V6 auto vibrates in 3rd gear

[mischf]

Does anyone know why my car would vibrate in 3rd? 1st and 2nd are fine, then as soon as it goes into 3rd and i go above 60ks, the whole car starts to vibrate, and it gets worse the faster I go till I hit 4th, then it disappears (I 'tested' it up to 140 in 4th and there's no vibes). I think it is either the gearbox, or, at that speed, the ratio of flywheel rotations to driveshaft rotations is causing some kind of resonance....


??????

[mischf]

?????????????????

[greenfoam]

My V8 does the same thing, in 3rd only, it's worst under load at around 100-120 it's running smooth again somewhere before 180. I suspect it's the rubber mount at the back of the gearbox, I'll be replacing mine soon so I'll let you know it that fixed it

[nathans1987]

i think its a common problem my mates does too. if its a speed thing its probably tailshaft. change oil see if that fixes it

[Pretender]

My car has now developed a shudder in third. It is very mild but I notice it though my wife does not.

Any news on the rubber mount replacement?

[greenfoam]

I have the mount but haven't put it in yet, but the uni joints might be a bit worn too. It wont be far away (the mount)

[andynogo]

That loverly CV joint in the tailshaft can do all sorts of weird things too. Had to replace mine after it started to get a speed related vibration.

Ain't that cheap either!

[Morton]

I get a vibration in 3rd too. Always have, and never thought much of it... interesting.

[somefool]

THREAD DIG. I get the same thing now. It started doing it a week or so ago, only under medium acceleration.
I drive like a grandpa normallly but in traffic when i need to get to the speed limit a tad faster: 2000rpm and untill it shifts into 3rd i can hear this insane vibration and i can feel it through the accelerator. Once it's in 4th/overdrive/whetever it is it is fine and smooth again.
My boss said it was the synchros wearing out and that sooner or later the box will need a rebuild

have you guys fixed / figured it out since 2007? lol

[Warranty Void]

I have always had it, I've recently (this year) replaced the uni's, rebuilt the auto box, new torque converter, checked all the mounts for cracks/faults. Again, it's only in 3rd gear. I'm doing diff gears and diff re-race soon, but I don't think that's going to help.
If anyone sorted this thing out I'd love to know how.