Zf Differential....

[Guest ScotMac]

Hi, i am still attempting to scale the differential learning curve!!!

 

Does anyone have experience w/ ZF differentials? Mine appears to be locked up (could be an ebay special!!!). The cwp appears to turn about an 1/8", but then stops. It is not in the "car", but i have bolted it to my workbench, and cranked on the input flange a bit, and definitely does not want to spin. I don't have any experience w/ ZF differentials, but it doesn't seem normal.

 

One possibility is that the outside bearings will not spin w/out the flanges inserted, but that seems a little strange.

 

Note, the workings of a ZF LSD are very different from the fluid-dampening based stock sierra LSD's. As i understand it, the ZF is more of a mechanical LSD, and in fact the amount of slip/lock can be adjusted by adding plates and changing the "ramp angle".

 

TIA, -sm

[Guest salty_monk]

Does it work like a Quaife?? A clutch Unit rather than the sierra viscous?

 

I wouldn't have thought it should be jammed if you are trying to turn the input flange, should spin freely although perhaps you have to overcome the torque of the clutch plates or something??

 

Couldn't find any real info for ZF on the net? Do they have a tech page with an internal shot so we can see how it works?

 

Dan

[Guest ScotMac]

Hi Dan, i don't think it is clutch based, but i could be wrong. They actually supply the diffs that cateringvans use.

 

I also struggled to find info on them. IIRC, i think i finally found them to be some very large/low profile german company, that does wholesale automotive parts.

 

-sm

[Guest ScotMac]

OK. It looks like i was wrong. It is a clutch type. Here is what appears to be a good thread on the ZF for a capri:

 

http://www.turbosport.co.uk/showthread.php...09&highlight=ZF

[Guest salty_monk]

Not like a Quaife then..... http://www.quaifeamerica.com/ a clutch type...

 

By the way... whatever diff you have, I hope it's the 7" you've picked up as looking at this Quaife application list Merkur's had 7.5"... (Assume the L/W uses 7" as most Sierra's did...)

 

This is interesting too, from Caterham site... basically says Quaife's don't work on "cateringvans"...

 

The solution to this problem is to fit a more complex differential with limited slip. There are several types of limited slip differentials (LSD) including the popular torque-sensing type, but this does not work satisfactorily with De Dion suspension. Therefore, we have developed a bespoke version of the ZF plate type LSD with ‘ramps' especially selected for the Caterham application.

 

I guess the custom ramps either lower or raise the torque require to lock the plates.

 

As to your diff, I can't see any reason why it wouldn't turn at the input flange, the clutch plates should not even be engaged at that point as surely it would simulate going in a straight line?? Maybe it has been rebuilt too tight or something??

 

Dan

[Guest ScotMac]

Found the ZF web-site, it is (quite appropriately) www.zf.com.

 

In typical german fashion, the site appears to be very well structured, w/ tons of information...and i can't find anything on ZF differentials!!!

 

I also took a look at the some of the caterham forums. They appear to be even more clueless than i am.

[Guest ScotMac]

Exactly my thought, Dan. ie, that it should spin, atleast until the diff is attempting to control the spin, when a wheel looses traction.

 

But yes, now that we know it is a clutch type, i am little less concerned. Also, the guy that sold it to me said that it had been taken out of a car, and fully reconditioned/rebuilt...so, yes, it could just be that the plates are too tight.

 

I am just worried that i will get it into the car, and then it won't work. And if you remember, the diff on the l/w is pretty much in there*permanently*!!!

 

Oh, and yes, it is a 7".

 

Thanks, -sm

[Guest ScotMac]

Isn't it true that even if the plates are too tight, it should still spin....since the plates locking up should just turn it into a "welded" diff, which obviously still spins. A welded diff would just not allow the wheels to spin *independently* of each other, but would still allow basic movement.

 

Hmmm. Want to continue w/ the build, but am stuck on this diff.

[Guest elwe]

How much force are you applying?

 

I have a spare non LSD sierra diff and it takes a long of force to turn the diff by hand using just the flange. I know the diff was working fine before I dismantled the car.

 

If its a push in type does this mean it doesn't have any oil in it? and might not have for a while? This might explain why its difficult to turn by hand.

[Guest ScotMac]

Right, Tim, I also thought of the oil issue. I clamped it down to my work bench, and cranked on the input shaft w/ a large torque wrench!!! It didn't budge (other than the 1/8" i mentioned, before locking).

[Guest ScotMac]

BTW, it looks like both the pinion and cw move that 1/8"...so, what is stopping it is in the diff, or in the outer bearings.

[Guest micky bigthumbs]

i found this on an alfa site

 

 

Gripper racing differential, 70% lock up on load, 40% lock up on over run, a racing must!

 

Its unique design gives it 70% lock up under acceleration ensuring huge traction out of the tightest of hairpins, whilst the 40% lock up on overrun allows the car to be positioned with greater accuracy on the approach to a bend.

 

The design of the original 2000 type Alfa ZF LSD means that preset lock up reduces with use, leading to frequent and expensive rebuilds to maintain in good condition. The Gripper Racing Diff does not suffer from these problems, allowing you to 'fit and forget', rather than 'fit and worry about the next time you need to rebuld the LSD'!

 

The Gripper diff is also available for fitment with small 1600 halfshafts which drastically reduce the unsprung weight of the diff unit over a 2000 type ZF LSD and thick 2000 halfshafts.

 

As fitted in the Alfaholics 2.0 Sprint GT race car. This diff is a racer's must have item!

 

 

 

with the l/w diff being hard to get to do you want frequent strip downs

[Guest salty_monk]

Well if it is one of those "gripper's" he won't have to...

 

The Gripper Racing Diff does not suffer from these problems, allowing you to 'fit and forget'

[Guest micky bigthumbs]

I dont think it is a gripper the plates were different ...i'll try and find the pics

[Guest ScotMac]

I agree, if the ZF was going to need constant rebuilding, it would NOT be a good match for the l/w.

 

I think it is just advertizing for the gripper stuff. ie, i am not convinced that the ZF stuff need rebuilding all the time. Also, i haven't seen a gripper for the sierra diff, and it is more expensive. I have seen many racers quote the virtues of a ZF diff (i bought it from a racer).

 

Well, a ZF that is not locked up, that is!!!!