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Thinking of buying 91 c4

A car salesman friend has a 91 c4 RS "clone" I can buy for around 17k. 120 k, all receipts allegedly upgraded flywheel, distributor, not sure about head gaskets.Red w/ black coupe . Supposedly super clean and well done. cup wheels, door pulls etc etc. I am concerned about the all wheel drive system, Everything Ive read says stay away due to complexity compared to later 993. If and when they break, what happens to the drive???. Does the car not move??? does it go slower???, Can you simply remove the forward driveshaft and just use the rear wheel drive. I dont care if it stops working, as long as the car will act like a C2. I dont need this car, as I have an 86 cab, and a 86 Ferrari 328, audi allroad, Thought it might be a fun car I can drive in the winter when the roads are dry. Tepps

Old 10-03-2012, 04:58 PM
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I'd be concerned too, there are all sorts of very expensive things that can go wrong w/ it.

Exactly what depends on the part that fails.

Unlike 993, 996, 997 to eliminate awd the trans needs to be replaced
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Old 10-03-2012, 07:24 PM
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Ari
 
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I have a 1990 C4. The AWD is phenomenal and I am more confident in it than I am in my 4x4 Silverado in shallow snow, ice, etc. If the AWD fails on me, conversion to RWD is a possibility though it involves replacing the transmission and some other stuff. That's an if. My car has almost 160,000 miles on the clock and the AWD is working perfectly. Your mileage may vary, of course, but I am so far happy with mine. The basics of what you need to know:

964 AWD is less transparent than later systems, in both the good ways (can deliver more power to front) and the bad (understeer)
964 AWD is more complicated than later systems, meaning it is harder and more expensive to fix if problems arise
964 AWD is harder to remove than later systems, as it will not drive with the front differential missing the way later systems will
Old 10-03-2012, 08:31 PM
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Gotta say I'm reluctant to go against Bill on anything Porsche related but the first-gen AWD setup has proven to be very robust. A search of this and the forum on Rennlist will reveal very few failures of any sort. There's a couple accounts of major mechanical issues, the controller can sometimes become corroded via leakage from the 'intensive windshield washing' tank, and sometimes one of the difflock actuators can leak requiring an expensive fix.

Generally accelerometer issues can be rectified by a good cleaning.

Aside from that it's just typical Porsche stuff that would be common to the C2.

I cured the understeer (at least minimized it) by removing the front swaybar; easy, cheap, and it adds lightness.

$0.02
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Old 10-04-2012, 08:45 AM
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early c 4 issues

Thanks for all of the replies. I am trying to get a handle on what actually happens when the system breaks.For example, does the car stop moving, lock up? No power etc, spew fluids .etc, etc. I am used to working on the audi AWD, which must be the same as the later 993 . Basically they always work, never break , never need service etc. etc. Are the parts impossible to obtain, ? service manuals, unobtanium etc etc. I dont mind taking an educated gamble,hoping that nothing catastrophic will occur. That said I could probably buy a 996 ,but I am not comfortable with the possibility of engine grenading IMS , d chunks etc. Some cars (VOLVO) have driveshaft and tranfer case issues, and the owners can remove the rear driveshaft and be on their way. A 95 or 96 993 would be nice, but it seems they cost twice as much. I am looking for a DD that I dont mind taking out in rain .Car will not be babied , basically a fun winter car, and I still have the Allroad .
Old 10-04-2012, 06:31 PM
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Ari
 
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Get the 964 if you intend to drive in actual winter road conditions. It is a more capable car on those conditions than any other. As to what happens when the AWD dies, it's uncommon enough that I have not read any first-hand accounts.
Old 10-04-2012, 07:07 PM
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Well, not everyone agrees but some have done well with the 964 C4. Others prefer the 993 styling anyway. That said, I might be interested if you pass.
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Old 10-04-2012, 07:34 PM
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Quote:
Originally Posted by tepps View Post
I am trying to get a handle on what actually happens when the system breaks.
As with anything based on UFO technology and more complicated than the space shuttle it depends on what lets go.

If it's a controller issue you get warnings lights, no ABS, and no PDAS (first-gen stability managment). The AWD is mechanical, so that will still work: 33% front/67% rear torque with open differentials.

If it's an accelerometer issue I think ABS and PDAS become somewhat hyperactive, but I've never had the pleasure and can't say for sure.

If you get an actuator leak I think you may have to replace it; it's rare enough I don't think anyone's come up with a freelance solution.

If Something Major breaks in the trans or differentials... you're flatbedding home.

Another known issue (which may also affect the C2) is bad solder joints in the dash clock. Seems odd, but a *lot* of info is passed thru that component so it's more than just a clock. Search the 964 forums for 'christmas tree'.

The climate control unit in both the c2 and c4 can break and be expensive to fix. The articulating spoiler requires maintenance. The alarms are known to be wonky.

I love mine and pretty much drive it every day; ~17k miles since July '11.
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Old 10-05-2012, 06:16 AM
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I've owned my 91 C4 since January, and it is my daily driver in ALL weather. I've owned several AWD and 4x4 cars/trucks, and this is BY FAR the best awd car I've ever driven. Its abilities in the snow are just incredible, especially with the differentials locked (which *cough*, you can't do in a 993 or later).

Seriously, I think the whole thing is a bit overblown. I've put 17k miles on my car since January, and I beat the piss out of it, in mud, snow, dirt roads, rain. Now and then I will get a sensor warning, but it usually goes away if I restart the car. I have a funky accelerometer, but I just haven't taken the tme to swap it out with the spare one I have.

Yes, it's a more complicated system than the 993, but it's not voodoo. I think some of the hesitations about the 964 c4 is based on misconceptions, either that or it has become easier to own/repair them than in the past:

- There is good softaware available that lets you diagnose issues through your laptop. You don't need to use a Bosche "hammer" anymore... that used to be a pretty significant barrier

-there are decent used parts available. Do a quick search in the used parts classifieds on this site and you'll see that there are always a couple 964s being parted out. There's a perceptions that sensors and accelerometers are nearly impossible to find, but I was able to buy some used ones just to keep as spares. No biggie.
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Old 10-06-2012, 09:22 AM
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You're OK as long as one of your planet gears doesn't decide to 'let go', the centre diff inside the G64 gearbox is a little known weak point. The planet gears on my C4 had let go on the previous owner and been fixed by an OPC with a bill for about 9k at 30,000 miles so I figured it was in good shape.

About 18 months into my ownership it happened to me, doing about 40mph with no warning, a loud bang! I know of two others who have seen the same issue. I eventually decided to spend the 1200 that Porsche wanted for the new part on a used G64 from ebay and had it rebuilt by a good indy (including new awd clutches and new synchros), so my C4 now has a fully rebuilt box, about 3K on top of the cost of the used box.

Incidentally there are two busted G64's on ebay UK at the moment - I bet I know what is wrong with them...

Had the engine resealed and had to replace the main clutch as well as the recovery guy burned it out trying to drive it off the flatbed truck. Not trying to put you off, just my experiences. Will I keep my C4 - damn yes!

There is a long thresd somewhere on rennlist which has pictures of the planet gear and describes the whole sorry story in more detail.
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Old 10-06-2012, 11:15 PM
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C4 awd

Thanks for the reply, I found an article on the system by Adrian Streather. Very informative, and definetely will buy the Bentley book if I buy the car. I looked for your saga on rennsport forum, but could not find it right away.I am going to check out the car in a few days,as the present owner has it in storage, as he has not used the car for a few years. This is the 1st report that I have heard of regarding gear destruction. Tepps
Old 10-07-2012, 07:01 AM
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Hi Tepps here is the main thread with the awd saga..

Ouch! What's happened to my 1990 964 C4 Cab trans? Help! - Rennlist Discussion Forums
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Old 10-08-2012, 12:27 AM
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Quote:
Originally Posted by klr10 View Post
...the centre diff inside the G64 gearbox is a little known weak point.
Well, it sucks that yours broke in that fashion (not to mention expensive) the fact that this failure mode *is* so little known implies that it's not an issue that regularly comes up. The referenced thread is exactly the one I had in mind when I said, "There's a couple accounts of major mechanical issues..." in post 4.

Before I leapt I read *every* C4 thread here and on Rennlist. There's no denying the C4 is mechanically more complicated and consequently has more potential points of failure. At the same time, Porsche isn't going to go to market with some half-assed solution (my last car was a Subaru with the 2.5 turbo; talk about half-assed...) so their first-gen AWD setup is beefy.

Do you need/want AWD? That to me should be the main question. I did/do, and it makes me happy everytime I leave a twisty on-ramp WFO near the top of third gear.
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Old 10-08-2012, 06:58 AM
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You ask the question: What would I do with my C2 if I got your C4? I wouldn't mind being in that kind of a tough position for a bit.

Well, what I'd do is I'd keep it a couple months until I knew I had the C4 sorted because the C2 really has been a winner for me. Maybe if the C4 was going good I'd move the C2 along but it would probably be a dog fight for the position. My C2 is 300 lbs lighter than my buddy's C4 and that can't hurt.

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Old 10-08-2012, 06:44 PM
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