Differential checks.

[CAR]

Having obtained a diff off ebay, of unknown quality (advertised as a Stag one but must be off an estate as the number starts MGA....) and with a slightly noisy diff in the estate, I would like to know what to check, and how, before replacing seals etc and painting it ready for install.
Obviously if it's cream crackered I don't want to waste time and money on it, and have to change it back for the old one.
The one in the estate is noisier than the pi, although the bodyshell will accentuate noises a bit, but I don't think it's about to give up, so I don't want to rush putting the other one in, but with the RBRR coming up, it would be nicer if it was quieter.

Also can anyone describe how to tell what the noises may be, could it just be a quill shaft bearing, or is a noisy CW&P an easy noise to diagnose? There is a very definate clonk when taking up drive, which isn't a UJ.


Cheers Colin.

[owen1183]

Hello Colin,

I too have bought a diff from ebay as an unknown quantity, in order to have a spare.

this is my list of checks

Drain oil
check breather is free & clean
open back cover & check bearings & crown wheel & pinion for obvious damage
replace thrust washers & check back lash
check quill shaft bearing
re grease all bearings
replace oil seals
replace gasket re-fit rear cover
fill with oil

assuming all is ok with bearings & crown wheel & pinion, gaskets and thrust washers are cheap, oil seals are cheap

shouldn't cost more than £20 I wouldn't think

If the Crown wheel & pinion have had it or if the bearings have gone you might do better to scrap it and buy another

Crown wheels & pinions are nearly £300

[owen1183]

after a quick check it appears that there ar eno thrust washers to set back lash in our diffs?

Can anyone confirm this?

If backlash is too great is there no way of adjusting it without replacing the CW & P?

Edit:

Just answered this myself, Chris Witor sells thrust washers to adjust backlash.

[Alec]

Hello Owen,

I seem to remember that there are two types, early ones that use thrust washers to adjust the pinion, and later ones with a collapsible spacer?. Shouldn't there be shims to adjust the crown wheel depth of mesh?

Alec

[Mike Stevens]

I believe the backlash (which can cause a 'clonk' as Colin describes) can be caused by the thrusts on the planet gears, (or whatever). The thrusts are selectively fitted on each side, thus moving the planet gear pairs in and out of mesh. I have read a very good explanation and restoration guide on the Stag list somewhere. I think I have it book marked at home. If so, Ill find and post it.

The other thing to look at is the crownwheel and pinion teeth. It's not easy to see the latter, but with the cover off the former is easy to see. There should be an even smooth wear on the drive side. Not odd marks or 'ridges'. Ridges is a bit excessive, but anything not smooth will cause a whine. It might also be worth cleaning the teeth and applying engineer's blue to see the teeth meshing. Plenty in the workshop manual for this.

How was the week away Colin?

Cheers,
Mike.

[Mike Stevens]

Found this piece on the SOC forum. It covers what I was trying to say. I think.
----------------------------------------------------------------
If you can turn the propshaft flange ten or twenty degrees before there is any movement on the driveshaft flanges, it is normally the thrust washers behind the smaller bevel gears in the diff that have worn thin. The shaft they are mounted on is held in place with a roll pin.

Knock that out, withdraw the pin and remove the small gears and their thrust washers. The center of the thrust washer doesn't wear and can be measured to find the appropriate thickness. The original thickness was stamped in but the numbers have normally worn away

This will normally remove most of the backlash in a diff and costs very little. I have never tried doing it with the diff still in the car, but if it is possible to lower it enough to remove the backplate it should be possible.

I have replaced the washers in my TR twice now and they need doing again, but it had done 145000 miles when it came out of a dolly sprint axle with knackered casing, and has probably done another 100000 since, still on the original bearings
----------------------------------------------------------------
Acknowledgements to Neil (flying farmer) on the SOC forum.

Cheers,
Mike.

[CAR]

How was the week away Colin?
Cheers,
Mike.

It was good thanks Mike, once we got there.
We did a little detour on the way down, to pickup some bits I had won off ebay near Bedford.
Once back in the car, the satnav said we would arrive at mum and dad's at approx. 2:15. We arrived just before 6:45!
We got to about 7miles from the Dartford crossing by 1:30 and sat there. Someone had broken down on the Dartford bridge and then their car had caught fire.
The pi got quite warm, but I didn't want to turn her off incase the pump decided to cavitate and leave us high and dry in the fast lane of the M25.
After a fair bit of mulling the problem (there was very little else to do!) I phoned Andy Roberts (thankyou for your help Mr. President) and he advised that even if the pump was hot enough to cause a problem, a bottle of water over her would soon sort the problem. Mind you the boot was crammed.
So I switched her off and she restarted fine. Luckily I had changed the rad 3 days before as the one on the car had allowed the pi to boil up going in to the BL day the previous weekend at Nene Park. So initially before turning the engine off we had the roof open,and heater and fan on full bore as an aux rad.
The car did us proud really, with lots of ultra reliable modern cars, golfs included, stranded at the side of the road. Who says the Lucas pump is a problem waiting to happen? I don't think it would have done so well if I hadn't run the direct feed via a relay to the pump when I bought the car.

How were your three weeks in France Mike.........yes stupid question I suppose

Colin.

[Mike Stevens]

Hi Colin,

Sorry to hear about the delays, but it seems to be the norm these days, especially on the M25. Hopefully when all the road works are finished (Huh!) things might improve.

Anyway, glad to hear that the PI behaved itself. Well, what did you expect - it's a Triumph!

So, what were the bits you got off ebay - a diff perhaps?

The 3-weeks was great. First week in Brittany with temperatures in the low 30s. 2nd and 3rd weeks in Normandie were a bit cooler but still hot in the sun. We also learnt a new French word - "Amortisseur". Shock absorber! We had to get them changed on Ann's 'modern' car. Luckily the 2 eldest lads came out for a week and they brought a new pair out which our neighbour got for us. A tatse of French life we'd not met before.

Back to reality now though.

Cheers,
Mike.

P.S. Tom, our eldest, has just got engaged. They want to have use of the Stag when they get married. AARRGGHH! Much fevered activity has started as I've probably only got 2 years to finish it!

[CAR]

Hi Colin,

So, what were the bits you got off ebay - a diff perhaps?

P.S. Tom, our eldest, has just got engaged. They want to have use of the Stag when they get married. AARRGGHH! Much fevered activity has started as I've probably only got 2 years to finish it!

Actually the parts were Dolomite rear arch repair sections, the rear part makes a pretty good substitute for the same area on a big saloon!

Congratulations to Tom, I'm sure you and Ann must be very pleased, and with two years to do the Stag, at least the wedding isn't something they feel they have to do. The Stag would make a great wedding car,(I have heard that grey primer can be 'mopped' to a pretty good shine ) particularly in the summer, I could see the pi ribboned up too.
The biggest problem I can see for you, is that the Stag at the moment is a pretty large and sturdy 'shelf', what will you do with everything that currently sits on top of it?

I will try and give you a ring at the weekend Mike for a bit of a catch up.

Colin.

[Mike Stevens]

is that the Stag at the moment is a pretty large and sturdy 'shelf'

AND cupboard!

Work on the Herald is happening at the moment (it's nearest the garage door), and is the nearest to completion. Then we'll see about getting the Stag out for it's top coat! (Yes, I know you've seen the garage Colin.) That won't be a trivial task.

Thanks for the phone call. It was a nice chat! Good luck with getting the estate ready for the RBRR. You must let me know the route when you can. We might be able to come and wave you on!

Cheers,
Mike.