Please double check my t-case repair plans

[ThinkingJack]

I am repairing the t-case on my brother’s 2002 Tahoe LT, 5.3 and NP246 case. He’s had the truck since new and it’s well maintained (205k mi). He went to change the t-case fluid the other day and the fill bolt was seized in the threads, rounded, and cracked the housing. I did search this forum and read old threads on it; very helpful. I have rebuilt one GM auto transmission before, and some manual trans, so I am pretty confident in what I’m doing, BUT: I’ve never worked on this exact transmission before.

He ordered the Dorman aluminum replacement, this:

https://shorturl.at/IxlXa

He and I took the t-case out today. When we started to remove it, a decent amount of fluid came out from between the units - red ATF. I understand this to mean the trans output is leaking into that cavity as it should have been dry? Bushing inside the trans is worn and/or the drain back is clogged? So, here’s my plan and questions:

1) I am buying this Transtar t-case kit, which will give me new seals and the paper gasket to the adapter to replace all the t-case in/out seals.
https://shorturl.at/vkwo1
2) What is between the t-case halves? Paper gasket? FIPG? I didn’t break it open yet. We did the water pump and pulled the t-case and called it a day.
3) If I take that transmission mount/middle adapter out, can I access the transmission output shaft in any way to address all that fluid in there? I have looked at videos, and I do not see an externally replaceable seal.
4) I noticed a slight leak on the left at the pan edge, I am assuming a shift shaft seal weeping a bit from above. I saw the tool for that and will replace that while under there.
5) I found some $15/$20 “Case saver” plates to buffer the t-case oil pump ears. Simplified stamped steel versions of the “Merchant” saver device it appears to me. Is that necessary with the improved Aluminum housing?


Also I cut one of the transmission support bracket bolts out; the exhaust and O2 sensor bung prevented removal. I need to get a new bolt and insert it from the other direction. Plenty of room; seemed weird they did that. I was NOT messing with the exhaust to get that bolt out. I will go to Tacoma Screw to try to match the bolt, if not available there, where is a fairly priced GM parts source to order one from (I don’t work on a lot of GM products - just our Mom’s Euinox, though I am contemplating buying a late GMT 800 or early GMT900 Tahoe to replace my beloved Trooper).

Appreciate any advice or checking my thinking.

 

[Fless]

Tagging @rockola1971 @NickTransmissions for comments.

 

[justirv]

I am repairing the t-case on my brother’s 2002 Tahoe LT, 5.3 and NP246 case. He’s had the truck since new and it’s well maintained (205k mi). He went to change the t-case fluid the other day and the fill bolt was seized in the threads, rounded, and cracked the housing. I did search this forum and read old threads on it; very helpful. I have rebuilt one GM auto transmission before, and some manual trans, so I am pretty confident in what I’m doing, BUT: I’ve never worked on this exact transmission before.

He ordered the Dorman aluminum replacement, this:

https://shorturl.at/IxlXa

He and I took the t-case out today. When we started to remove it, a decent amount of fluid came out from between the units - red ATF. I understand this to mean the trans output is leaking into that cavity as it should have been dry? Bushing inside the trans is worn and/or the drain back is clogged? So, here’s my plan and questions:

1) I am buying this Transtar t-case kit, which will give me new seals and the paper gasket to the adapter to replace all the t-case in/out seals.
https://shorturl.at/vkwo1
2) What is between the t-case halves? Paper gasket? FIPG? I didn’t break it open yet. We did the water pump and pulled the t-case and called it a day.
3) If I take that transmission mount/middle adapter out, can I access the transmission output shaft in any way to address all that fluid in there? I have looked at videos, and I do not see an externally replaceable seal.
4) I noticed a slight leak on the left at the pan edge, I am assuming a shift shaft seal weeping a bit from above. I saw the tool for that and will replace that while under there.
5) I found some $15/$20 “Case saver” plates to buffer the t-case oil pump ears. Simplified stamped steel versions of the “Merchant” saver device it appears to me. Is that necessary with the improved Aluminum housing?


Also I cut one of the transmission support bracket bolts out; the exhaust and O2 sensor bung prevented removal. I need to get a new bolt and insert it from the other direction. Plenty of room; seemed weird they did that. I was NOT messing with the exhaust to get that bolt out. I will go to Tacoma Screw to try to match the bolt, if not available there, where is a fairly priced GM parts source to order one from (I don’t work on a lot of GM products - just our Mom’s Euinox, though I am contemplating buying a late GMT 800 or early GMT900 Tahoe to replace my beloved Trooper).

Appreciate any advice or checking my thinking.

If I recall the t-case halves are sealed with a RTV, I don't recall specifics. I replaced the hyvo chain and all rubber. I did add the case-saver for added comfort. If you plan to do the clutch pack, you'll need a special tool (always, right?) to determine proper shimming. J-44295 KENT MOORE SHIMMING TOOL. You could probably have that shimmed at a local shop for reasonable cost. This tool (used) is around $400+.

 

[NickTransmissions]

1) I am buying this Transtar t-case kit, which will give me new seals and the paper gasket to the adapter to replace all the t-case in/out seals.
https://shorturl.at/vkwo1

That kit should be correct for your T-case

2) What is between the t-case halves? Paper gasket? FIPG? I didn’t break it open yet. We did the water pump and pulled the t-case and called it a day.

All the internal components, including the chain/sprocket set, gear set, clutches, etc - cant recall if RTV only or a gasket (Think it's just RTV) - use Permatex Ultra Black if so.

3) If I take that transmission mount/middle adapter out, can I access the transmission output shaft in any way to address all that fluid in there? I have looked at videos, and I do not see an externally replaceable seal.

There's no rear transmission seal on 700-R4s or 4L60E transmissions so nothing to service; the output shaft will have a little inboard-outboard play as well as slight bit of side play but shouldnt move in/out much or side-to-side much...

4) I noticed a slight leak on the left at the pan edge, I am assuming a shift shaft seal weeping a bit from above. I saw the tool for that and will replace that while under there.

You can use the tool to yank out the seal or drop the pan, remove the 15mm selector shaft-to-rooster comb nut, slide the selector shaft out then pull the old seal out with a flat blade screw driver or small pry bar then install the new seal w/a 15mm deep socket (i think 9/16" will also work). If you drop the pan, install a new pan gasket and filter then reinstall the pan and torque all 16 bolts to 98-100 inch lbs. You will prob need to go around twice to three times to fully compress the gasket...DO NOT use a flimsy rubber gasket or a cork gasket...Only a composite gasket ($2-$5 at hard parts suppliers) or a Victor Reinz molded steel/rubber gasket.

5) I found some $15/$20 “Case saver” plates to buffer the t-case oil pump ears. Simplified stamped steel versions of the “Merchant” saver device it appears to me. Is that necessary with the improved Aluminum housing?

Not sure - perhaps @rockola1971 can comment

Also I cut one of the transmission support bracket bolts out; the exhaust and O2 sensor bung prevented removal. I need to get a new bolt and insert it from the other direction. Plenty of room; seemed weird they did that. I was NOT messing with the exhaust to get that bolt out. I will go to Tacoma Screw to try to match the bolt, if not available there, where is a fairly priced GM parts source to order one from (I don’t work on a lot of GM products - just our Mom’s Euinox, though I am contemplating buying a late GMT 800 or early GMT900 Tahoe to replace my beloved Trooper).

Appreciate any advice or checking my thinking.