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I purchased a 95 G30 van a while back, it was a clean van with just 106k. The biggest downside was it's a light duty G30 so it's really 3/4 ton running gear with the 5.7/4l60e. When I got it the transmission was slow to reverse and had a layer of gray clutch material in the pan.
I serviced the transmission about a year and a half ago and found the separator plate with a stuck ball. I put in a new separator plate, screens and a Sonnax boost valve and the transmission really has not been bad, but I pulled it yesterday to look inside and do a refresh/update as the van is used for towing an open car trailer. If it has not been touched 22 years with marginal transmission, my luck is running out and I did not want to be stranded. I worked as a diagnostic technician for 17 years, not a transmission tech at all, so this forum has been a huge help to me. I just thought I would post a few random 4l60e questions as needed.
My first question is the converter. The van was built in 1994, so I was wondering if the converter looked to be a replacement? From what I saw in the valve body and pan it did not look like the transmission had been touched other than maybe a service. When I pulled the transmission, the converter had what looked to be an 07- date code. When I tried to clean the grease off the rest of the code was removed too, so not sure if 07 is a date or some other number.
Last edited by doninmedford; 07-14-2017 at 10:53 PM.
Reason: Spelling
DGHF is a low stall converter with a Carbon Clutch, You don't see carbon clutch converters in Non-PWM transmissions from the factory very often.....The converter itself could have been warranted by GM when the vehicle was still under powertrain warranty.....It doesn't appear to be a "reman".
Since this a 1995, it is a pwm unit. The front pump will have "pwm" stamped on it and the valve body will have two solenoids in the front. The slow reverse is common on 1993 - 1995 units, and will lead to a "no reverse" as soon as all the clutch material is just about gone from the low/reverse clutch pack. This happens because these clutches are on when the transmission is in park, and when going straight into any forward gear, these clutches are not completely off yet, and drag a little when the vehicle is starting to move forward. This eventually wears these clutches out. TransGo and ATSG offer some help here, which I include in my rebuild kits. Even when you rebuild this transmission, you always count to one after you go from park to any forward gear. That one second is enough to release the L/R clutches.
Thank you for the information. I appreciate the help. The slow reverse that I mentioned above was really bad, 3 or more seconds to go from drive to reverse. For some reason when I put in the new valve body plate and the boost valve, the problem got much better and it's been OK for about a year now. It's still there but maybe 1 second. I am not in that big of a hurry, so I don't mind waiting like you said, but the 3 seconds plus was noticeable as a problem. I have both the ATSG books, they are older 1999 versions though. I will be sure and check them and do the updates.
Do not replace the low/reverse piston as said by ATSG. The L/R piston in there now is fine. Drill the hole recommended by ATSG in the L/R piston and do the back cut on the manual shift valve (as per TransGo Shift kit instructions) carefully. And wait the one second, and you will be fine.
I emptied the case this morning, at first things didn't look that bad, even the pan was clean this time, where before it was gray. Then I got to the bottom of the case and the low reverse clutches are bad, real bad. I guess there was not enough friction left on them to dirty up the pan after the last service. Thank you both for the help, I appreciate it.
Let a pro correct me or confirm, but I recall reading that the low/reverse clutch in the early 4L60E had some revisions and if you pick the wrong parts, you end up with no clearance and rapid wear.
In any case (no pun intended), make sure you the low/reverse clutch has clearance after reassembling it. Apply air pressure to the low/reverse feed hole in the case and watch that the clutch moves by .040 or so. They is a small slot in the case that lets you see this.
Hello, yes PBA referred me to the ATSG updates and that was removing the captured ball at the rear of the valve body and the .030 drilled hole in the low/reverse piston. I do have clearance, maybe too much? It looks like about .065. I have a micro set of feeler gauges I can stick down in the case slot you talked about. The hot spotted steels were the same thickness as the new ones, minus some abuse. I think I am OK there. I reused my original wavy plate. The low reverse clutches were toast. The thinnest one was .033 the thickest was .083. The new all measured about .089.
I am trying to do a good job, so I am replacing all the bushings. All has gone smoothly until I got to the smaller inner bushing in the reaction shaft. The old one was very sloppy, the new one is binding a bit. Is there anything that can be done or just order a different brand bushing and try again? Thank you for the help!
Put the pieces together that are binding and take a dead blow hammer or a rubber tipped hammer and hit the outside of the part in different areas till it moves smoothly. This should fix this. .040" - .060" clearance is fine. Use turbulator steels here if you can. Same for the reverse/input drum.
I am sure this project would not have gone as well if it had not been for the help here. I do have a complete turbulator steel set (I saw you recommended them in another post).
I tried the tapping method it's still very tight. Forcing it onto the shaft and turning shows a high spot at the bushing line. It's like the bore of the reaction shaft bore was slightly undersized or the bushing was made thick. To fit in the bore it's pressed up slightly there. I will try a different brand and wait a few days to complete the project.
I took the L/R clutch pack out and measured the stack out of the transmission it's at 1.19. I ordered a thicker steel to bring it back up to the minimum 1.2
Last edited by doninmedford; 07-18-2017 at 09:47 AM.
Reason: Added more info and picture.
I had the same problem with that bushing this spring when I put mine back together. I ended up sanding the outside of a new bushing before driving it in. I took off .1mm.
So I might suggest ordering two new bushings, if the first one still binds, sand the second?
PBA's suggestion is good too. I wish I had thought of it. Would have saved me having to buy two more bushings myself.
Thank you for the feedback. I think if its still tight after the second bushing replacement, I will take it to a machine shop that has a hone for connecting rod bushings. Those are far more accurate than me sanding them by hand.
I was looking through the TransTec rebuild kit papers and the low reverse clutch overall height is listed 1.15-1.18 as the proper height while my older 1999 ATSG manual listed the specs 1.2 - 1.24 that is quite a difference. The stack right now is right in the middle of them at 1.19 I do have a thicker steel on order if needed.
While I am waiting for parts to show up, I thought I would ask another question.
I installed a Superior brand shift kit in the transmission about a year and a half ago. I am attaching a scan of the diagram. In step 7, the instructions for the servo it says to trim the piston seat 1/8 - 3/16. I never did that because I could not figure out what they were trying to do there. The kit worked well, but I never installed their stiff cushion spring either, leaving the servo mostly original, except for the slightly stronger release spring under the c-clip. Should this be done now? I saw that TG and Sonnax are not telling installers to trim their piston with their kits, so I figured whatever the intent was, it was safe to skip. This time I am installing the Corvette parts this time around, and can make the changes if important.
A few parts are here. Most are just standard upgrades, repeated many times here so I will not post them. The 74140-01K Sonnax HD backing plate kit is here. The parts do appear to be much higher in quality than the factory parts. I am not sure if my application really required them, but Sonnax recommended them for towing use. Since the 3-4 clutches are a trouble area, I decided to go with these. The Sonnax video of the stock plate flexing worried me a little.
Last edited by doninmedford; 07-20-2017 at 06:57 PM.
Using the thickest GM apply and backing plates for the 3/4 clutch is always recommended to prevent flexing the frictions. The Sonnax ones look even better; good choice!
07-14-2017, 11:08 AM
1995 4l60e HD Questions 
