MGA tech stuff

Ok So I am going to pull a “James May” on you all and bore you with a whole bunch of techy stuff.  But I am so proud of my efforts I have to tell somebody.

Regular readers of this fine website will have seen the photo I sent in last week following a major failure with a broken rear axle. The upside was I was able to fit a complete new (old) differential I had in storage onto the MGA with a minimum of effort or expense.  After a couple 4 hours sessions I had the old Differential disconnected out on the floor,  parts swapped as needed and the new one in the car and bolted down. Only one casualty with a broken anti rattle spring ($.87)  and I took the opportunity to put in new brake shoes and make a couple other fixes that made sense while it was in pieces.

I took it out for a spin in the rain last night (shop tip –adjust the brakes before you roar off across the driveway)  and WOW what a difference in the drive, and that was just first gear.  With the newly rebuilt engine the new Five speed transmission  I had to calculate the difference in the gear set-up from original to now and have prepared a chart.

Gear Ratios                                   First   Second  Third   Fourth   Fifth
Original MGA Standard Tranny with                                             
4.3:1 original ratio rear end          3.65    2.21       1.37      1.0          -     
New Ford Type 9 transmission    3.65    1.97        1.37      1.0       0.82  
Now with 3.9:1 low ratio Differential                                         
rear end from Wolseley 6/80        3.28    1.77        1.23      0.9       0.73  
% Reduction in RPM
 from original                               10%     12%     11%     10%     27%   final drive*    
*At highway speed- 4500 RPM is now 3285 RPM   
      
So a huge reduction in final drive will make this a real highway cruiser and save gas wear and tear on the car and the driver on those long haul drives.  Anybody up for Stowe this fall?

Ralph