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Just rebuilt an '03 4l60e and I forgot the o-ring on the input shaft so I have no lockup obviously but I also have a slight drag in reverse and slight forward movement in neutral. I'm assuming both of these problems are because of a partial apply of the forward clutch. So my question is, can the missing o-ring cause this or do I need to be looking further into the trans? It is also worth mentioning that this trans was working good before the rebuild but had to be torn down for some welding on the case. Trans had 90k on it so I decided to put new clutches and seals in when I put it back together as well as a shift kit and corvette servo, however, I did not replace the molded pistons in the input drum. Any insight is much appreciated, thanks!
You can air test those seals by sliding the reverse input drum and forward input drum over the pump. Go to Sonnax's website and download the instructions for their Sure Cure Kit. On the last few pages, it tells you how to air test these drums.
Yeah, no bueno! LOL I've been going through the ATSG manual looking for places where a cross-leak could occur and I guess I'll just go through the trans checking those areas and see what I come up with.
Finally had time to work on it tonight and here's what I found so far. The plastic spacer between the pump and reverse drum is trashed, and there's a slightly damaged area on the pump gasket. All the Teflon rings look good. Any thoughts on the spacer?
You can air test those seals by sliding the reverse input drum and forward input drum over the pump. Go to Sonnax's website and download the instructions for their Sure Cure Kit. On the last few pages, it tells you how to air test these drums.
Just did all the tests on that page, the only one that failed was the one on the valve body(forward abuse valve). I also took another look at the 2-3 shift valve that I installed and I realized that I forgot to drill the hole in the valve body. Idk if either of these could have caused my problem but I'm all out of ideas here.
I don't know what would happen without the hole drilled in the valve body, but that is the 3rd mistake that you have found that was made so far. You may want to slowly go through the whole trans again and double, triple check your work. Also check that all of the valves are installed correctly in the valve body.
To keep the plastic spacer between the pump and reverse drum in place when installing into the trans put some assembly lube between the pump and washer.
I finally got it all back together, and it's working perfectly! I had to replace the forward clutches and steels since they were burned, I also replaced the pistons in the input drum while I had it apart again. Put it all back together with new valve body gaskets and a new pump gasket. I still don't know exactly what caused my partial apply issue but I'm glad it's fixed. Thanks for the help!
did you check end play the first or second time around? i wonder if you didnt have something seated correctly, maybe in the input drum. either way glad it's working now.
did you check end play the first or second time around? i wonder if you didnt have something seated correctly, maybe in the input drum. either way glad it's working now.
The first time, I went by feel and if felt good. This time I checked with an indicator and it was dead on.
4l60e Expert Help Needed! 
