Big Vibrations Issues!

[abr33]

Hi all, I fitted my new large 2 piece tailshaft, along with 2nd hand 4.11 diff, I opened diff and cleaned etc, see shaft in the 'what tailshaft do you run' thread. I have a coppermix single clutch which gives gear noises at low revs as its got no damper, but at 120 it feels like being on the ripple things on the freeway, its terrible! The diff felt good and appeared ok when I cleaned it, but it got super hot (70 degrees ish) in under 10 kms driving. Please help I have a trackday in a week!

[The Dan]

Hi all, I fitted my new large 2 piece tailshaft, along with 2nd hand 4.11 diff, I opened diff and cleaned etc, see shaft in the 'what tailshaft do you run' thread. I have a coppermix single clutch which gives gear noises at low revs as its got no damper, but at 120 it feels like being on the ripple things on the freeway, its terrible! The diff felt good and appeared ok when I cleaned it, but it got super hot (70 degrees ish) in under 10 kms driving. Please help I have a trackday in a week!

The people who made it need to balance it again or possibly the length has been measured incorrectly?

Also make sure your centre bearing is in its natural position.

[GTSBoy]

And make sure the universals are set up correctly. Possibly doesn't matter so much on a 2 piece, but it probably still does.

[WMDC35]

/\ on the 2 piece the uni's need to be lined up, did it come bolted together?, still if the diff is getting hot may be binding somwhere?, if you need to get to the track maybe just get another diff, did you have the old tailshaft to try as a comparason?

[abr33]

No, my shaft was the donor for centre spigot and sliding spline, It was bolted together when they balanced it, and it was balanced to some crazy tolerance. And uni's were setup to within a thou of perfect. The centre bearing could be lowered 5mm to get shaft perfectly straight, but that shouldnt affect it.

Its very bizzare, I expected gearbox noises to resonate through it, but not a death vibe.

How could anything in the diff be causing this and how could it get so hot?

Its never been shimmed either..

I have my 4.36 diff which is lazy but will get me out of trouble. I will get a genuine good condition shaft sent out today incase it all turns to shit. This is pretty sad though...

[34GeeTeeTee]

How do you mean "lazy"?

Also, interesting on the gearbox noise... How much noise are you getting? Is it just a light sound? (sorry I know it doesn't help your problem but it's related to a similar convo I had this week)

[WMDC35]

it is unusual for a diff to cause that much vibration, if it wasn't getting hot i'd be pretty much only looking at the shaft, diff must be binding or something, hopefully trying the other shaft will shed some light on it

[The Dan]

Is it possible the shaft was damaged in transit?

Even a small dent or knock will put the out of balance

[abr33]

It had been dropped in transit, small scratch mark on flange. But iv narrowed it down. Old diff back in, and its between 115 and 130 kmh. , its doing my head in, diff and box within well under 1 degree. Is a harmonic imbalance plausible?

[The Dan]

It's your tailshaft.

take it back to them personally and have it rechecked for imbalance while you wait

[abr33]

Its 2 hours each way to them, im going to try fitting the factory rear half, ans see if that fixes it

[WMDC35]

as above, it's got to be the shaft, i'm sure they won't mind checking it

[WMDC35]

Its 2 hours each way to them, im going to try fitting the factory rear half, ans see if that fixes it

the 2 piece is balanced together so unlikely to improve anything

[abr33]

And obviously ill get it sorted. Im thinking some sort of damper is needed

[abr33]

the 2 piece is balanced together so unlikely to improve anything

But the factory rear is rubber driven

[WMDC35]

ok, maybe just put the factory one in complete, should tell the story

[abr33]

I only have rear half lol. Factory front in transit

[abr33]

After checking everything yet again, all angles are perfect, and the vibration is worse at diff end. I was told not a good idea to undo centre loint and fit factory rear half as its not balanced together, but they should both be balanced anyway so ill have to try it. Anyone got any further experience/input?

[abr33]

I put factory rear half on, the vibration is almost gone. I think I can still feel the slightest bit still but not sure. Definately a balance issue with the shaft.

[abr33]

So I had the shaft rebalanced again. This time far more accurately than before. Been running stock shaft, no issues at all. Put on new big one again, same vibration! Anyone got further ideas before I loose the plot??