Diff diagnosis / upgrade

Post by **67trav** » Tue Nov 11, 2003 9:59 pm

Hi all
I suspect that at sometime in the near future we're going to need a new diff. Noticable most when the car has warmed up, quite a harsh rubbing-grating type noise from the rear, mostly on overun (throttle backed off after running constant speed). Anyone think off any other likely cause? (Have checked the diff oil, of which there is sufficient)

Also, as we run a mildly tuned 1275 (in late-ish Traveller, with std gearbox) we could probably do with upgrading to a higher ratio (3.9:1)? as we rev rather high and would like to be able to drive a little less frenetic. I wonder about where we are going to get a good 3.9 diff (I have seen a company advertising new crownwheel/pinion sets from Middx, but have no experience off them) - Anyone else got any advice on obtaining good replacements and what models would the 3.9 have come from originally (Riley 1.5 / Wolseley 1500, etc?)

Advice much welcomed.

Cheers,

Ben

Post by **Kevin** » Wed Nov 12, 2003 1:04 am

The 1275cc Midget also had a 3.9 along with the Wolseley but the Riley one I think is higher at 3.7, so Iwould think the Midget one easiest to aquire.

Post by **Kevin** » Wed Nov 12, 2003 12:43 pm

Just noticed that the Birmingham minor centre do all the ratios as well
http://www.morrisminor.co.uk/index.htm

Post by **Willie** » Wed Nov 12, 2003 8:07 pm

It is common for a diff to 'sing' when pulling but,I believe
that if it sings on the overrun it is usually a sign of poor
condition. The advertiser in the club magazine will
exchange your 4.22-1 diff unit for a rebuilt 3.9-1 unit
but charges more for the privilege. having owned a
1275 Midget with a 3.9-1 diff I can say that they worked
very well together but,of course, the Midget is much
lighter than your Traveller.

Post by **67trav** » Wed Nov 12, 2003 8:29 pm

Thanks for the replies chaps.

Look like getting hold of one might not be so much of a problem then. What is a the job like to do? The straight replacement doesn't seem too bad, but is there any setting up to do (backlash / shimming, etc.?)

I just hope I can attribute the noise (more of a din) to the diff., as my previous experience of diff noise is indeed as Willie describes, 'singing', this is more like grating / scraping (painful!). It would be a shame to do the diff, only to find it is something else, but I can't think anything else at the rear of the car would be making a noise on overun (rear prop UJ, half-shafts, rear springs/bushes seem less likely to me than the diff(?))

Cheers

Ben

Post by **Willie** » Thu Nov 13, 2003 7:46 am

Now you have arrived at the problem! Anyone can
fit the new crown wheel and pinion but to do it properly
is a highly skilled job involving dial gauges and accurate
bearing preloads etc. Going by my
experience with the last three so called rebuilt diffs the
'experts' just bolt them on and that's that. Also,if your
diff unit is showing signs of excessive wear then the
planet wheels are also likely to be worn and the thrust
washers could be virually worn away so a recon unit
might be safer.

Post by **Willie** » Thu Nov 13, 2003 8:03 pm

Further to the above,if you do end up fitting an exchange
diff unit then it is a pretty straightforward job provided
that you have the necessary parts to hand first. You will
need new paper gaskets for the half shaft/hub joints,
new rubber sealing rings for the same joints, a new
diff unit to axle gasket. You have to pull the half shafts
out by about six inches to allow the diff to be removed but
that is sufficient if,like me, you have a narrow garage.
I would advise jointing compound on the half shaft/hub
joint. Rear axle oil will definitely drip out when the
half shafts are pulled out so remove or cover the brake
linings first! The half shafts are only secured to the hubs
by a single countersunk screw once you have removed the
brake drums.

Post by **rayofleamington** » Thu Nov 13, 2003 8:17 pm

how easy is it to get the halfshafts back into the new diff?

Post by **Peetee** » Thu Nov 13, 2003 8:27 pm

how easy is it to get the halfshafts back into the new diff?

Quite easy really. As you put the halfshaft in you will feel it bang aginst the diff casing. Then it's just a case of taking back the halfshaft a 1/2" or so, tipping them up with your hands around the hub end so that they are horizontal and repeatedly trying to feed them in. When the go they slide in easily.

Post by **67trav** » Thu Nov 13, 2003 9:53 pm

Thanks Willie
That gives us some ideas of the way forward (in hope that to find a properly recon'd exch diff will be possible). If I can find one then I'm happy enough to fit it (or at least attempt to).
Cheers for your help again
Best Regards
Ben

Post by **Willie** » Fri Nov 14, 2003 8:10 pm

RAY, as stated it is pretty easy to re-engage the half shafts
the reason that they do not just slide into engagement is
that they are NOT in contact with the inner diff bearing,they
merely pass through it so there is enough clearance to
let them drop down and not line up with the splined wheel
in the diff. Just a question of lifting and turning the shaft
until it goes in.