Overdrive

[Mr Tiger]

The thread on buying a Stag has reminded me of some questions I have about overdrives.

Do all A types operate on 2nd, 3rd & 4th and all J types on 3rd & 4th only?
Are A types available in 22% and 28% and J types 25% only?
Is there a visible difference between them? I can't seem to find any plates on mine to identify what type it is.
Is one type stronger or more reliable than the other?
And finally, the one that has really been puzzling me - does a 25% overdrive mean the revs increase by 25% when you go from o/d to direct and decrease by 20% when engaging o/d?

I'd be grateful for any info.

Thanks,

Chris

[Mr Tiger]

Thanks for your reply. You've given me plenty to consider. I'll need to check whether mine has a vertical or horizontal solenoid.

I've just been though the handbook for the car. It states the ratio for 4th is 1.00 (:1) and o/d 0.82

I've not heard of an 18% overdrive but if the revs decrease by 18% on engaging then they will increase by 22% on disengaging.

This does seem counter intuitive but perhaps this is the way these are graded i.e.

22% drops revs by 18%
25% drops revs by 20%
28% drops revs by 21.875%

I could be completely misunderstanding this of course.

I'd be grateful if anyone could clarify.

Thanks,

Chris