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MG MGB GT V8 Factory Originals Technical - Final Drive Ratio

Hello to the list,

I have a T5 Tranny with a .65, 5th gear ratio. Originally, I will be installing it with my stock MGB rear end.

My intentions are to go with a narrowed Ford 8 inch and a 3.23 ratio in the future. However when I formulated these intentions I had originally assumed that I would be getting a tranny with the more common .73, 5th gear overdrive ratio.

I have read the posts and talked with people that have this combination the consensus seems to be that they are basically pleased with it. However I do not know if transmissions used were had a .73 or a .65 overdrive ratio.

My question is:

What seems to be the most satifactory rear end ratio when using the .65 overdrive ratrio. By satisfactory I mean, a low gear that is not redundant and a top gear that still retains some aspects of usability/performance (not so high that one is constantly shifting to maintain the RPMs). I am told that the low gear with the 3.23 ratio rear end is very usable, but I am concerned that the final drive ratio might be too high ( I am estimating that the engine would be turning around 2100 RPM at 60 whereas with the .73 ratio it would be turning 2400 RPM. My other concern is that with a rear end ratio lower than 3.23 (3.50 or 3.73) may result in a first gear that is to low (redundant). The engine is a slightly modified 215, but I will be using it primarily at 5000' altitude and above..

Your comments and opinions would be appriciated.
Larry Diede

We run 5 speed V8s with a .78 :1 5th and a 3.09 rear end.This gives 27-28 mph per 1000 revs in 5th. Overall that compares ok with a .65 and 3.9. I expect your 4th is 1:1 and so on down the box which will give you poor intermediates. I should try and change out the 5th gear ratio in the T5 for somthing lower and use the 3.23.
robert pulleyblank

This thread was discussed on 22/11/1999

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