wkoperwhats

I purchased an '89 Carrera 4 back in January that has been absolutely fantastic. I recently started having the following problems that I believe (hope?) are related:

1. At low speeds (<40mph) it feels at though the center differential is having a difficult time determining which wheels (front/rear) to direct power. The engine runs smoothly, but the car will rhythmically - and every so slightly - hesitate/lurch forward, but only while *slowly* accelerating. It's not enough to make the car un-drivable, but it is annoying. Under spirited acceleration, everything soothes out and the effect isn't noticeable at all. Once you reach 35-40mph or so the problem disappears.

2. At high speed (>70mph), the car vibrates almost exactly like it needs a high speed tire balancing. This started happening simultaneously with the first issue and seems too coincidental to not be related.

Can anyone give me an idea of what to check first? Is the center diff clutch pack hydraulically operated, and if so, is there a way to test the fluid level in the system?

Cheers.

DrewG

Does it feel like binding when you are turning at low speeds?

wkoperwhats

Not at all.

For the high speed wobble, one thing that was suggested was to get up to speed and then step on the clutch to see if the wobble persists. Unless there's some mechanical (hydraulic) connection between the main clutch and the center differential clutch, I'm not sure what this would show, but I'm willing to give it a try to see if there's a difference.

DrewG

I had a lot of your symptoms, and mine was a broken planetary gear.

tbennett017

This might seem really basic, but I'd check to ensure that the tires are correct. A lot of people forget that they need to match circumference exactly. The C2 does not have this requirement, so a lot of folks with the C4 are at risk of getting the wrong tires that are not correctly sized. I'd check that before going too far.

wkoperwhats

Following RicardoD's incredibly well documented hydraulic bleeding procedure, I completely flushed and bled all the hydraulic fluids. I was fortunate enough to be able to *borrow* a Bosch Hammer from a friend with a german auto repair shop in town, and that made bleeding the diff-locks almost too easy :-) The first couple of squirts from the longitudinal lock sounded a bit odd, but I bled out the full recommended 250cc and the fluid was coming out nice and clean toward the end.

I am happy to report that all traces of the issues that I had when I started this thread are completely gone. The car drives as smoothly as ever, and other than having to remove about a thousand nuts holding on all the undercarriage protective covers, this was one of the easier bits of work I've had to do to this car. I'm still recuperating from the nightmare of changing spark plugs a month ago.

wkoperwhats

BTW, does anyone know how to change the title of this thread to include "[SOLVED]"? I think that (as thread starter) I can close it, but that's not really what I want to do.

Goughary

The one thing Ricardo doesn't stress in that thread is to be careful to never let the fluid out fast at high pressure when bleeding the accumulator....tends to cause the internal bladder to fail prematurely...otherwise I follow exactly the same procedure as well. It's very good to have as a reference. I'm down to about an hour and a half to do the full bleed from the time the jack goes under the car to torquing the wheels...so simple in the end once the confusion lifts...

Did I? And then turn the key? Now wait, was that before this? Hang on, where is the menu for bleeding the locks? Is that 7mm, or 9mm...uhhhhhh hold on....wait, lemme read that again. Dammit the battery went dead on my iPad....ugh...

Sound familiar?

wkoperwhats

Not at all ;-)

I'm returning the Bosch Hammer tomorrow to Dave and I'm just trying to figure out some of the other fault codes on the Heater System. I can already see that I'm going to *need* one of these...

Goughary

Get a pdt999 - cheeper than the hammer and you can do 99% of what the hammer does.

Unfortunately, when the euro fell against the dollar, they pulled the price off their website and now make a special price depending on country. So have a buddy in Europe buy one, and then pay him the equal dollars, you'll save a bunch.