Help with rear end noise

[Vox]

Hi all,
Haven't been on here for a while.
I am after some opinions on some rear end noise I am getting.

Once I get above about 65 I start to get a drone from the back end, which gets louder the faster I go but disapears if I take my foot off the throttle. Rear seems fairly quite below these speeds, not exactly silent but nothing you really notice.

I am thinking it is a worn diff but before I spend time & money searching for a better used one I was wondering if it could be anything else, perhaps quill shaft bearing? I have a new one of these and believe they can be replaced in situ after the diff and prop have come out (which I have done before to change the oil seals).

Background of car - 1972 2000 manual (non O/D) saloon with what I believe is the orginal 4.11:1 diff. Car now has 105,000 miles on it and I have done about 12,000 of them in the 6 years I have owned it.
Prop shaft was re balanced early on in ownership and one half shaft was swapped for another used one due to slight bearing noise - neither change made any noticable difference to the noise from the back although the prop re-balance did wonders for cutting vibration!

The noise has always been there and I wouldn't say it has got any worse but I don't do motorway speeds that often but I was carrying a passenger in the back down the M40 the other night and he thought the noise was hilarious as he couldn't hear our conversation in the back!

Any thoughts appreciated, plus also a line on a good diff if that is the way to go would be a help.

cheers
Chris

[Mike Stevens]

It certainly sounds like the diff to me, especially as it changes when you take your foot off the throttle.

Have you checked the oil level? If it gets low the crown wheel and pinion can 'pick-up' and get damaged. Sadly, I have done that a 'few' times in the past!

Cheers,
Mike.

[Vox]

Hi Mike,
Thanks for the reply.

Diff had a bit of a drip from the front so I put a new seal in. Also put in exchange output shafts from a Stag specialist (as I don't have a press to to push out the stubs to change the seal) which annoyingly seem to seep a bit. Breather is clear. I also took the back off and put a new gasket in there for good measure and couldn't see any obvious damage/wear to gears.

Oil level was good when I got it and has been maintained (and the leaks more or less fixed as above) but could easily have been run low at some point in its life.

I shall have to start a hunt for the proverbial 'good' used diff. Don't mind spending a reasonable amount for a definitely good diff as exchange ones are well out of my price range!

Thanks
Chris

[Dave B]

I would start with the quill shaft bearing if I were you, since you say you already have the parts. The symptoms you describe are exactly the same as my 2500, ie noisy on a light/trailing throttle at 60/65 mph. I recently drove another 2000 with a shot diff and it was a completely different noise, a gear whine from about 35mph onwards, both under load and on the overrun.
I will watch this thread with interest to see how you get on, as its on my to-do list!

[Vox]

Hi Dave,
Your noise kicks in at the same speed but sounds like it is the other way around? Mine is noisy under throttle but goes if there is no throttle.

I agree that changing the quill shaft bearing is the next step as I already have one ready to go in and it can't hurt. Might take me a week or so to get around to it though as my wife and I were out on our 70s motorbikes last night and problems developed with both of them and we are meant to be doing a photo shoot for a local photographer a week saturday but are doing a tour of Abbey Road recording studios (50th anniversary of the Beatles album) this saturday so sunday will be working on the bikes.

Thanks for your input!

Chris