[torsen] Re: Torsen differential

Brendan Rudack rudack at ucsub.colorado.edu
Tue Nov 19 02:30:07 EST 2002

On Sun, 17 Nov 2002, Brett Dikeman wrote:

> The ONLY, and I repeat ONLY cases of failed torsens which I have
> heard about in 7-8 years, have involved:
> -monkeylads putting vehicles on 2-wheel dynos
> -towing with only two wheels off the ground
> -lack of tranny oil or similar problems(improper oil, too-old oil, etc)

Here's another case to add to your list.  Our Formula SAE(FSAE) team broke
the Torsen in our car during practice last summer.  FYI a FSAE car is an
open-wheeled, 5-600lb, 600cc (~75 hp, <45 ft-lb torque), rear
drive,racing-slick clad,
mid-engined racecar.  We use a Torsen in a rear-diff application.  The
Torsen in question is the older style M021-DHU (university special) like
the unit found in a '88 90Q.  Anyhow, it appears that shock-loading broke
a thrust washer, and bits and pieces chewed up the bronze bushings.  I was
driving and noticed that car seemed very
tail-happy and quite exciting to drive.  The diff was not biasing.

> -opened up a used torsen diff and inspected it for wear?(no, since
> they're not user serviceable)

Guess that depends on the user....
They are servicable.  I have all the specs for the various, bushings,
bearings and thrust washers should you wish "tighten up" your Torsen.
Torsen, happily provides this info. on the basis that the user will
machine the parts.  The Torsen blueprint (free) even provides re-assembly
notes to insure the diff. is timed properly.

Getting the car running again before an autocross was actually quite
amusing.  The guys thought we were finished, so I brought in an old 01A
trans I had laying about. Turned out to be great for parts...
They were all shocked... Darned Audi owners and their darned crap.

> The problem in road driving(Audi learned this way back) really
> appears to be that it has ABSOLUTELY NOTHING TO DO WITH RACING.

Would shock loading occur in a street car if wheel spin on snow/ice were
present following by the tire(s) regaining traction on the pavement??

Brendan Rudack
University of Colorado
Mechanical Engineering
"complaining is like a rocking chair.  It gives you something to do but it
doesn't get you anywhere"

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