Please Help - 4l80e transmission not shifting to 3rd or 4th
 

Please help, I’m lost and not sure what to try next. I put a 5.7 350TBI and 4l80e transmission (from a 1993 GMC Vandura – G3500) into a ’67 C10 truck. Both the engine and tranny were rebuilt with ALL new parts. There’s not an old part on either. I have an Affordable Fuel Injection harness built and I’m using the original VSS buffer as a stand-alone harness. I am not getting 3 or OD – just Reverse, 1st and 2nd gear. I can stop and go and it shift really smooth into 2nd gear, but no 3rd or OD. I have gotten 3 & 4th one time in the last three weeks. Any suggestions would be greatly appreciated – I took 15 months to build this ride and still can’t drive it out of my neighborhood.

Re: Please Help - 4l80e transmission not shifting to 3rd or 4th
 

Hopefully some one will chime in with some answers, A problem I had was the vss sensor on the transmission. Might try unplugging this and see if it's different when you drive it.......On mine 4L60E..at 30 mph it was telling the engine it was going 150mph. Coughed and died.

Re: Please Help - 4l80e transmission not shifting to 3rd or 4th
 

Does you wiring have the ability to pull trouble codes or see live data?

Smitty

Re: Please Help - 4l80e transmission not shifting to 3rd or 4th
 

Unfortunately, no!! I do have an OBD1 scanner from Autozone and no codes come up, and I'm not able to see live data. I plugged and pulled tss and vss with no luck.

I do know the obd1 port works because I pulled the TPS and it threw a code. I'm at a lose for what the heck is going on. Everything on this the engine and tranny are brand new.

Re: Please Help - 4l80e transmission not shifting to 3rd or 4th
 

Base on my ATSG Manual on 4L80Es, it states condition: First and Second Gear only, inspect component: Solenoid B - Stuck in "off" position, loose connector, no voltage to solenoid, solenoid o-ring failure, no PCM signal to solenoid. Inspect component: 2-3 Shift Valve - Stuck. Inspect component: Quad Driver Module - Failed.

Possible codes: 68 Overdrive Ratio, 81 QDM & Solenoid B Fault, 85 Undefined Ratio, 87 Solenoid B Stuck Off.

What does all that mean, it means to check solenoid B since it's that most likely problem. Get a multimeter and put it on ohms so you can check resistance of solenoid B (2-3 shift solenoid). Unplugged the big plug on the side of the transmission and you will probe the to prongs of B and E to check the resistance. If the resistance says OL on the multimeter then the solenoid B is either not plugged in, solenoid B is bad, or the wiring harness in the transmission could be wrong.

Here's 2 pics of the wiring diagrams to help you check.

https://i.pinimg.com/564x/db/68/41/d...b452b51e19.jpg

Even though this says diesel the transmission still is wired and works the same.
https://www.dieselplace.com/attachme...am-png.622578/

Re: Please Help - 4l80e transmission not shifting to 3rd or 4th
 

Update - I dropped the pan and tested the solenoids - tested fine. I also tested connector on side of tranny - tested fine as well.

Put it back together and went for a few drives. I am able to get 3rd (and something 4th) gear but I have to let off of the gas pedal at about 27 to 30 MPH to get it. It seems to shift to 3rd a bit smoother on a slight decline. Also, when in 3rd going up a slight incline it shift to 2nd real easy and will sometimes go to limp mode.

I was able to get an error code 87 with a cheap obd1 scanner (autozone). Unfortunately, the company that built the standalone harness said it is not build for a live scanner so I won't be able to scan it while I drive to get a better idea what's going on.

Again, the engine and transmission from a 1993 GMC G3500 Vandura. Not sure where to go from here.

Thanks,