1994 GMC k1500 Transmission Squeak?

[Matt06]

Hi
I have a 1994 gmc K1500 240K km. Had a rebuilt transmission about 20000km ago. I just noticed a squeaking sound coming from either the transfer case or the transmission. I put it in neutral and rotated the driveshaft by hand. It squeaks only when its rotating forward, not in reverse. Cant tell if the sound is coming from the transmission or the transfer case, but definitely coming from that area.
I saw a couple other sites/threads mention it could be the low roller clutch or a snap ring at the rear of the transmission? There wasn't any conclusions posted so not sure if that ended up being the problem for them.

Any help appreciated

 

[NickTransmissions]

Hi
I have a 1994 gmc K1500 240K km. Had a rebuilt transmission about 20000km ago. I just noticed a squeaking sound coming from either the transfer case or the transmission. I put it in neutral and rotated the driveshaft by hand. It squeaks only when its rotating forward, not in reverse. Cant tell if the sound is coming from the transmission or the transfer case, but definitely coming from that area.
I saw a couple other sites/threads mention it could be the low roller clutch or a snap ring at the rear of the transmission? There wasn't any conclusions posted so not sure if that ended up being the problem for them.

Any help appreciated

If you're hearing a "screeching" like sound, its the low roller one way clutch in the center support. A screeching clutch is a healthy, happy clutch.

I have a few YT videos on my 4L60E and 700 playlist showing me rotating the 3-4 clutch hub/ring gear assembly when installed in the case and the screeching sound occuring when i rotate it. That's the same sound you're likely hearing.

ETA: if that low roller clutch fails you dont have any forward movement in any forward range setting so as long as you have movement, its fine.

 

[Matt06]

Ok thanks, Ill take a look at your videos and compare the sound. Just seems odd it would start happening now and not right after the rebuild

 

[Matt06]

Compared the sounds, and can confirm it sounds similar. So its gotta be the low roller one way clutch. I also pulled the pan to double check the fluid. It did seem fairly dirty, no metal shavings and a layer of powder on the magnet in the pan. There was a layer of finely ground something (would it be the clutch material?) along the surface of the pan and the filter case.
I had dropped the pan and replaced the fluid that drained about 1000km after the transmission was rebuilt and I do remember the fluid looking similar then. I didnt flush the fluid then so it could just be clutch material from the original break in. Would this dirty of oil be normal after a transmission rebuild? Ill try and attach some picture of the filter and oil

 

[Matt06]

On the picture with the filter, there's a part on the metal that I wiped to show how much of a layer of material there was on the surface.
So I'm going to put a new filter in and try and flush as much of the old fluid out and put some new stuff in. Ill drive it for a week and recheck the fluid to see how it is then.

 

[NickTransmissions]

How does it smell?

Fluid looks a bit dirty for only 12,000 miles or so. While there's always going to be some grayish colorer matter that percipitates out of the fluid and coats various surfaces. However your fluid looks like it may have some burnt clutch matter but that could also be the lighting.

 

[Matt06]

As far as I can tell it smells pretty much the same as the new fluid. Ya the picture does make it look a bit darker than it is, it still has some pinkish/purple hue to it but it is definitely darker than new fluid.
I tried to get some better pictures comparing the old fluid to some new stuff. The old fluid is on the left on the paper towel picture.
Anyways I flushed as much of the old fluid out as I could and filled it up with new stuff, took it for a drive and it still shifts fine. Ill drop the pan next weekend and see how it looks then.
Is there anything that would cause a larger than usual amount of clutch to be worn off? I had put a shift kit in it when I was rebuilding it, but it doesn't really shift that much harder compared to how it did before the rebuild.

 

[Matt06]

Well after driving it for a little over a week, I dropped the pan and the oil still looks good so I'm assuming the transmission is fine for now.
Thanks for all the help @NickTransmissions

Side note, if it is wearing on the clutches more than it should, is there any adjustment that could be done to help reduce the wear?

 

[NickTransmissions]

Well after driving it for a little over a week, I dropped the pan and the oil still looks good so I'm assuming the transmission is fine for now.
Thanks for all the help @NickTransmissions

Side note, if it is wearing on the clutches more than it should, is there any adjustment that could be done to help reduce the wear?

You're welcome...If you haven't done so already, install a Transgo SK4L60E shift kit ($45) w/ a Sonnax LB-4L60E early boost valve kit ($20) along with a Corvette 2nd gear servo ($15) - those three things should mitigate or slow any clutch wear due to sub-optimal conditions in apply circuitry and help firm up the otherwise sloppy 2-3 shift all those things have from the factory.