Mitchell Overdrive

[JayJay]

Originally Posted by Y-Blockhead

Besides it is fun watching people discuss why it has "three shifters".

You could tell them the stubby one with the button on top is for the 4WD transfer case...


JayJay

[alexiskai]

Originally Posted by JayJay

You could tell them the stubby one with the button on top is for the 4WD transfer case...

I tell them it's to eject the rumble seat occupants.

[Model A Ron]

Thanks everyone for your comments. Did anyone put in an OD with 33% reduction with stick rear end? I am thinking 33 would be a bit much but would like to know your thoughts.

Ron

[Bud]

I have a Mitchell in my 31 S/W town sedan, but with a 4.11 rear end gear. I plan to remove the 4.11 and replace it with a 3.78 ratio.

[Ranchero50]

Originally Posted by Model A Ron

Thanks everyone for your comments. Did anyone put in an OD with 33% reduction with stick rear end? I am thinking 33 would be a bit much but would like to know your thoughts.

Ron

I think it really depends on what you are putting it in and what's been done to the engine. My aluminum bodies speedster with 3.54 gears flies with a very tired short block with a high compression head and custom manifold / header. No O/D and it'll pull 55 very easily. Some flavor of O/D is on the list once the body is skinned out and the blown B engine is built. Goal is 75+ for 30-40 minutes (daily commute). Might even happen.

[TerryH]

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Regarding having 33% OD with stock 3.78 rear end: most folks seem to agree that is too tall for most cars unless you have a souped up engine. I have a heavier Town Sedan, with a 5.5 head and stock gearing. The standard Mitchell 26% seems about perfect.....I can still pull modest hills in OD, and 55 is my most common cruising speed, which is just fine with that setup.

[Aarongriffey]

A few years before Mr. Mitchel died he told me he ran one in his 3/4 ton Ford pickup with 390 engine with no problems. They should easily take what little abuse a model A engine can give them.

[Synchro909]

Originally Posted by Aarongriffey

A few years before Mr. Mitchel died he told me he ran one in his 3/4 ton Ford pickup with 390 engine with no problems. They should easily take what little abuse a model A engine can give them.

Quite so. I have seen a cutaway of an O/D and they are built so they can handle much more power than a Model A will ever put out. I have one friend who has one of these O/Ds in his '56 Victoria and has had for many years without trouble.

[Jack Shaft]

Very stout..they actually speed shift too, the synchro works as fast as you can throw the lever

[Model A Ron]

If one were to install a Mitchell would you need a High Compression Head? If so would it be a 5.5 or a 6.1? What is the stock compression head and how much is too much for a stock engine in good shape?

Thanks
Ron

[Bruce of MN]

I have a 6:1 and an OD, installed at the same time, so not scientific. I do think that an OD with a stock head would be ok, unless you were in very hilly country. For the great benefits of the HC head, I would go for it, with the right gasket and break in.

[TerryH]

I have the heavier Town Sedan, so I added the 5.5 HC head the same time as the Mitchell was installed (this was before the newer 6.0 heads were available). I think this makes a great combination if you drive your A much.

[Synchro909]

Originally Posted by Jack Shaft

Very stout..they actually speed shift too, the synchro works as fast as you can throw the lever

Synchro is getting a bit weak in mine - same with the gearbox which went in at the same time.
Crunch, crunch, crunch!

[roadster_30]

Our club has installed 6 Mitchell Overdrives among members and everyone loves them. I especially have enjoyed it and downshifting is a breeze. Two Thumbs Up!

[whirnot]

Be careful with youtube videos. That guy says to set your preload just where it was. You are taking it for granted that it was right. I took a rear end apart just yesterday that the pinion nut was actually loose.
I just took my first 75 mile drive with my new Mitchell.
The first time I used it, I thought I had an issue with my pickup because it lacked power. It was a windy day. Later I thought, of course it has less power, you are in a higher gear!
If you have realistic expectations, it's wonderful. Especially for splitting gears. Two high, fits the gap that is normally an issue with model As. I am one of the few that has a cable shifter, and I would not have it another way. Split shifting from two high to third low and back and fourth is easy! Not sure why do few use it.

[daveymc29]

Originally Posted by Bud

I have a Mitchell in my 31 S/W town sedan, but with a 4.11 rear end gear. I plan to remove the 4.11 and replace it with a 3.78 ratio.

I have a 26% Mitchel O/D and the Mitchell tranny also in my Roadster. Did that so if I keel over the bride can drive normally to get home. It also is a bit peppier engine than stock and I run 600 X 16 and hyd. brakes. Very responsive and does well on the highways and over the Sierras. Cable shift. 55/60 mph fine, 65 when bored.

My coupe has a B/W OD, 33% with 4:11 rear. Never over the Sierras but very good on the highway and local hills, so I fear no problem over the mountains, It is also cable shift. Advantage to that is keeping the floor open to getting in on the right and sliding across to drivers side if and when necessary, 55/60 on highway, 65 if pressed by traffic.(Just until I Can get to the far right lanes.

The best for looks is to use the Laycock (Volvo) O?D and a switch either hidden or mounted on the shift shaft or be creative and build a know for the shifter with a built in switch. Mitchell told me 4:11 gears and a 33% overrdrive is ideal for most occasions. I do agree. Volvo can be had in 33%, though when I was looking no one had one and a $400 B?W showed up, I had the 4:11 gear so here it is. Works for me, again using 600 X 16 tires.

[Tom Endy]

There is an organization in the Model A kingdom in Southern California known as the “BLT Guys”. BLT stands for Bryan, Larry, and Tom, the original three members that started the organization. What this organization does is install Mitchell overdrives and Mitchell transmissions. It has the full support of the Mitchell Manufacturing Company. Over the last few years the organization has grown to include many new members. The BLT Guys charge a reasonable fee and donate the money to the Model A youth restoration program.

An installation takes place on a Saturday morning at Tom’s house, in the city of Westminster, beginning at 9:00 AM. A Mitchell overdrive installation takes 4 to5 hours. Several hours more is required if a Mitchell transmission is also installed. Coffee is served and the owner is requested to bring the donuts. The owner can participate in the installation process, or just sit and watch, or not even be there.

The Model A youth restoration program is a 503c tax deductible program that every two years awards financial assistance to youths between the age of 12 and 21 who are restoring a Model A. The BLT Guys get the credit for the donation, but the owner of the car is given the tax credit that can be used as an income tax deduction. Since August of 2020 the BLT Guys have accomplished six Mitchell installations, two of them included a Mitchell transmission. The last installation was a week ago.

The BLT Guys have all the proper tools and technical knowledge to safely do the task. We do not pull the rear end with the spring attached because it is a dangerous practice that too many in the Model A kingdom subscribe to. We leave the spring attached to the frame where it remains safe. We have a tool to pull the pinion assembly without destroying the pinion bearing pre-load. We always check the pre-load and re-set it if necessary. We can also replace the bearings and the double race if necessary. We carry the stock and charge the owner only for the new bearings; no additional labor fee is charged.

This service is available to anyone in the Model A kingdom located in Southern California.

Tom Endy

[nkaminar]

Tom, Do the BLT Guys also serve Bacon, Lettuce, and Tomato sandwiches with the Mitchell overdrive? Inquiring minds want to know.

[Gufshoz]

I've seen several photos of an install with the shift lever. Could those of you who use a cable please post a pic?

[Y-Blockhead]

Originally Posted by Gufshoz

I've seen several photos of an install with the shift lever. Could those of you who use a cable please post a pic?

Steve sent me this picture when I was considering getting the cable shifter so I could see how it was mounted. I decided against it.