After chasing down electrical gremlins and getting pretty steady 14 volts the trans has been working perfect for 3 weeks or so. Then yesterday while backing out dad's driveway reverse goes away. 5 mile drive home and it never gets out of 2nd. Limp home mode? Pull up code 87 then clear codes. Getting a 12 code now. Still no reverse. I can hear the trans shift when I put it in reverse, but it just slips and will not move the truck.
94 6.5 TD F-vin 4x4 GMC 4L80E 175,000 miles. The guy that had the truck before me said all electronic parts in trans were replaced and a new torque converter was installed.
Any ideas?
Ted

Reverse is completely mechanical. Possible causes are lo/reverse band and direct clutch. Direct clutch is also used in 3rd and lo/reverse band also provides engine braking in manual lo.

Time for a rebuild huh?

Local, highly regarded shop says it's rebuild time. Before taking it apart he said it looks like "direct clutch". Going to put a new heavy duty converter in too. He said I'm looking at around $2100 :( Using the best parts he knows of.. Oh well thats not really too terrible, and it will be like new when I get it back..
Thanks,
Ted