Differential problem?

Post by **rcbowman** » Sun Mar 16, 2003 8:16 am

Okay, a puzzle for you all.

One day, suddenly, whilst I was driving, the engine stopped supplying power to the wheels. The engine itself still runs perfectly. There was no noise of grinding or other such catastrophic sounds. My first time through trying to diagnose the problem made me think it was the clutch. I replaced it, though it seemed fine (though the release bearing was worn down to the metal). Clutch is now working perfectly. The problem remains.

Here's what happens: When in gear, propeller shaft spins, so both clutch and gearbox are okay (several other checks confirm this). If the rear wheels are off the ground, the engine turns the wheels, but you can stop them (both at once) pretty easily. On the ground, it doesn't produce enough force to move the car. But the prop shaft continues spinning.

Okay, so that should mean the differential is dead, but there is not now and never was any grinding noise. Also, when the car is off the ground, the wheels run smoothly, whether the engine drives them or I spin them by hand. No hesitation, no catching and gliding, no noise.

It sounds to me like maybe it's a limited-slip differential whose thrust spring has failed, so that it's halfway in contact, so that it drives the wheels weakly but smoothly. Does this make any sense? I don't really know much about LSDs. I've run across references to after-market limited-slip differentials for the Minor (they say it's the same part as the Sprite), but the first parts guy I talked to about it said there was no such thing. Any racers know for sure? Could a previous owner have put in an LSD in it, and could the LSD have just failed?

Or on the other hand can anyone come up with a plausible failure of the normal differential that could act this way? Or - I don't know - any other solution to the puzzle? After all the extra work I've done recently, I don't want to start taking apart the rear end without a little more certainty I've isolated the problem.

Thanks

Reed C Bowman

Post by **Willie** » Sun Mar 16, 2003 9:03 am

Lo, of course you have either a broken half shaft or a stripped
crown wheel and pinion. Whichever way you will have to remove
the half shafts as a first step so you should order the necessary
paper gaskets and rubber sealing rings(for the halfshaft/hub joints)
AND new paper gasket for the differential joint(get two they break
easily). If one of the half shafts comes out with the spline end missing
then you have found your trouble. Whatever you find you will have to
remove the diff anyway to remove the broken end and clean it out.
If you need a new diff unit do not buy just a crown wheel and pinion
as it is a highly specialised job to fit them properly. The trouble is that
most of the Minor specialists are not selling exchange diff units at the
moment because they are having trouble finding suppliers of high
quality! I would encourage you by saying that the fact that either
of the wheels still turning suggests that the crown wheel is still being
driven so a broken half-shaft is the most likely fault.
When my half shaft went there was a very slight click and that was
it! You can buy exchange 'toughened 'half shafts from the Minor
specialists, The surcharge if you do not have one to exchange is
not a lot

Post by **rcbowman** » Sun Mar 16, 2003 6:24 pm

Hm. This is helpful. Both wheels are driven, though, and evenly. And turning one by hand turns the other. So I don't see how it can be a half shaft. And I still don't see how all the symptoms could be caused with a normal differential.

What you say about refurbished differentials of quality being lacking at the moment is of concern - most of the parts places I've seen do have differentials on offer. Is there something I should check to be sure they have replacements of sufficient quality?

RCB

Post by **Willie** » Sun Mar 16, 2003 8:33 pm

well it is possible that the end of a broken half shaft is dragging
on the bore of the differential carrier, if you keep rotating the
diff after a half shaft breakage then usually the broken end will
grind into the metal of the carrier and make a right old mess of
it. In doing so it could drag enough to rotate the wheel so that you think
it is 'normal' It actually makes no difference...you have GOT to remove
the diff unit whatever the problem so arm yourself with the necessary
gaskets and oil and enjoy yourself! With regard to the exchange
differential problem it is not the quality of the parts so much as the
inability to set the units up correctly. The usual result is' whining'
which quickly appears after fitting. I have just fitted a unit which*
made it impossible to exceed 45MPH without shaking the car to bits!
(the pinion to prop shaft flange was bent)! That was from a long
established specialist!!!

Post by **rcbowman** » Mon Mar 17, 2003 4:58 am

Thanks for your suggestions, Willie. I shouldn't have doubted you on the broken half-shaft. I finally got up the nerve to take the *#!$% thing apart today and sure enough it's the left axle that's torn away at the end of the differential end gear splines, in an awful mess. I'm truly amazed not only that it wasn't making a horrible din, but also that it ran so smoothly and evenly by engine and hand when the wheels were off the ground.

There's chatter scarring on the end gear collet, but since that doesn't appear to contact the axle in normal operation, and since the splines seem fine, I guess I can clean that up and put the old differential back in. It appears fine otherwise (actually, it's beautiful: a lovely piece of machinery, I think), and I think I was careful enough in driving out the end of the axle, though its break had jammed it in rather nastily.

Thanks again for your help.

RCB

Post by **Willie** » Mon Mar 17, 2003 8:19 pm

Glad you found it....if you mean the scoring is on the hole through
which the half shaft passes in order to engage the splines then you
are correct ...the half shaft does not actually touch it (except when
its busted)!!! If it's not too late you should carefully check the other
unbroken half shaft to see if you can see a 'step' on the splines
between the section which engages with the planet wheels and the
unworn section? This is the area which will shear one day so if it's
bad you would be advised to change it while you have the axle in
bits. (If you buy the 'toughened' half shafts they come in pairs anyway)
good luck

Post by **rcbowman** » Wed Mar 19, 2003 4:36 am

Yeah, I'm pretty well resigned to buying the hardened shafts. The ones I can get locally are so godawful expensive, that I may as well buy from England, and what with the huge transatlantic shipping cost, there's no reason not to pay the extra money for hardened ones.

Also it has been pointed out to me the old axles were not really designed for the power of the 1275 engine which someone seems to have put in the car. Not that I'm complaining about having that engine, mind

Post by **Chris Morley** » Wed Mar 19, 2003 3:21 pm

Hello Reed,

I think you can safely say that the extra power of a 1275cc engine accelerated the demise of your half shafts.

What year is your car? I'm thinking that if the diff & rear axle comes from a 948cc car (37bhp) then the 55-65? bhp from your 1275 engine is more than it can take. The set-up from a 1098cc (48bhp) should cope better although the half shafts eventually give way even in standard minors.

For a U.K supplier, I can recommend East Sussex Minors:

http://www.morrisminorspares.co.uk/

Part : DIF146. Half-Shaft (Hardened) EN32TZ £60.00(Pair) .

That's about $88. They have a facility for you to ask questions on the web site. If you tried to airfreight the parts it would cost a fortune, but surface freight should be less if you can wait a few weeks. Ask for a copy of their parts list as well. If you need smaller items then this might be a good opportunity to get them at the same time.

Post by **Cam** » Wed Mar 19, 2003 3:24 pm

The standard axle with hardended halfshafts should take the power of a stock 1275, assuming everything else is OK (diff gears, bearings, etc).

So you should be OK as long as you don't gun it everywhere!

Post by **Willie** » Wed Mar 19, 2003 8:08 pm

Remember..the same half shafts were fitted to the Riley 1.5 ltr
cars. The problem is age, they can't go on for ever!

Post by **Chris Morley** » Thu Mar 20, 2003 2:21 am

I understand it's a matter of metal fatigue caused by the ongoing twisting motion imparted to the halfshafts during acceleration. The greater the amount of force (ie: bhp ) the greater the twisting motion. In fact the half shafts do twist slightly which is why it's necessary to put old halfshafts back on the 'right' side.

It stands to reason that the half shafts fitted to Riley 1.5 cars would have broken much sooner. Any Riley owners out there who can confirm this? As it is many Minor half shafts have lasted over 30 years, probably including mine.

As replacement is so simple perhaps I should also fit a pair of hardened halfshafts. But will this accelerate the failure of any of the differential components?

Post by **Kevin** » Thu Mar 20, 2003 1:56 pm

Chris I had a Riley 1.5 in 1969 and during my ownership of 6 months it broke no less than 3 halfshafts

so I sold it I don`t know if hardened half shafts were available then, but I then bought a Ford Anglia which had 3 advantages over a Moggie, 1st a heater that gives out a reasonable amount of heat, 2nd an inverted rear screen that meant very little misting or condensation problems, and the 3rd and best an early warning system this was created by the will it or wont it starting system that is best described as a tin can full of washers coughing, that let the whole neighbourhood know when I was trying to start the thing

, after that I went back to a Moggie

_________________

Post by **Chris Morley** » Fri Mar 21, 2003 12:30 am

Kevin - Three times in six months!!! Blimey..

Now either you were the original 1960s boy racer or the halfshafts were hoplessly weak.

Which was it?

Post by **Kevin** » Fri Mar 21, 2003 1:21 pm

Chris - I would like to think it was the latter but the car had a previous owner called James White who was one of the lesser known Great Train Robbers

(did not know that when I bought the car) and he had a Modified Cylinder Head, Rejetted Carbs & improved Manifold along with a Girling Powerstop Servo fitted to the car, so the car was a bit quicker than a standard Riley 1.5 in a straight line, however the cornering was still very much Morris Minor style and the Servo gave the brake pedal a bit more feel, so that if urgent braking was required it reduced the sensation from Blind Panic to just plain Panic I am just glad there were a lot fewer roundabouts

in those days

Post by **rayofleamington** » Fri Mar 21, 2003 4:56 pm

Now either you were the original 1960s boy racer or

Having seriously abused my Minors (1980's boy racer) I've never broken a half shaft not even with a 1275.
I used to find it fun to drop down to 2nd at 40 and drop the clutch whilst braking to lock the rear axle and slide the rear end out, not to mention wheel-spinning 3 point turns.
All that forward and reverse loading of the halfshafts should have broken something, but it was fine and I had that car for 11 years.
I guess I was lucky but eventually the car gave me my come-uppance in the 90's as I saw off 3 gearboxes in 3 months whilst commuting daily. That put me off Minors for a long time.

Girling Powerstop Servo fitted

Ah yes just remembered what I was going to 'put off doing' this weekend.. ;-)

Post by **Cam** » Fri Mar 21, 2003 5:14 pm

I used to find it fun to drop down to 2nd at 40 and drop the clutch whilst braking to lock the rear axle and slide the rear end out

Ha Ha, that's fun, and that's what 40MPH speed cameras are for!! as soon as the graduations on the road end, drop into 2nd and boot it sideways!!

Girling Powerstop Servo

or should that be Girly Powerstop Servo

Sorry!! (we have had that discussion before

).

Post by **rcbowman** » Tue Mar 25, 2003 4:52 am

Wow -

I thought I was still watching this thread, but I guess I'm not; I didn't get notified of all the further discussion.

I did indeed order hardened shafts, from ESM, whom I like, and have ordered from once before this. I just got them today, and one of them doesn't look good. I've put the good one on along with my remaining normal shaft, and I'm e-mailing ESM about the condition of the other to see what they want to do...

But at least the car runs again after WAY too long.

Thanks, all, for your discussion and advice.

RCB

Post by **rcbowman** » Thu Apr 17, 2003 9:00 am

Oh, dear. I shouldn't have left that post there without followup so long. When I contacted ESM about the problem (transverse hairline cracks at the inside corner of the splines) they said it was a problem their supplier of toughened shafts had had before. They thought the problem had been solved earlier, but after my complaint they rechecked their whole stock and sent me a new shaft free of charge (this is from Sussex to California, mind you).

I call that excellent service.

Morris Minor Owners Club

Differential problem?

Differential problem?

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