There are two distinctly different MGB rears.  Later MGB axles use tubes pressed into a central casting and are very easy to distinguish from the pressed housings.  The early style ”Banjo” rear,  used from 1963 to 1967 is made from pressed steel and has full floating axles like trucks.  It was this early one I wanted for reasons of safety as if the axle breaks you do not loose the wheel and while I had not heard of a Morgan doing that there are certainly plenty of examples of other cars doing it with dire results.

Many Triumphs are now sporting different axles as a result with the Dana 24 “Jeep” axle and the eight inch Ford being popular options.  I looked at those and did not like the weight.  Besides, we need to preserve the British aspect of out Morgans.  Any of the removable carrier assemblies from almost any MG can be interchanged with the B.  This makes a wide variety of ratios available and the business of changing ratios a one hour job.  The standard B axle ratio is 3.9 to 1 while most of  MGA rears will carry 4.3 and the Magnette sedan 4.88.   Others were used as special tuning options on the sports cars. There are however, several different splines used on the inner ends of the axles so it may be necessary to change the spider gears if you want to install a different differential.

Once I located and purchased my axle, it was treated to a complete tear down and rebuild with all new bearings and seals along with a lot of rust removal and painting.  The hubs are retained by a 1-5/16 nut that is recessed into the hub.  I managed to get them off with a large adjustable but have since learned that an SK340142 socket will work.  I cut all existing brackets from the housing with a torch in preparation to making it fit the Morgan.  Fortunately I had a spare Morgan 7HA/2 housing on hand and could take measurements and make comparisons very easily before taking my car off the road.  I made spring perches by using 2x4 steel tubing and using a 21/2” hole saw to cut it to fit the axle.  A drill press is pretty essential for this part.

At the same time I drilled the holes for the spring center bolts in the bottoms of the new brackets. Accuracy here is important as those holes locate the housing on the spring.  These axle housings are slightly tapered where the spring mount goes and I chose to mount everything in the car before tack welding the mounts to the housing.  It is essential that the pinion angle be set correctly to avoid drive shaft vibration.  This I did by using an electronic level placed against the pinion flange of the old rear before removing it and then setting the new rear in exactly the same position.  Placing 2” wood blocks between the frame rails and the springs while someone is standing on the back of the car will make everything much easier.  Otherwise it is difficult to reach the nuts on the U bolts and the spring may drop down as you remove them.

A bracket for the parking brake bell crank must be fabricated unless you plan to cut it off the old housing.  I welded two pieces of 3/16 plate together to get the desired thickness and then welded a steel bushing to them to accommodate the bell crank pivot.  The old rear had three brackets for the brake cable attachment and cutting one the extras off to use on the new rear was the simple answer.

A word of caution here.  In order for the Morgan parking brake mechanism to be used it will be necessary to reverse the brake assemblies and rotate them to a different position..  That is right - left to right and rotate until the parking brake lever is in the 10 o’clock position.  It would also be wise to bend the brake levers about 1/2” upward towards the 12 o'clock position as the brake rods will want to hit the top of the frame if you do not.  I solved this by putting the entire clevis on top of the lever after learning of the problem near the end of the project and I will bend the levers the next time they are out.

Because the B rear will move your wheels out about 3/8” on each side you might want to check tyre clearance before you start.  I am using 5-1/2 inch Dayton wire wheels and had some tyre rub on the wings before beginning.  Moving my wings outward was necessary to gain clearance.

Why go to all of this trouble?  Well, in my case I had a very noisy ring and pinion in the old 7HA and the parts are both difficult to find and quite expensive.  The additional safety of floating axles and the availability of different ratios were factors in my decision.  The fact that parts for the MG are very available and relatively cheap was also a big consideration.  Victoria British Ltd. has anything you want including the special wrench to fit those hub nuts.  I paid $250 for a good used rear and spent about that much for the rebuilding parts.  It took most of a week to do it and the results have been just fine.  The slightly larger diameter of the MG brakes have not affected brake balance.

Further information on MG rear axles can be found on Larry Hoys website.
http://pages.prodigy.net/larryhoy/BritishCarHome.htm/MGtechnical.htm

I would be happy to council anyone wishing to do this job.

Don Greimel
Ph: 410-272-2552
Fx: 410-939-0000
email:  dgreimel@aol.com