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MG MGB Technical - The clunk remains . . . grrr . . .

Gentlemen-
First, let me thank you for the knowledge I have selfishly sponged for the 2 months I have had my 71B Roadster. As my 'learn how to work on cars' experience, it has not disappointed. Plenty to fix. I had the clunk, and spent 8 hours (like I said, I am a beginner) replacing the thrust washers. I also replaced the U-joints for good measure, and checked for hub spline wear as well as I could, and they seemed fine. The washers were indeed worn, with the fiber washers gone, and the little ring around the outside of the brass washers. Put it all back together, fired her up, and went for a test drive. The sound has not gone away, but has changed a bit, and feels like it is coming from directly under my seat. I am guessing that what I was initially hearing was actually a symphony of evil noises, and I simply removed one of them. I looked all along the exhaust system, and while it isn't loose anywhere, I did note some markings on both the steering rack and the header. Its a Peco header, which I have heard may have more clearance issues than the average animal, but could that produce a sound that is similar to the rear end clunk? Maybe it reverberates down the exhaust and I feel it the hind quarters? Any other ideas on what could product a sound similar to axle clunk? Thanks guys, appreciative as always.

Shea
S Knight

A loose nut on the third motion shaft output flange can do it, sounds just like the worn diff washers. Worn slip joint in the driveshaft as well. Markings on the rack and header - where? and what is next to them? What is the state of the motor mounts and especially the gearbox mounts? If the power unit is leaping about, all sorts of clunks result; of course, once you replace the mounts, the exhaust won't fit anymore and you'll have to reposition that!
FRM
http://www.usachoice.net/gofanu
FR Millmore

I know the nuts on the flanges are good, I checked those. I will check the slip joint. The marking on the rack and header are where they would interfere with each ofther. In other words, it looks like they have banged each other a bit. Thanks, that give me plenty to check . . .
S Knight

I presume you mean column and header, the rack should be nowhere near the exhaust :o)

Another thing to check is that you have the correct length propshaft - if your slip joint is running out of travel, it would go clonk when it hit up against the gearbox.

Good luck,
--
Olly
Oliver Stephenson

Heh. Yessir, I meant column. The thing by the headlight fluid container . . . :(
S Knight

Check the axle/ rear spring u-bolt nuts for tightness. I found mine to be very loose and after torqueing them properly a lot of clunking went away. Another good tip is to replace the rubber pads (item 20 in the Moss catalog) at the same time.
Andy Blackley

I meant the big center nut that holds the flange to the 3rd motion shaft, have to take the DS off to get to it.
FRM
http://www,usachoice.net/gofanu
FR Millmore

Two clunks I have in my car:

1) rear shocks need replacement. Over the winter, I had lots of distractions and didn't top off my leaking rear shock. When it ran low enough on fluid, it would clunk over a bump.

2) I also replaced the thrust washers in my differential. Like you, that helped, but there's still a clunk. I have some play at the input shaft to the rear axle, and that's a job that needs special tools.

Raise the car up, put it in neutral, grab the driveshaft and twist it back and forth. Have some play in it before it actually turns the rear wheels? There's a small acceptable amount, and then there's what my axle's got. The good news it that this seems to be a common problem, and the axle is tough enough to drive this way for a long time. I'm sorry I can't recall the measurement of acceptable play. A search in the archives could find it.
Matt Kulka

Cool, thanks gentlemen. I have plenty to think about before I can get under her again this weekend.

Shea
S Knight

This thread was discussed between 04/07/2004 and 07/07/2004

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