Limited slip differentials on vintage F cars

I'm pretty sure my 330 has "positraction"...it leaves two rubber stripes when the rear wheels spin.

It has all the 60's muscle car stuff...3 deuces, tuned headers and dual exhaust, 4 speed trans, positraction, puts out 1.2 horsepower per cubic inch.

I know that's not much of an answer...I can only guess that it was a standard feature.

 

alot of models have clutch type zf lsd

 

Ferrari used the ZF limited slip differential long before Chevy - Ford etc. Here is one with the matching outer case removed - from a series II 500 Mondial.
Image Unavailable, Please Login

 

This type is commonly reffered to as "cam and paw". I found this type in factory TR racing cars.

 

Cam and pawl, also known as Chicklets.

 

While the early race cars had the cam and pawl differentials from the 275s and up pretty much everything has the clutch type positraction differentials. Up until recent years with E diff cars which are basically mini auto trans clutches.

I am sure there are exceptions which Dyke can comment on.

 

This is going back in this thread, however, the original ZF limited-slip unit is totally different in concept from the later American clutch type limited-slip differentials.

 

Brian: Early 275's used the cam and pawl units. At roughly the introduction of the Long Nose cars, the factory began to use "clutch" type LSD's. All 330 GTC and later cars used Clutch Type units. The ZF cam and pawl unit does NOT need LSD additive in the gear oil. No clutches, no additive needed.

 

I'm not sure what you mean by "later", but I've always considered 1957 and up Chrysler "Sure-Grip" being quite similar concept to ZF limited slip setups I've encountered in Daytona transaxles.
Or perhaps I'm not looking at or understanding them correctly ?

 

You are thinking of the ZF clutch type. Not the ZF cam and pawl type.

 

Timo: Daytona's use clutch type LSD's, similar to the GM, Chrysler and Ford units.

ZF developed the Cam and Pawl style LSD around 1935 for use in the Mercedes-Benz Gran Prix cars. Most Italian and German performance cars of the 1937-65 era used this style LSD. It was amazing for its time, but is not actually a very good way to limit slip. As Brian stated, the "chicklets" do only a fair job of locking the axles together and they are a high wear item. We replace them consistently in the Maserati race car transaxles. Luckily, Crosthwaite & Gardiner can supply them today.

ZF went to the "American" style LSD, as I stated, in about 1966 and this is what is used on the late 275, 330 GTC, Daytona, Boxer, etc.

While the "American" style unit is superior to the original 1935 ZF design, it also has its limits, as if you want aggressive locking action, as in racing, clutch life is not very long, and the units can "ratchet" and "clunk" when the car slowly turns sharp corners. Modern additives can minimize the "clunking" but they also reduce the effectiveness of the limited slip action.

Finally, for American cars, the old Detroit Locker style is extremely effective and durable, but very "clunky" and "crude" in action. 1965 Shelby GT350's used them and the next year they went to the standard American clutch style as owners thought they had destroyed the entre rear axle when they turned a slow, tight corner.

Enough of this, hopefully my ramblings have made some sense.

 

Sorry. Had to...

 

Brian & Dyke,
I wasn't aware of ZF's history with these and my ZF differential/LSD (<- that just seems/sounds weird) experience is only with transaxles found in Daytonas and alike, but thanks to Dyke's brief summary I learned something today.
And yes, I've heard of Detroit Locker, but never serviced or worked on one.
There was another type used among some hot rodders when & where I grew up, but that involved some welding ...
... and they didn't seem to last very long nor offered any limited slippage.

 

Thanks to Dyke I did too. Was not aware of the origin of the cam and pawl type but it makes perfect sense. Coming off turn 1 at Avus they needed both tires driving.

 

The Detroit Locker was offered as part of the "Drag Pack" option on the Ford 9 inch rear on select muscle cars.

 

Dyke,

Appreciate your early history lesson. All I have to offer is this shot of a chicklet, only the end views show in post #4.

Best regards,

Robert


Image Unavailable, Please Login

 

Was not aware of that. Have rebuilt a number of 275 transaxles including long nose comps and never ran into one.

 

I am in the midst of rebuilding a 275 GTB/4 transaxle that suffered some minor damage to the LSD. As many of the experienced people here know the ZF Clutch type differential has many adjustments to regulate the amount of lock up or breakaway torque.
The main method is adjust the stack height of the clutch pack with clutch discs of varying thicknesses. These were not easy to find but were at one point routinely available. I have actually reproduced some thicknesses.
ZF engineers were clever and racers that still use this set up won't use anything else, many going as far as installing shims to the clutch pack to achieve the exact amount of lock up desired.
The breakaway torque is of course related the engine torque so different dispalcement engine will require a different clutch pack to achieve the same result. Unfortunately the only clutch discs available from Ferrari parts vendors are 2mm.

 

You can ask limitedslip.de the guy knows everything about ZF Diffs. He has a ton of parts available. He also suggests diff settings for specific cars and needs.

i only mention him, as i‘m a very happy customer. He gets money from me, not the other way around.

 

W O W ! ! !
a very informative side. thank you for posting, never heard before

 

The site appears to be entirely in German. Does he speak English?

 

Hi David

I think so. If not, drop me a PM and I can translate.

 

If you right click, it will allow you to translate. Took me awhile, but well worth it.
Regards,
Alberto

 

Just posted an ad in Classified for some tools and parts I had reproduced. Please check it out.
Image Unavailable, Please Login