'94 2DR 4x4 Trans slipping in reverse only

[italie]

Hello,

My '94 Yukon with 200k (350, auto, 4x4, 2dr) on it is having trouble with reverse only. It feels like when you are driving a manual trans and have the clutch pedal half engaged. The truck moves backwards, but it would not have enough torque to get up an mild incline. If you give it gas it will shudder a few times and eventually seems to catch, but I still think that it isn't 100% at that point either.

It's been brutally cold here, and started after a week long sub 10f spell.

Fluid was a little burnt, so I had a power flush done (no filter unfortunately). That didn't help, but adding a some Lucas oil did seem to help it engage quicker and lessen the shudder quite a bit.

All forward gears shift beautifully.

I've heard that no reverse is commonly caused by the sun housing, but can this also cause just slipping? Any ideas on what this might be?

(I realize I'm probably headed for a rebuild, just gauging how long I have. I'd like to wait until it gets a bit warmer...)

[2000CAYukon]

If it is the sunshell, you should have issues with 2nd and 4th as well.

A slipping reverse can be the lo-reverse clutches. If you are going about 30 MPH and drop it in 1st gear, do you feel it slip? Or does it grab well? Do this with the engine at normal operating temp.

I have a 90 K1500 truck and it also slips in reverse on cold mornings. I usually drop it into neutral and rev it a few times and it is fine. I believe my issue is that the lo-reverse piston seal is not holding well when cold. I say this because if I drop it into 1st at 30 MPH, it still grabs well (after it is warmed up). I know that I have a 700R4 (4L60) and you have the 4L60E; however, the share many parts.

For me, until I completely lose reverse (or worst), I will keep driving it. I don't notice the issue unless it is cold outside.

One warning is don't let it slip much in reverse (try revving the engine in neutral) because if it is slipping that will cause the clutches to wear out faster.

//2000CAYukon

[italie]

Thank you for the reply. No troubles with 2nd and 4th, so that's a sigh of relief.

I tried dropping it into first at 30mph, no trouble at all there. Lo-reverse piston seal sounds like a decent diagnosis to me. I think I'll do the same as you, wait it out until it gets worse.

Thanks again.