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MG Midget and Sprite Technical - knocking drivetrain

Afternoon all,
Hope someone can offer some advice please.
1500 midget. Passed MOT on Friday, first time.
Driving to work this morning no problem.

Once engine had warmed up I gave it a bit of welly and a repetative clonking noise started. The noise is only present when driving, not with the engine running when stationary. There is no noise when pushing the car forwards and backwards in the carpark, so I'm thinking prop shaft or diff. It noise doesn't seem to repeat quick enough to be the prop, so I'm thinking diff problem.

I have just crawled under the car at dinner time. The prop shaft doesn't seem loose of worn at the joints. There is quite a bit of backlash though, but I think it was there to start with. Also, a backlash problem would be one clonk as the slack is taken up, not a continuous repeat clonk.

I must admit I have never checked the diff oil level in three years because a PO bust the plug square off. Does anyone have any ideas what might be causing the noise, and how to fix it?

Many thanks as usual for any help. Sorry for the the chapter and verse description.
Ben.
B Whiteley

UJs still a prime contender.

Is the noise road-speed or engine-speed related?

Any difference when driving / on over-run?

Whereabouts is the noise coming from?

I'd investigate removal / refilling of diff as something good to do anyway.

A
Anthony Cutler

Thanks for the quick reply Anthony,
The noise is road speed related. The noise seams to be mostly on accelaration and over-run. It seams to diminish if I keep a light load on the drive and just cruze. The noise seams to be coming from the rear, and over my left shoulder, which could be the near-side or the centre.

How would I check if it was a UJ? Do you just put a lever in the joint and feel for play?

I have only done a half mile since the noise started so sorry for the vague answers. I'll know more when I get home tonight and lift the car up.
B Whiteley

Yes - check if there's any movement in the joint using screwdriver or similar. Of course the front UJ is inside the tunnel...

A
Anthony Cutler

My '78 US 1500 floor pan has an opening at the front u joint...fairly easy to reach it.

I assume the UK 1500 would be similar.

If the u joints have ANY play...they should be replaced.

I also would find away to either check or top off the differential oil, the same with the tranny!

Dave :)
Dave Rhine ('78 1500)

I had a similar problem last Summer, but mine was more of a vibration than a clonk.

It ended up being bad joints, bent drive shaft & bent differential input shaft flange.

I replaced the joints, had the shaft straightened & balanced & replaced the bent flange (thanks again David Leib)...it's been smooth as silk since.

Good Luck

Dave :)
Dave Rhine ('78 1500)

besides the U-joints to check, and the fluid level in the axle housing, another thing to check is do you have wire wheels? The splines wear and make a clonk noise when you lift and re-apply the throttle sharply.

Also, a badly worn half shaft (where it splines into the differential), or a badly worn differential (crown wheel and pinion) can make clonk noises the same way. Though, admittedly, a worn diff will usually make other noise while driving that comes/goes with power on / coast driving that you did not mention.



Norm
Norm Kerr

This thread was discussed on 17/05/2010

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