I realize this messes with the VC and or center diff but can someone explain how and why both or sometimes only one goes?

Basically I'm looking to buy an AWD car but it was towed about 5km from the back wheels and I want to know the kind of damage I'm looking at.

I'm a FWD guy turned AWD so this stuff is sorta new to me.

I know the center diff is in the transmission. Is the VC in the t-case?

The VC is also in the transmission. When you take the outside cover off, the VC is right under there.



The Center Differential Repair VFAQ shows it quite well (which is where I stole the above picture from).

That makes sense to me. Would the t-case be damaged as well?

No, the Tcase should be fine. You should only need a VC.

And center diff. Would it not depend on what broke first? (ie - rear diff, t-case or center diff)?

Our cars have Front and Center Open Diff.

I would like to have the writing abilities to be able to explain it for you but it is normal operation for an open Diff.

You "might" observe a slight difference doing the same (turning the Wheel while that end of the wheels are in the air) on a Rear LSD Car.

As for the VC I'm pretty sure that you can use any year VC as they are all of the same.

Ghislain.

Ok this is a bit confusing. I wish there was a site that I could read regarding what the VC does.

What breaks on your car when you begin to use different sized tires on the fronts then on the back? What gets worn out?

Hmm.. I thought that if the vehicle was towed with the front wheels only on the ground, that the T-Case would more than likely be killed as well... No first hand experience with that though.

Rear wheels on the ground definately.

Ok, I apologize, I'm at work and little out my mind today. After I read your first post, I thought you meant it was towed with the rear wheels off the ground and the front ones were down. I thought it sounded weird, but I had seen it done before and didn't think any more of it.

Anyways, I know it's really basic, but if you wanted a general idea of how VC's work, check this page out. How Viscous Couplers Work

So basically the VC's fluid burns out and the center diff and the t-case are fine?

Yes the only affected part should be the VC.

XCase is a simple 90deg Gearbox and pretty much the only thing that can hurt a Diff would be a lack of Fluid or a hard impact.

The VC is the Component that takes the abuse when the vehicle gets towed with two wheels on the ground.

See the VC as a Limited Slip Component. Like in the link Steeve include you will see that it has two sets of Paltes. These Plates can only slip a bit, they are packed pretty tight. Towing a vehicle with only two wheels on the ground causes a lot of slip between the two sets of Plates.

By towing a vehicle by "only 5 minutes" subjects the VC to 5 minutes of abuse for which it was not intended to.

A VC should only see a slight difference (slip) of wheel rotation between the front and back. That is not a lot of slip, it is even minute compare an improper tow job.

This is why AWD vehicle owner are anal about it.

Ghislain.

So effectively I can find a good VC out of a blown transmission and drop it in and call it a day?

Yes you could replace a VC in about 20 minutes.

The hardest of the job is to jack the car up and drain the Tranny Fluid.

I would defenately also check the torque on the Input and Intermediate Shaft Nuts. They have the bad tendency to loosen up. This is totally unrelated from the VC coupling abuse, but it would be good to check it up while you are at it. All you'll need is a torque wrench (100ft/lbs) and a 36mm Scoket. You can use a Penny (copper) between the two Gears or leave the Left Front Wheel on the ground.

All in all this is way easyer that to replace FW Bolts that keep on breaking...

Hope you enjoy buddy.

Smart a$$ Giz.

my car(AWD) was towed like 10-15 away from my house
(back wheel on ground front in air)
and my car still runs fine... so i dont know if im just lucky or i dont notice any thing...so maybe 5km wouldnt do any thing.. though im not very car smart so dont listen to me.

questiont o those that know stuff (sorry for hi jacking your thread but same topic..) but would you notice the samages right awy fromt he wayt he car drives/feels (or would it not move at all) or somehting that gradually breaks and one day it all makes sence?

Possibly. The center diff could also be damaged. The spacer washer between the center diff output gear (MD727551) and the side gear can get burned up and some nasty welding occurs.

On the upside you get a welded center diff for free.

On the downside you get bits of steel floating inside the tranny and less spider gear tooth engagement.

Good info Rob.

I never experience a busted VC or Diff myself but you would probably get the feeling that not as much power is getting to the Rear Wheels. The car could even be very sluggish.

Grenaded Center Diff ain't pretty at all. Schrapnell gets everywhere and does lots of "colateral damage". You should even hear grindings.

Ghislain.

I'll just have to take the VC out, call it dead and replace it and have a look into the center differential and check for terrible wear.

You'll have to take a bit more in order to get to the Diff.

Has anybody here got this far inside a Tranny without removing it from the Car???

Ghislain.

I tried to do the teardown in a 2G once. No dice. Supposedly it is possible in a 1G.

I'd be concerned about getting dirt falling in the tranny.

Clearly. It's outlines in vFaq but it's not much harder then what I said. I have gear pullers and a nice TW and air tools.

Then you have it all my Mang!

Ghislain.

I've had a similar experience where my AWD was towed with the front wheels up it was dragged about 30 ft. I am doubtfull anything is wrong but i recently noticed when moving it in reverse it dosen't want to roll, it stops almost immediatley after i let go of the gas. Could it be this VC or could it be a sticky e-brake?

Jack the car's back wheels and check if the parking brake drag.

Again, I never experienced it myself but it is a posibility.

Ghislain.

We had the VC and the centre diff out of my 97, without removing the tranny from the car.

Went in through the wheel well, and just kept removing things until we got to them.
Didn't take too long... hardest part was getting the suspension stuff out of the way.

Thinking about it again, I remembered that I was trying to get the input shaft out. I could see doing the center diff in the car (2G) since you don't have to remove the middle portion of the tranny case.

I dont think the middle portion of the tranny case clears the inner fender on a 1G.

I am pretty sure the VC comes out in 1G's with the tranny in the car. Once the end cover is off it is a snapring. As suggested maybe it might not clear the frame or something, MAYBE


and when trying to be practical and reasonable I can't see how 5 minutes of towing could damage the centre diff. Even VC might survive.


I wouldn't even worry about it too much. Just drive it. the VC might be worn(dead) but the worst that it does it that it doesn't lockup very good.

I am pretty sure my centre VC has been dead for a while and the only downside is that the car is more likely to get stuck in snow when it is 3' deep. So what?!


and it certainly doesn't make the car undrivable. If the VC is worn, it is like not having it there. Which is totally OK.

The VC comes out no problem, we were debating the center diff on a 1G.

OT: Whats wrong with your Accent? Shoot me a PM if you need any help with it.

one time i was having a problem with 3&4th so i took the end cover off the tranny, unbolted the two big 36mm, then took of the vc, then got the next cover off, and i belive you could get the center diff out if you wanted (it would make it easier if you take the t.case off, one less thing to line up!). i didn't take the diff out or the next big cover. i just fix a stupid roll pin that was coming out!!!

don't forget you can pretty well do anything in the car by removing one or two engine mounts and moving it around, but then i have all the hoist and stuff so it makes it easy.
good luck.