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MG MGB Technical - Prop Shaft - which one?

Hi
In trying to sort out my car so that it sits level we have noticed (as it is up on a four poster lift on it's wheels) that the prop shaft appeared fully extended.
The car is a GHN3 with overdrive and the banjo axle. According to the parts books it should be fitted with prop shaft AHH 7487 - I purchased the one on the car as this part from Moss about 4 years ago. The shaft measures 29 inches closed and about 31 inches when fully extended. However the gap between the o/d flange and the axle flange is 31 inches too. Therefore there can be no movement in the prop shaft to allow for axle travel. The rear u/j is beginning to show signs of wear (through overloading?).

Has anyone else had this problem and if so what was the solution.


George
G R Wilder

George, If you have the 3 synchro trans it should have AHH 6512 listed as the part number. It is listed at 31.125" long. If, however, you have the 4 synchro trans, it uses the 30" long shaft, part number AHH 6481. RAY
RAY

Ray
Must have different part numbers in the USA as the Uk Moss and BMC parts books list AHH 7487 as the 3.125 long propshaft. This is this shaft which is too short. Only had the car 25 years (but the current propshaft for 4 years) and I have not lengthened it!
Thanks for you comment
George
G R Wilder

George
Go to this valuable site. Click on propshaft (on the left side) and scroll down to 'length'. This may shed some light on your problem.

http://www.mgb-stuff.org.uk/
DK McNeill

Sorry

first click on 'spanners' then you will see the 'proshaft' link

Kent
DK McNeill

Hi Folks:

The "D" type 3 synchro o/d gearbox is approx 2 inches shorter than the non o/d gearbox. The correct drive shaft with a banjo axle is from a any 1968-80 4 synchro drive shaft. If the car had a tube type axle then you would need one from a 3 synchro GT with a tube axle.

Good luck:
Rich Boris 67 B roadster
R. Boris

Hi
I found the answer.
Using data from the pages of Bee and Vee ( Paul Hunts MGB pages on the net - very informative ) on the dimensions of the shaft components taken from Leyland Manuals and Hardy Spicer sources I have established that Moss sold me the wrong one. They gave me the non overdrive version which is shorter even though I asked for and was invoiced for the correct shaft. It does fit just but when under a car on axle stands one does not notice the "just" - both U/Js are failing after 6000 miles or so - too much strain.
Now to see what Moss will do - a free exchange?

Thank you all for your comments
George 251 GRW
G R Wilder

Hi
I have spoken to Moss London and they will do me a new one at exchange price even though mine is not now the correct exchange. Will collect it tomorrow. All sorted quickly and efficently

Apparently all their prop shafts are new now as it is no longer economical to recondition them but they still offer an exchange price.
George
251 GRW
G R Wilder

George, The part numbers that I supplied were from the BMC parts book that I salvaged from an MG dealer many years ago. I have a'67 B that I've had since '72. I also experienced the same driveshaft length problem when installing an OD trans. I purchased a new shaft too but it was the proper length. RAY
RAY

I put in D type OD in my 67 GT. and purchased a drive shaft from a late model B. The shaft does fit, but is it all the way extended. From the Bee and Vee information, I am wondering if the 32" would have been better
Bruce-C

Ray
The part numbers I used are from the Heritage CD of the BMC Parts Book for 1962-69 MGBs and from the Moss UK parts books. They are also the numbers used by all the UK parts suppliers I can find. I wonder why we have different numbers for the same prop shafts?

Bruce-C
According to the parts books supplied by Moss in the UK a GT (all had tube axles) with the 3 snychro box and O/D should have the prop shaft part AHH 7486. This is also confirmed by the BMC parts book I refer to above. This is the one to fit the 32 inch measurement between O/D drive flange and rear axle drive flange. A prop shaft from a late B is AHH 7487 (which fits all 4 synchrobox/tube axle cars) is too short for your application. So I think you are right in your thoughts - you need the longer shaft.
George
251 GRW
PS Tried to send a scan of the parts book but the BBS said the file was too large (1.1mb)
G R Wilder

I can say that the Late model will fit, but it is streched out as far as it will go. Going to find the 32" for safety.
Bruce-C

This thread was discussed between 16/04/2009 and 19/04/2009

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