mitchell over drive

I have a slightly stronger opinion. Here in the Bay Area, Freeway driving and hill climbing are part of daily life, if you're going anywhere other than to the corner store. Before I had the Mitchell OD (standard 26%), that meant much engine lugging or uncomfortable/disconcerting over-revving. Adding the Mitchell OD transformed my Model A from a curiosity to downright usable transportation. (Though I do try to remember someone's quote that, in a Model A, 'Drive no faster than your angels can fly')
 
I installed one in my 29 Tudor. I love it, but if I do it again, I would choose the 20% reduction rather than the 30% reduction.
 
Tom is right about a high compression head. I have a Mitchell in 3 cars. One with a stock engine - OK but not getting the full benefit of the O/D. The next has 5.5 head and downdraft carby - much better. The third has 5.5 head, downdraft carby and a touring cam - really excellent.
A note here for anybody new to these O/D's. When starting cold (say, first thing in the morning) do at least 2 miles before you try to engage the O/D. The oil needs time to warm a little or the synchro will lock you out of gear. (I use the oil recommended by Mitchell) A minor thing but worth remembering if you are to get the max enjoyment out of it.
I wouldn't be without one now that I have experienced them.
 
How about rear end ratios with a Mitchell? Should we go with the standard 3.78:1 or should we drop back to a 4.11:1?
 
The Mitchell overdrive is 26%, pretty well suited for a 378:1 ring & pinion ratio. The Borg Warner overdrives were 33% and it was too high for a 378. This is where the 411:1 ring & pinion was better suited.

Tom Endy
 
Thanks Tom. I've got an old Borg Warner in our 28 Tudor and I wish I had went with a 4:11 rear end. I once installed a 3.25:1 ring and pinion in a 35 Ford. Big mistake. Pulled too hard. Then I found a set of 3.78 gears for the 35, installed them and have been happy ever since. The car came originally with 4.11's and it was too slow. I may eventually buy a Mitchell for the 28. The Borg set up is not very user friendly, although it's worlds better then nothing at all.
 
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