G'day all, I have a Brat/Brumby with a dual range 3.9 ratio 5 speed in it. Pushing 14" road rubber. I have a noise coming from the gearbox or front diff which is a loud mechanical click/ grating.

Only happens when lifting off the power, dissappears when under power or clutch is in.

Worse in 4wd

Quite loud when going slow and turning....

What is there to go wrong in the front diff??

Any suggestions would help greatly.

Thanks

Matt

Sounds like an axle to me - front outer joint's make those nasty clicking noises - especially going slow and turning - just as you describe. Check for failed boots - that can indicate a joint failure.

 

GD

It sounds more internal and substantial than a CV (which are both brand new, inner and outer) is there a crown and pinion in there?

 

The fact that it only comes in when I back off make me scratch my head!

Check for play in the stubs comming out of the tranny - if they wobble around then you have a bearing going out inside the tranny. Only thing to do is replace it or rebuild it. There is a front diff - ring and pinion gear - just as you surmised. Again - not really serviceable easily. Replace or rebuild the tranny if this is the case. I hope it isn't and you just got a bad axle. I've had rebuilt axle that didn't last more than a few thousand miles because the quality of the rebuilt units seems to be fairly poor from a lot of the rebuilders we have here in the states.....

 

GD

Generaldisorder, That is what I feared!

Many thanks for the prompt reply,

onto the hoist for me...

These 1:3.9 boxes are rare here,

I will check the CV again though.

Thanks

i would suggest the inner DOJ of the axle. usually it acts up under deceleration. can you feel the noise through the steering wheel?

Yes I can feel it through the wheel!

Pardon my ignorance, but whats a DOJ ? I'm guessing Driveshaft and Output and Joint.

Or the outer joint..

Bloody thing is new, I might have a dud?

DOJ = Double Offset Joint. The inner joint on the drive axle.

CV(J) = Constant Velocity Joint. Outer joint on the drive axle.

 

I've had a New Axle go belly up on me in less than 500 miles, so yep you could have a bad one there.

All of the bad DOJ's I've had caused massive vibration under acceleration. And didn't change much while turning. Stopped virbrating completely if you coast..... doesn't sound like your problem to me. Your problem sounds like a bad outer joint, or bad wheel bearings.....

 

GD

the inner DOJ is rebuildable, but the outer cv end is not.

 

the double offset joint is like a cv joint, but it allows in and out motion like taking the flex of suspension, rather than having turning radius like the cv joint. think of the doj like a slip yoke

I've got to go with GD on the DOJ's. DOJ's normally vibrate under acceleration and go quiet when you let off on the gas. I've never had a DOJ click like the CVJ's will. Another thing to look at before you get too involved with this, is to check the tightness of the axle nut(s). If they become loose, all kinds of noises can start to appear; grating noise like a wheel bearing, clicking like with a CVJ, and the noise can come and go when turning. Again the axle nut itself doesn't loosen, the axle can reseat itself if it wasn't properly installed (you have newly replaced axles, right?), but when the axle re-seats it has the effect of taking the load off the castle nut. Very easy to check; re-torque back to 145 ft-lbs (or more; more is okay).