Worn out T-case chain

[The Dark Side of Will]

http://www.snowmobilefanatics.com/forums/11-general/66204-what-hyvo-chain.html

User claims to work for Morse TEC, the division of BW which made the chains.

Links to this page: http://www.borgwarner.com/en/MorseTE.../MorseTEC.aspx

Also mentions that the snowmobile chain production may have been sold to Emerson power transmission

http://www.emersonindustrial.com/en-US/powertransmissionsolutions/Pages/home.aspx

[101]

Will's Dark Side:

Wa appreciate the continuing research!

My iX is a member of the "chain gang" as well - and when I am eventually forced with a decision of having to spend $900 for the chain from BMW vs. pulling the front driveshaft and having a 2WD iX poser, I'd have to choose the latter. That would be a shame!

Keep digging!

[The Dark Side of Will]

You're welcome!

(If all you do to convert to RWD is pull the front driveshaft, you just turned your viscous coupling into a time bomb.)

[spdracrm3]

You're welcome!

(If all you do to convert to RWD is pull the front driveshaft, you just turned your viscous coupling into a time bomb.)

wrong again ..... front output will spin at same speed as rear output and therefore no damage occurs to VC, many many cars have been made 2wd this way and after thousands of miles put back to Awd with no problem

[nando]

it's probably already shot by now anyway

[101]

Unknown.

It's a "new to me" car that I flatbedded home that wasn't running, was missing the front driveshaft, had a rusted out fuel tank and leaking brake lines among other things. I've only driven it 20 miles since it's been put back together. That's when I noted the noise coming from the transfer case area which I assume is the chain since the splines look very nice.

Hopefully I'll get around to the jack test this weekend. Fingers crossed!

[The Dark Side of Will]

wrong again ..... front output will spin at same speed as rear output and therefore no damage occurs to VC, many many cars have been made 2wd this way and after thousands of miles put back to Awd with no problem

Umm... please tell me this is sarcasm.

[spdracrm3]

Umm... please tell me this is sarcasm.

nope not at all

what kills VC is output shafts spinning at different speed (ie 2 wheel towing) if you remove the front drive shaft the VC will have the two outputs locked together (front output socket has no load so will freely spin at the exact same speed as the rear output due to locking provided by VC) ...therefore no difference in speed between the two shafts = no damage to VC .

[The Dark Side of Will]

nope not at all

what kills VC is output shafts spinning at different speed (ie 2 wheel towing) if you remove the front drive shaft the VC will have the two outputs locked together (front output socket has no load so will freely spin at the exact same speed as the rear output due to locking provided by VC) ...therefore no difference in speed between the two shafts = no damage to VC .

Go research how the center diff inside the VC works, then come back and tell us all about it.

This has been covered dozens of times before and I don't feel like wearing out my keyboard educating you.

EDIT: I guess I can be a nicer guy than that...

WITHOUT the VC, but with the driveshaft, the car moves by routing 2/3 of transmission output torque to the rear and 1/3 to the front. This is accomplished by a planetary gearset. Both driveshafts turn the same RPM.
If the front tires are on ice, then all the torque goes to the front driveshaft and the rear gets none. This is how an open diff works.

WITH the VC, as the front tires slip on the ice and accelerate, an RPM difference develops between the front and rear driveshafts. This RPM differences causes the viscous coupling to exert a torque on the slower shaft. It's been posted* (by YOU!) that this torque is 50 ftlbs at 150 RPM. I think it's proportional to the square of RPM, so the torque transfer goes up very quickly with speed difference.

The viscous coupling transfers torque based on the speed difference. Not having a front driveshaft is just like having the front tires on ice. The speed difference between the front and rear outputs is what causes the VC to send torque to the rear.

With a good VC, the car will drive without the front (or rear for that matter) driveshaft, BUT that will be at the expense of continuous slip across the VC with the VC transmitting ALL of the drive torque. This grossly overloads the VC, causes it to develop a lot of heat and can blow the seals out and spill the silicone all over the inside of the T-case, killing the VC.

* http://www.r3vlimited.com/board/showthread.php?t=337266

[spdracrm3]

" I don't feel like wearing out my keyboard educating you."

likewise!

just tired of the mis-information being spread about how this T-case works

"The viscous coupling transfers torque based on the speed difference. Not having a front driveshaft is just like having the front tires on ice."

wrong the output shafts will be turning at different speeds on ice if one set of wheels is slipping ,without a front shaft the outputs will spin at the same speed (other wise the jack T-case test wouldnt work)

[The Dark Side of Will]

just tired of the mis-information being spread about how this T-case works

Then stop spreading it ;-)

wrong the output shafts will be turning at different speeds on ice if one set of wheels is slipping ,without a front shaft the outputs will spin at the same speed (other wise the jack T-case test wouldnt work)

Here's the data point that demonstrates why it doesn't work the way you think it does:

Viscous coupling torque:
0 RPM: 0 fltbs
150 RPM: 50 fltbs.

That's it.

A conventional clutch pack LSD has a spring and frictional preload such that at 0 RPM it has 65 ftlbs of preload. You seem to think that a viscous coupling works like that. It doesn't. A viscous coupling does not have any preload torque.

So here's how things actually work in the T-case (using some convenient numbers for example only):

150 ftlbs at 1000 RPM at the T-case input
Planetary gearset wants to send 50 to the front and 100 to the rear.

With the driveshaft and 3.91 diff gears, this turns into 195 ftlbs at the front axle and 391 ftlbs at the rear axle and the car moves forward.

WithOUT the driveshaft, the front output will start to speed up. At 0 RPM, the VC exerts 0 torque, so the VC can NOT keep the front output from turning while the rear is stationary.

As the front output accelerates, the VC will develop increasing torque until it hits your data point of 50 ftlbs at 150 RPM. At that point, the VC is redirecting all 50 ftlbs of the front driveshaft's torque to the rear driveshaft and the car moves. The front output is turning 1075 RPM and the rear is turning 925 RPM with all 150 ftlbs showing up at the T-case input.

Obviously, the viscous coupling is dropping 150 RPM and 50 ftlbs... So we calculate 50 * 150/5252 = 1.43 horsepower. That's 1.43 horsepower or 1,065 Watts of waste heat developing in the viscous coupling. It dies quickly.

[spdracrm3]

just show me ONE IX that killed its VC by removing the front driveshaft.......

[The Dark Side of Will]

Irrelevant. (Difficult to diagnose; most people aren't abusive enough to just pull the driveshaft and go on their merry way).

Tell me why I'm wrong.

[spdracrm3]

Irrelevant. (Difficult to diagnose; most people aren't abusive enough to just pull the driveshaft and go on their merry way).

Tell me why I'm wrong.

so you have no proof ?

as stated ,every single IX i have followed a write-up on that pulled the front shaft due to stripped/noisy front splines and driven thousands of miles until it could be repaired had had Zero issue with AWD functionality once repaired (one was driven 3 years as a 2wd). so explain away or prove otherwise.....

[The Dark Side of Will]

No, I'm not going to go destroy my VC to demonstrate anything.

So every example that you've "followed" passed the jack test afterward? Links/Citations?
How many of those later had the T-case torn down to investigate the VC?

*IF* the VC survived, then that would show that it can take a pretty hefty continuous heat load. Impressive. I'd have to do some calcs on exactly how much, but it's a lot.

Even if that's the case, your understanding of the T-case is still flawed. :p