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MG MGB Technical - 1969 roadsterPropshaft

HI
I need a little help to know difference between size of 4 syncronized gearbox USA model propsshaft and for a roadster with overdrive. I bought one for my B through british ebay but it's shorter than old mine. I suppose they had sent a wrong shaft.
Thank you
Rui
Rui Fonseca

For the 4-synchro model, the propshaft is the same, whether overdrive or non-overdrive.

Here is some info on Paul Hunt's website...

http://www.mgb-stuff.org.uk/propshafttext.htm#length
Dave O'Neill 2

Rui. As Dave notes, all of the four syncro transmissions used the same prop shaft. I have converted a 68 GT, 77 roadster, and two 79 roadsters from standard four speed gearboxes to four speed with overdrive gear boxes and used the original prop shaft with each. No problems noted over a number of years service. But, it is a good idea to replace the U joints when doing the conversion--simply an insurance against having to do the job a month or year later. Some of the cars have been running the OD gearboxes and replaced U joints for over ten years with complete lack of any problems.

Les
Les Bengtson

Rui, does your B have its original Tube axle or possibly the earlier Banjo axle fitted? If it has the Banjo axle, it will require the shorter driveshaft. RAY
rjm RAY

Thanks for those informations. So I presume propshaft I had receive is for a banjo model, mine is a tube model axle.Now I hope seller assumes the mistake...
Rui Fonseca

Rui, how short is the propshaft? The propshaft has a slip joint, so will extend. See attached picture.

Andy

Andy Robinson

Andy, please see atached photo of both propshafts

Rui

Rui Fonseca

Looks about 2" shorter from your photo Rui. You can check the measurement of your old propshaft here at Paul Hunt's website

http://www.mgb-stuff.org.uk/ps2.htm

Propshafts come in these lengths: 30" (76.2cm), 31 1/8" (78.9cm) and 32" (81.3cm)

Andy
Andy Robinson

Hi Andy
I measured both axes and old is 76.2 cm length and the shorter around 73 cm in the "shrunk" position.
It will be possible to stretch the new one to old and longer length?

Rui
Rui Fonseca

"It will be possible to stretch the new one to old and longer length?"

No. The sliding joint is there to take account of axle and engine and gearbox movement relative to each other. The joint is designed such that at the extremities of expected movement, there will still be sufficient length of splines in the sliding joint to transmit the full power of the engine. By measuring the splines there is about 2" of movement where the splines remain fully engaged, i.e. about 1" either side of a nominal central position. If you 'stretch' a short prop-shaft 2" then you may only get a very short amount of splines still engaged, and it could come apart altogether under some circumstances.

However I'm a bit confused by your measurements. The three lengths of 76.2cm (3-synch, no OD, Banjo), 81.3cm (3 synch, OD, Salisbury), and 78.9cm for all other combinations given by Alan are the fitted lengths i.e. between the gearbox and axle flanges. You say yours are 'shrunk', do you mean fully compressed? If so that is going to be about 4cm less than the fitted length.
Paul Hunt

Paul,length between gearbox and flanges the flange and the is about 79 cm. There was the old shaft fully compressed length 76.2 cm. The new shaft I bought has only 73 cm. See photos. My question is whether the new, shorter can be fitted without mechanical problems.

dlist

I think you would be running the risk of damage by fitting the shorter shaft in place of the longer.
Paul Hunt

Might the basic question here by, "Why did you purchase the second prop shaft?". The 1969 under discussion used the same prop shaft for standard and overdrive transmissions. This has been made clear. So, why was a second prop shaft purchased?

It would seem that, if the original prop shaft is serviceable, the proper action would be to return the second prop shaft to the seller, with a note that it is not a correct four syncro prop shaft, and request a refund. If the original prop shaft is in some way damaged or not capable of being used, the correct solution is to source the correct prop shaft for the application, not to continue trying to adapt the incorrect unit.

Les
Les Bengtson

Thanks for all tips. I suppose then I had receive a wrong part, maybe for other model...
Rui
dlist

This thread was discussed between 13/01/2016 and 16/01/2016

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