dma550

Hey guys

Sorry for the barrage of spam lately.... I'm hot on the trail of a couple of cars

Having c4 as a stop word (allowed in the search) would help immensely... I can't search on c4 (too short) so here is the question:

The c4 drive is somewhat maligned by Anderson and others, though I find the car drives nicely, and fits my needs. My question is whether there are reliability concerns with the 964 c4 AWD setup, versus the other issues I need to know about when buying a 964.

For instance, if a 1990 c4 with 77K is well maintained (all intervals met), are there longevity concerns with the AWD setup, or is this perhaps not worth worrying over versus the other things that can go wrong.

Are there PPI checks (other than the obvious fluid leaks) that should be done with a C4?

Thanks again,

-DMA

garrett376

As usual, when something is more complicated, there's more to go wrong or break. That being said, I love my C4 - it is a little more maintenance - one more diff to drain and fill (probably never need to do that again!), and the PDAS locks need to be flushed every two years.

In everything I've heard from owners, there is no additional reliability problems, or longevity issues.

When checking the PDAS system, of course be sure all the warning lights appear with ignition ON. Do a search for "warning lights" to see some pictures (I've taken a few). If all the lights are there, a quick check of the PDAS warning system is to jam on the brake pedal a bunch of times really hard (when stopped of course) and the warning and alarm should appear/sound as the pressure drops. Also, you should be able to engage the system with the dash console lever, drive off and have it disengage (blinking light goes off automatically) at 25mph (somewhere in that speed range - see Adrian's book for specifics).

Also checking the front differential for leaks would be advisable, although it's probably more important to check the steering rack while you're up there!

I wouldn't shy away from a C4 - I am actually looking into a C4 as a race car so the same issues you're questioning, I've been researching for a while now.

That's my feeling from everything I've learned - I'd be interested to hear other's opinions on this issue, too (especially Adrian)...

C4TT

I can say that my 1990 Carrera 4 has been handling 650HP on the original drivetrain without a hickup. That must tell you something...

I would say stock power would last for a long while...

Cheers,

Greg

JasonAndreas

Use an asterick in your search term; C4* and you won't have to worry about minimum string lengths.

Youcef

I tend to agree with Garret on his comments and his advice on checking out the system operation.

I have 1990 C4 and I have over the past year replaced both diff lock actuators because they were leaking. I have no had a problem since these were replaced, but may have been in a better position to bargain if I had looked at these while I was buying the car.

If you do go for a C4$ I would suggest that you look at cars where the suspension mods have been done by the PO. If you intend to drive the car quickly in its stock form you will quickly get fed up with the understeer. The undertseer is easily reduced....buy Adrians book to find out how!

Youcef

Adrian

Dear Garrett,
My opinions and the way to purchase a 964 are all contained in my book. This is why I wrote it. The buyers guide (chapter 2) provides all the data to sort out good from bad.
As a basic comment though. My C4 (1989 model year) very recently did a trip to Le Mans and back. Approximately 10 hours each way and cruising at 160 kph plus on the autobahns. All I did was fill it up with petrol and wash it. This is the second year my C4 has made the trip problem free.
I allowed others to drive my C4 in France including a rennlister.
Most of the 964s I saw at Le Mans were actually C4s.
The AWD system is bullet proof. PDAS (traction control) is the system which may let you down which is exclusively C4. However this system provides the most reliable and confidence building assistance in the snow and ice.
Ciao,
Adrian
964C4

Johnny G Pipe

I'm about to put about 3-4000 miles on my 94,000 mile C4 in 10 days. I'll let you know.

garrett376

Hi Adrian - what do you mean by the PDAS system letting us down?

And I've been meaning to ask you - the torque split of the C4 - is that mechanically performed by the front having a more "flexible" driveshaft thus transferring less torque to the front differential? That's what your book makes it sound like, but I was not sure! Thanks

Adrian

I get a lot of emails from people with PDAS problems. Some are finger trouble, some are lack of knowledge about warn lights etc but many are genuine failures. This system is somewhat complicated and can be impacted by other work carried out like replacing the brake fluid.
If any system is going to cause C4 owners headaches it is going to be this one. The 964s are aging and the differential locks (multiple clutch plates) are wearing out. The control unit is not well placed and is subject to water damage (corrosion). In numbers the problem level is still very low but I expect it to rise as parts wear out. The lack of knowledge my mechanics of the system also adds to frustration and extended time in fixing it.

The standard 31/69 drive split is set up in gear drive (inline differential) which is the power transfer unit.
The actual torque transfer, rear to front or vice versa is initated by activation of the longitudinal differential lock and the additional torque is transferred by the flexible driveshafts to the front or rear differentials depending on which set of wheels are spinning (lost traction).
Ciao,
Adrian
964C4

dma550

Wow guys... thanks for the insight. Also, thanks for the wildcard tips.

-DMA

jeff4510

New post and new member Hi all, I have an 89 c4 that has a problem. After sitting for 24+ hours the awd idiot light comes on and stays on long enough to trigger the audible warning (10+ seconds). This only happens after sitting, it turns off quickly if it hasnt sat. How long should it take for that light to turn out? According to this http://www.porsche964.co.uk/technica...overviewR1.pdf it is a pressure warning light for the hydraulic AWD fluid. I see no visible leaks so what gives? Does anyone have experience with this?

Thanks!

garrett376

Sounds like you need to purchase Sweden's #1 best-seller - 911(964) Enthusiast's Companion - this will tell you that it's OK for the light to come on and go for a while.

I get the beeper when it sits for just 8-10 hours; that's after about 15-20 seconds of the light being on. As far as I know, it's OK.

Weissach

Is it possible to do away with the AWD and just make it a rear wheel drive??

Adrian

Yes, sell it and purchase a Carrera 2. Seriously this is the only way to convert a C4 to a C2 and have your life in order afterwards. Unless you have very deep pockets and then you can afford both anyway.
Ciao,
Adrian
964C4