4L60E Difficulties

Hello all,

I have a '93 Sierra extended cab with a 350, and a 4L60E automatic. Currently I have around 292K on the engine and trans. Heres the problem. A month ago I was driving and noticed it would not go into overdrive. This has happened before and was due to a low trans fluid level. This time the fluid level was fine, although a tad darker than new fluid. I parked it for 2 weeks, and when I drove it again, it wouldn't shift out of first. So I called around asking mechanics what might be the cause and they mentioned the shift solenoids. I'm positive its stuck in first, because from a dead stop it would throw you back in your seat by slightly getting on the gas (second is definitely not that stout in mine).

I put in new shift solenoids in the valve body and it didn't help a bit. I took out the servo and cleaned it, which was not really contaminated to begin with. I am at a loss and being a college kid, I don't have the cash to hand over to let somebody else work on it. the mechanics here wont suggest anything without hooking it up to a diagnostics unit first. My dad says it might be that the sun gear is worn out.
Does anybody have a clue what is the malfunction here???

That is a lot of miles on a 4L60E without a rebuild.

Does reverse work? If not, then it could be a broken sunshell (fairly common).

The valve body could be worn and the shift valves could be sticking. The spacer plate can also get worn (check balls can wear a whole in the plate).

When you reinstalled the servo, how did the seals look? Did you replace them? A bad servo or worn 2-4 band will cause you to loose 2nd and 4th.

//2000CAYukon

I rebuilt it around 280K and only because it had minor minor slippage when shifting. I still have reverse, it just won't kick out of 1st though. I have tried to run up the RPM's to try to get it to throw into 2nd, but it never would. The seals on the servo looked fine, after i cleaned it thoroughly, i inspected each seal inside and out and found nothing the matter. As for the check ball sticking, I had the valve body drilled on one of the check ball positions, by a transmission specialist, to avoid sticking. And all of the seals, gaskets, filter were changed at 280K, along with the friction plates and the like. And now I have two new shift solenoids.

I rebuilt it around 280K and only because it had minor minor slippage when shifting. I still have reverse, it just won't kick out of 1st though. I have tried to run up the RPM's to try to get it to throw into 2nd, but it never would. The seals on the servo looked fine, after i cleaned it thoroughly, i inspected each seal inside and out and found nothing the matter. As for the check ball sticking, I had the valve body drilled on one of the check ball positions, by a transmission specialist, to avoid sticking. And all of the seals, gaskets, filter were changed at 280K, along with the friction plates and the like. And now I have two new shift solenoids.

It would be good to start with the basics. In 1st gear both shift solenoids are ON. The PCM turns off the A solenoid to shift into 2nd. You need to make sure this is happening and a scan tool is probably the best tool for this. If the solenoid is turning off, the shift valve (1-2 shift valve) should move so that the 2nd gear circuit gets fluid.

//2000CAYukon

Thanks for the information. The one thing that gets me though, is that they are both brand new. As soon as I replaced them, I got in my truck and it would not work. It was the same as before I replaced them, this is what makes me and my dad to believe that this problem is stemming from another source. The solenoids were my first troubleshooting step due to the fact that they are relatively inexpensive and easy to replace. But its something else.