Crown Wheel and Pinion Replacement Options??

[jonathan]

Hell, Ross, that sure was a long and painful ordeal! Really glad you got it sorted eventually. And some good advice if anybody ever has to go through the same thing!

[Overdrive]

Cedric thanks that sounds like good advice. Time is of the essence becase we are set to leave for Namibia next week so I took it to a prop shaft place. The guy there says that they have had some similar cases and they tried everything even buying a new prop from Nissan and it could not solve the problem!

It really odd becuase you only feel the llike harmonic vibration between abouit 95 and 110 kph when its under load. Take your foot off and its gone. A quick inspection showed nothing wrong.

Interestingly my prop is mounted back to front so that if it comes out instead of acting like a plow it will just bounce along the road. That is so sensible. Why would Nissan (and other) engineers do it the other way round in the first place? I just dont get it. We will see what the prop shaft fundis say tomorrow.

[Peter Connan]

Overdrive, when the prop is mounted back to front, there may be insufficient clearance between the prop and the cross member just behind the transfer case for the axle to articulate properly. Particularly if you have a lift installed.

I wonder if it's not bent?

[ricster]

hmmmmm....interesting....keep us posted

[Overdrive]

Well today the prop shaft specialists balanced it and checked the universal joints. Found nothing amiss and the vibrating problem is still there. They also warn that the bracket supporting the long range tank is rubbing against the prop shaft but they don't do that so I took it to my local to see what he can do. Friction on the petrol tank. not nice. So the current theories to explain the vibration are: a) tank rubbing on prop shaft; b) flat spots on rear tyres (they were balanced recently so it should have been picked up). c) something in the right rear hub d) AN Other..... Any suggestions?

@ Peter I asked them to check on that as well. They said they couldn't fit the prop shaft the regular way because its too wide with the long range tank there. So I suspect that when the moegoe who made the long range tank realised that he had made it a bit too big he switched the prop shaft around to try and solve the problem. This is why second hand vehicles are so much fun. You get to fix everyone's problems.

[Peter Connan]

Aye, that's a bit of a problem you have there mate!

I would strongly consider jacking up the rear end by the bumper or towbar, and check that the propshaft doesn't touch. I also wander:

If your car has a lift, the rear gearbox mounts should also be replaced, to lower the rear of the gearbox. The purpose of this is to keep the propshaft angles the same. If they are not the same, there will be a vibration. But this will probably cause your propshaft to rub.

Thus I have just introduced another possible cause, without eliminating any. Sorry.

[ricster]

If I'm not mistaken, Rods GQ is still standard suspension.

I'm going to take a shot in the dark here. If the prop shaft is backwards then the UJ position is now at the back and extremely close to the fuel tank( close to the rear axle. Please correct me if I'm wrong). Does the vibration harmonic sound change with the amount of fuel you have in your tank? I'm probably going to make may name donkey now but, noise and/or the rotation of the UJ is like helicopter blades chopping the air. This chopping of air creates a frequency, this frequency in turn is possibly amplified by the fuel tank. The fuel tank is basically like a speaker, and amplifies the frequency to an audible level at that speed. One could try a temp check by sticking a piece of soft spongy material. Maybe a piece of cardboard or aerothene ( bubble foam stuff they put under wooden flooring )firmly stuck to the side of the fuel tank, then take it for a drive and see if there is any change, even a "pitch" change ( from an A- sharp to a B flat.....ha ha)

Another view, again based on the harmonics and sound frequency, your tyres may just be at that point where at that speed the rubber hitting the tar creates a frequency that is audible over and above the normal, and as you speed up or slow down the frequency dissipates into normality.... similar to the propshaft.

[Grant]

Well today the prop shaft specialists balanced it and checked the universal joints. Found nothing amiss and the vibrating problem is still there. They also warn that the bracket supporting the long range tank is rubbing against the prop shaft but they don't do that so I took it to my local to see what he can do. Friction on the petrol tank. not nice. So the current theories to explain the vibration are: a) tank rubbing on prop shaft; b) flat spots on rear tyres (they were balanced recently so it should have been picked up). c) something in the right rear hub d) AN Other..... Any suggestions?

@ Peter I asked them to check on that as well. They said they couldn't fit the prop shaft the regular way because its too wide with the long range tank there. So I suspect that when the moegoe who made the long range tank realised that he had made it a bit too big he switched the prop shaft around to try and solve the problem. This is why second hand vehicles are so much fun. You get to fix everyone's problems.

Gearbox spacers are needed when the suspension is lifted more than 75mm and is essential (as Peter said) to get the prop shaft angles back n line. These are available at Mega world OME. Post some pics of the offending tank please.

If you are looking at replacing the tank, suggest you visit Northern Offroad. There tank is a replacement and is 136 lt.

[Overdrive]

Thanks for all the help guys.
As far as I know there is no suspension lift. It is as I bought it and it looks standard to me. The problem is more vibration than noise and the vibration seems to be coming from the back and underneath the vehicle. Today the lorry is with the mechanics so I cant empty the tank to test Cedric's harmonics idea. The tank has been empty before and I have not noticed any increase in noise. But if I somehow banged or moved the tank on my last off road adventure then it could be different.
For the same reason I cant take pics of the tank. If I get it back tonight I will try and do that - given my very limited photographic skills - I know which button to push and not much more.
Grant I talked to Northern Off road (they made a tank for my previous patrol ) but they wont touch this one because they didnt make it. But yes it if comes to replacing the tanks then I would start there. I am hoping my mechanic can 'maak 'n plan' so that I dont have to dip into the holiday money.

[ricster]

ha ha...like I said.... it was a shot in the dark....