Chassis/cabin vibration at highway speeds only

[Mozza1219]

It's a good thought, but it doesn't line up with the vibration being speed specific?
Driveshaft is still with the shop.

[twright]

It's hard to say. The good part is this should be easy to find: Drive until it vibrates and then climb under the car. If the exhaust is touching ANYTHING, that can be the source of your vibration.

[Mozza1219]

Got the driveshaft back. The guy said there was a bit of a vibration in the diff end of it, so they put another small weight on. Bolted it all back together as above. Problem still there.

Spent today rebuilding the front brakes, changing the seals on the pistons because I think they were catching a bit. There was a bit of dirt in there, but nothing crazy, brakes definitely don't catch anymore. Drove the car. Problem still there.

Replaced the front strut top mounts because it's one of the last things I never changed on the front suspension. Problem still there.

Replaced the engine mounts. Problem still there.

Starting to lose hope in this car, no matter what I replace it doesn't seem to make a difference. Vibration now between 80-95km/h. Smooths out at higher speeds, but quite 'vibraty' at 80-90km/h.

Trying to get my hands on a set of wheels and tires that I can just borrow for the day, but this is proving to be tricky.

Exhaust seems to have good clearance from front to back, it's been re-done too.

Any help/advice is appreciated.

[twright]

[QUOTE=Mozza1219;n10046635]

I took a closer look at the wheels and yes, one wheel is definitely in worse shape than the rest. The other 3 are ok, with the exception of 1 which also has a slight warp in it. So that makes 1 bad wheel and 1 sort of bad wheel right?

So I got my spare wheel from the boot and went through each wheel, swapping it out one by one. The spare is in perfect condition and the tyre seems ok.





THIS is the cause of your vibration. Swap a set of wheels/tires and try it again. Or, get the wheels straightened.

The vibration on this car will not stop until the wheels/tires are sorted out.

[Mozza1219]

Thanks Twright. I'm arranging to borrow a set of wheels in 2 weeks and will report back after testing.

[Mozza1219]

Another update.

Disconnected the cv shafts today and ran the car up to speed whilst on jack stands. Unsurprisingly, vibration happening between 45mph to 60mph and then sort of smoothing out after that (but not really, the frequency just seems to change).

I've pretty well convinced myself that something has gone wrong with the tailshaft rebuild (replacing unis). I suspect that the rear uni is not perfectly centered. I've been through everything else, apart from the diff bushing, but I doubt that this would be causing such a vibration. and its still in one piece. Going to try and get my hands on another tailshaft, which is tricky in Australia but we'll see. Worst case scenario the yokes get cut off and a new serviceable uni gets installed.

Will report back once I get a new tailshaft, balanced and installed.

[jbontke]

Good job in being through!

[Mozza1219]

Good job in being through!

Thanks mate. It's either more money down the drain or it'll actually lead somewhere but I've got a rear half section of a tailshaft on order so we'll try that out and go from there.

[Mozza1219]

Replaced the rear half of the tailshaft with a 2nd hand one. Unis are in moderate condition so no idea how long they'll last.

Vibration is gone now (went on a 30 min test drive).

I suspect the unis were not properly aligned on the rear of the tailshaft so it was always off centre. The shop tried to fix this by welding a big weight on back of the shaft but that didn't work.

it's hard to explain but out of the 4 directions the uni can bend in, one of them always felt like it couldn't reach as far as could. This wad because the yoke was hitting the other side of the yoke too early which was caused by the uni not being centred properly.

I'm disappointed in the tailshaft shop but at the same time I'm relieved that it's finally gone.