C4 AWD system

carreracat · Mar 10, 2006

hello all,

i'm still looking for a 964 and currently have a C4 undergoing a pre purchase inspection.
can anyone tell me the basics of the operation of the the all wheel drive system?

i have heard conflicting stories. some say that the drive is split 31% - 69% at all times. others say that it varies depending on the road / driving conditions.
i have also been told that at anything above 50kmph the system reverts to rear wheel drive only and there is no override - this seems odd as i've through many corners at higher speeds where i would have thought AWD would have come in handy.

one last thing - on the C4 i'm currently looking at ('89) there is a round switch on the centre console just in front of the gear stick with an image of a AWD drive train above it - what does this do as the seller doesn't know!

Dave Wilkinson · Mar 10, 2006

Mark,

As you have been told, the torque split IS 31/69 under "normal" driving conditions. On the 964 C4, the AWD system uses a mechanical centre differential, unlike the later 993 and 996/7 cars which use a torque sensing diff. Outside of the "normal" driving conditions the C4's PDAS (traction control) system will take control of the diffrential locks to vary the drive according to it's movement sensors - a system which is completely automatic and not controllable by the driver, with NO facility to disable it. Rest assured, there is NO need to disable it since it works very well.

The rotary switch you mention onthe centre console is the diff lock actuation switch. If you get into a situation where traction is difficult, like loose snow or mud, the diff lock can be engaged to improve the traction. This diff lock will automatically disengage over speeds of 40kph. The small yellow light above the diff lock switch is the PDAS activation light - which will flash when PDAS normally activates in slippery conditions and will come on permanently when the diff lock is activated manually.

BTW, because of the mechanical AWD system, a 964 C4 should NEVER be towed with only 2 wheels on the ground and should NOT be run on a 2WD rolling road. In the same vein, don't be talked into disconnecting the front drive shaft to enable the rears only to drive a 2WD rolling road - is doesn't work!!!

Best of luck with your PPI - I hope it all works out and I'm sure you'll enjoy the C4. Keep in touch on the forum and let us know the outcome.

Best regards

Dave

Edited to correct the PDAS de-activation speed (to 40 kph instead of 30 as originally written)

carreracat · Mar 10, 2006

Mods on car:
Gemballa exhaust
Big Red Brake Calipers
964RS brake discs
Ruf suspension
Newly upholstered interior
Resprayed exterior (midnight blue)
18'' Ruf wheels
Carbon race induction kit

Just got PPI result back, what do you think?

Safety Related Items Requiring Urgent Attention

Several lightinf faults, rear fog lamps not working correctly. Front driving lights com on when the brake pedal is depressed. (Suspected to be caused by incorrect wiring after recent respray)
Windscreen wiper blades need changing

Non Safety Related Items Requiring Urgent Attention

Front oil cooler pipes leaking
RHF outer drive shaft CV boot split
RHR inner drive shaft CV boot leaking grease
Front boot floor badly corroded (completely through) under battery
Broken exhaust mounting bracket
A/C blower fan resistor needs replacing (no low speed)
Number plate lamps incorrectly fitted (respray wiring again)

Items Requiring Non Urgent Attention

Front antiroll bar drop link rubber covers broken
Slight engine oil leaks from timimg chain covers & chain box-crankcase joint
Slight engine oil leaks from cam chain tensioner cover
No space saver spare wheel
Front brake colling ducts not connected after respray

Non Critical Observations

Exhaust headers rusty
50% left on front brake pads
40% left on rear brake pads
Cylinder barrel air delfectors corroded

Dave Wilkinson · Mar 10, 2006

Mark,

I think the only issue which would worry me a little is the corroded floor under the battery. I suspect it's not an uncommon problem given what battery acid can do - remember the old Minis?? I suspect a new floor section would have to be welded in. The wiring issues are just annoying but not a major problem to fix. CV boots are not that horrendous although I think you'll need a 4 wheel alignment done after they're fixed - not a bad thing though since I suspect it's likely to need it. It looks like the previous owner wasn't too particular so alignment checks might have been ignored anyway.

The lack of the space saver wheel is no big deal - with the big red brakes fitted the space saver won't fit anyway. That's probably why it's been removed.

Given some of the tasty add-ons which are fitted the car sounds an interesting buy. The price needs to be right, of course, and it will take a good few hundred ££ to get it right. You didn't mention if the respray was in the original colour or if the colour was changed. A colour change will impact it's resale value but that may be less important if you plan to keep it longer term. I just love those 18" Ruf wheels!!!

Regards

Dave

Alexander_Drobik · Mar 10, 2006

I would walk away - the rust front floor is bad news and I am sure there are better cars out there. The respray and lack of putting it back together well also looks odd - what was it like before the rushed job I wonder? It does not like the car was well looked after to me.

chrism964 · Mar 10, 2006

I would agree with Alexander. Walk away. All that car will do is eat into your bank account. There are so many decent 964s out there why bother buying one with that list of problems even if it does have some good sounding add-ons.

carreracat · Mar 11, 2006

Thanks for all the advice guys (especailly Dave and Rob from previous threads too), I've decided to walk away. The owner did offer to have it all sorted for me but I got the impression he was just too keen on getting rid of it.

Unfortunately out here (Singapore) there aren't too many to choose from so it's back to the hunt for me! The mechanic who carried out the PPI (a Brit expat too) thinks he might know of another one in better condition for sale so I'll chase that up.

Just to make you all feel better, the UK isn't the most expensive place for cars this car was on the market for S$98,000 which is about GBP35,000, and that isn't a bad deal here. Think what you could get for that in the UK!! Turbo 3.3, possible a LHD 964RS....