Req Ideas - Vibration

[Pezhead]

Hey guys,

I just had some work done on my R33 GTR. I had the transfer case totally rebuilt and ended up having to replace the clutch and flywheel as the old ones were stuffed. Both pressure plate and flywheel had stress fracture cracks throughout so it was unsafe. I replaced them with an OS Giken Twin plate and on their recommendation do the pull to push conversion which gives the pedal a much more progressive engagement feel. I must say it's pretty good for an 800 ps rated clutch! ( I went with the "C" model).

Anyways, I got the car back last night. When I accellerate hard there is a vibration somewhere on the car as you can feel it throughout the whole car. It is only a slight vibration but definately noticable. It is worst up to about 60 kph where it then smooths out. It primarily does it on acceleration as I can cruise all the way up to freeway speeds without noticing it.

The shop did notice that my front shafts were very stiff as I don't think the front Atessa has been working for quite some time. This is the first time it has worked since I've owned the car (about 1 year).

The shop and I agreed I'll drive it today and tomorrow and see if it is just the drive train needing to loosen up.

Any ideas of what else I should check?

Appreciate the input!

[bigmikespec]

What was the reason for the Atessa not working? What needed to be done to fix it?

Mike

[gun32gtr]

transfercase rebiult would have been the cause as he stated

[Pezhead]

yeah, the transfer has never been right. The plates were stuffed and the housing and shaft. Got blue hot. Ended up replacing all the inners.

drove it to the mall just now and the rear diff is so stiff it is acting like a locked diff. Around tight full lock turn the car lurches as the rears lock up. It's never done that before.

[some_cs_student]

Does the dash gauge for the AWD system show any action when the vibration happens?

And if so, how's the front diff?

The rear diff will do that vibration when turning it will locks very hard, sorta normal for a GTR diff, also happens if the wrong fluid was used in the diff...

Oh, any chance you can PM me the cost of that transfer case rebuild? My transfer case also died recently, it wasn't the clutch plates though, it was a shaft inside the case...

[Pezhead]

Dash gauge works fine, reads just a little of the bottom when you take off. If you take off hard it does give a but more, but never above 1/2 way.

The front diff previously was found to be dry. I opened it up but found that it wasn't worn too bad. I didn't find any noticeable scratches or anything in the teeth. Maybe there was an odd wear pattern put on it and now that there is power going to the front it could be causing a vibration.

I'm going to take it for a bit of a cruise now and see how it goes.

thanks guys, keep the ideas coming.

[Pezhead]

UPDATE:

The shop had an interesting thought. Are my diff's the same ratio? I know my motor has been replaced so could the front diff be a differient ratio? If they were then maybe that's why the box was stuffed in the first place. They are going to do a test @ 50/50 on the Dyno to see if the ratios are the same. God I hope they are.

Also I took it for a drive for about 80 k's sunday. It drives fine at speed - no significant vibration. There is a little vibration at 60 kph cruise but that's the only spot it seems to do it on cruise. Had it up to 110 yesterday and was smooth as at that speed. It seems to have dissapated to about 1/2 as bad as when I first picked up the car.

So maybe it is just a stiff front drive shaft getting worked in with power for the first time.

Anyways, hopefully the shop can check it out and tell me if it is OK.

Thanks for the input guys.

[Pezhead]

The shop confirmed today that I seem to have 4.30 rear and 4.11 front - wow that's bad!

So going to have to decide which route to go. I'd like to go the 4.30 in front but a) they have to find a source for the gears as they are rare for the GTR's and b) costs twice as much.

hmmm....

Well, wanted to let you fellas know what's up with the drivetrain issue.

[Swiper the Fox]

I have a matched crown-wheel and pinion spare if you need one...it came with my cusco 1.0 way front diff and i never used it.