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MG MGA - Rear Axle clunk
|I have a MGTD fitted with an MGB engine and transmission and a MGA BANJO TYPE REAR AXLE. The rear axle has a great deal of internal play that is causing a clunking noise when shifting from forward to reverse and vice verse. The problem is not the universal joints. |
I suspect that this problem is caused by worn thrust washers. I am looking for confirmation of this diagnosis and also asking if anything else can cause this problem.
Unfortunately, I do not have the workshop manual for the MGA and I am hoping that someone would be kind enough to make a copy of the section that pertains to taking the unit apart and reassembling it and mailing, faxing or scanning and sending by email. I have also tried to find an archived article on the specific subject of replacing the thrust washers on a MGA Banjo Axle but was unsuccessful. If you know of one, I would appreciate it if you would forward the link to me.
One more question... I am also experiencing clutch chatter/judder. Could play in the rear axle cause this problem?
My contact information is:
1018 Curisha Point South
St. Helena Island, SC 29920
843-838-0822 (phone and fax - if faxing, call first)
|Clunk is accompanied by about 1/4-inch backlash (free-play) at perimeter of the input flange. This is most often a result of worn thrust washers. If you will replace these, know that they should all be brass or bronze material. For the side thrust washers, the large flat ones, current offer from many suppliers may be cheaper fiber parts that are originally from the late model MGB (1968 and later) tube-type axle. Life of the brass/bronze thrust washers was about a quarter million miles for me. Life of the fiber washers is far less, in some cases less than 100,000 miles. I hate the fiber thrust washers. A year ago I hosted a tech session where we replaced the fiber thrust washers in half a dozen late model MGB all in one day. http://chicagolandmgclub.com/photos/b_clunk_11|
Everything you want to know about the MGA rear axle: http://mgaguru.com/mgtech/rearaxle/ra1.htm
MGA Workshop Manual here:
Rear Axle Section (1.3-MB pdf file) here:
|Wire wheels can give a similar sound if they are not tight enough on the splines.|
|I once had a problem with diff clunk and it turn out to be a carrier bearing spacer being dislodged. You will know for sure when you remove the diff!|
Barney, where do you get the bronze side gear thrust washers - Moss only provide the fibre type?
|I don't know yet. It has been on my pet bitch list for a few years now. I figure late model MGB owners would be wanting to install the bronze parts from MGA and early MGB in their tube type axles. But just about the time the word was going around the supply of the proper parts disappeared. We did a bunch of them at one time last year, ordered the parts en mass for a discount, but all we could get was the fiber crap for the side plates. Everyone without exception would have been willing to pay double the price to get the metal parts. It's not a big deal to get a couple sheets of flat stock and punch out 1000 flat washers. I don't know why Moss Motors doesn't commission a production run.|
There are many sources for generic brass and bronze washers available on the internet. (See the below link as an example) Do you, or does anyone else, know the dimensions of the MGA thrust washers and if the metal is a special alloy. If I can get the information, I will do a search and let everyone know what I have found.
|The flat thrust washers are 2.5" OD and 1.5" ID. The bronze ones I took out on mine were 32 to 34 thou thick and I replaced with fibre ones measuring 36-37 thou.|
The convex washers were 1.5" OD and 23/32" ID; thickness on the old ones was 31-32 thou and on the new ones 35 thou.
The backlash on my axle at the input was around 4 degrees and I estimated that over a quarter of this was due to crown wheel/pinion backlash and there will be more due to wear in the half shaft splines plus diff. sun/planet gears. I estimated that approx. one third of my backlash will be removed by replacing the thrust washers. I will measure it again after travelling a few hundred miles after giving the cup washers a chance to bed in.
I remember looking around at the time for material from which to make bronze washers but without knowing the metal specification I concluded it would be risky venture...........Mike
|As I promised, I did an internet search for metal thrust washers for the MGA and MGB Banjo rear axle. This is what I found;|
Replacement Copper thrust washers are available for the two conical washers. They are available from Victoria British in Lexena, KS. Unfortunately, I could not find any metal flat washers from any of the MG suppliers or generic washers from the various thrust washer suppliers on the internet,such as Oil-lite. So we are stuck with fiber washers.
I just replaced the two sets of thrust washers in my rear axle. They solved most of the clunk problem. I still have some play between the crown wheel and the beveled pinion gears. Is this a difficult repair?
This thread was discussed between 29/11/2012 and 12/12/2012
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