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MG MGB Technical - replacing rear end

when replacing bad rear end with new one how do you trt to stay in balance with driveshaft, univ.
l.f. frank

LF-
If you carefully examine the adjacent ends of the two halves of the driveshaft (propshaft), you'll notice two small arrows that, when the two halves of the driveshaft are properly joined, will be in alignment with each other. Take care to align the arrows found on both the sleeve and the splined section of the shaft so that the U-joints (Universal joints) will be properly operating aligned parallel to each other in a single plane, and then slide them together. These arrows can sometimes be difficult to locate, so you may have to look hard for them, as they were hand-stamped at the Hardy-Spicer factory and sometimes are either faint, incomplete, or both. One arrow is stamped onto the female sliding sleeve, which is a machined forging. The other arrow is stamped onto the tube of the main shaft just beyond the weld, not onto the male spline shaft.
Stephen Strange

LF-
I should add that it should be noted that whenever a driveshaft (propeller shaft) is installed, the axis of the flange yokes on both the transmission and the differential must be aligned parallel to each other in order to avoid producing unequalized thrust forces that will damage the bearings of the U-Joint (Universal Joint) as well as result in driveline vibration.

Stephen Strange

Also, if you are not changing the driveshaft, then it does not matter which way the rear flanges are re-connected.
Art Pearse

UJ orientation is only an issue when *reassembling* a dismantled prop-shaft, not when simply installing a previously assembled and balanced one. I've seen sliding joint orientation marks in photos, but mine don't have them. Even then you still need to mark all four yokes for the UJs, if you keep those marks in a line it doesn't matter if you don't have stamped marks for the sliding joint.

Prop-shafts are balanced as an assembly can be bolted to the gearbox and axle flanges in any orientation. However if removing and replacing a prop-shaft it is good practice to mark the flanges the principle being that if it was balanced like that before then it makes sense to keep it that way. Manuals stress this although it is unimportant. What is far more important, and certainly my Leyland and Haynes manuals don't even mention, is if that you dismantle the UJs or sliding joint then you *must* mark all four pieces beforehand as above, as incorrect assembly is far more likely to affect balance than simply how they are attached to gearbox and axle.
PaulH Solihull

A mis-aligned propshaft (yokes not parallel) is still in-balance, but when running with an offset (as per design) the rotational speeds at either end don't match throughout the revolution. This leads to a great deal of stress on the joints on part of each revolution. the joint is not a "constant velocity" joint, but one end offsets the error in the other, if aligned correctly.
Art Pearse

Yeah but that still only relates to reassembling a dismantled prop-shaft, not to attaching a properly assembled and balanced prop-shaft to the gearbox and axle.
PaulH Solihull

Agreed. It will cause vibration, but not because of imbalance.
Art Pearse

Sorry,I'm coming to this thread late, but could be of relevence to me. The bit that interests me is the flange alignment issue. Am i to assume Steve, that the mating surfaces of gearbox and axle flanges should be parallel to one another. Is this just in plan view or side elevation as well? The latter would be affected by spring wind-up, the former to some extent, by uneven spring wind-up (un-matched springs, tramp). Also new to me is the issue of the prop flange end yokes are matched to compensate for the lateral, drive line, off-set. This is interesting stuff...............every day, in every way eh.
Allan Reeling

Allan, the driveline offset (horizontal) is compensated for in the same way as the vertical offset, and yes, ideally the drive and driven flange faces should be parallel. The out-of-straight angle at the front should be opposite to the angle at the rear.
Art Pearse

Driveshaft alignment is shown in the attached image.
A and B should be parallel (also C and D) when viewed from the end.
As already stated by others, this is only important if the splines have been separated.

Mick

M F Anderson

Thanks for that, but as somebody said in another thread, "in 40 years who knows what's been done and more especially how well it was done"
Allan Reeling

Note that Haynes has the orientation of the yokes shown incorrectly on the exploded drawing, but correct on the assembled drawing. But that is yoke orientation, Allan is asking about something different as I understand it. However given the crudity of location and amount of movement in the MGB axle I'd say the gearbox and axle flanges are going to be anything but parallel most of the time.
PaulH Solihull

Well that whole thing about yoke orientation is new to me. I'm getting that "non" constant velocity feeling at low speeds, which might be explained by non orientation. It's a new car to me so anything could heve happened in the past, and judging by other things i've found!!!!!!
Allan Reeling

The angles would have to be way off to get a 'non constant velocity' feeling, what you could have is a seized UJ. BT, DT.
PaulH Solihull

Just an up-date. I got under the car over the weekend to check the yoke alignment...................way out!!!! Plus, strangely, the rear Hardy Spicer, although not showing signes or wear, was "fluted" on the inside of the cups. So new joint and aligned joits, result................smooth!!!
Al
Allan Reeling

If you are swapping out a rear end from another car, realize that the brake slave cylinders are a different size between the roadster and GT.
werner haussmann

This thread was discussed between 28/11/2010 and 18/12/2010

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