?? Regarding testing a Quaiife ATB DIFFERENTIAL

[mspirito]

We have recently installed a Quaife Limited slip differential and are unsure of how to test this. It seems as though we cannot get the two wheels to spin independently of each other. Is the Quaif edifferent from other LSD's in that sense that it takes much more torque to break them loose?

[Walt Fricke]

Jack the car up on one side. With a wrench turn the engine over. The raised side wheel should turn, and the wheel on the other side should not be trying to drive the car off the jack.

The Quaife supposedly provides no useful lock if one of the wheels is unloaded entirely, or loaded no more than some small percentage - say 10%. So this check should tell you.

I think there is enough internal friction, though, that with both wheels off the ground, turning one will cause the other to turn in the same direction if the transmission is in neutral. However, by holding the other wheel, you should be able to turn the wheel and have all that turning be done in the transmission.

I can't say as I have ever thought to test the couple of Quaifes I have installed in my cars. Spent plenty of time getting the lash right, but that was it. They seemed to work fine (within their limitations) on the street, autocross, and track.

[Matt Monson]

A Quaife isn't a limited slip differential. It is a torque biasing differential. If you jack up the car and spin one wheel the opposite will will spin the opposite direction.

Why do you feel the unit needs to be tested?

[mspirito]

When the car is up in the air on the rack we cannot get the two wheels to spin independently at any time. It acts as though the differential is fully locked all the time, we have put quite a bit of torque and cannot seem to get them to act anyway other way than fully locked. The differential looks really good I bought it from a parts dealer who said it was in great shape but we are unsure as to how this differential is supposed to behave. Because it is unlike the normal differentials that we have traditionally tested with the torque wrench. Thanks in advance for the help

[Matt Monson]

Which direction are the wheels spinning? In the same direction?

Let me finish dinner and I will get you some internal pictures that might help.

[mspirito]

They are spinning in the same direction thank you

[Driven97]

That does not sound right. It should act like an open diff (opposite directions) with the car in the air.

[mspirito]

Exactly that's the Issue. Doesn't make any sense it looks beautiful

[Jon B]

Originally Posted by mspirito

...we cannot get the two wheels to spin independently at any time. It acts as though the differential is fully locked all the time, we have put quite a bit of torque and cannot seem to get them to act anyway other way than fully locked.

You may have the wrong axle flanges necessary for this differential, and they are locked on to the differential housing because they are too short.

[Geary]

You haven't told us what year and model vehicle. It wouldn't surprise me one bit to learn that the G50 model Quaife is STILL made incorrectly after all these years.

The issue is that while one flange installs correctly, the other sits too deep. The deep side locks up on the diff body.

The fix is a small shim installed beneath the stub.

[Jon B]

Originally Posted by Geary

The issue is that while one flange installs correctly, the other sits too deep. The deep side locks up on the diff body.

Paul, I'm not sure what you mean by "sits too deep".
A flange that locks itself to the differential housing does not extend far enough into the differential, and does not fasten itself to the diff internals. It would be too short in depth.
As I recall, early Quaife TBD's for Porsches were based on dimensions of the 69-75 ZF LSD, which used flanges 5mm longer than the standard Porsche differential.

[Geary]

I guess we need to learn what year car we're talking about.

To reiterate: on the G50 model, the design was (still is?) incorrect, so the flange's shaft on one side ended up being too short .. but because it isn't the flange that's incorrect, I say the flange sits too deep.

So, pretty much the same issue, but only by 1-2 mm, not 5mm like the early flange length difference.

[mspirito]

Mystery solved , whoever had reassembled this differential had flipped around one of the internal gears thereby making the endplate offset three extra millimeters . This resulted in the differential staying locked all the time. Once we disassembled the differential it was obvious that this gear had been positioned 180 degrees upside down therefore making the differential essentially locked and useless.

In the photograph you can see the gear that stands proud. Where I have indicated with the drill bit there was a gap of 3 mm because the gear did not sit into its normal recess. Once we figured that out everything went together properly. Unfortunately we had sent the transmission case cover to the machine shop to mill off 3 mm before realizing that the differential had been assembled incorrectly. This is unfortunate because the person I bought this part from is a reputable seller and his contact that sold him this piece apparently was not representing this differential for what it was. Such is life
Turning a four or five hour differential job into a 10 hour job. With the added expense of machine work.

[PcarPhil]

Interesting. My 3.6 G50 cab has a Quaife ATB diff installed (I purchased the car this way). I'm thinking I'll test the diff by spinning the wheels with the car in the air and see what happens.

The diff I have seems fine. I know it's providing torque biasing (locking) and I think I'd know if it wasn't unlocking but I'll test it to find out for sure.

[Driven97]

Well, that's a bummer, but at least the mystery is solved.

[Matt Monson]

One should never need to machine their case or sidecover when installing an aftermarket differential. Folks should take that as an indication that something is very wrong and not proceed without further investigation if they ever encounter a similar situation. Glad the op figured it out and resolved it. If you tell us what gearbox this is, someone here may be able to provide a replacement sidecover for the one that has been machined.

[Tippy]

No, he's not going to tell which gearbox it is, Matt!

[mspirito]

It's a 944 Turbo gearbox that is being used with the 6.2 GM Erod motor

Requisite 911 content

[Tippy]

Sweet!

[Walt Fricke]

The machining just provides more clearance than is needed now that the diff is correctly assembled?