[bmodracer]

4L80E Sticks in second when cold...need help

1995 6.5 turbo diesel 4X4 126k

Occasionally when its cold outside the transmission will not shift from second to third. I have found out that if I shut it off and turn it back on it will shift fine. When running a diognstic I get codes 85 & 87. One thing is that I do not get the #12 code. This has been going on for over a year. Any help would be great!!!

 

[Alvy]

Bmod,
I've read through many threads here about problems with shifts and especially my problem with no O/D until 200 degrees problem which I still haven't figured out but it sounds to me that your B solenoid (2-3) is sticking/defective. I've been told that you should have a reading of 20-40 ohms across this solenoid but I don't have a pinout as of yet. My problem I have determined so far is definately temperature related but as we all know warm oil flows better than cold oil so your valve hanging on the 2-3 until it gets a little warm sounds probable. Located in valve body viewable when pan is removed. 87 is a high ratio code relating to the 2-3. i am not sure about the 85, maybe the transmission goohoos can help out you and me. Mike L. or GMCTD please respond to us, please.

 

[JKC]

trans

I had the same problem with my 93 3/4 ton 4x4 suburban and i thought i would try some synthetic fluid. So i pulled the pan, drained the fluid, changed the filter, and i even flushed the cooler and lines. Then i filled it with royal purple synthetic fluid and that totally fixed the problem.

I drove the truck for another year and never had another problem with it.

 

[bmodracer]

I'll check the B solenoid (2-3) and replace if necessary and while at it change the fluid and filter.

Thanks!!