Center Diff install complete!!: WHINE FOUND!: NOW WHINING!

[skoobywrx]

update!

this is what happens when you add the #35 washer when its not called, source of the whine:





Update:
installed a new Center diff..........Without the thrust bearing. mine didnt have the thrust bearing to begin with.

Again did some rotations in a parking lot, and no binding.....

but now i get a whine....?! any idea?


Update....

First test drive, it was fine, nothing out of the ordinary...now i got some chirping in the wheels when im doing tight corners, like entering a parking stall.....

Went to the suby junkyard and they suggested some GM LSD additive.....

Is the center diff the issue? straight line the car is fine, normal turns is fine, its when i try to do a u-turn or parking stall entering is when it starts to buck and chirp.

HELP!!!

So i picked up this car about a week ago, and i discover new things everyday! while looking at my fuel tank, i removed the exhaust, and and looked up and saw this:



Car runs and pulls great. if i bought the shaft, would there be any issues?

there isnt any wierd sounds or grinding. ive been driving since last week. and i believe the previous owner (a grandma) drove it for 5 years.

guess its time to hit the local junk yard.

[brand]

I doubt it just fell off, and I doubt granny took it off, so I'd wager there's a reason it's off. So I'd expect to find something else that's need to be replaced on the rear side of the drivetrain.

[Buffman]

unless ujoints were bad. If something in the rear diff was bad, it would be apparent by driving..

[Kecksauce]

unless ujoints were bad. If something in the rear diff was bad, it would be apparent by driving..

Yeah I was thinking that too. All else fails, find a cheap replacement shaft and see what happens.

[skoobywrx]

unless ujoints were bad. If something in the rear diff was bad, it would be apparent by driving..

Yeah I was thinking that too. All else fails, find a cheap replacement shaft and see what happens.

yeah, i hope thats just it.....install a replacement shaft, and its good to go...

hope the rear diff isnt toast, i dont feel anything wierd or any vibrations. wish me luck!

[evolutionmovement]

Wouldn't this mean the center diff is likely toast from always transferring power to the front?

[PhyrraM]

I think it's an automatic. (grandma comment, and most SSs are autos)

If so, I believe he should be OK. Come to think of it, think the shaft was most likely removed due to torque bind?

[skoobywrx]

I think it's an automatic. (grandma comment, and most SSs are autos)

If so, I believe he should be OK. Come to think of it, think the shaft was most likely removed due to torque bind?

its a manual....no wierd noises or grinding.....hope its ok

[fishbone79]

I'm having trouble imagining a mechanical scenario where removing the rear driveshaft would be beneficial to an MT drivetrain (barring anything seriously wrong with the rear end)... Maybe it was towed on a dolly at some point and someone neglected to replace the missing driveshaft?

I'd just replace it and listen closely for strange whining or anything like that from the rear end or tranny for a couple hundred miles. The center diff is pretty robust, I'll bet it's fine.

One other thought, are you sure it was a grandma who owned it the whole time? Any chance this is a botched AT--> MT swap with the wrong gearing and someone didn't replace the rear diff? What does the final drive on the rear diff say (should be written right on it), and what is the TY # on the tranny? Such a scenario is not at all unheard of...

[skoobywrx]

Yep im pretty sure....the last owner grandma had it for 5 years. i read the title so i know she was the owner.

yeah, swap is unlikely....looks too clean....

rear diff number, im trying to remember off of the top of my head, like 3.9 something..

thanks for your guys's help. if it doesnt work out, i just ill keep it a fwd car...ftl

I'm having trouble imagining a mechanical scenario where removing the rear driveshaft would be beneficial to an MT drivetrain (barring anything seriously wrong with the rear end)... Maybe it was towed on a dolly at some point and someone neglected to replace the missing driveshaft?

I'd just replace it and listen closely for strange whining or anything like that from the rear end or tranny for a couple hundred miles. The center diff is pretty robust, I'll bet it's fine.

One other thought, are you sure it was a grandma who owned it the whole time? Any chance this is a botched AT--> MT swap with the wrong gearing and someone didn't replace the rear diff? What does the final drive on the rear diff say (should be written right on it), and what is the TY # on the tranny? Such a scenario is not at all unheard of...

[evolutionmovement]

How does it get the power down? Is torque steer bad? Mine will be fwd turbo when I get it running, so I'm curious.

[skoobywrx]

well i havent launched it, if thats what you mean. on the hwy when i get on it a bit, it pulls quite nicely

but in the NW i would like to get this back to awd.

[skoobywrx]

looks like a 92-94 shaft should work? nothing older, how about a newer one like a 95+?

[fishbone79]

95 should work on that, make sure it's an MT shaft though. The front half of the AT shaft is a different length.

[PhyrraM]

Knowing the way the center diff works on a 5-speed......something is screwed up. If your getting decent power out of the front wheels, the center diff is locked up somehow (Welded, destroyed, etc..)

I can saw with virtual certainty that putting a driveshaft in there without getting the transmission checked out is going to be a bad idea. Think about a 4x4 driven on the pavement while still locked up.

If the center diff was normal or broken, but 'open' you would get almost no power to the front wheels.

[fishbone79]

I've driven my MT without the rear half-shafts in. I had power loss (probably ~25-30%), but the car acted surprisingly normal, and the trans suffered no ill for the ordeal (the circumstances of which can be explained if you're interested).

Since he has nothing to compare it to, we have no idea if he's seeing a significant power loss or not. The way the center VLSD works, in this case it should transfer the bulk of the power to the front wheels because the rears are effectively 'slipping.' When the rear wheels spin, the rotating speed difference between the transmission main shaft and drive pinion shafts increases, activating the viscous coupling, which transfers the majority of the torque to the front (a default 'locked' position, but not intended as such). It does this basically by minimizing the differential in revolution to the best of it's ability. Parenthetically, this characteristic of the center diff makes it quite possible to drive with a different final drive ratio at the front and rear wheels (essentially, for all the center diff knows, the car is in a perpetual turn, and transfers the torque where necessary).

I'm not suggesting that this is good for the diff at all, but if it's not been driven like that for too long, it's probably fine.

Josh has some tech articles scanned in on the action of the center diff if you'd like to read how it works.

[skoobywrx]

OK, how would go about checking the center diff out?

Knowing the way the center diff works on a 5-speed......something is screwed up. If your getting decent power out of the front wheels, the center diff is locked up somehow (Welded, destroyed, etc..)

I can saw with virtual certainty that putting a driveshaft in there without getting the transmission checked out is going to be a bad idea. Think about a 4x4 driven on the pavement while still locked up.

If the center diff was normal or broken, but 'open' you would get almost no power to the front wheels.

[skoobywrx]

i have no idea how long its been like this. could be like 2 days prior to when i bought it or 5 years.....

if there something wrong with the center diff, would i hear it?

also....how would i test this? if i got the car on to stands and put the prop shaft, and started to roll the wheels, would this cause a fatal car failure? ie tranny fail?

I've driven my MT without the rear half-shafts in. I had power loss (probably ~25-30%), but the car acted surprisingly normal, and the trans suffered no ill for the ordeal (the circumstances of which can be explained if you're interested).

Since he has nothing to compare it to, we have no idea if he's seeing a significant power loss or not. The way the center VLSD works, in this case it should transfer the bulk of the power to the front wheels because the rears are effectively 'slipping.' When the rear wheels spin, the rotating speed difference between the transmission main shaft and drive pinion shafts increases, activating the viscous coupling, which transfers the majority of the torque to the front (a default 'locked' position, but not intended as such). It does this basically by minimizing the differential in revolution to the best of it's ability. Parenthetically, this characteristic of the center diff makes it quite possible to drive with a different final drive ratio at the front and rear wheels (essentially, for all the center diff knows, the car is in a perpetual turn, and transfers the torque where necessary).

I'm not suggesting that this is good for the diff at all, but if it's not been driven like that for too long, it's probably fine.

Josh has some tech articles scanned in on the action of the center diff if you'd like to read how it works.

[PhyrraM]

The only way I know how to test it would be to put the driveshaft back in and see if you get any binding on tight turns, such as parking.

Is it possible you actually have a FWD transmission installed? I can see the front part of the driveshaft in the pic, so I would assume it's plugged into a transmission.

[skoobywrx]

i believe it is plugged into the center diff, im not 100% sure, as i was working on the fuel issue.

what do you think about process of testing:

1) get car on jacks
2) 1st gear and make sure the center diff is turning the shaft
3) put prop shaft in and again put into gear and and slowly let the clutch out.
4) if no bad noises are made, drive slowly

thanks for your help.....this is just nuts

[skoobywrx]

i believe it is plugged into the center diff, im not 100% sure, as i was working on the fuel issue.

what do you think about process of testing:

1) get car on jacks
2) 1st gear and make sure the center diff is turning the shaft
3) put prop shaft in and again put into gear and and slowly let the clutch out.
4) if no bad noises are made, drive slowly

thanks for your help.....this is just nuts

the other wear and tear items, ie fuel vapor lines, and clutch slave cylinder going out, i can deal with, but this?! what the heck!

[entirelyturbo]

If the center diff is seized up, and your tires are all the same size and wear, then it will probably drive pretty normally going straight.

If you take a sharp turn though (like pulling into a parking space), it will probably buck and jump and chirp tires, like a locking 4WD system like PhyrraM said.

[fishbone79]

I think your plan sounds pretty good... I mean, if you slap the driveshaft on and there's an issue with the tranny/center diff when you drive around, the only part you'd really risk harming appreciably would be the tranny itself. The rear diff won't be affected much.

[skoobywrx]

harm the tranny or do you mean harm the center diff?

I think your plan sounds pretty good... I mean, if you slap the driveshaft on and there's an issue with the tranny/center diff when you drive around, the only part you'd really risk harming appreciably would be the tranny itself. The rear diff won't be affected much.

[PhyrraM]

The tranny contains the center diff, so he kinda means both.