Outer Limits 4x4 Board

Hi all
Just bought a 91 Sierra soft top for $2500 (not a bad buy).
Had a patrol before and can already see this is going to be a better 4by.

However, took it on the highway for the first time yesterday and it makes a grinding noise (from underneath centre of car) for about 1 second every 500 metres or so. Really weird, I think it could be the gearbox.
Only does it when going over 80km/hr.
Any ideas?

if its coming from the centre of the car undenearth it could be only 2 things gearbox or transfer case
but if its only happening every 500m for a second thats strange cause if the gearing was stuffed it would happen constantly

could be driveshaft vibrations, tcase mounts, or even just mud under there... its most likely happening through the bumps in the road.

ok its only happening in 5th gear.
It just did it before so I changed back to 4th gear and stayed at 80km and it didn't do it.
It is probably the teeth in the 5th gearing.
Is it possible to just get 5th gear fixed or would you have to get a whole new gearbox?

it can still be driveshaft vibes or tcase mounts - it can be related to the vibrations caused at certain RPM etc... check tcase mounts and unis first...

if it is a buggered gear though - best to look at if you're planning bigger tyres in future or not - if so, hold off till it dies and you can do reduction gears and tyres at the same time... otherwise a new box from a wrecker will be the cheapest option and is an easy bolt-in solution.

righto thanks for your help.
I've got 32s to put on it so I'll try and kill it this weekend

hey mate, i suggest dumping the oil in both the cases and putting in some VMX 80.. it WILL feel alot better, and you will notice a difference noise wise.. not a permanent fix.. but certainly a worthy addition. there was a thread recently about it, check the first few pages..

check wheel bearings