The MGA With An Attitude
REAR AXLE UPGRADE, MGA to MGB Banjo Type - BT-205
This article is sent compliments of Brian McCullough
Rear axle: MGA Axle housing- used because it was cleaner, knew it was the correct angle (not sure about the B axle in the A), had proper pin location, correct stampings on the case,
MGB 3.909 differential -the whole differential gear assembly dropped out of the B Banjo axle- fits right in no needed alterations as long as a person uses:
MGB axles/half shafts. These are wire wheel shafts so we had to use the right hubs for our application.
The MGB BANJO style rear axle was used for donor parts for the MGA.
Here is a list of parts for a “proper appearing” MGA axle with ALL of the upgrades:
MGA wire wheel splined hubs were used to get the 7/16” studs rather than the 1/2” studs of the MGB so in the future, no ordering issues would be brought forward. These fit right onto the MGB axle shafts.
MGA bearing hubs were used to have the 7/16” studs as well, again, so there would be no confusion. I believe these are strong enough for most cars as long as the bolts and nuts are in good shape.
MGA wire wheel spline hubs- used for fine thread and the 7/16” studs- The early MGB fine thread hubs could have been used, but we wanted the 7/16” hubs- again, no later confusion for future owners. (In the year 2057- I’ll be 82 years old and don’t think I will remember so well by then!)
MGB REAR BACKING PLATES! As long as we upgrade the front to MGB discs, why in the world would a person not consider this?
MGB shoes, springs, wheel cylinders, and hand brake parts
MGA hand brake cable (same unit as early MGB)
MGA drums for the 7/16” bolts AND to make the car look correct from the outside. I am pretty sure we could have used the early MGB banjo drums and probably even the MGB tube type drums, but they have 1/2” bolt holes and do not look proper.
MGB rear brake hose (braided) to match the front MGB braided lines that come in the kit. Please note- the MGB hose is shorter and since the car already has a 12V battery upgrade, we altered the battery tray to come closer to the rear axle- off this we used a small L shape bracket of 1.5 inch by 1.5 inch bolted to the back with a hole drilled in it to have the brake line fit through. The Tee fitting was also from the MGB banjo axle- the steel brake lines were new, but duplicates of the MGB banjo style since the backing plates are MGB style. (pictures available)
Dayton 60 spoke chrome/widest wire wheels we could get along with a set of 175/65R15. (Also Doug Jackson’s mgbmga.com Composite rear leaf springs and tube shock conversion and ah... that’s a different part of the story.)
[NOTE (from Barney): MGA halfshafts can be used with the MGB differential if you change the differential sun gears to match the splines on the halfshafts. MGA halfshafts may be 10-spline, 26-spline, or 25-spline. All MGB are (originally) 25 spline.]
Other notes on the rear axle conversion:
I did not check the outer distance of the MGA and MGB rear axles. They may have been the same, but I did not pay close enough attention.
The axles used were both wire wheel axles. The car being upgraded was an early 1957 MGA with MGB rear axle from about 1964. Wire wheel axles in most cars are 1 inch narrower then their disc wheel counterparts.
Yes, I know. I am in trouble! I have sacrilegiously trampled on the MGA rear brakes. Being a Spridget guy and also listening to the old Metropolitan, Minor 1000, Austin A30/35/40 guys who have upgraded their front brakes to discs from later Spridgets, I hear it all the time - ‘...I don’t need to upgrade the rears. The old click adjust, although they are not as fine of an adjustment, still work very well... But I just needed more stopping in the front!
Okay. Whatever. I love the old ‘click adjust’ that the MGAs, my Bugeye and other British car stayed with, but realize that if you upgrade one end of the car without the other... Well, lets just say one of many problems is like installing the wrong master cylinder into the car. Anyone had the experience with the 1963-1965 Spridget Master cylinder 3/4” bore in an MGA? Yes? Lots of travel and hardly any action, or too large of MC in another car allows a brake pedal to be too hard to push and you cant stop the car/clutch works incorrectly. I believe that installing the correct rear brakes give a tweak better stopping feel.
Also, the rear brakes, as long as we need to replace them- have you looked at the price of replacement parts? How about sleeving wheel cylinders and so on? Frankly, the MGB rear brakes from a banjo axle (nope- tube type backing plates Will NOT fit) have the market. FAR more cars, less pieces to stick Cost much less! Two pistons are better than one slider type wheel cylinder as well. To me, for a car that is a driver that a person does not care about originality, this is a bolt on process that makes the car better, safer and can be changed back without welding, drilling, cutting or general desecration. Purists rejoice - alterations not permanent.