AWD system
 

Anyone know how similar the AWD system used in the 964 is to the one used in the Vanagon Synchro (bus)?

Randy,

As far as I know the two are quite different. There are two different synchros though. VW had the... Quantum wagon which was the exact awd system from an audi 4000, but the vanagon was true 4x4 4wd, not AWD.

C4s were the first and only all mechancial awd Porsche made, but they had TCS, and diffs, etc... which I don't think the vanagons ever had. The vanagon was more like a 4wd truck complete with "low gear" for slow speed off road use.

Vanagon uses visco clutch between rear and front wheels just like 964, 993 and 996 did. Note that first year of 964 C4 had completely different system derived from 959: a computer operated clutch between front and rear. System proved expensive and cumbersome and was later replaced by visco unit which hang on until 997. As far as I know, 997 is going to get a Haldex computer-operated clutch for C4 and Turbo.

That being said, neither C4 or Vanagon ever had "real" 4WD with center differential. They only had locked middle axle with power feed to front going trough some "slippage" component. Usually a visco diff or in rare cases (964C4 89', 959, 997) a computer-operated clutch.


Here's more info on Vanagon:
http://gerry.vanagon.com/cgi-bin/wa.exe?A2=ind9604&L=vanagon&D=0&P=99494

997s are still viscous... the 998s are getting the haldex though, which... i'm not too happy about.

I'll bow to Goran's knowledge on the vanagon though.

The 964 C4 AWD was very different from the 993/996 etc viscous longitudinally coupled AWD.

964 used a unique transmission w/ twin parallel output shafts and 2 hydraulically controlled clutch type diffs, one longitudinal and one transverse on the rear wheels
the hydraulic pressure is varied and controlled by a computer w/ long. & transverse accelerometer inputs as well as wheel speed inputs from the abs wheel sensors, std f/r split is 31/69 but it can be varied

the 993/996 e ts AWD is just a simple non computer controlled device that can be simple removed to convert to 2WD, not so w/ the 964 which is a very complicated integrated system.

I haven't a clue about the VW systems.

I have a friend with 89' 964 C4 and he said that computer operated clutch was only available first year and then replaced with standard visco setup similar to 993, 996 and (thanx for correction) 997.

Are all 964's equipped with this computerized clutch or was it really there only for one year?

Thanx.

Well I don't see the problem with Haldex. It's virtually the same setup as with visco, with a difference that it can be locked in a very short amount of time where visco diff need some time to shear/heat up.

I had a pleasure to drive SAAB 9-3 Turbo X equipped with new generation Haldex clutch and it worked flawlessly. It is set up so it locks in pre-emtive fashion w/o computer waiting for a wheel to slip first.

Your friend is wrong, all 964 C4 use the computer controlled clutch set up, It is very similar to the Audi V8Q setup, very space age very effective, very expensive.

later Audis and Porsche from 993 on use the viscus silicon center diff and a standard lsd or electronic ABD rear diff(sometimes both in the same trans).

the 964 trans is unique to that model and not interchangeable w/ others or changeable to 2wd mode, the 993 up trans can be swapped to other chassis or changed to 2wd w/o much fuss.

OK, but I fail to see similarities with Audi V8? Audi V8 (up to 1994) had a Torsen differential in the middle, Torsen in the back and open differential in front. UrS4 (1992-1994) had same layout but rear differential was open one that could be fully locked on demand (but it unlocked automatically above 15mph). Reason I know this is that I've just bought a V8 Torsen rear diff for my UrS4 (so I can swap in instead of old open one in the rear).


As far as I understand, 964 had basically same layout as 993 (no middle differential) except that there was electrically operated clutch instead of visco clutch between the axles. Audi Quattro (older ones) had a mechanical differential between axles but 964 had no middle differential at all but a clutch between pinion drive between front and rear differential.

Regards,

Nope, the first series Audi V8Q(I had a '90 3.6), not the later A8Q, had a computer controlled clutch pack system, if you insisist I can scan the literature, they did use a torsen rear differential. I believe that they switched to the torson ctr. diff for the A8, I know that my 2000 S4 and 2004 S4 both had/have torsen ctr diffs. I believe that my 4000SCQ and 90SQ also had torsen ctr. diffs, the 4000 did have a locking feature w hich was electronicly controlled but I think that the switch just actived a solenoid on the ctr diff.

Again I don't understand the reluctance of some people to believe factual info. The 964 and 993 are totally different AWD systems, do some research, please.

Dear Bill. I just did some research, at least for Audi V8 -90 3.6L. It doesn't have any sort of space-cadet mumbo-jumbo computer operated clutch differential. It has ordinary plain-vanila Torsen diff in the middle (just like all other Quattro cars made after it) and rear Torsen diff (which was in later cars replaced by open diff that was locked 100% with a vacuum-operated fork when button is pressed and unlocked automatically as soon as speed was above 15mph).

Take a look here:
http://www.vagcat.com/epc/cat/au/V8/1990/90/52/997727/

Article number for center differential used in V8Q -90 3.6 6-speed manual is 01E409751F. 5-speed manual used 016409751A.

http://forums.pelicanparts.com/uploa...1220129040.jpg

Regards,
Goran

Do some more research
http://forums.pelicanparts.com/uploa...1220129961.jpg


http://forums.pelicanparts.com/uploa...1220129989.jpg

OK, I did more research.

It turns out that auto equipped Audi V8Q didn't have Torsen center diff but open center differential that was lockable by computer. Manual tranny V8Q had indeed Torsen center diff. So we were both right and both wrong.

Further, it seems that 964C4 didn't have center diff at all, but fixed-split system with clutch in-between.

So to round it off, it seems that 993,996 and 997 have same system (fixed split) but electrically operated clutch is replaced by viscous device. 998 will replace viscous device back to electronically lockable clutch again, this time made by Haldex.

http://www.difflock.com/offroad/difflocks.shtml

Regards,

As far as I know there was no manual trans for the V8s in '90 maybe that came later and maybe the used torsen ctr diffs I had a '91 200TQ w/ manual that had a torsen ctr diff.

All 964('89 -94) C4 used the G64.00/.01 or /.02 trans it is significantly different from the 964 G50 or later 993 G50 which has an input shaft parallel to the output shaft, on a 993C$ the forward end of the output shaft is splined and a passively activated silicon fluid coupling sends power to the front diff . The fuluid coupling can be removed to convert to 2wd w/ no adverse effects on the trans. A new cover is used and the frt diff is also removed.

The 964 G64 on the other hand has a hollow output shaft, w/ another shaft running concentricly on roller bearings inside of it. The variable computer controlled clutch pack ctr diff is connected to the outer shaft, power is variably directed to the front diff. The inner shaft carries power to the normal rear diff.
964 cutaway of drivetrain
http://forums.pelicanparts.com/uploa...1220132842.jpg

964 clutch pack ctr diff
http://forums.pelicanparts.com/uploa...1220132931.jpg

964 G64 shafts #26 is the hollow outer # 23 is the inner
http://forums.pelicanparts.com/uploa...1220132962.jpg

993 G64 & g50 shafts
http://forums.pelicanparts.com/uploa...1220133428.jpg

993 ctr diff
http://forums.pelicanparts.com/uploa...1220133455.jpg

The auto ctr diff was an electronically controlled clutch pack like the 964, look at the V8 sales info posted above, it was not user lackable, the computer could send power to either end but could not lock it in the sense that the 4000 torsen or a Chevy truck ctr diff can be locked

I guess it depends on what you mean by a center diff and open, 964 fixed split is f/r 39/61 which can be varied on demand by the computer controlled ctr clutch pack diff. varying torque to the front axle. The ctr differential function consists of the concentric shafts and clutch pack

the 993 system is fixed 50/50 but again the viscous clutch varies power to the front diff, the differential function is 100% in the viscous clutch
993 G64



http://forums.pelicanparts.com/uploa...1220134744.jpg

Here is a photo of the LSD from the 964

http://blobs.autobahnparts.com/media...64462590000000

http://blobs.autobahnparts.com/media...64520270000000