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MG Midget and Sprite Technical - strange noise

Hi

have a 77 MG midget
today as i was driving along it developed a awful sound
only making noise while in gesar and moving. if you press the clucth it stopes

Have a listen and see what you think

http://www.eircooled.com/sound.wav

Thanks
James
jk Kelly

Sounds like it could be a UJ on the propshaft.
Guy Weller

how can i test this?

Thanks
jk Kelly

One test - which won't proove definitely that it is the UJ, but does eliminate some other possibilities - is to drive the car at about 20 mph and slip it into neutral to see if it still happens when free-wheeling. This would suggest drive-train but not gearbox.

Actually, if it stops when you depress the clutch travelling and then perhaps my suggestion of a UJ is wrong anyway
Guy Weller

IS gets alot quieter when i depress the clutch or slip into neutral

Here another sound clip i've included commentry

http://www.eircooled.com/sound2.wav

Cheers
jk Kelly

I think maybe you are right Guy it s
does sound like the Propshaft.

Get under the car James and try to turn the propshaft back and forth to see if there is play in the UJs

I assume that the engine is firing correctly as from the wav file it could be an engine misfire and a blowing exhaust. It is vey difficult when you are not there.
Robert (Bob) Midget Turbo

Being its a 1500,

When was the last time you looked at the thrust washers...1500s are notorious on wearing out thrust washers, good for around 40-60,000 miles, I hope its just a U-joint, if not thats where Id look next is the thrust washers...granted Ive never heard an engine run with worn out or fallen out thrust washers, but I guess it would sound similar as to that kind of knocking. and the fact that it gets quiter when the clutch is depressed. and in nutral, mmmm

Gryf can probably give some insight, he just changed his about 2 months ago...luckly engine in repair.


you might try jacking the car back up agian, have someone run the engine and shift thur the gears while you look at the crankshaft pully to see if it moves back and forth as they shift thur the gears from 1st to 4th and back agian...if you see the C.pully moving in and out of the engine...thrust washer time...just be carful the car doesnt fall off the stand while in front of it going thur the gears.

Prop
Props Black Hole

Prop could be right about the thrust washers.

But you can eliminate possible engine problems if you do the freewheel in neutral test and switch off the engine (but don't lock the steering !!) A worn UJ will often sound louder when under load or being driven by the engine, but with the freewheel test it would still be apparent and without the engine noise is easier to hear.

If it is UJs pumping some grease into them should quieten them down for a short while. They will still need replacing but it at least would confirm where the noise had stopped coming from and confirm the diagnosis.

Guy
Guy Weller

You can eliminate possible engine problems if you do the freewheel in neutral test and switch off the engine (but don't lock the steering !!) A worn UJ will often sound louder when under load or being driven by the engine, but with the freewheel test it would still be apparent and without the engine noise is easier to hear.

If it is UJs pumping some grease into them should quieten them down for a short while. They will still need replacing but it at least would confirm where the noise had stopped coming from and confirm the diagnosis.

Guy
Guy Weller

Agree...sounds like possibly a u-joint.

I had a terrible vibration in my '78 drivetrain...turned out to be worn u-joints, a bent drive shaft and bent differential flange, but vibration got better when taking out of gear (no load on drive shaft).

Check u-joints.

Dave
DL Rhine

Wow DL,

what did you hit to make that kind of damage
Props Black Hole

How much of a job is it to fit new UJ's
Does anyone have a guide to the job?
I'm new to mg's but fair handy with cars mostly old vw's

I'll get some help to check the trust washers (engine is running sweet) and grease the joint tomorrow

Thanks
jk Kelly

I think you ought to find out what is the real problem first. :-)
Robert (Bob) Midget Turbo

Prop

Wasn't me, no idea...bought the car, drove it home, but couldn't get over 25-30mph...choke stuck almost closed (Webber DGV).

Got the little beast running somewhat ok...took it for a brisk test drive & discovered the vibration at about 40-45mph...feared the worst: tranny or diff, luckily it turned out to be only driveshaft problems.

Dave

DL Rhine

Jk,

If it is the U-joints, drain the fluid out of the tranny, un bolt the 4 screws off the diff, and take the whole drive shaft to a transmission shop...Its cheap to have them replace the UJ, I want to say 30 dollars for both ends not including the cost of the U-joints.

drop it off on the way to work, pick it up on the way home.


Prop
Props Black Hole

If it's the thrust bearing, won't idle drop when the clutch is pressed?

And you don't need to jack it up and shift gears to see this prop, just look at the pulley, engine off, have someone press the pedal. Or put a DTI on it (You've got one don't you prop?)
Alex G Matla

Man DL,

I guess thats why it was for sale...certianly glad it worked out for ya.

There really needs to be laws for misrep when it comes to selling cars, we have laws in place for houses and those problems are so much more evident, then problems on a car, I mean really...Theres no way the dive shaft and flange got bent driving down the road and they didnt know it, can you imagine the clamer and noise that had to have made, not to imagine the jaw and teeth jaring impact they had to have felt when it happened. I know I wouldnt have want to experiance that, Id been sore for 3 days and in bed for at least 1 after that wham bam! It reminds me of the guy that bought the midget several months back it started banging about 5 miles down the road, after buying it on line and just picking it up for the 1st time, He barely got home, looked at it several days with other people then finally pulled the head...end result WRONG HEAD!! The pistons were slapping and slamming into the clyinder head...the sellers response...we had that fixed several months ago, and never had a problem...sadly the guy wouldnt fight them no matter what...took the whole responsiablity on his shoulder, saying he bought it, he should have known of the problem...god just sicking. bit thats proof people will screw over other people if given half a chance, and no real protection agianst lying and fraud (or lack of notification of a known problem,,,same as lying) when it comes to selling cars.

I mean granted, a fan belt breaks, a light bulb burns out, ect ect...thats expected, its wearable item....but the wrong head on an engine thats banging away after it gets heated up... a bent drive shaft and flange... and then for them to state " Its a lovely little ride, not a single problem, worked flawless the entire time we owned it". I mean come on, thats just fraud pure and simple.

Id hoped you at least jumped there throats when you found out if they hadnt informed you

Prop
Props Black Hole

With incrediable Fortune and luck Alex,

Im glad I dont have alot of experiance with thrust bearings other then what Ive read and delt with on my engine rebuild, recently....But now that you mention your thoughts...Id think your correct, it does make sence.

Sorry I dont own 1 DTI...I got 2 of them.


Prop...Have DTI, will travel...Prop
Props Black Hole

Robert is right, you do need to do some more tests to determine what the fault actually is. So far you have only had suggestions.

If it is the UJs as I suggested, then the John Twist video on U-tube shows you how to replace them:

http://www.youtube.com/watch?v=gDX17xf9grA

Guy
Guy Weller

Ignore what Prop says about draining the tranny (gearbox).

The 1500 propshaft has a bolted flange at both ends, whereas the 1275 and earlier had a splined shaft that went into the rear of the gearbox and kept the oil in place.

I'm not sure what the Datsun 'box uses.
Dave O'Neill 2

Thanks Dave,

I wasnt aware that the 1500 had a front acessiable flanged/yoke. I assumed the yoke was U-jouinted to the drive shaft like the 1275.

Prop...always learning...Prop
Props Black Hole

And as for the thrust washers, yes, I replaced mine recently, mainly for peace of mind. I've heard all the stories about the rear washer wearing thin and falling out, but I suspect that this would occur mainly in cases of prolonged neglect, coupled with clutch over-use. Mine showed only moderate wear at around 86K miles (pictures here: http://www.flickr.com/photos/safety_fast/sets/72157620901424182/), but as I don't know the history of the engine prior to my purchase of the car over thirteen years ago, they may not be original. But I'm pretty easy on the clutch, so maybe that helped.

-:G:-
Gryf Ketcherside

I had a good look at this today

It looks like its the bearing in the diff
I checked it for oil and put in about 300ml before it came to the fill level.

I plan on taking a right look at this tomorrow

I'm guessing.
I take off the bolts off the driveshaft
then take the nose cone off
After that What should I expect?
Is it much of a job to repalce this?
If it is the bearing, What else would be needed ie. seals etc.
any diagrams?

Thanks for the help so far lads

Cheers
James
jk Kelly

So James,
What brought you to the conclusion that it is a bearing in the diff?

Guy
Guy Weller

well both UJ's have no play in them

with one wheel off the ground
I had it in gear I got my stethoscope and could hear the strongest sound comming from the diff

When it was reved a bit the whole rear axle was wobbling

It may be something more serious than a bearing but 90% sure its something inside the diff

Also so the fact it was very low on oil wouldn't have helped things
jk Kelly

What are the common issues with the diff?

cheers
jk Kelly

Got halfshafts???

ya know like the milk commericals...got milk?

Anyway half shafts, are the weak spots ...they like to break under load, but clearly not a problem you have

So any ideas where the oil is leaking out from


Prop
SheBoyGan5 from Prop

I haven't noticed any oil leak
I only have the car a couple of weeks
jk Kelly

there was a little oil on the bottom of the diff today.
I guess its being leaking since i topped it up.

I have drive shaft disconnected and the is a clunk clunk in the diff when i turn a wheel
Sound file below.
http://www.eircooled.com/sound3.wav

Could it be a halfshaft?

:(
Jimmy
jk Kelly

The most likely things to fail in a Midget diff are

1. The thrust washers under the spider gears and/or sun gears wear out. This wear is accelerated if using a Midget in time-honoured fashion ... vigourously with lots of wheelspin (autotests etc)! The wear creates a clunking noise when you change from forwards to reverse, or go from power on to power off (and vice-versa) with the accelerator.
If it only the thrusts, it is cheap and easy to fix - the four thrusts and the gasket are about 10 quid.

Under free load with the car jacked up as you had it, it might make the sort of sound on your clip. (Though it sounded like UJ to me too, obviously not from your recent post)

Even if they aren't stuffed, I'd replace them anyway unless they were perfect because the consequences of leaving them a bit sloppy can be quite expensive. (Another thing I found the hard way in my youth!)

2. If it has been like 1 above for some time, then the differential cage will wear too because there are no thrust washers to protect them. Same symptoms, but worse and louder.
Solutions:
If the wear in the cage is minor, then you may get away with oversize thrusts. These are available for both the sun gears and spider gears, similar price to standard ones from memory.

However, if the wear on the cage is too much, then you will need to replace it. A second hand cage is reasonably easy to get - from memory all the rear drive A series cages are the same, it's the housing that can vary with the ratio. You will need to set up the crown wheel backlash to the same as it is now (unless the diff had a whine in it too) so I suggest you measure the backlash before you pull the cage out of the carrier - that way you'll know what to set it too.

(The manuals tell you how to change the backlash, or if need be you'll get plenty of help here. If the worst comes to the worst, get a workshop to do it ... and give them the inistial backlash you measured.)

3. The spider pinions themselves can wear, the sun gears also. Solution is to replace them with good second hand ones which are relatively plentiful as Morrie shopping baskets didn't get as much grief as Midgets from their owners!

4. If there has been slop in the pinions and sun gears while the car has contiued to be driven hard, the spider pinion can shatter. (Been there, done that). This is made more likely by lots more power from an uprated engine.

If you are unlucky, a fragment of broken gear will get caught between pinion and crownwheel and you will need a whole new diff. (Been there done that too)

However, I don't think this is your problem, as when the pinion shatters you lose all drive and from what you say that's not a symptom. A broken halfshaft loses all drive too, so unless it's bent I don't think you have that problem.

5. Some types of differential cage bearing have plastic ball separators, which can unhelpfully break and allow all the balls to slush around This will cause the crown wheel and pinion to run out of mesh and whine, or even whoop-whoop as the clearance varies due to the cage wobbling (another lesson learned the hard way). Your noise sounds too clunky for this but I can't rule it out. Usually renewing the bearings will fix it.


And if you have a heavy right foot you could also follow our solution to all of the above and fit a limited slip diff!

Paul Walbran

wow...thats intresting,

Im looking forward to seeing what you find out


Prop
SheBoyGan5 from Prop

The diff cage actually broke on my MGA. A dirty great crack opening and closing, depending on accelleration.

It sounded a lot like that, but louder under load. I just swapped the whole thing out.
Nick

Any tips for getting the pinion nut off with the axel off the car?
jk Kelly

Nick: Been there done that too, with a ZA Magnette in an autotest :-(. Have yet to see it in A series diff but nice to know it was not a unique occurrence!

Jimmy: get a bit of flat bar steel about 2" x 1/4" and a couple of feet long (or a bit less). drill 2 holes to match two of the holes in the pinion flange and bolt it to the flange to take up the reaction torque from undoing the nut. It can help to have a half shaft in one side of the diff head to stop it sqirming around.

(If you are really tricky about the flatbar, taper it to almost zero at the outer emd thyen with a few suitable holes to lighten it further it's weight then exerts the correct torque for pinion bearing pre-load measurement.)
Paul Walbran

Thanks lads

Found my problem

www.eircooled.com/mg1.jpg

www.eircooled.com/mg2.jpg
jk Kelly

Bugger! How familiar are you with the various lternative ratios for the A series?
Paul Walbran

not at all familiar
Can you tell what ratio is in it?
Do those ingraved numbers mean anything?

from the link below
i'm guessing lower is better.. lower meaning you can go faster and cruse with lower revs but will loose some accelartion
http://www.mgcars.org.uk/andyjennings/mg-midget-axle-transmission.htm

Also whats the capacity of oil in the diff? do i use gearbox oil. 75-90 ok
jk Kelly

As there are 11 pinion teeth, you have a 3.7 diff (11/41).

These were fitted to later 1500 Midgets and are pretty rare. They also seem to fail with alarming regularity, possibly because they have more pinion teeth than any other A-series diff, meaning that the teeth must be narrower in order to fit them all in.

The 3.9 diff - as fitted to most 1275 Midgets - is more plentiful, as is the 4.2, which was also fitted to Morris Minors. There used to be plenty of them in Ireland, but I'm not sure how many are left.

If you don't have any luck, I do have a 3.7 diff, plus a couple of 3.9s.

daveo138 (at) yahoo (dot) co (dot) uk
Dave O'Neill 2

Count the teeth on the crownwheel and the pinion (although its probably stamped on the crownwheel and/or the diff casing)divide the crownwheel teeth by the pinion teeth - on a '77 1500 its likely to be a 3.9:1 diff (10/39) - you can get taller gearing with a 3.7:1 diff (11/41) but they tend to come at a premium price on Ebay

Edited to agree with Mr O'Neill who went to the trouble of counting your pinion teeth himself!
J A Bilsland

Also, I forgot to answer your question about oil.

I don't remember the capacity offhand, but you really MUST use EP90 oil, not just any 90 weight gear oil.

EP is for extreme pressure, as hypoid bevel gears do exert a lot of pressure at the point of contact between the teeth.

I would also advise you to use a good quality oil. I bought one brand of EP90 oil from my local motor factor and promptly destroyed three or four diffs in the race car. The last can of EP90 that I bought was 'Unipart' from Partco and I didn't have any problems.
Dave O'Neill 2

Oh good grief!!!


you can use the more common 3.9...seriously, Ebay is your friend, these things are as common as dirt, compared to the 3.7...I think bruce hamper got one recently for like $35 it was in great shape...just replace the pumpkin, and leave the black arts to the devil worshipers...

I wonder with the fluid so low, it just over heated


Prop
SheBoyGan5 from Prop

I've ordered a good second hand one so lets hope it all goes together nicely
Fingers crossed for monday

Thanks for your help guys
IF i have any other bother i know where to come
:)
jk Kelly

This thread was discussed between 13/09/2009 and 17/09/2009

MG Midget and Sprite Technical index

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