Hey all,
I'm pretty new to the world of dealing with the internals of an auto transmission, but I've been running into some issues with the slightly tired 4l60E thats in my partners 2003 GMC Sierra, with the 5.3, aux cooler, reg cab/short bed, 2wd, and it sees fairly heavy off road use. Somehow the g80 in it hasn't blown up yet, but thats a different topic... I came across this forum in the course of researching our issues and this place has one of the bigger knowledge pools of this trans that I've seen.

So... background. My partners truck has 220k on it, original trans and It basically didn't have any issues until last year when one of the shift solenoids died, so we tore into it, replaced the A and B solenoids, added most of the stuff from a transgo HD-2 shift kit, because we needed the first gear hold thingy for off road use.
We didn't pull the valve body or drill out the sep plate or do the boost valve, or replace/refresh the fwd accumulator piston or the 1/2 piston, but noted that the original plastic ones were loose in their bores. I also didn't do the 2nd servo mods.

Then a few months ago we started having a really pronounced 2-3 flare but once it shifted it held 3rd fine and held 4th fine, at that point I swapped in a 'vette piston a few weeks ago and that helped the flare and the truck otherwise drove fine. I wanted to get the rest of the stuff in the kit done, so I tackled that over this past weekend, and found/did the following:
- replaced 1/2 accum piston with an AL one, added one of those gold washer thingies. its a transgo piston in the OE config
- replaced the fwd accum piston with a sonax pinless piston as the pin/bore for that piston was shot
- replaced the separator plate with a transgo plate as the original plate had a couple check ***** smashed through it, drilled it to the HD-2 instructions and reused the steel check *****
- new gaskets
- checked the band free play and added one of the large OD gold spacers to the band, as two spacers didn't give enough free play. One spacer gave me a little under .1" travel in the cover. Getting the cover/snap ring back in was a HUGE pain after adding a spacer/oring to the cover and I spent a good hour trying to get it back in, complete with the stupid cover fully popping out a few times.
- installed .500 boost valve, parts installed correctly in it.
- new filter/gasket/etc. Fluid level is good. Its a truck pan and we have the correct filter for it.

So, today, it started to not hold 4th on the freeway on a test drive then stopped shifting into 3rd shortly after. 1/2 shift still felt fine on it, but we're going to try to hold off on driving it until we know more.
I don't have a trans pressure gauge, but i'm considering picking one up for this. A lot of the things I've been reading are leading me to the 3/4 clutches not applying due to insufficient pressure on the apply servo (or whatever it is), or the 3/4 clutch pack is done.

Any ideas what else could be going on or ways to troubleshoot it minus dropping the trans?
A thought I have is that I might have damaged the seal on the 4th piston during the reinstall yesterday, but i suspect that might be wishful thinking because I don't want to pull the transmission on this thing, but its starting to look like its something we'll have to pull it.

 

220K and a 3-4 clutch failure is the most common issue with a 4L60E. Having build hundreds of 700R4's and 4L60E's, do not waste any more time and energy trying to band aid repair it. I'm 99.9% sure you will pull it and find at least a .050-.100 3-4 clutch clearance.
Tear it down, clean it all out and find the parts you will need to completely rebuild it. You will spend less time and energy by not putting off the inevitable.

 

This thread has the most resources I have seen to date yet. See post #14
https://ls1tech.com/forums/automatic...kit-4l60e.html
Thanks @5.7stroker for putting this together for the masses...

 

Normal.

 

This poor truck sees a lot of high speed desert miles, and low speed, higher rpm crawling in 1st/2nd (totally different use than most of yall use your cars/trucks for, but it is what it is) so it has a remote cooler with a fan and luckily heat hasn't been an issue. Kinda curious if folks have recommendations for internals to help it live longer in this environment. Any other internal things to look for?

I'll start digging through that thread and seeing about getting a list together of parts and seals to get. If we do this, we should be doing a new torque/rebuilt torque converter right? I've only ever done stuff internally with manual transmissions, so the magical slush boxes are totally new to me.

 

Dana at Pro-Built Transmission will custom tailor the parts that will suit your needs. Yes, the torque converter should be replaced.

 

I'll prob get something out to him soon, see what we'll need.

Any one with suggestions for special tools to make this easier? Sounds like it'll need a T50+ but i like to start getting tools and stuff ahead of time for projects like this..