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Overdrive ratio from 22% to 28%

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saniloc

Freshman Member
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Hi,

I read that some of you have change the overdrive ratio from 22% to 28%.
I have a BJ8 and i thought to do this change after changing the ring and pinion for a 3.54 to cruise on highway.
I searched on internet and I have not seen a tutorial on this modification. If you have a link, i will be very interested.

Can you explain me what parts (maybe with moss reference for parts) should be changed and how to do it?


Regards.
Nicolas
 
Thansk, my post was misleading, I'm not looking for information on mounting the ring and pinion but about changing the overdrive from 22% to 28%.

Regards, Nicolas
 
Sounds like a fairly involved project as you'd have to find most of the gears out of a 28% OD which pretty much means buying a whole unit off a Jag or whatever car used that ratio. You'll get a cruising speed reduction of less than 200rpm for all that work.
 
FWIW --
I have a 3.54 with a 5 speed Toyota W58 which I think is 22% (.783 5th). 3000rpm is about 73-74mph. My buddy Peter Roses has a 3.54 with the 28% OD on his BN6 - he's seeing about 80-81mph at 3000rpm. Both speeds are on the GPS.
 
The RPM reduction going from a 3.91 rear end to a 3.54 is about 11%, or 275RPM around 2,500RPM. The reduction in NVH is significant, esp. over 8hrs of driving.
 
Nicolas, If you want a 28% overdrive then you must find a 100-6 overdrive unit. The overdrive units are interchangeable.
 
BoyRacer said:
Nicolas, If you want a 28% overdrive then you must find a 100-6 overdrive unit. The overdrive units are interchangeable.
Click to expand...
Thanks Richard, i see on moss that 100-6 had 28% overdrive.
Do you think it is easier to completely change the overdrive unit rather than the corresponding parts?
I will give a look if overdrive units for 100-6 are selling, but i think with the price + shipping (i am living in france), it will be a very expensive upgrade. Maybe change the parts if i have to repair the overdrive one day...
 
I did this in the 1980's by putting in a 100-4 sun gear into the overdrive of my BJ8. Healey Surgeons told me about it and sold me the part. Worked great.
Doug
 
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