More 4L60E Problems - Lack of 3rd gear without unplugging harness

[spectre1995]

Well after about a year's hiatus from working on my C10, I'm finally finding the time to get back on it. When I last turned wrenches on it, I wasn't able to get the transmission to shift past third.

Recently, I've done a bit of diagnostics based on posts I've read. I'm concerned I may need to have the transmission rebuilt but that's not currently in the budget.

So far I've done;

-Shifts from 1-2 and 2-1 just fine. When it reaches the redline on 2nd, it doesn't even try to shift into 3rd. It goes all the way up to the redline in 2nd gear, and will only shift down back to 1st when slowing down and won't shift up to 3rd. I've read that a failing or failed clutch will cause it to shift from 2nd into a neutral gear instead of 3rd, and that a failed solenoid will cause it to be stuck in 2nd instead. Hopefully this is the case!

-Verify +12v at the pink wire on the transmission wiring harness connector. Reading 11.9v

-Manually commanding the transmission, listening for the audible "click" of the shift solenoids:
-1-2: Click
-2-3: Nothing
-3-4 Click
-4-3: Nothing
-3-2: Click
-2-1: Click

-Disconnecting the wiring harness to force the transmission into "limp mode" - Transmission went into what I believe to be 3rd gear. Very slow moving from a dead stop.

-Checked transmission fluid dipstick - fresh fluid, nice bright red color, within "full" range when at operating temp.




I ordered a new set of solenoids and filter, so I'm going to try to see if replacing one of them solves my lack of automatic third gear. I read that by disconnecting the harness, if it shifts into and stays in 3rd gear without slipping, that the transmission is mechanically sound (i.e. clutches still intact), and that the issue could lie with a stuck shift solenoid. Aside from that, is there anything else I can look into before I call it quits and send it off for a rebuild in a few months?

[TheMechanic]

Screenshot 2023-08-26 121314.jpg