MM HALF SHAFTS

[BLOWNMM]

Hi Guys
smithskids (sorry I don't know your name) - in a post of Sat May 07 2016 in the thread 'Re Head Stud Torque Check - Hot or Cold?' you make mention that the MM axles are much beefier than the standard Morris Minor ones and over engineered. Are you using a MM split case diff in your 1325 cc. MG engined car? Have you any documentation to support this as a question of the strength of the MM gearbox and rear axle has surfaced. I have always been of the belief that the MM box was much stronger than the smoothcase and also considerably stronger than the ribcase. I have attached a copy of a post by Rob Thomas which bought the subject to light.
[url]•
Re: Slick Shifting
by RobThomas » Thu Jul 21, 2016 7:46 pm
MM box and back axle share design and components with Wolseley 4/44, 15/50 and MG YB and Z-types so is over engineered for the 27hp Minor. The 6-spline half shafts, for example, cope with 60 bhp in the Nuffield axle'd Z-types. T-type gearboxes look similar and I'd expect they us some of the same components.

MM with a TC engine and box would be nice.




I'd be happy if anyone could refute this info with any facts since it might be helpful in expanding the knowledge of the group.



RobThomas
Minor Legend

Posts: 1558
Joined: Thu May 11, 2006 7:34 pm
Location: Cardiff
It would be good to get some positive documentation to support the claims of the strength of the MM box and rear axle.
Bob

[RobThomas]

The Nuffield axles and boxes started, I think, with the Morris 10, 1100cc, 37hp and finished with the TD/TF, MGZB/YB, Riley (90hp) and others. A look at a TD axle and box shows them to be near enough twins. The later MGs had thicker input shafts and different ratios but not a lot else.

When Austin absorbed Morris and stuffed the 803 into a Minor they had so much gearbox trouble that the factory team converted the MM box to fit the 803 to make it reliable enough to test run the rest of the car.

Doesn't offer anything like conclusive proof but might be a starting point for googling.

YB Gearbox bearings...I guess you've measured the MM ones already?

Gearbox bearings:
YB: (one of each except where specified otherwise)
Constant mesh pinion:
Ransome & Marles LJ 1¼G(w/c)
Layshaft roller (x28):
Ransome & Marles N 5/32" x 1"
Mainshaft (centre):
Ransome & Marles 1/LJ 1 1/8G
Mainshaft (rear):
Ransome & Marles LJ25
Selector (x18):
Ransome & Marles 5/16" steel balls
Mainshaft (x60):
Ransome & Marles N3 x 25mm
3rd speed gear (x18):
Ransome & Marles N3 x 28mm

[Declan_Burns]

I have my doubts about fitting a TC engine and gearbox. The XPAG engines are approx. 7 inches longer than the Moggy engines and the exhaust is on the other side. It is a big heavy expensive lump and the gearboxes are not great either. The 1275 Midget option would be a lot better and easier.
Regards
Declan

[RobThomas]

I wasn't being serious, Declan.


http://www.mgccyregister.co.uk/technica ... roduction/

Bob. Might be useful for selecting optional box ratios?

[BLOWNMM]

Rob
Bearing sizes MM box - input drive gear and mainshaft rear R&M 2LJ1G or FBC LS10 SG 2.5" X 1" X 5/8". Rear extension housing 6205. Mainshaft centre and laygear bronze bushes. Hope this is of some help. As far as changing gear ratios with the HP and torque band of my blown motor the MM ratios are almost perfectly spaced which is just what I need - unlike the crapp ratios of a smoothcase. Hoping smithskids can shed some light on the subject.
Bob