Rumbling diff or hub? RRC

Both diffs will be turning anyway, so I'm not sure where he gets that conclusion from!

Don't drive it at all with a prop removed, in doing that you are forcing he viscous coupling to take the full torque of the engine to give you any drive.

You wouldn't necessarily need to move the pads back, if they are loose they will probably click anyway.

The thought was that the diff only rumbles when driven, i.e. if no drive = no noise then it is the diff that is the source of the rumble.

Can the viscous coupling not cope with the full torque? Surely it does when a wheel spins?

Also ISTR seeing ads many years ago in LRO for disconnecting the front diff to as to convert your RRC to two wheel drive. Supposed to save fuel. Also I thought a contributor here mentioned carrying a pair of short i.e. front drive shafts to temporarily replace broken rears when off roading.

Mmm. Without lifting a wheel I can't prove it, but it doesn't feel like a pad click - more like slack being taken up. I know that all I have to do is take the wheel off rather than sit here typing pure speculation!

Richard

Yes, but the point that was being put forward was that the diff would still be turning (and possibly rumbling) unless the halfshafts were also removed.

You probably wouldn't need to put a lot of torque through it though, just get it rolling at a fair speed on the flat.

Martin

Indeed. What I'm trying to avoid is any sort of dismantling work on the front hubs and associated magic drive-with-steering-challenge! If the diff becomes more than a good suspect for the source of the noise I'm thinking that I can, according to the Haynes BOL, remove each hub and halfshaft in one lump by unbolting it from the axle and pulling it out far enough to remove the splined end of the drive shaft from the diff.

Plausible?

That would also provide enough excuse to replace the original brake hoses, possibly with Goodrichs (unless they are to be avoided?).

I do already have a spare diff - i.e. the one which was on the back, who's replacement did not cure the source of the rumble.

So a 30mph stroll along my local roads might be too fast? The rumbles are most apparent at 40 + I have an unavoidable gentle, short hill to negotiate to get onto main roads.

Thanks Martin

Richard

Yes, and you may also want to remove one end of the track rod to give yourself more room, no need to touch the drag link, just wind on the left lock. You should have enough length on the brake flexibles without disconnecting any. If the swivel housings are in good condition I like to leave them secured as the bolts are sometimes a bit of a bugger to remove and can also break in if you're not careful. I prefer to remove the brake caliper securing bolts, hang them out of the way then remove the hubs and stubs and just pull out the halfshafts, doing it this way gives you the opportunity to check everything while you're in there but it does necessitate refilling the swivels when finished.

I wasn't thinking of limiting the speed, just the weight of the right boot. :-)

Martin

Thanks Martin

In all possibility it might be easiest for me to swap the diff so as to eliminate it as a cause of the rumble. I hadn't thought about de-mounting the calipers - sounds good. I'm reluctant to dismantle the hubs because of setting the correct degree or lack of slack in the bearings. Would a generous soaking of the swivel-to-axle bolts with Plusgas not be sufficient to ensure worry free removal? Just how careful must one be to avoid breaking the bolts? Doing it as a DIY job means that I can leave the bolts soaking for a fair time.

I take your point about a gentle right foot.

Richard

Before you go too far I'm not sure that you have yet covered all the easier possibilities. As you suggested, you don't want to take the front diff. out unless you really have to.

Has this rumble always been there or has something been done after which it has appeared?

This rumble ... is it accompanied by any vibration? If so where does the rumble/vibration appear to come from.

Does it occur at '40 mph' only or 40 mph and upwards? Is it worse accelerating or decelerating? Does it make any difference?

Have you checked the propshaft UJs (front and rear) - actually disconnected one of the flanges and checked the UJ bearings for dryness/grittyness etc.? Are the UJs of the rear shaft in the same plane and are the marks on the sliding portion aligned. Same for the front but with the spline marks aligned the UJs are about 45 degrees out of plane. You mentioned vibration at the steering column/floor: the front shaft's a possibility. Is there any sign of physical damage to the shafts or evidence that a balance weight may have dropped off/rusted away? Are the splined sections free to slide?

Check also that the propshaft flanges are secure i.e. the big nuts securing the flanges to the pinion shafts. Presumably all bolts are tight.

Handbrake over-adjusted?

Swivel pin bearings OK?

Are both tyres on each axle roughly the same size (circumference)?

This model had a vibration damper on the front diff casing - is it still there? I'm not sure what effect it's removal might have: we had no problems without it on earlier models so what's different here?

The click is almost certainly the pad moving in the calliper. I was once too enthusiastic cleaning rust away from a calliper and ended up with sloppy pads for some time until the rust/dirt re-accumulated. The pads do reposition themselves and it is not necessary to reverse to get give the pad clearance again.

AFAIK it has always rumbled. Except that I originally thought that it only occured when cornering but I cannot remember in which direction

Yep

If so where does the

O/S/F and I can feel it through the throttle pedal and to a lesser extent through the steeering wheel. And hear it.

Doesn't seem to be made worse when accelerating or decelerating. Apparent at all speeds above ~ 25 mph. Also continues (I think) if I select 'N'

The rear shaft is as it was when I did the diff but I will check UJ alignment. I haven't checked the front shaft UJ's. When doing the rear diff I found that one of the grease nipples had been broken off one of the UJs.

Apparently not

I don't know. How can I check?

Other than being identical make and apparently same age, I haven't compared them

Damper is still in place

I think that you are right about the pad. I _really_ should make the easy checks for that. The only thing that casts doubt in my mind about pad slop is the sense I have that the click is something inside - it doesn't have the sound of a click in free air - that's really unhelpful but I just have a gut feeling about it. Also it doesn't happen the instant I tap the brake.

Thanks for suggestions that might wind in my enthusiasm for assuming the worst. I need to do some more grovelling under the front.

Still, at least I know that it isn't the rear diff!

Richard

Sounds horribly like a cv joint sulking. could be the click as well?

That has been my fear from the outset. What do I do? Wait for it to explode and wreck the hub? ;-) Or instruct my spannering bloke to open it up? How does one know that a CV joint requires replacement? Don't say it rumbles and clicks! Are they frighteningly expensive (time and parts)?

Richard

Drive slowly at full lock in both directions. It'll be very obvious if something is on its way out. The noise is more of a heavy rattle than a rumble. If you drive really slowly its a regular clonk.

Doesn't sound like that (fortunately!). My Dad's old VW camper had CV joints which made that noise - an awful 'death rattle'.

Richard

Fix it now if it's the problem. You'd be well able to fix it yourself in a relaxed Sunday of twirling spanners.