3.91v lsd

[325ix]

[/B]
What? No.

Also, they usually fail open on ix's, although rear vc failures are fairly rare.

I've never noticed the vc's losing effectiveness in extended track driving either.

I was gonna say, what would be the point then if they spin in the snow.

[strang3majik]

The same reason VC transfer cases suck for snow. Maybe with rearends it works differently, but a VC in a transfer case will spin the rear wheels and then lock 4wd, however in the snow theres not enough to make it lock.

But these usually fail open? Now that is weird. Every failed vc I've ever come across failed locked. Now normal clutch type diffs usually fail open.


And exactly...a vc is better for handling...like I was saying all the joys of an open diff, and once its starts slipping it locks both wheels.

In my experiences (not BMW) snow usually has so little resistance it won't lock though.

[Vivek]

So can you run one of these in a non-iX e30? From reading this thread it seems like no one agrees on whether it starts to gain lock or lose lock with decades of use.

[lambo]

Increased heat decreases the viscosity of a substance. Since a Viscous Diff relies on the high viscosity of the fluid used, as it gets hotter it will become less effective. In theory, at least.

[Vivek]

So would it not necessarily wear out over time, unlike a clutch type diff?

[lambo]

So would it not necessarily wear out over time, unlike a clutch type diff?

I'm sure after constant use over an extended period of time the fluid will start to break down.

[Wanganstyle]

So would it not necessarily wear out over time, unlike a clutch type diff?

I think you failed to read my clearly stated above post. I do build all sorts of LSD's

everything wears over time/stress/abuse. My own VLSD is such an example

[Vivek]

Ah, sorry I did miss that. Thanks for the info.

[nando]

The same reason VC transfer cases suck for snow. Maybe with rearends it works differently, but a VC in a transfer case will spin the rear wheels and then lock 4wd, however in the snow theres not enough to make it lock.

But these usually fail open? Now that is weird. Every failed vc I've ever come across failed locked. Now normal clutch type diffs usually fail open.


And exactly...a vc is better for handling...like I was saying all the joys of an open diff, and once its starts slipping it locks both wheels.

In my experiences (not BMW) snow usually has so little resistance it won't lock though.

Really? Lol. Wanna drag race me in the snow?

[Wanganstyle]

Really? Lol. Wanna drag race me in the snow?

Or dirt or rain.... Nothing beats AWD for low traction.

[strang3majik]

Really? Lol. Wanna drag race me in the snow?

My jeep was horrible in the snow before the transfer case vc went out. Now I can hardly make a turn and it chirps tires (I take the front driveshaft out in the summer to make it drivable) so now it's awesome in the snow but doesn't turn for Shiz. Lol

Like I said, I'm speaking from experience with another brand. But technology is usually the same regardless.

[///digitalme]

i have a 3.91vlsd on my car and love it...its my daily so i dont track or anything, still locks really nice and its better than the 4.10 open diff i had before :D

[nando]

My jeep was horrible in the snow before the transfer case vc went out. Now I can hardly make a turn and it chirps tires (I take the front driveshaft out in the summer to make it drivable) so now it's awesome in the snow but doesn't turn for Shiz. Lol

Like I said, I'm speaking from experience with another brand. But technology is usually the same regardless.

Well, it's not the same at all, apparently. I don't know how the Jeep works (it sucked in the snow? really? what's the point then?), but the BMW VCLSD and transfercase definitely do not need a preload to lock.

A functioning E30 transfercase can move the car normally with the front or rear wheels completely off the ground. They typically do failed open but failed closed isn't unheard of. Basically there are seals in the VC housing that either get old or they get overheated (improper towing, mismatched tires, low TC fluid level, etc) and when they fail the sillicone fluid leaks out and of course the VC stops working. the result is the transfercase (or rear diff) turns into an open-differential.

Some transfercases have the the torque transfered directly through the VC, a lot of cheaper AWD cars do this actually. Maybe those ones need a preload? I think they older VW synchro vans worked this way, not sure what other cars do. It's crummier as the VC can't really take the constant stress and when they fail the car can't move at all.

If you don't believe the BMW doesn't need a preload, do a youtube search on "325ix jack test". The specific video I'm thinking of they built a cradle for the wheels to sit on (they were concerned about running the car with the axles completely unloaded). They test 3 cars. The car with a burned out VC (failed open) does not move with the front or rear wheels off the ground (I know this guy personally, his car was towed improperly across town, destroying the VC - they had to buy him a new transfercase). The cars with good VCs move normally, the ones with a bad VC just spin the unloaded wheels.

An autopsy done on a car that fails the jacktest will reveal that the VC has been overheated, the seals have failed and the fluid has leaked out. Also, the plates inside it will usually be warped and the special surface on them will be wiped off. In an extreme case the VC can actually crack but by that point the seals were probably done already anyway.

I'm not sure how it fails closed since it's fairly rare on BMWs, I guess the plates being warped and touching could result in them welding together? or getting so warped they can't rotate differentially anymore?

I'd think the jeep might be more similar to the BMW, some sort of gear or planetary based differential with a VC as a locking device, rather than the crummier and much less effective VC-only t-case. Or maybe it's something else entirely.

There's another very well respected AWD car company that uses VCs in most of their transfercases. Ever heard of Subaru? They're known for being great in the snow (although, the later, heavy ass pigs are not that great, I have one).

[Wanganstyle]

Subaru background here...........

Subaru center diffs definitely fail-and are open when they do.

[mikeedler]

I have a 3,91v in my green car.
It worked great for the 9 laps I put down at the Ring this year, never felt like it wasn't working correctly to me.
I have gravel in my back yard, and when I pull a U-turn, I can def. feel and also see that the VC is grabbing and working- on reg. road surface, it works just fine.

I think for almost all applications, the VC is just as good- and alot less chance it is worn out.