4L60E won't shift into reverse correctly

thecraft · October 22, 2006

Okay, I tried posting this in another forum and got nothing out of that, so I'm hoping you guys can help me out with these two problems I'm having with my '95 C1500.

The first problem is that my transmission (4L60E) has trouble shifting into reverse. It rarely shifts into to reverse properly, maybe 10% of the time at the most. Most of the time it will engage, but the truck rattles like crazy and moves very slowly. Sometimes if I rev the engine a bit while it's doing this, it will engage with a jerk. The rest of the time, the truck will just sit there. If I rev the engine, the transmission will engage with a violent lurch... I left a couple of tire marks in parking lots doing this. It's been doing this for a while now (since the previous owner had it) and seems to be getting slowly worse. The only temporary fix I found is to shift back and forth between Park & Reverse until it finally engages right. The transmission works perfect other than that!

The second problem isn't serious, but I like to get rid of that annoying SES light. I used the ol' paper clip trick to retrieve the service codes and turned up with "32 - EGR open command did not change MAP sensor signal. Normal EGR flow should cause slight decrease in manifold vacuum which would change MAP sensor signal." which makes sense because my EGR valve hasn't been taken off since the truck was built. However, I don't have any of the symptoms of EGR problems like rough idle and engine knock. Anyways, if I take off my EGR valve, how can I check if it is working correctly? Can I clean it with something like carburetor cleaner or do you think I would need to replace the valve? I've also heard of the EGR passages in the intake manifold clogging, rather than the valve itself. If this is the case, would it be safe to clear it out without having to take the whole manifold off? I don't wan't a piece of carbon falling into the valves...

Thanks for your time & help!

SPARK CHASER · October 29, 2006

Is it possible that the parking pawl inside the transmission is not disengaging properly?

nick1500 · October 28, 2006

your tranny is f**ked up, get another one

95Sierra2500 · October 29, 2006

Definately sounds like your reverse sungear has broken (it's spun-weld together). I'd suggest dropping your pan and filter, checking for flakes or metal chunks in the oil/filter. If you find any, I'd suggest a rebuild. I bet it'll take care of the problem.