Automatic T-case R&R/mix-match T-case build

[The Dark Side of Will]

My dad's '90 LazurBlau 4D/Auto has had a driveline vibration problem since he replaced the T-case with a junk yard unit after the chain started slipping in the car's original unit. The driveshaft splines were fine.

The vibration is definitely driveshaft speed rather than wheel speed.

He had already pulled the front driveshaft and driven it. The vibration persisted.
Today we dropped the exhaust and rear driveshaft. Started it an ran it on jack stands. The vibration is still there, so it's coming from INSIDE the replacement T-case :/

The guibo needs replacement and was reinstalled backwards, but wasn't bad enough to cause the vibration we're getting.
We indicated the driveshaft in multiple locations first:


It had 0.015" TIR or less and wasn't missing any balance weights. There's a tiny bit of play in the rear U-joint, but, again, not enough to cause the problem.

Dropping the T-case in an autotragic car is significantly more difficult than in a stick car. The T-case bolts on with NINE studs, two of which can only be accessed through the shifter hole, but interference from bosses for the T-case case-half bolts makes it impossible to use a flex socket and extension like you can for the stickshift T-case. Feck. You have to get a cheap wrench and "modify" it.

Also, when you pull the T-case, this is left:



How do I get that shaft out of the trans? I tried pulling on it and it doesn't want to come out. Pull harder? Pee on it?

This is that GDMF T-case. We'll use its good chain and the good VC and other components from the original unit.

[The Dark Side of Will]

Why is it vibrating? I don't know.
The VC isn't working well. If the level of silicone fluid has dropped until it's at the bottom of the seal, that would make the entirety of the silicone eccentric weight and could cause vibration, BUT as the silicone flowed out to the perimeter of the VC due to centrifugal force, the vibration would go away. That doesn't happen with this vibration. I have no idea how anything could become an eccentric weight inside the T-case. Weird.

[The Dark Side of Will]

To those who have split the T-case, how do you do it?
We took all the case have bolts out and removed the rear output yoke. When we pry the case halves apart, they separate a little bit but pop right back together.

Do we need to use the mounting holes for the stabilizer weight to pull the rear case off while pushing on the output shaft?

ETA: Found an overhaul thread here: https://www.r3vlimited.com/board/sho...d.php?t=406860
It doesn't mention anything other than the yoke and case half bolts to get the thing apart, so I guess we'll just keep prying.

ETA2: Rebuildable VC mod: https://www.r3vlimited.com/board/sho...d.php?t=406859

[flyboyx]

its been a while since since i took off an auto tcase, but why do you need to take off the shaft? i saw an auto xfer case for sale somewhere when i did a national cl search yesterday. seems like it was listed for 250 or 350?

i have a hard time believing that much vibration is coming from internally but then i'm not there working on your car. you will want to be really careful taking parts out of your old xfer case if it was skipping the chain. there is probably a lot of other mechanical issues in there too.

[The Dark Side of Will]

My dad had previously driven it without the front driveshaft. Vibration still there. We didn't remove the front driveshaft this time, but we disconnected the rear one from the T-case, removed the guibo and it STILL shook as we ran it on the jackstands.

We got the case halves apart.

There are two locating dowel pins in the casing. If the casing doesn't separate easily use flat face punch to tap out the dowel pins.

We had to do this to separate them.

We started with the car's original T-case. That's the only unit we've taken apart so far. I can grab the ring gear and the VC housing and turn them very slowly by hand, so I'm pretty sure this VC works just fine. I'll get a measurement of the chain deflection to compare to the other unit. This one's also full of rusty looking sludge on the inside. I thought that was silicone fluid from VC failure after seeing it in the rebuild thread. I don't know why it would be inside this unit.

We'll pull the replacement that vibrates down tomorrow. We may just swap the ring gear/output shaft/VC assembly from the original T-case into it, clean everything up and reassemble.

[The Dark Side of Will]

Pics:

Breaking loose the output flange nut:



Pulling the flange/yoke:



The output shaft splines are unnervingly small. Do people really run over 400 HP through these T-cases?



Rusty goo inside:



Chain deflection measurement between 2.660 and 2.700 depending on how hard I squeeze.

[Kershaw]

Holy crap, why is it so rusty in there?

[monticello]

Also, when you pull the T-case, this is left:



How do I get that shaft out of the trans? I tried pulling on it and it doesn't want to come out. Pull harder? Pee on it?

It looks like there is a snap ring right where the intermediate shaft and the trans output shaft come together.

[Kershaw]

Wouldn't that snap ring be stopping it from going to the trans though? There's nothing I can see to stop it from pulling out unless there is some internal snap ring.

[The Dark Side of Will]

Holy crap, why is it so rusty in there?

Dunno. It's kinda weird. As you can see, the parking lock wheel is rusty too.

This could be the vibration problem:



Because of this bearing on the back of the VC, the forward drum that transmits torque between the VC and front output was loose on the front output gear in this T-case instead of tight (pressed? stuck?) like it is on the original T-case. Also, this VC is pretty weak compared to the original.

The chain has less deflection, though:



And another angle on the input shaft that's stuck in the back of the transmission:



The trans output shaft *IS* specific to the iX. The auto T-case input shaft is *ABSENT* from RealOEM.

It looks like there is a snap ring right where the intermediate shaft and the trans output shaft come together.

The snap ring limits how far the shaft goes into the collar, but doesn't retain anything.

ETA:

Wouldn't that snap ring be stopping it from going to the trans though? There's nothing I can see to stop it from pulling out unless there is some internal snap ring.

Right.

[flyboyx]

The trans output shaft *IS* specific to the iX. The auto T-case input shaft is *ABSENT* from RealOEM.

i think it is in the transmission diagram if i recall correctly.

[The Dark Side of Will]

I haven't seen it. Link?

The trans output shaft is there, but the diagram shows the RWD part.

[Nisse Järnet]

Matti has put 1000hp through that transfer case, if it's the same between auto and manual that is :)