An elusive vibration

[NJV6]

I have a troublesome one and putting a call out there for any ideas....

I have a vibration, most noticeable at 80km/h, goes away about 85 then comes back at about 105. It disappears at a speed Mr Plod mightn't be happy about.

It is a 1994 3.5 Manual - these have a CV joint instead of a universal on the front of the rear driveshaft. There was a bit of movement where the driveshaft goes into the rear of the transfer housing on the splines so thought, ah that'll be it. I had a new bush made up out of brass. The driveshaft itself has no splines.

The transfer case has a new bush and the output is nice and firm now. Slides in and out nicely still.

I am running out of options

I have rolled the old original diff housing from behind the shed (for those that don't know I changed housings when I put in the factory locker and 4.9 ratio as housings for ABS equipped ones are slightly different) in case by some reason mine was bent and diff head (original 4.636 ratio) under it to see if it made any difference. I also put the original factory springs back in to see if it was the driveshaft angle.

This did seem to help to the point where i could accept it but it is definately still present. The vibration does seem worse depending on my mood!

I have free wheeling hubs on the front so no front driveline is turning.

With the transfer case in Neutral, take the engine revs to 2300 - 2500 in 5th where it is worse and its perfectly smooth (admittedly no load on gearbox)

The tryes have been balanced a couple of times. BFG Mud terrains @ 20000km.

New transfer case/gearbox mount.

Still does it when slipping it out of gear and switching engine off at 80 - 100kmh but possibly not as noticeable, most noticeable just holding the speed, the vehicle has always had a vibration under hard acceleration in 2nd and 3rd gears as it goes through 3000rpm.

Does it in 4H as well. (hubs in, centre diff unlocked)

I am down to CV joint or transfer case. There is obviously something inherintly not right with the transfer case for Mitsubishi to hang a big weight off the tail housing.

To me, it feels like a 'fine' vibration, not a 'coarse' one like tyres. Like something going fast ie. pre crownwheel.

Any ideas?

[Lynx]

Hey, Just throwing it out there, but what about brakes, maybe a warped disc or somthing??

Cheers Daniel

[tallsam66]

Maybe driveshaft out of balance.

[Pedro]

[quote]With the transfer case in Neutral, take the engine revs to 2300 - 2500 in 5th where it is worse and its perfectly smooth (admittedly no load on gearbox)[/quote

drive shaft out of phase, although a CV type joint at the front should stop this,
is there anything solid connecting the motor/g box to the chassis, ie exhaust hard against the chassis,

I remember driving one of these years ago around Manfield and remember a coarse vibration about mid range which surprised me.

as you say with a big bloody weight hanging of the back of the g/box it aint a good sign


Pedro