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1G Slipping Under Boost- Transfer Case?

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fourgsixthree33

10+ Year Contributor
1,244
46
Oct 25, 2010
Athens, Pennsylvania
92 GSX, 5sp, 4 bolt rear.

Ever since I built this 1G, there has been a loud humming noise at cruise/decelerating. The other day, I took the car for an hour and a half ride to see a DSM buddy. On the way home that night, I was just cruising around 55MPH and I heard a louder humming noise. It lasted a few seconds and honestly I was waiting for something to break or fall apart. But, the noise suddenly went away.

Several minutes later, I did a 3rd gear pull when passing a slower vehicle. As the car transitioned from the right lane into the left, the car swerved around like torque steer in a FWD. (Note this road wasn't a very "even" or "flat" road.) At that moment, I thought I broke a CV joint. Which is also what this felt like, breaking a CV joint during a pull.

A few miles later, I did a 2nd gear pull. This time, there was no swerving (now on a flatter road) but the car "slipped" soon after going into decent boost. Similar to a slipping clutch, but not at only real high load/RPM/boost. Anyway, I continued on and went home. The next day, I went out and jacked up the car. I was expecting to see a torn CV joint boot or something confirming a broken axle. Everything looked fine. So I pulled off each CV joint boot on each axle. Again, everything looked fine and no broken pieces were visible.

I warmed up the car and went for another drive. Nothing seems abnormal when just driving around regularly. No slipping under moderate acceleration when out of boost. No slipping pulling out of the driveway or backing up or anything. It only slipped/slips when WOT under boost, in any gear.

So I came home and jacked up the car, this time lifting all 4 wheels off the ground. I started the car, put it in gear, and slowly let out the clutch. The front wheels both spun, but not the rear. Is this normal? The front AND rear wheels are supposed to move correct? Not just the front? I'm hoping my transfer case is f***ed. Quick, easy fix. The other thing that could cause this would be a blown front diff. But I would imagine I would have more problems and slipping under more driving conditions. Opinions?
 
Is the noise like a rattle hum or aby thing I know when my t case had the drain plug fall out and the fluid drained, I thought it was my exhaust slapping around or something. If the rear wheels arnt moving at all I would agree it could be tje transfer case. Is the driveshaft moving at all?
 
Almost sounds like the viscous coupler might be toast. I've seen a few of them crack from over heating (usually when towed improperly), so you could pop the end cover on the trans off to take a look. Might be causing intermittent function, normal driving it's fine but as soon as you load it up, it slips or vectors power incorrectly.

Another option is a rear factory lsd going out.

If this were something mechanical like a diff or t-case I'd expect to hear some carnage report or more harsh drive train sounds.
 
Thanks for the replies guys. I can't describe the humming noise really, other than that it was just a humming noise. I haven't really heard a clanking noise or anything like that.

I should have a working transfer case and center diff./VC from my wrecked 95 AWD. The transfer case will work, I know, and the center diff should be interchangable too, correct? How much do I need to remove in order to service the center diff with the engine and trans in the car?

Aside from IC piping and stuff. Practically anything in the bay that could have been removed/relocated was moved which will make the job easier. But what about like the motor mount and stuff?
 
While you can do it in the car if its your first time i rec removing the trans. Drop the exhaust and transfercase. Two axles trans mount and some transmission to engine bolts and the trans is out. Then the outer cover on the trans comes off. Two lock nuts and a snap ring. Then you have to pull 5th gear and idler gear off (gear puller needed). Then you can pull the center diff out. Vfaq has a good how to.
 
Being that it's intermittent, my money is on the viscous coupler. Under load it seems to be slipping and is a likely culprit. Usually with a center diff you'd notice some significant noise or "clunkiness" to the reactions, same with a transfer case.

Keep us updated on what you find!
 
A little update. I took the car up to the shop today and put it on the lift to verify that the rear wheels would not spin when in gear. Again, the fronts spun while the rear did not. I noticed some fluid on the transfer case as well, although I couldn't pinpoint where it came from.

On the way home, I did a 2nd gear pull while watching the speedometer. The speedo rose while the "slipping" occurred. So I pulled off into a dirt parking lot and with my head out the window, I watched the fronts spin rocks while the rear wheels just rolled.

So, I took a video right after pulling back onto the road as I attempted to spin through first. The front tires easily spun on the pavement as if the car was on ice. Then I finally mashed the throttle in 2nd gear. It's clearly in FWD mode. It does not slip in 3rd 4th or 5th either. Though it will torque steer like a mofo.

Now what do you guys think? Makes more sense to be a center differential issue. USUALLY when a transfer case goes, it makes the car full RWD mode. Not FWD. Or it completely locks up all together.

Video. (PS, I am aware that roasting the front tires with a failure in the drivetrain is dangerous and could potentially make my problems worse. I don't plan on driving the car any more until the issue is fixed. Just had some FWD flashbacks there for a bit LOL.)

You must be logged in to view this image or video.
 
We already told you the problem is in the center diff or viscious coupler. Usually if you break the transfer case you hear and see it LOL. Center diff also. Thats why i rec. removing the transfer case and see if the output shaft spins
 
Drain the Tcase fluid and see if you even have any fluid in there. I know when my Tcase leaked from the rear seal, it made a loud hum like something was going to break and I pulled over and the noise went away. I could drive the car fine but the Tcase was toast.
 
Remove transfer case and with all wheels in the air put the car in gear. The output shaft should spin with the front wheels. If it dont move at all (or very slowly)center diff or viscous coupler is bad. If its spinning either the splines on the output shaft are stripped or the transfer case is blown
 
I got some great news. I jacked up all four wheels off the ground and pulled the transfer case. Input shaft still spun when in gear. So, I removed the cover off of the transfer case. I found the problem.

The output shaft spun the first gear/pinion inside the transfer case. But the teeth are chewed to helll. So power would get to the transfer case, but the output side of the transfer case (driveshaft side) was not spinning.

Now, this seemed very interesting here. How would a bad transfer case allow me to still drive the car in FWD, I asked myself. So, I tied up the driveshaft and let the car down. I could still EASILY move the car forwards and backwards. Sooooooo...seems to me that I have either a welded center diff or a VCE, yeah?

Uploading pics now.
 
There was some fluid, but not nearly as much as there should have been. It looks like the seal on the output shaft side was leaking. There is tons of fluid in that general area of the transfer case and transmission.

I definitely haven't noticed any hopping, chirping, etc in regards to having a welded center differential. So I could still have a VCE, correct? What years of our 1G's came with an LSD? The rear is a 4 bolt LSD rear.
 
Consider yourself very fortunate that the failure did not cause the transfer case to lock up while you were driving. You would have likely needed to buy a new pair of pants/boxers. I bet you will be regularly checking the fluid from now on. It wouldn't hurt to also replace the yoke on the driveshaft.

Yoke kit:

https://www.extremepsi.com/store/product.php?productid=23260
 
Yeah, I have heard horror stories about people's transfer case completely locking up while driving. F-that ha. I definitely got lucky, hopefully it didn't cause any damage on any of the transmission parts. When I put a new transfer case on her, I will post back.
 
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