TD/TF HIGHER RATIO DIFF MODIFICATION.

Summary by Harry Pyle

WHAT YOU NEED TO DO - if you don’t or cant do the complete Job yourself.

1)    Obtain Crown Wheel and Pinion Set (from wrecker, MG supplier etc) for the ratio you have chosen. e.g. 4.1:1 ex MGA/B

(With 15" TD/TF wheels this would give very close to the same

TOURING PERFORMANCE OF THE TC with 19" wheels + 4.55:1 diff.)

2)    Obtain Pinion Bearings  from Bearing Service or Similar

TD/TF outer bearing Cone 15100S   Cup 15250X

Cone 3188(S) or 3193(T) or 3199     Cup 3120

3)   Take your complete rear end assembly together with the above bits to Differential Specialists who are equipped to set up and assemble the new diff.

4)         Take your finished car to Automotive Instrument Service at Welshpool to calibrate your speedo to the new diff ratio. They have already done at least one TF over the past years.            '

5)         See attached chart for diff ratio comparisons.

6)     HAPPY LONG LEGGED MOTORING !!!!!

DIFFERENTIAL RATIO COMPARISON CHART

USING THIS FORMULA THE FOLLOWING FIGURES HAVE BEEN CALCULATED.

1000 x 60 divided by (DIFF RATIO x WHEEL REVS PER MILE) = MPH/1000 RPM (engine)

For the TC calculations a near new Dunlop B5 was used and a constant of 730 (86 ¾ inches) wheel revs per mile was obtained.

For the TD/TF calculations a near new Michelin 165SR was used and a constant of 813 (78 inches) wheel revs per mile was obtained.