4x4Sierra2500

iTrader: (6)

A little background: I rebuilt the 4L60 in my wife's 07 Envoy Denali (5.3, ported heads and 212/218 cam) a few years ago (planetary broke, 3-4 clutches were OK) with decent parts: 7 stack of BW HE clutches in the 3-4 pack (about .035 clearance off the top of my head), rebuilt valve body with all the Sonnax fixes and parts of the HD shift kit, corvette servo, HE band, wide bushings, etc. 40k cooler. Blocked 3-2 valves, plugged 4th accumulator, loctite on input shaft to drum splines, air checked everything, and a bunch of odds and ends I'm sure I'm forgetting. Not the first one I've rebuilt, and they all lasted at least a few years behind mild motors by the time I sold them.

It's her daily driver, and it's not like it has a 6.0 in front of it. She was driving in town, lost 3rd/4th suddenly, pulled over immediately. Iit w checked the fluid when I got there, looked like new, so no immediate signs of long term 3-4 slippage. I haven't gotten it out of the car yet because I've been wiring my new shop, setting up the lift, etc, but I did order the seal set and clutch set.

Here's the issue: I decided to try the GPZ clutches in the 3-4 since it was going to be apart anyway. I got them yesterday, and there is what seems to be a HUGE variation in thickness from one to the next, and even .003" or more on the same clutch. I had a couple BW HEs left over from last time (because I had to use 2 .080" plates to set clearance and measured them, and there was about .0005" or less variation across the plates, also checked some Exedy HE plates I also had, same story. But on the GPZ100s I measured about a .002" variation, and on the 105s, 0.003" or more on the same plate. I measured thickness at every other tooth, and there was frequently a 0.002" variation just two teeth apart. In addition, one of the seven plates was made in 2024, and it was 0.0623"-0.0652" thick, while the other 6 averaged around 0.066, but for example plate #3 I measured was 0.0662"-0.0696" thick.

Is this typical? This is the first time I've gotten GPZs, but on all the other 4L clutches I've checked in the past, this seems excessive. How would i even be able to get a consistent clearance? Should I just send them back and get more BW HEs? I have to order everything online pretty much, nearest WIT trans is a little over an hour each way, so I'm trying to have everything I will need for sure on hand, so if I have to make a trip once I get it apart and find something damaged that isn't a seal I already have on hand, I'll only have to go once.

Finally, I am thinking a seal on the 3-4 circuit blew out for it to go suddenly like it did, like a input shaft seal maybe? I obviously wont know for sure until it is apart, but I did my best to address 3-4 hydraulic issues during the rebuild. I didn't have the tune/pressure curve aggressive, nor did I eliminate TQ MGMT, or the wife would have complained. Just looking for some tips on where to look so I can get it back together ASAP once it is apart.

FranksCustomTrans

Honestly I have never put that kind of time into measuring them individually, Though I have indeed used GPZ many times and they have worked very well .

Tranzman

I agree with Frank, I don't measure individually.

I have used GPZ-100's in the past with very good luck.

I currently use either GPZ-105's or B/W HE for the 4L65E. My go to 3-4 clutch stack is 7-.065 frictions & 6.095 steels and this is almost always perfect with the 4L60E apply plate and a pressure plate. Occasionally I need to use a .106 steel to keep my clearance where I want it.

I stock several .060, .078, .095 & .106 steels for setting clearance.

Don't sweat the small stuff, just set your 3-4 clearance to around .025-.040 and the 2-4 band to .090 - .125

4x4Sierra2500

iTrader: (6)

Thanks y'all, I'll just check the clearance after air cycling it a few times. I am using the Sonnax HD backing and apply plates, I had to use two .080 frictions last time, so I ordered the gpz 100s and 105s in case I had to do the same.

vorteciroc

Completely normal.

Higher quality (of manufacturing) Frictions and Steels will vary less (Borg Warner), they are usually slightly less mass produced.

This is where Tolerance Stack up comes from.
Always inspect total End Play.

PBA

Over the last few years. I have found the "quality control" on the 3-4 clutches (all brands) is not what it used to be. I take my calipers with me when I buy clutches somewhat locally to me. I can go through a hundred and get maybe 50-60 of them not varying more than .0015". When ordering on line. I end up sending back many clutches.