Mitchel Overdrive

SANTA Ray

SANTA Ray

Member
A friend and I will soon be starting the rebirth of an A400. It will have a touring motor (insert bearings,B Cam) standard "A" trans but we need some input for the differential.

If we use a Mitchell Overdrive, or any other, what rear gear should we use? Thinking the 3:54 gears but not clear on the % ratio for the overdrive. I can't find a contact phone no for Mitchell does anyone have one?

Appreciate any help please don't get off on oroginality. This car will be done according to spec but will be a touring car. The Mitchel is probably the only deviation that will be made and that can be removed anytime and returned to stock with no damage to the vehicle.

THANKS
 
26% is most typical for the Mitchell. (It is what I have..I like it.) With a stock ratio rear end and the touring engine you are describing you should be good to go. I am assumming you are including a higher compression head...5.5:1 or 6:1 are available from Snyder's.
 
I have a touring engine with a Brumfield 5.9 head, and a Stipe IB30 cam in a 29 Tudor with 21" wheels. The engine does not have inserts and I am also running stock Zenith carb and distributor. I also have the 3:54 rear with a Mitchell 26% OD. This combo works very well in the hills and grades as well as flat ground. On flat ground I can run 55-60 all day long with 22 MPG.

When I talked with Mitchell about the % OD they recommended the 26% with the hi speed rear i.e., 3:54 or 3:27. If you have the 3:78 or 4:11 rear then you can go with the higher OD % which I think was 35 or 36%.

Specifically you do not want the high speed rear with the higher % OD it will cause to much lug on the engine.
 
Hi Ray,

Mitchell is listed in the stickies at the top:

TRANSMISSIONS
2. No known website: Mitchell Manufacturing (800) 859-2088 (California) mitchmanfc@frontiernet.net

In my rig I have an F150 4-speed OD transmission, 4th gear = 0.78:1 OD (22% or 27% depending on who is doing the calculations) with the stock 3.78 rear end. This combination works well for me.

Engine has 5.5 Snyder head, Stipe IB30 Cam, Insert rods, Babbitt mains, Weber carb.

Everything I have is bolt on and can be reverted to stock.

Good luck with your project!
 
Here is the phone number and email address for Mitchell manufacturing.

You may want to verify that a Mitchell will fit in an A400 as I recall from a friend there was some discussion about interference with the A400 floor pans.

Mitchell Manufacturing (800) 859-2088 (California)

mitchmanfc@frontiernet.net
 
My suggestion would be to stick with the 378 R&P differential ratio with a 26% Mitchell. Be sure to tell Mitchell that you are ordering an overdrive for an A400. They provide a different model for cars with the drop floor pan (Victoria, A400, 2 door phaeton). The stub shaft is slightly longer putting the overdrive more forward. They also shave material off the top aft end of the unit to better clear the floor pan. You can also glue a strip of 1\4" rubber along the area where it is shaved. Another option is to replace the 8-leaf rear spring with a 10-leaf. It is a close fit, be very careful driving over speed bumps.

Tom Endy
 
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