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MG Midget and Sprite Technical - Knocking From Back Wheel
|For many months I have heard a short clunk from the back off side wheel when I drive off, I am sure the noise was there before I renewed the brake shoes, cylinders etc, I keep thinking its the brake shoes but they seem to be in correctly, anyone any ideas?|
I now seem to hear it also when driving off and each time changing gear, so something is knocking somewhere at the back. If it helps its a 1500 with wire wheels.
|Could be, its one part I have never touched, is there anything that can be tightened up or changed if there is play?|
Check the bolts that secure the rear lever arm shock absorbers to the triangular mounting plate. If they are very slightly loose then as you take up the drive the shock body moves with a slight clonk.
|Thanks Guy, would never have thought of that one, it is sort of a clonk and just a bit worrying not knowing what it is.|
|Worn splines on the wire wheel/halfshaft?|
|Dave O'Neill 2|
|I believe I read somewhere that if you loosen the wheel nut slightly and put the handbrake on, the play at the wheel rim should not exceed 1/4" rotationally . Any more and it suggests seriously worn wire wheel splines on the hub, wheel or probably both.|
Do you have the correct (narrower) while wheel axle? If not, it is likely that if standard half shafts are fitted, the end of the spline in only "just" engaged and this could wear prematurely.
Spline hub wear: see here http://mgaguru.com/mgtech/wheels/wl104.htm
give a nip up to all your rear suspension hardware... id lay good odds thats the problem
|Prop and the Blackhole Midget|
|Yes its worthwhile - because it is easy to do - to check all the other rear suspension bolts although in my experience they tend not to cause clonking noises. Just rear axle steering and other unwanted symptoms! The point about the shock absorber is that as drive is taken up the damper arm is pushed up and if those bolts are just a little slack you do get a single "clonk" noise as the damper body moves against the mounting plate.|
I have no experience of wire wheels. I know the splines wear so perhaps it is that, but I know which one I would be checking first!
Not what Tim has described, but a clonk from the rear when applying the brakes can be loose backplate mounting bolts - the 4 little ones that secure them to the axle casing.
I have had the same sort of noise as you describe, after spending hours looking and tightening everything I could think, I am sure I have found it. Rusty rear springs especially after winter when its not used so much. I oiled the rear springs and the noise went away. What put me on to this was the noise stopped if I was out in the rain, the water must have been acting as a lubricant. Now i oil the rear springs every time I grease the front suspension - every 4 months.
|M J Pearson|
You'd get the clonking noise when accelerating/decelerating so if it's absent then, likely to be something else so if it's not loose bolts, splines, or springs :) and if your ujs are old they may be greasable - check for a nipple. If they are a pump of grease may help.
To check -
'Another sign of wear is a clonk when you accelerate or decelerate, or a regular knock when the car is moving.
A sure sign of something breaking up inside the bearings of a joint is rust-coloured dust around the spider. Fit a new joint or shaft immediately.
To check for wear when no dust is evident, grip one side of the joint firmly and try to turn the other side against holding pressure. There should be no play in the joint at all.
Make another check by inserting a large screwdriver between the yoke and the spider and levering it to see if there is any play. If you feel any play, fit a new joint or propshaft.
The symptoms of a worn joint — the clonks or apparent play — are very similar to those for excessive backlash in the crown wheel and pinion.
Be sure that any play you do feel is in the joint, and not the rear axle.'
(Extract from http://www.howacarworks.com/transmission/how-to-check-u-joints)
|Springs on older cars were often heavily greased and then wrapped in leather gaiters, or later with Denso tape. The idea of the wrapping was to keep road grit out which otherwise sticks to the grease (or oil) and increases the wear rate. More modern springs are sometimes interleaved with nylon (or maybe its PTFE?) layers to provide a dry form of lubrication that doesn't hold the grit as oil does.|
|An alternative to Nylon or PTFE tape is low-friction self-adhesive tape from igus. There's a write-up here for a Morgan that will be attempting the Peking to Paris Motor Challenge and has had its rear springs fitted with the tape. http://www.machinebuilding.net/ap/a1845.htm|
|That tape looks like it might well be worth a try if using multi-leaf springs - even for normal road use it should give a more compliant ride. They make the same comment about grit and dirt causing rapid wear with greased or oiled springs, though maybe not so much on UK tarmac roads!: << usually heavily greased or lubricated, which in dusty, sandy and dirty conditions can lead to premature failure>>|
I see the article is dated April 2015, but assume that it refers to preparation of the Morgan for the event this year. I don't think it was held in 2015.
|Thanks to all for the suggestions, the rear off side leaf spring was replaced last year so hopefully thats OK, the article on the u joints is good especially with the pics which helps explain how to test etc, a very good few points to check, thanks all.|
|Several months ago I started investigating the above clunk and I was sure it was coming from the diff/prop shaft area, so after both UJ's were replaced I was happy that the problem was resolved, until the first run after refitting the prop shaft and the clunk was still there!|
Several weeks later after greasing the rear off side bearings, I was surprised to find the clunk had disappeared. After a week or two it has slowly re appeared, whether that is due to the grease wearing away or becoming thinner and less effective due to the recent 30 Deg C temperatures, but I would not have thought worn bearings would have caused a clunk, hopefully I am wrong??
|Why are you greasing the rear wheel bearings? They are lubricated by the diff oil.|
But presumably to get at the bearings you needed to strip out a few components in that area? I wonder whether the strip and replacement disturbed the status quo.
|my car passed its first MOT with the shocks barely attached. I got a nasty clunk over bumps and some rather brown trouser handling!|
if it clunks when heavy acceleration or gear changes it could be a slack diff. my does that, to be sorted soon. :-)
I am also confused as to why you would be greasing bearings Tim?
|Malcolm Le Chevalier|
|If greasing the bearing made it disappear, but it slowly re-appeared, it would suggest that you have a bearing problem.|
|Dave O'Neill 2|
|I have spent the last 30 years with a company car, so what is obvious too many (diff oil lubricating rear bearings) is not obvious to the less experienced midget owners!|
I had a noise from front bearings a couple of years ago and a good application of grease sorted the problem so thought giving the rear bearings a grease whilst the wheel and drum was off may be a good idea and it seemed to work for a couple of weeks.
It could well be the diff, but just wanting to check all other possibilities first, but I would not have thought that worn bearings would have caused a clunk, but would love to be wrong:)
|About a week before I went to Le Mans Classic, I fitted my spare diff because I thought the clunk I was getting was a sloppy diff.(see "Noise from differential" thread).|
All was OK until I got into France, when the clunk came back, so I'm thinking that the probability of two diffs with the same fault is low.
Guy's suggestion about loose shocker bolts seemed reasonable, so yesterday I got under the car to investigate. I couldn't find any loose fixings anywhere, so I got a friend who is a pro mechanic to stand to the left, right and behind the car while I drove it back and forth. He said the clunk seemed to be more from the right side, so I'm now wodering if it's the outer end of the drive shaft which is a splined press fit into the wire wheel hub, moving on power take up and power off. I've got a spare pair of shafts so I'll try changing at least the one on that side and see what happens.
|Hi Bernie, |
It will be interesting to hear the result of changing the drive shaft, mine appeared ok, but it will be interesting to hear if this fixes your clunk.
|Bernie, are you sure its not worn splines on the wheel and or hub, or even the spinner not done up tight enough.|
|My Mk4 clonked in the same way and among several things i did was putting in another diff (mainly though to get a better ratio), new hub extension, swap wheels round, replaced bearings etc. Still knocked.|
My MGA also clonks. Just ignore it now! Bl**dy wire wheels!
|Tim. I'll be doing a trial and error session tomorrow an d will report back.|
Trev. I'm pretty sure outer hub splines are OK and spinner tight enough, but I'll double check. Fresh shafts should help there.I'll also swap wheels around to see what, if any difference there is.
Graeme. That's depressing :(
|As a guide Moss say that if you put the car in gear (jacked up) to prevent the half shaft turning, and just loosen the knock off, there should be no more than about 5mm rotational play at the wheel rim. Any more suggests excess wear in the hub spline or wheel spine.|
|I fitted fresh drive shafts and it has made no difference. Still clunking on take up and over run.|
So it looks like I'll be leaving the 3.7 in for now, while I strip my 4.2 and fit new thrusts. I hope that will cure it. It's probably about all I can do because the sun and planet wheels are unobtainable according to the Moss catalogue.
Would a thicker oil, say 140s help,or am I clutching at straws? Straw. That reminds me of the old stories about dodgy car dealers and what they used to put in engines, gear boxes and axles to quieten them down.
Back to the drawing board!
|In the "old days" we used to wrap a layer or two of aluminium foil around a worn spline to take up any slack. I guess the modern equivalent might bi PTFE tape. Might be worth a try, nit as a solution but to see if the noise stops, as a means of narrowing down the problem.|
Is it noticeably from one side only? If it is then try swapping the rear wheels over and see if the noise moves! If it is a single clonk on take up and overrun it could be torque reaction with wear in spring hangers,shock mountings or even the shock lever arm.
Try MGOC for the gears. They had them about two years ago.
|I have not read any reports of the sun and planet gears being prone to wear. The thrusts are though. Been doing mine today, was undone by some previous bodgery though, see my rantings in the other thread.|
Good news is it is not that difficult a job. If I hadn't had issues I could have done the whole thing in a day.
|Malcolm Le Chevalier|
|finished my diff thrust washer replacement, results are superb. no more clunks.|
for reference, if you take your diff apart, I had 25+ thou float on all plant and sun gears. new standard sized thrusts removed this (I had slight oversize too, they were too thick and made the gears bind a bit).
|Malcolm Le Chevalier|
|" they were too thick and made the gears bind a bit"|
Cheap limited slip diff!
|Dave O'Neill 2|
|One of those jobs that seems a bit daunting until you try it. Then you find it is easy-peasy and very satisfying how nicely it improves drivability by reducing drive-train snatch particularly at low speeds.|
And it costs next to nothing!
|ha ha, too right, but I can't be bothered taking it apart again! :-)|
excuse the crappy grammar previously, I am on my phone and in a bit of a rush
happy Saturday. cheers!
|Malcolm Le Chevalier|
If you think the noise is caused by worn splines there is an easy fix which worked on my TC, Mk2 Jag and my wife's MGA.
Thoroughly degrease only the taper section of the hub and the taper section inside the wheel centre with paint thinners. Make sure they are VERY clean and dry. (Leave the splines, knockoff taper and threads greased.) Apply the strongest "Loctite" to the dry tapers (680 High Strength) Fit the wheel carefully ensuring no grease gets on the tapers. I always tighten the knockoff VERY tight while pushing the wheel the same way as the knockoff is being tightened. This moves the wheel splines back against the hub splines so the acceleration slack is taken up and the Loctite only has to hold braking torque.
Good luck with solving the knock!
|R L Schapel|
If you have trouble getting sun and planetary gears, I have a box-full of s/h ones, wired in sets. (See image) I used to convert Morris diffs to fit TCs and in doing so, I removed the Morris spider gears. I have enough to know that there are many good sets among them. The conversion used the big flat washers and shaft, so I don't have many spares of those but each set does include the small dished thrust washers.
Trouble is they have to be posted from South Australia! I did send a set to a chap in the UK last year. I think I charged him about $80 AUD (about $60 US?) including postage.
|R L Schapel|
|Bob. Thanks for the offer, but I'm pretty sure all my gears are OK.|
BTW the guy you sent the gears to is my friend Les Robinson. His diff is now working well.
Malc. Good to know yours is sorted. I'll be doing my 4.2 soon followed by the 3.7.
|If you remove the cage to fit new thrusts,but leave the pinion in place, does the pinion pre-load have to be reset on reassembly, or is it not affected by the removal and refitting of the cage?|
|It's not affected.|
|Dave O'Neill 2|
This thread was discussed between 27/03/2016 and 09/08/2016
This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.