Mitchell trasnsmission or overdrive?

[48thames]

I have never driven a stock model a before, so I can't compare the 2, but the few miles that I have put on my tudor with a B trans with later gears and mitchell over drive, so far has been a joy to drive. Going up the hill in second high is just right for where I live.

[P.S.]

Originally Posted by Jason in TX

I run the volvo overdrive on the bottom. Here is a photo showing the mitchel and the Volvo. Mitchell is mechanical lever on the floor. Volvo is an electrical switch hidden under the dash rail. flip of the index finger and you are in or out of overdrive in any forward gear.

No speedo?

[Kevin in NJ]

Before you spend some major cash---

Everyone is quick to spend your money, but you should really think hard about what your are trying to do and what you currently have with your car.

It is CRITICAL to understand that a proper rebuilt Model A should drive like a factory car. So you should be tooling around not thinking twice about running 60 MPH all day long. The car should be comfortable to drive at that speed, that is it should track nice down the road and handle bumps with no problems at that speed. Of course, you should have no troubles laying into the mechancial brakes and expect them to stop like drum brakes with thin tires- which is pretty dam good.


If your car is done right back to factory then you should have no problems driving for days at 55 MPH or better and not feel like you are abusing the car. The car should be able to pass some of the modern cars going up hills. Throw in a new B type cam and a high compression head that car will do all the above with more pep. You should also be getting in the low twenties for MPG.

This is all based on personal experience with A's in our family and what I know from reading about the history of the A and how it was driven back when they were just an everyday car.

I bring all this out as too many people feel they need to spend $$$$ for an overdrive and really do not run enough to make any advantage over a factory car. If you are planning on running ten of thousands of miles then you may be better off with an overdrive. If you are just planning on a long trip here and there then you should be fine for the 50,000 to 80,000 mile the driveline should give you even running at the 55 MPH speeds most of the time.

Most important is you should have a car capable of running those speeds before you add the extra stress of the over drive.

[Jason in TX]

Originally Posted by P.S.

No speedo?

I run the speedo at the stock location. When switched to overdrive, the speed drops 27%. Now I just add about 25% to my speed in my head.

I do need to make a longer cable to go to the back of the overdrive so that it will be the right speed all the time.

[Glenn C.]

I have three vehicles now with Mitchell transmissions & overdrives. Two of the three with 5.5 compression heads. Great in all. I steered away from the Volvo set-up, when a couple of friends told me that with the Volvo you cannot back-up with the overdrive engaged or the gears will pile up. Right or wrong.....I don't know ??

[Kahuna]

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Glenn C
You are correct. Overdrive must be disengaged before using reverse with the Volvo/Gear Vendors OD.

[TDO]

I went with the GM T-5. First, I had the transmision. 2od price. End up with little over a A $1000. It works great here in the hills and mountains in WV. Not saying it's the best way to go. I'm satified with the way I went. The only thing I know about the other overdrives is the price.

[Arlyn Bieber]

I'm running a 6-1 head, B cam and carburetor, large intake valves , CW crank, lightened flywheel with V-8 pressure plate, 3.78 rear end and a 33% Mitchell OD on my '31 Slant Window sedan. Love it, wouldn't change a thing!!!

[Dtolson]

With a 5.5. Hp head and standard 3.78 gear, what speed should you cruise comfortably?

[Barry B./ Ma.]

I would say, 45-50, 55-60 with a Mitchell overdrive.

[hotrodalley]

I have a 26% Mitchell, a 36%Mitchell and a Mitchell Synchronized Transmission. I absolutely love the transmission. Having the ability to downshift from 3rd to 2nd is fantastic, and allows me to slow down and take corners without worrying about lugging the engine. I am running babbit. I am running this transmission with a 26% overdrive, but really only use it for 1st and 2nd high. That is because I have a cam that is too radical. I know, its a bit of a waste.

In my coupe with 3.78 gears, a snyder 5.5 head I run a Mitchell 36% overdrive and I like it a lot. I am very careful not to lug the motor but I suspect I am putting somewhat of a strain on it. I do like the ability to get up and cruise at 60-63 mph.

[TerryH]

With a standard 3.78 rear end, and a decently rebuilt engine, you should be able to comfortably cruise at 50. There are some people who will insist that a bone stock Model A will run 60-65 mph all day long....if it is carefully rebuilt and balanced to original factory specs. In all my years of owning and driving Model A's, I have seen very, very few owners drive their stock geared Model A's much more than 45-50 mph.... most will not even consider getting on the freeway....even those that have been recently rebuilt. Most just do not want to push their cars that fast, even though they could. That is the beauty of an overdrive in a Model A.....you can then easily drive them 60-65 mph without feeling like you are really working the engine to death. Of course, your steering, brakes and tires need to be up to it, but I have logged lots of freeway driving here in S. Calif. and think nothing of it........I usually get in the right lane, run up to 60-65, and cruise very nicely. And with the overdrive, I then drive surface streets at 45--50 in OD, and it is amazingly quiet. The Mitchell is so easy to use, I use it a lot...very versatile. One final thought...if overdrives are so unnecessary, then why do most modern cars have the equivalent of OD when in top gear? They will all cruise at the same speed without them.......there must be some advantage to running your engine at lower rpm. Of course, if you just drive around town, or very few miles, than you probably don't need it.

[nickair]

With the better roads we have now days compared to the Model A era now higher speeds are easy to obtain. Makes sense to me that an overdrive is in order if you wish to take advantage of highway cruising. Also, a point to consider is that the highest torque is available at around 1200 RPM then torque declines as the RPM's go up, if I remember correctly. With the RPM reduced by an overdrive (at a given highway cruise speed) the torque is actually increased. Most every modern car has overdrive as an engineering standard. Overdrive allows more efficient engine operation at a highway speed.

[Jdubwikk]

My Dad put the Mitchell OD and synchro trans in the 30 Coupe he had and that car runs great. The only issue is the low OD % compared to the Borg Warner in my Sedan. My engine turns 2K @ 57mph with the 36% OD and standard trans. Hope that helps.