Gearbox Rumble

After a trip to Avon Dasset's Future 4x4 site, my gearbox has developed a new noise.

When it came back from the MOT it had developed a vibration at about 40mph.

(I think this was something to do with the Hand Brake test where they tore accorss the car park and slammed it on to test how efficent it was...... not going back there me thinks)

We then went to Avon Dasset and mid way through the day, some thing went very tight that stoped the truck in its tracks.

It soon went away with some rocking back and forth and we carried on with the rest of the day and proceded to drive home.

Now about 2 weeks later...

I was driving along and let off to slow down for a corner, a high wineing noise came from the gearbox and when I went back on the gas, there was a rumbling sound that has quitend down now but not gone away completly.

The more gas I give it, the less the rumbling noise. It seems that when there is hard drive, the noise is not there.

Im in the process of building a new gearbox but this is not going to be complete untill October.

What do you think the problem could be and how long will the box last if I continue to drive it?

Your thoughts appricated.

Sorry, don't know about the gearbox, but I think you should go back there and test your airbags by driving flat out at that **** that tested your handbrake..

Me thinks you should not have left the mot centre without them fixing your transmission.

I have to tell them every time not to test the handbrake on the rolling road...they look at me as if i'm from the moon...then if they ask why I ask to speak to someone who hasn't had a brain transplant with a Fresian.

look on the bright side at least you made it further than my mate when he went back to collect his 150 yards and bang
arguement insued and 1 gratis recon box fitted later

Right,

I have come to the conclusion that this problem is in the Transfer box...

I have come to this conclusion because;

I get the rumble in every gear.

I still get the rumble if its rolling along in neutral.

This means that what ever is making the noise must be constantly moving when the vehicle is in motion.

The rear main shaft bearing is good as I have seen this recently ruling out the gearbox, these bearings are pretty massive as well.

Now moving on to the transfer box;

The output shaft bearings are pretty big and if they went, they would go completely.

This just leaves the intermediate shaft and roller bearings.

I have heard that the intermediate shaft has a hardened coating, once this coating gets pitted the shaft can wear down very quickly destroying the roller bearings.

Does any one agree with my findings?

Luckily I brought an old gearbox from Mr Hat Man that I'm currently reconditioning.

This box has a nice shiny intermediate shaft and some decent roller bearings, so this week end I will have a go at swapping things over...

I was planning on a new shaft any way and new bearings so they wont be going to wast in my old box.

Doesn't the mainshaft constantly turn when in neutral then? If not, then I've got problems. Could also be a wheel bearing or diff, I had the same problem actually, I never suspected the gearbox, changed all wheel bearings, then UJ's then Diffs and that cured it.

The front of the main shaft turns at the same rate as the engine.

This rules out the front mainshaft bearing as the rumbling noise gets quicker as the weels go round faster, not as the engein increases revs up and down through the gears.

The rear mainshaft bearing is a taper roller bearing, a large one at that. For this to break up and fall to bits as taper roller bearings do, there would have to be a hell of alot of movement on that shaft.

I just replaced the carsalated nut on the back of the main shaft so its all nice and tight so I cant see it being that bearing.

I have had wheel bearings seize up before and this is 100% not a wheel bearing noise, plus if a wheel bearing is making this much noice, I would expect the wheel to lock up or at least be pulling hard.

I thought it could be the diffs, but they just sound like their usual selves.

I had a friend drive along slowly whilst I walked along side and listened to the rumble.

I put my hand on the bottom of the transfer box this morning after a 5 minute drive to work and its warmer than usual.

The front prop is off, so it wont be the front output bearing, plus this shaft doesnt turn unless 4 wheel drive is engaged.

After all that, its the rear diff.

The noise is traveling up the prop and making it sound like the gearbox...