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 Since the T Series was designed in the late thirties and after the war the roads it was meant to run on were twisty little outgrowths of roads designed by the Roman Legions, and upgraded to horse drawn carriage.  The car was designed to run in town and on existing highways such as shown to the left. Speeds of 50 Miles per Hour were considered to be normal highway speeds, and the car had the capabilities of sustaining that speed and more for passing.  It was after all a performance car in its day.  Today with suburban highway speeds of 45 to fifty, and Interstate Speeds of 70 the car is operating at near itís rev limit.  The normal solution is to replace the standard 5.125 rear end ratio (4.875 for the TD Mark II) with the MGA rear end (ratio 4.55).  This will give according to reports which will give 65 MPH @ 4250 -4300 RPM instead of approx 5200 RPM with the standard rear end.  The cost of this conversion is about $1000 if you exchange the rear axle for a modified one.  The upside for this conversion is of course the lower engine RPM's at highway speeds.  This is more important to me because I have to use essentially Interstate to get from where I live to most parts of town.  The downside of this modification is performance.  From most reading that I did on the subject on the internet, hills that were easily negotiable in 4th gear now require 3rd gear. 

After additional research I found what I believe to be a better solution.    The gear box on my TD needed work; It would pop out of second gear when I lifted off the accelerator (most likely a synchronizer), and difficult to get into 3rd without grinding.  So I figured an easy $1000 for new gears and synchro's or a replacement gearbox anyway.  In England you can buy a  Five Speed Conversion for the MG (T series, MGA, & MGB) it is based on the Ford Sierra Type 9 Gearbox.  The kit comes complete, and unless you look under the car, the only hint this is not stock MGTD is the gear selector lever shows a five speed pattern.  The best part is that gears 1-4 are the exact same ratio as the original TD, and 5th gear gives the car a drive ratio of 0.96:1 which should give highway performance approximating the TD MKII's 4.875. Still a little stronger than the MGA's 4.55 but it should keep the RPMS under 4400 @ 65 MPH. 

 Note:  Photos will follow as we proceed, first we pull the engine, then the mods... stay tuned

Last modified: April 26, 2005

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