Transmission won’t shift

[Slade]

I have a 1995 gmc k1500. I had the 4l60e transmission rebuilt less than 1000 miles ago, but it’s sat for a year and a half. When I try to drive the truck the transmission won’t shift, and the gear indicator light comes on and off randomly. I replaced both the a and b shift solenoids because that’s what codes the truck was throwing but it didn’t fix anything. Any advice would be appreciated.

thanks

 

[thegawd]

what codes are present? is there like 6 or 7? can you see the prndl light? do you have a speedo?

 

[Slade]

what codes are present? is there like 6 or 7? can you see the prndl light? do you have a speedo?

It currently throwing codes 66, 67, and 81. Speedometer and tachometer both work fine. The prndl light comes on and off at random.

 

[jjester6000]

I have a 1995 gmc k1500. I had the 4l60e transmission rebuilt less than 1000 miles ago, but it’s sat for a year and a half. When I try to drive the truck the transmission won’t shift, and the gear indicator light comes on and off randomly. I replaced both the a and b shift solenoids because that’s what codes the truck was throwing but it didn’t fix anything. Any advice would be appreciated.

thanks

Sounds like you have a bad trans computer, is it sluggish leaving off? With out a computer the trans will still have 3rd and reverse, so it would be leaving off in 3rd.

 

[Slade]

Sounds like you have a bad trans computer, is it sluggish leaving off? With out a computer the trans will still have 3rd and reverse, so it would be leaving off in 3rd.

Thank you for your reply! It is very sluggish on take off. This is probably a stupid question, but is the transmission computer the same as the PCM? Because I cannot find a TCM or transmission computer for a 95.

 

[thegawd]

or a bad ignition switch if taking off in 3rd. I am not entirely familiar with limp mode on the obd1 system.... but it could possible be the ignition switch, bad wiring or the plug has come loose. pin e, a pink wire is 12V positive and should read exactly the same as the battery. any variance at all points to the ignition switch.

Al

 

[jjester6000]

Thank you for your reply! It is very sluggish on take off. This is probably a stupid question, but is the transmission computer the same as the PCM? Because I cannot find a TCM or transmission computer for a 95.

I'm pretty sure that it is, but I could be wrong. The only time I've ever messed with the electronics of a 4l60e was when I hotwired one to shift without a computer using toggle switches (one for A solenoid, one for B, and one for lockup).

You also said that the shift indicator flickered, well you might just have a bad connection to the computer causing it to not shift.

 

[1997]

just been thru shifting issues with my 95.

suggestions before loading up the parts cannon:


1st you need to get the wiring diagram, they are posted on here, thank hatzie.
https://www.gmt400.com/threads/88-95-service-manuals.43575/

2nd you'll need the pin out for the PCM/ECU, google its easy to find.

I found it easy to pull out the ECU and test everything from there (behind Passenger side glove box) , just pull the blue connector and becareful with the pins. All the trans solenoids are controlled there.
Manuals give you the spec's etc.

Since you have muliple codes etc, look for the common items. You can pull fuse 20 (10amp DS cab) and see if that changes anything.

report back and good luck.

 

[Slade]

Thank y’all for the information everyone! I’ll be doing some tests this week and I’ll let y’all know how it goes

 

[Slade]

Thank you everyone for the comments and information y’all have given me. I have gone through and looked for loose/disconnected wires and I couldn’t find anything out of the ordinary. I ended up replacing the ignition switch which didn’t fix the issue, but it now allows me to manually downshift the truck via the prndl lever. Seems like a step in the right direction and the truck is a little more drivable. It seems the only thing left that could cause the issues is the computer(?) Again id like to thank everyone for the information, and if you have any more tips or ideas feel free to throw them my direction.