1986 110 Vibration/grumble from drivetrain

[dave88sw]

Hi

I have a 1986 110 that i've converted to a 300tdi.  The front and rear axles are original (with only 85000 miles on them), the transfer box is in the original location, so the props are original and the gearbox is an R380.  The car was laid up for over 15 years (it had never had an MOT logged on the online system, which came in 2005, other than that, i don't know when it was on the road).

The problem i have is that, when driving in 4th or 5th (although i think it's speed related, rather than gearbox), at speeds above 50mph, all is quiet and smooth, unless i slowly release the throttle.  At neutral throttle, i get a grumbling noise and a vibration that feels like it's under my feet.  If i fully release the throttle and it's on the overrun, the noise goes and if i accelerate it goes, it can be difficult to make it do it but get the throttle just right (or wrong depending how you look at it) and it's definitely there.

I would normally assume prop uj, but they both have no play at all and i've regularly greased them with grease out of all 4 caps.

My next guess would be transfer box output bearing or front diff pinion bearing but has anybody got any better idea?

 

Thanks

Dave

[Retroanaconda]

They would be my next guesses as well, but you need to take the props off to properly inspect them. I’ve had occasions before were no play was noticeable when fitted to the vehicle but upon removal it was clear.

Removing the front and rear prop in succession and going for a test drive (gently, with difflock engaged) will also isolate the issue to the front/rear of the drivetrain. Ensure you secure the handbrake drum with nuts/washers if doing this on the rear as the little screw will not hold it on its own. 

[dailysleaze]

As above. It was a bad diff pinion when that noise happened to me.

[dave88sw]

Thanks for the replies, it's useful to get others opinions on these sorts of things. I'll pull the prop sometime this week, check the Uj's thoroughly and check the diff pinion nut is nice and tight.

I think, considering the low cost of the parts and the fact I have a slide hammer attachment to do the front transfer output bearing, I'll do that next to rule it out.

Thanks again 

Dave 

[Sigi_H]

First I would do is to drain Diff oils and see if there is something metal shiny in it. This is to prevent Diffs from secondary damage. If the noise is coming from prop shafts, they are gone anyway. Keep on riding then to find the exact point

[Snagger]

It’ll be the prop UJs binding.  You may find some play once you remove the props, or binding in the movement of some of the bearings.  The likelihood is that once you strip them, you’ll find wear ridges in the spider journals.

[dave88sw]

Well i found some time this evening to have a look, i drained the front axle, it had plenty of oil, nothing worrying came out.  Took the prop off, both UJs are smooth in all directions and have no play.  There is a tiny amount of play in the pinion bearing but i really mean tiny and the same in the transfer output bearing.  Both are smooth when rotated.  So having not really found anything, i greased the prop and stuck it back on.  When i took it for a drive, the noise is pretty much gone, if i really listen for it, i think it's still there but it's greatly reduced.  Don't know now whether it was the oil change or the prop that's given the improvement but i'll just keep an eye on it for now.  I'm not overly concerned, it's easy enough to avoid making the noise and nothing i've found is ready to pack up.

 

[Snagger]

I don’t think there should be any play in the pinions.  That will not only allow vibration but will allow bad mesh of the gears.

[cackshifter]

Try having a feel of the U/Js after a drive. If you have a hot one, it's a sure sign. (Careful, they can get fing hot)

[dave88sw]

Well, I should have replied to this sooner as the noise hadn't in fact gone, it just seems to be better some times than others.

I think it's more of a vibration/resonance issue but i can't pin down what it is.  Having found play in the diff pinion, both prop sliding joints and the front output bearing of the transfer box, i have swapped the front diff, fitted 2 new props and changed the transfer box bearing.  Both axles have fresh oil, as does the transfer box.  The wheels have recently been balanced too. 

So, any opinions as to where i go next?  I'd really like to get to the bottom of it, it worries me that it might be something that's about to fail.

 

Thanks

Dave

[western]

What are the hub bearings like, maybe a strip/clean/inspect/replace or regrease/refit is needed. 

[dave88sw]

All 4 hubs have been off, had new discs on the front, 3 out of 4 wheels had new bearings, the 4th was regreased because it was in good condition.  I've been right through the whole car, i really can't think what's causing it. 

[Snagger]

My RRC gets a rumble from the front end accelerating through around 55mph.  I replaced the prop UJs, the diff (even though the original seemed good), CV joints, wheel bearings and brake discs.  None made any difference.  There is some very slight wear in the stub axles, where the wheel bearings sit, so I think they may be the cause.  The ridge is tiny, barely catching, but that slight diameter reduction could be allowing the inner races to chatter.