How to tell if Shelby Limited Slip

[Joe Anderson]

89 CSX # 53 , Shelby test car used in the Motor Trend Special Shootout Article ( may have the rare limited slip ).

Just purchased this car last week......

And will be lifting the car on a hoist this afternoon,how do you tell if it has the limited slip.
Was told that the Shelby unit was a little different,and may engage at different points?
Anyone know how to tell if it has the 1989 Shelby Limited Slip,or what style it was based on?

Thanks,Joe

[looneytuner]

I'm no ex spurt bit of both wheels turn may be an indication. I think with a regular dif you can turn one wheel and the other will not turn. Or just do a burn out

[tryingbe]

Jack up the car, put it in neutral, turn one wheel by hand.

If the other wheel turns the same direction as the wheel you turn by hand, you have some type of LSD. If it doesn't, you don't.

You can also verify which type of LSD (block lsd or obx/Peloquin/Quaife) by taking an axle out and look at the differential.

[Joe Anderson]

Think I did that with a regular Dif .....and they both turned in opposite directions ( like there was still some pressure on the other wheel )
Any other Ideas?

[A.J.]

Think I did that with a regular Dif .....and they both turned in opposite directions ( like there was still some pressure on the other wheel )
Any other Ideas?

There are no other ideas. Tryingbe is correct. If both wheels spin the same direction in neutral you have a limited slip. If they turn opposite directions then you do not. Asking the question different ways will not give you a limited slip diff if you don't have one.

[Joe Anderson]

Ok,

Thanks for that....just wanted to make sure there was nothing else to figure in

[Chris W]

Ok,

Thanks for that....just wanted to make sure there was nothing else to figure in

Joe,

From what I recall the Shelby posis did not kick in until enough centrifugal force (speed) was achieved. Jacking it up and hand spinning would indicate an open diff so using the methods described above would give you an inaccurate conclusion. I believe removing the cover would be one of the only ways to determine if its a shelby "cheater" posi unit. They were designed to simulate non-posi units so that the officials would not know they had LSDs.


Chris-TU

[Joe Anderson]

Chris,

What was the Shelby unit based on,and any articles or pictures anywhere?

[A.J.]

Joe,

From what I recall the Shelby posis did not kick in until enough centrifugal force (speed) was achieved. Jacking it up and hand spinning would indicate an open diff so using the methods described above would give you an inaccurate conclusion. I believe removing the cover would be one of the only ways to determine if its a shelby "cheater" posi unit. They were designed to simulate non-posi units so that the officials would not know they had LSDs.


Chris-TU

Since he has an '89 he's probably got a 555. It's not as simple as taking the rear cover off since it also holds in the differential itself. And since it's a 555 he's probably got the extra spider gears which is better than an open diff but not as good as a true LSD.

[Dr. Johny Dodge]

people sometimes confuse limited slip diffs with positraction (GM) ,sure grip (Cryco) or tracksion lock (Ford)

limited slip is just what is says it is in name
it transfers power away from any wheel that is overspeeding compared to the opposite wheel and often leaves a burn out mark that has one stip starting before the other .. or dug slightly deeper

posi , etc is full time power to both wheels but with a diff that allows one wheel to speed up of slow down to allow for the inside radisus the wheels travel turning a corner

now , a detroit locker type diff is full time power to both wheels that keeps something like an old trans am car running straight at power when a wheel is on a different surface than the other - like one wheel's in the dirt or grass and the other is still on the track
this keeps the car from turning by being steered by the rear axle

[85boostbox]

Well said doc. In my Silverado SS is have a G80 locker. Front differential is limited slip. And transfer case is a viscous coupling which works a lot like a limited slip.

[4 l-bodies]

Here is pic of claw and pawl cheater diff.that Shelby sold. There also were some other LSD's as well that sold thru the whittier plant. I thought it was only available on 525's. Had one in SC that I sold. People called them by lots of names; Chicklet was one because of parts inside resembled the gum (see first pic). As Chris mentioned it would pass the open wheel inspection looking for LSD diffs if rotated by hand. Woked like centrifugal clutch and would lock up with increased RPM.
Todd

[Joe Anderson]

Would the unit look physically the same in both the A555 and A525 ?

Could you see it in both transaxles when the Dif cover is removed?

Really want to know the Motor Trend 89 CSX has the Cheater Posi.

[tryingbe]

You can also verify which type of LSD (block lsd or obx/Peloquin/Quaife) by taking an axle out and look at the differential.

Do that.

[zin]

Interesting, I'd never really considered the need for a "stealth" LSD, and though I was aware of the "chicklet" design, I never really considered it due to its design being prone to wearing out, loosing its effect... but with the stealth requirement, it (along with viscous couplers) suddenly rise to the top!

Mike

- - - Updated - - -

Interesting, I'd never really considered the need for a "stealth" LSD, and though I was aware of the "chicklet" design, I never really considered it due to its design being prone to wearing out, loosing its effect... but with the stealth requirement, it (along with viscous couplers) suddenly rise to the top!

Mike

[4 l-bodies]

Interesting, I'd never really considered the need for a "stealth" LSD, and though I was aware of the "chicklet" design, I never really considered it due to its design being prone to wearing out, loosing its effect... but with the stealth requirement, it (along with viscous couplers) suddenly rise to the top!

Mike
Mike the claw and pawl doesn't wear out. The only weird thing with the C&P design it sounds funny sometimes when making left turn under heavy throttle. Mine was in my SC for 20+ years with no signs of distress. Are you confusing that with the Phantom grip? Those wear out and lose their effectiveness, not this one.
Mike Bachman told me a million years ago of a couple or few LSD's for 555's that sold through Shelby dealership. I do know of one GLHS that has one installed with a555. Entire tranny came came Whittier plant. If memory serves me diff was part Siemens and part Dana. Then there was the Future Auto clutch type LSD's.
Here is a couple other pics of yet another LSD for our cars from WAY back in the day. I don't know much about this one either except it was installed in either a a525 or a465 4 speed. Looks like it had a rough life. I sent these pics to Cliff Ramsdell years ago and he said he has seen a few of these too. Can't remember what they were called. Guy that owned this raced ice and road rally stuff in L-bodies in WI and MN.
Todd

[Joe Anderson]

Wonder how many were produced by Shelby,and what there worth in dollars?
Which one was more common in the A555.

[cordes]

If it is a Shelby 555 unit then it should be a viscous coupling type of diff. I think the only way to verify this is to pull it and look. I have one in 89 CSX 42 but I have not seen it yet. I want to pull mine to see if it is set up like a 555 diff. If it is then I'm pretty much stuck with the 3.85FD. I would love a 3.50FD to drop the rpm at freeway speeds. We were turning close to 4K rpm most of the way back from CA.

[zin]

I think that's a Torrinson LSD, saw them in the GM performance parts catalog in the early 90s for fwd cars ...

The "chicklet" style would "overrun" the "chicklet" which could cause wear, eventually making them ineffective, and possibly causing other issues, not that this would be a problem in a situation where things are checked regularly, such as racing.

The basic design seems flawed to my mind, but I'm rarely thinking in terms of niches like race only, mostly long term durability.

I will admit, given a choice between having one of these and no LSD, I'd take it in a heart beat!

Mike

- - - Updated - - -

I think that's a Torrinson LSD, saw them in the GM performance parts catalog in the early 90s for fwd cars ...

The "chicklet" style would "overrun" the "chicklet" which could cause wear, eventually making them ineffective, and possibly causing other issues, not that this would be a problem in a situation where things are checked regularly, such as racing.

The basic design seems flawed to my mind, but I'm rarely thinking in terms of niches like race only, mostly long term durability.

I will admit, given a choice between having one of these and no LSD, I'd take it in a heart beat!

Mike

[cordes]