944 vibration update - what to do?

toolboy62 · 12-01-2005, 04:10 AM

So I picked up my car last night... reason I took it into the shop was that it had a real bad vibration at just about 80 MPH. Well I picked it up, they only charged me $85 but apparently all they found was a bunch of loose bolts especially the left outer CV. The vibration is still there. DUH! if you have a serious enough vibration, it will shake all the fasteners loose, even I know that...

What do I do? I suspect the problem is that the kid that works on all the 944s has a concrete ass and is completely insensitive to NVH problems. He also told me once that I had nothing to worry about when I took it in telling them that I had a CV going bad, could they please find which one it was and replace it - and sure enough one of the CVs shat the bed at about 2AM on the B-W Parkway two days before Xmas. They do good work for issues that you can troubleshoot with gauges, but vibrations... don't seem to worry them. Do I take it back and insist it get fixed? Find another shop? If the latter, where do I take it? (I'm in Bowie, MD and don't know of too many shops I'd trust with a Porsche.) I SWEAR this is either a) a bent rim or bad tire or b) a bent stub axle or bad bearing... (or worse yet, the transaxle disintegrating, but I don't want to think about that)

I just don't have time to work on this myself, between my job and trying to get my '55 coupe back on the road, and it would be so nice to have a shop that could just fix stuff without prompting... I have had this issue with other (VW oriented) shops as well, they eventually do a good job but you have to ***** a lot and take the car back 2-3x for the same problem before they really dig into it. If it were easy, I would have already fixed it myself...

...very frustrated... I just want my car back, that's all I want! It's been like three months now...

nate

Techno Duck · Techno Duck's Garage

Any idea where the vibration seems to be isolated to? Front, rear? Left side, right side?

If you suspect a bad tire or rim, take your car to a wheel place and have them rebalance the wheels and rotate your tires if applicable. They will tell you if you have either or these problems and you rule out your wheels not being balanced at the same time. Perhaps you need a highspeed balance. Thats usually a pretty cheap solution.

NICKG · 12-01-2005, 07:18 AM

bad torque tube would also do this...most shops do not road test cars at 80mph just so you know and it isn't really all to safe to do that on a lift either(especially if vibration is the problem) since the car can fall off the lift. are the wheels balanced properly? alignment? does it vibrate at idle ? what about different engine speeds at a stop ? bent wheels vibrate progressively worse as the speed goes up, same with badly balanced tires.

toolboy62 · 12-01-2005, 08:37 AM

I am thinking it's not the torque tube as it appears to be road speed dependent not engine speed dependent, i.e. it is real smooth running around town, I don't feel any unusual vibration until I hit at least 75 MPH road speed. I'm not saying that isn't it, but my best guess at this point is that it is somewhere outboard of the driver's side outer CV joint. I just don't know what, and apparently the wheel bearings are not very user friendly...

nate

NICKG · 12-01-2005, 08:48 AM

did you try doing 75 in a different gear? like 3rd or 4th? might be a bad tranny, wheel bearings don't vibrate, they make a deep groaning sound, when cv's go bad they only do it when they are being powered, not in a coast situation. what you are describing is exactly what my 928s did when the torque tube was bad. does it go away after a higher speed is attained? or just get worse, do you have to be on the gas or not?

nynor · 12-01-2005, 08:49 AM

put your spare on the rear and see if it goes away. try it on both sides.

toolboy62 · 12-01-2005, 09:58 AM

don't have a spare, is the problem - I've got two good spare rims but no tire on either one of them. All I have is the original, 18 year old collapsible spare, no idea if it's good or not and the idea of running it at 80 MPH is not appealing to me. I wish the body shop had told me before they gave me a new tire :/ they apparently didn't like the way the tread got chewed up by the fender lip, but it didn't look crucial to me.

I haven't tried going faster than 80, traffic is heavy enough around here that there's really no opportunity to go significantly faster than everyone else, and quite frankly, until this is resolved I don't feel totally cool doing that anyway. I have not tried shifting gears at speed but I don't feel the vibes in any other gear at the same RPM. It does get progressively worse from the speed at which I first notice it, until 80 MPH where this awful beat frequency starts and your body starts vibrating in sympathy. I concur that it's not a CV as they are all brand new, and this happened before and after I changed the driver's side axle.

If it's the torque tube or transaxle, this might cost more to fix than the car is worth. Funk.

nate

NICKG · 12-01-2005, 10:06 AM

do you have aftermarket wheels?, have you checked the brakes? what about a front end inspection, ball joints, etc. try doing that speed im a different gear..betcha it will be the torque tube unless the car is an automatic...then it is almost assured to be the flex plate.

toolboy62 · 12-01-2005, 10:10 AM

no, wheels are stock late offset 15" phonies. Brakes do not drag, I am 100% certain of that as I adjusted my e-brake when I changed the driver's side axle and the wheels spin very free. Front end is OK according to three different mechanics (two that I've taken the car to and one that did the state safety inspection.) I repacked the front wheel bearings maybe 6 mos. ago and they appeared pristine at that time. I did not detect any perceptible play while I had the car on the lift.

Only thing I did notice was that whoever did the tire torqued the lugs down REAL tight, but I have retorqued them correctly.

nate