusiam]

One in the transfer case???? Possibly the output shaft speed sensor?

Have you tried the mystery switch on pin #6 to force a shift?

 

[Pipevine]

Ok wired in the mystery switches. One for lockup and one for OD. When monitored with multimeter while driving. Both have 14v starting out. The LU jumper grounds out to . 1v - 0v at around 40 mph and a slight bump is felt, almost feels like a light shift. The OD jumper grounds out to . 1v-0v at about 48 mph. Nothing is felt or noticed regarding rpm change at that point.

 

[Pipevine]

Update. I hooked a gauge into the OD port on the left rear side of trans. It read zero psi in drive until i hit about 25-28 mph at which point it jumped to 30 psi. There were no changes in pressure regardless of speed after thatbpoint until i slowed down to under 10 mph at which point it dropped back to zero. So what should i do or look for at this point.

 

[cerberusiam]

Based on the testing, pull the OD unit and have it rebuilt. Bet you will find the OD clutches burnt and the piston sealing rings tore.

 

[Pipevine]

Oh hell. How much does that cost or is it something i can do myself? I know it requires a press and i would need to fab a press tool and need an intermidiate shaft to keep everything aligned, but ive got a press and can fab whatever needed and surely i can come up with a junk intermidiate shaft. Pulling the overdrive housing is no big deal so with all that in mind how hard is it to rebuild the overdrive?

 

[cerberusiam]

It really isn't that hard if you have a press and the manual or carefully layout lay out the parts.

 

[Pipevine]

Recommendation on parts., this is a fully built Dtt trans that has already had the overdrive rebuilt once. Trans was supposed to be able to handle 750rwhp no problem. Billet input and output, triple disk tc (been thru 4 so far) It has less than 75k miles on it and had the od rebuilt 30k ago.