Rallas

iTrader: (9)

I was hooking up my NA6 VSS signal from the cluster yesterday and testing it in Tunerstudio while the car was up on jackstands. While doing this I noticed that the passenger side wheel was spinning a lot faster than the driver side. This is on a Torsen 3.636 diff. I was only idling the engine in 5th and 6 gear with speeds around 30/40mph.

Is this normal or is something wrong with my Torsen?

I had a Torsen 4.3 for years before I made my recent VVT/6 speed/ Torsen3.636 swap. I never noticed this behavior on the 4.3. I still only have about 100 miles on the new engine/clutch so I have not driven it in anger enough to feel if the Torsen is working in turns.

fooger03

iTrader: (2)

E-brake starting to stick?
Is passenger wheel warmer to the touch after driving?

technicalninja

No load at all on the driven wheels commonly equals different speeds unless you are running a spool or have welded spiders.
Any form of "differential" can vary wheel speed when there is no load. This is how you can turn the car without either spinning the inside wheel or dragging the outside.

If you have ever pushed a locked rear end car around you will notice that it pushes fine in a straight line only. The slightest amount of turn locks the puppy down so you end up "moving" it on a floor jack under the driven wheels.
It is a PIA to do. That same car is a bitch to drive normally but works fine when driven in a "sporting" manner...

Torsens can spin a single wheel if it is off the ground (only one) or on a frictionless surface (ice)

Every single independent rear suspension car I have tried a locked rear end in has ended up breaking stuff; axles, hubs, rear end housings and mounts.
It just doesn't work very well.
The welded rear end or spool works best in a solid rear axle car, Mustang, Camaro, drag race stuff...

Rallas

iTrader: (9)

First thing i checked was to see if parking brake was dragging. I did not notice any parking brake dragging when turning the wheels by hand. I did not check to see if the rotor or hub was getting hot. Might try that again.

I understand that a Torsen will spin the wheel that has no traction, but I was not expecting this behavior with both wheels in the air.

I am now also hearing a weird squeek coming from the rear end under deceleration. Under acceleration I don't hear anything. At least not over the exhaust.

Godless Commie

iTrader: (2)

Unless the diff components are welded together, a diff will favor the axle it is directly connected to if both wheels are spinning in the air, ie, with no resistance.
That happens to be the passenger side in a Miata.

By the very definition of a diff setup, if you were to stop one wheel, the remaining one will rotate at twice the speed. This is because of the relationship between the crown and spider gears.
And by "twice the speed", I mean, if the driveshaft is spinning at 41 rpm (assuming a 4.10 diff), the wheel will spin at 20 rpm instead of 10. If both wheels are allowed to rotate freely, both will spin at 10 rpm.

Based on these facts, a noticeable speed difference between two wheels spinning in the air is expected.
"Expected", because a road car on jackstands is not a lab specimen in perfect conditions. There is drag, friction and the like in a number of rotating components.
As soon as the wheels contact the pavement, all those tiny impediments become moot, and the wheels rotate in unison, because they have bigger fish to fry - like, dealing with a metric ton of inertia.

CoralDoc

This summary sentence made me LOL. Nerds unite!

Rallas

iTrader: (9)

I got a chuckle out of that statement too.

Rallas

iTrader: (9)

So I tried the same wheels spinning example with my brother's 99 with 4.3 Torsen on the lift. Both of his wheels were spinning an nearly the same speed, at least I couldn't tell an obvious difference.

Put my car on the lift and did the same thing. At first in 1st gear and idle speed it looked like both wheels were about the same speed. As I changed to 2nd and up to 4th the passenger wheel began to spin way faster than the driver side. At one point the driver side wheel was spinning so slow that could stop it with light pressure. There was almost no drag on the driver wheel. I noticed no appreciable differences in wheel, hub or rotor temperatures during this test.

Then I removed the calipers and pads to make sure I had no brake drag going on. Still the same result in difference in rotation speed. Though some of the chirping noise went away. I also discovered at this point that there is a very faint noise coming from the 6-speed that sounds like what I hear in the cabin. I couldn't load the drivetrain up enough to see if I could recreate the sound that I hear on deccel or in reverse.

I am getting closer to 250miles on the new engine/clutch and drove it a little harder yesterday. It felt like the passenger wheel was the spinning every time I got on it, almost like an open diff does. Not sure how to measure this for sure, whish I had my VR sensors hooked up on both rear wheels to check actual wheel speed vs. just my paranoia convincing me that the passenger rear is always the first to break loose.

codrus

The one to break loose first is going to the be one with the least traction. In a straight line with the tires, surface, etc being equal that's going to be the one with the least weight on it.

--Ian

Rallas

iTrader: (9)

I fully understand this principal, I just do not remember my old 4.3 Torsen breaking loose the same wheel every time, no matter if going straight, left or right.