Hello all.
I am a new member and new to building transmissions. My wife's 2005 Tahoe decided to start slipping into 3rd a month ago. I checked the fluid and it was pristine, no burnt smell at all. To be sure I took it in to a local lube business and ordered a CHANGE. They flushed it instead... FML. It's a mile away from my house, still slipping. I decide to research and talk about it with someone I know. My wife drove it to work two days and it completely lost 3rd and 4th. It's not a far drive by any means. So I decided to change the shift solenoids, A and B.
After I drop my pan I noticed my fluid was no longer pristine at all. It looked like burnt motor oil. No metal shreds, but looked like some degraded clutch material. I still haven't gotten a grasp on that, since the fluid looked GREAT before my 'change.' And less than 25 miles it is burnt up??
Anyways, I had no choice but to try to rebuild the transmission as I have recently lost my job and with two kids, money's tight. This is my first time rebuilding a transmission. I would like to think I am mechanically able, and so I took on the task by myself. I did not rush the job and I spent two weeks trying to do as thorough a job as possible. I bought a $400 rebuild kit with all the seals, bushings, springs, and filters. I researched the main culprit of the 3/4 clutch loss. Check ***** in accumulator was not leaking. Sun shell was not broke, but a little loose I replaced with 'the beast'. Changed all solenoids except TCC and the metal plate with the circles on it, sorry forgetting it's title. The separator plate was slightly worn in the spot where the check ball can lodge itself, I flattened that spot with a ball peen. The rear piston(?) at the very bottom of the drum assembly which is a high failure rate of 3/4 pack was worn and loose fitting, I replaced it.
I didn't feel any excessive play in the valve body or accumulators. Still replaced the springs and checkballs.
Btw the 3/4 clutch pass was completed burnt out and the friction played were bowed from the excessive force inflicted by the high pressure of, I'm assuming that leaking rear piston.
Put it all together and reinstalled it, I was nervous to say the least. After some issues with the seal on the dipstick down tube I eventually got it started with no leaks filled her up and gave it a test drive. Perfect. No slipping good shifts. Plenty of hold power. 6 miles later on the way home, boom. Slipping to 3rd and quickly depreciated to no 3rd and 4th.
I'm at my wits end and nearly my wallets end. I don't know what to do. I'm going to test drive it again in a little bit, as I think maybe when it got warmer 3rd couldn't overcome 2nds pressure. Endplay and clearances were good as well. Idk if I'm forgetting anything else atm.
I really don't want to have to drop the transfer case and exhaust and transmission all over again.
I'm thinking I should replace the wiring harness and the odd looking flat sensor that sits on top of the valve body.
Please any thoughts would help at this point. I need to get this done ASAP so I we can both have a working car and I can get back to work. Thank you,
~Nate Dogg

 

You most likely have a hydraulic leak in the 3rd clutch apply circuit. I would not drive the vehicle anymore, as it will cause more damage to the trans. The trans will have to be pulled and gone through again. This time you will need to check for worn bores in the valve body and pump. Check for leaking where to input shaft presses into the input drum and the 3rd check ball capsule.

Go to Sonnax's web site and under the 4L60e section download the instructions for their Sure Cure Kit. The last few pages of these instructions tell how to check for hydraulic leaks.

 

I checked the checkballs for leaks and I checked for any play in the pump and valve body. My tools and where I can redo this work is 10 miles south, if I just keep manual shifting 1 and 2 can I drive it there? It has just 10 miles since the rebuild, could 3/4 clutch pack be burnt already? Thank you for your response.
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Yes, if it is slipping they are burnt.

How are you testing the valve body and pump bores? Did you check the input shaft? The 3rd check ball capsule only has one check ball in it, which other check ***** are you referring to?

 

The checkball in the servo, I also replaced the other checkballs* my bad*
I visually inspected each bore on the valve body and checked for wear or damage on all the moving valves.
I tested the input shaft with compressed air the rear(front?) Piston pressurized. I'm starting to go back over what I did. I did not change the Teflon seals on the shaft and I checked them but I'm wondering if I knicked the lower seal on the input shaft with the pump. I remember it binding at one point during installation. The checkball was tested with mineral spirits and tranny fluid*

 

Changed springs too. I didn't use any precise tools on the valve body technically

 

Unfortunately it does sound like you either have a leak in the 3rd clutch apply circuit or else very low line pressure. The line pressure can be checked with a trans or 300 psi oil pressure gauge. Maybe a buddy has one to borrow. A new one is the ATD-5550 on Amazon for $37. If pressure is low, it could be a leak in the pump area, a defective pressure control solenoid, or leaks in the valve body.
There are many places the 3rd clutch apply fluid can leak. Yes, the servo is one of them. Another is the the 3rd accumulator "cartridge". Often overlooked are leaks between the input shaft and the input drum. Sonnax has a reinforcement ring kit for this.
Checkballs are not your problem - if you messed one up (left it out), you would get very abrupt shifts. I cannot remember any posts here where a slipping 3rd gear was caused by a valve body problem. (correct me if that is incorrect).
Maybe that gives you some ideas of where to look.

 

I wish you were wrong lol. Darn it, I'll take her back out this next week. After all the parts and fluid and tools I've had to buy for this I'm at roughly $700. O.oI was hoping doing it myself would be more cost effective. If I put any of the servo apply pistons in backwards, could that create this problem as well? The only thing I read in the valve body that can cause this is line pressure lost from the valve that moves erratically from pmw(pwm?) solenoid. Which I did not repair, I wanted to do the sonnax method, but I'm sure the reaming tool is expensive af. And I wasn't sure if there is another, more cost efficient, route.

 

Central Valve Bodies has an oversized Drop in AFL, (actuator feed limit valve) that no reaming of the valve body is required. This is a good part to install.

Once you have the trans apart before going back together you need to go to Sonnax's web site and under the 4L60e section download the instructions for their Sure Cure Kit. The last few pages of these instructions tell how to check for hydraulic leaks. If you don't perform these tests and correct any issues you find, you will be pulling the trans apart again. Because if you installed everything correctly and the trans started slipping that quickly you have a major hydraulic leak.

 

Like Mr Bond wrote, it sounds like a "major hydraulic leak". Unless you left something out, I doubt its in the valve body.
My guess is a seal on the 3/4 apply piston in the input drum or even a teflon ring on the input shaft.
While there are very expensive seal installers, all you really need is a "Transtar lip wizard" which some rebuild kits include. Ask for one at a trans shop; many use Transtar rebuilt kits and they will have many extra "lip wizards" to give you for free.
You can compress the teflon rings with strips of plastic from a Coke bottle and a hose clamp; go snug and not overly tight. Let it compress for a few hours or even overnight. Take them off just before you install the pump. I then give it overnight to expand before I turn on the engine.

Keep posting here; its your thread and we are happy to try and help.

 

Thank you guys <3
I'm out of town roofing this weekend and I will repost around Tuesday after I drop it again.

 

So I don't think we need to vote because I'm pretty sure I'm getting the idiot of the Year award. Any chance leaving this seal out would cause a nearly immediate 3-4 clutch pack failure??
eh, to be honest I took my time with this thing but I got frustrated at one point and started muscling the seal for the input drum.And I didn't test all of the input drum. I'll post pictures tomorrow. 3/4 Clutches are pretty much burnt. It's okay I will try again.

 

Scratch that that was installed. I'm going to pressure test the input drum next and I'll let you guys know

 

I realize now what I did, the snap ring was a real pain in the *** to get in and out and I bent it slightly. It caused one side of the spring to push up allowing the Pistons to unseal. I fixed the snap ring and put it all back together and my three four clutch is sealing nicely. Took me five or six times to figure it out pulling the input drum apart and putting it back together, didn't help my dumbass kept checking the lubehole thinking it was the three four clutch, stooopid lol. For good measure I am going to change the Teflon rings out as well. I'm quite sure they are in decent shape but I'm confident I can get them changed out without causing any harm.

 

Great to hear that you figured it out. Now that you too are a transmission expert, you can start helping others here. 😊

BTW - You will NOT win the "Idiot of the Year award"; heck you are not even in the running. Many (most, all?) of the regulars here have been in the running at some time or even won the award. 😊
While you thought you had left a part out, I learned that leaving extra parts in the trans also does not work. (Like a random steel washer between the main body and the valve body.)