Best overdrive

[w0ivb]

] What is the best way to obtain near hiway speed; overdrive or overdrive transmission for a model A ?

[quickchange]

Mitchel Gear splitter. many advantages over a 5 speed . least thats for me .

[Pete]

You need to do your own research, then read what others like and then decide.
There are 3 methods in common use.
5 or 6 speed transmission, top gear being OD.
Middle of the driveline OD. As with Mitchell, Ryan or Volvo type.
Integral with rear end as with a Columbia.
All are expensive and all require machine work to install.

[Art Bjornestad]

Also Borg Warner

[QGolden]

There is a lot of information here and on the HAMB. It would take you a solid weekend to digest everything the you can find doing a couple of searches.

Start here:

http://www.fordbarn.com/forum/search...archid=3639519

[Bob-A]

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I've got a Borg-Warner over drive, but the next one I get will be a Mitchell. Any O/D is good if it is built right and treated right. But the
Mitchell is built simpler and more foolproof to me. The 4 and 5 speed newer car/truck transmissions are nice too, so I'm told by the owners.
But the old crash-box Model-A Ford tranny's are part of the true Model-A
experience to me. And I'm going to stick with mine.

Bob-A

[CarlG]

Originally Posted by Pete

You need to do your own research, then read what others like and then decide.
There are 3 methods in common use.
5 or 6 speed transmission, top gear being OD.
Middle of the driveline OD. As with Mitchell, Ryan or Volvo type.
Integral with rear end as with a Columbia.
All are expensive and all require machine work to install.

One more you didn't mention was the F150 4-speed OD. Required no machine work to install. Kit was completely bolt in.

[BRENT in 10-uh-C]

Originally Posted by CarlG

One more you didn't mention was the F150 4-speed OD. Required no machine work to install. Kit was completely bolt in.

Maybe I am misunderstanding but how is there was no machine work involved in retrofitting one to be installed in an 'A'? The ones I have seen required several hours of machine work. What am I missing?

[Ron W]

I have the F150 and love it! Ron W

[Ron W]

Brent, is there no work in the others? It's a matter of who does it. Ron W

[kenparker]

In answer to Brent's post. I am one of several that build the F150 OD. I cannot answer for how the others build their kit, but for my kit, this is how I do it. I do all the machine work - and there is lots of it. When the customer gets the "kit" all the "machine" work is done. All the customer has to do is the final installation. I even include the extra and unique bolts and nuts required as well as the gaskets (U Joint cover and TT to Banjo gasket.).

Now to address the initial inquiry. Before anyone buys or install any kind of OD for their "A" I recommend they do all their homework. Research every type and style of OD, then analyze your driving requirements and driving style, then make a decision. Not everyone needs an overdrive. Also if one wants and OD in order to drive faster be very sure your engine and equally as important their brakes can handle the extra speed.

[Pete]

Originally Posted by BRENT in 10-uh-C

Maybe I am misunderstanding but how is there was no machine work involved in retrofitting one to be installed in an 'A'? The ones I have seen required several hours of machine work. What am I missing?

Hee hee. I guess if you just whip out your wallet and have someone else do the job, there is no work involved.(for you)

Oh, I didn't mention the F150 conversion because I consider it the absolute least desirable of the choices.

[tbirdtbird]

let us know how you make out

[Charlie Stephens]

I have 3.54 gears in my '31 RDPU and don't feel it is worth the money to go to an overdrive. I run mine comfortably at 55. What do you consider "highway speed"? Anything over about 55 and the fenders act like airplane wings making the car uncomfortable to drive. If you are passed by an 18 wheeler pushing a lot of air you will find yourself in the next lane without moving the wheel.

Charlie Stephens

[Kevin in NJ]

Do you really need an overdrive?

People seem to miss the point that the A was designed to be driven 60 MPH. See the original ads. Read some of the stories about the A's being driven when new. They got 50,000 to 80,000 miles on an engine before redoing the babbitt.

Of course that requires the engine returned to its original specs such that it is tightly balanced which many are not very close these days.

If you are not going to be putting thousands of miles on your car each year then an overdrive is not needed to be able to run 60 to 65 for extended runs on a regular basis

There is a lot to getting the A running 65 comfortably. Most is attention to details with getting the original parts back to factory tolerances. A properly set up back to original A is a pleasure to drive at 65 and a dream at 45.

You will be putting out some serious $$$ for the overdrive. Before you do that you should be perfect comfortable with your car running 65 as it is. If the car is not running nice then it will not be better with an overdrive.

Keep in mind I am not saying the overdrive is bad. Just that it is probably only worth the money for people who do some serious miles on their car.
Anyway something to consider.

[Tom Endy]

My recommendation would be a Mitchell 26% overdrive. It is not difficult to install and does not molest the Model A, except for a small slot in the wooden floorboard and floor mat of carpet. It is easy to operate and will work well with the standard 378 ring & pinion, and covers just about all driving conditions. Even though it is a $2200 investment it holds its value. It adds that much value to the car, or can be removed and sold for close to that value. They are well built and the manufacturer stands behind them and the Mitchell folks are nice people to do business with.

Tom Endy

[John LaVoy]

Several years ago we reviewed the various overdrives that went into the torque tube. Each has a plus but the Mitchell seems to be more versatile because you can shift in and out of overdrive at any time, where the Borg Warner you need to have the ability to "coast" slightly when engaging it, which means that you can't shift into overdrive if you are climbing a hill. We like being able to engage 2nd high on some of the passes we have encountered. But the Borg Warner is nice on the flat lands. We have around 50,000 miles on the Phaeton with the Borg Warner and about 25,000 miles on the sedan running the Mitchell. The other plus to the Mitchell is it is all new nothing to machine or work on just pull the old torque tube and install the new one with the Mitchell.

[TerryH]

I guess is if you have one of the rare stock Model A's that really can cruise effortlessly at 65 mph, than you really do not need an overdrive..... I have never seen one in our local club, so the folks who do want cruise at 55-65 mph, and have their cars in good running order, do install some form of overdrive. I would suggest riding with someone who already has one first, and see for yourself how they work. I rode in a friends nicely restored Roadster, with a Mitchell OD, and came away very impressed, and immediately had one installed in my car, and have never regretted it. With the stock 3.78 rear end, the 26% ratio is about perfect and the unit is bullet proof.

[CarlG]

I guess we can put "Best Overdrive" on the list with:

What kind of oil
Which Radiator
Alternator vs generator
12 volt vs 6 volt
Anitfreeze or water
etc vs etc

[tbirdtbird]

On page 102 of Schild's "Restorer's Model A Shop Manual" it shows a chart with multiple torque, HP, compression, and speed curves, from a 1930 factory catalogue. 60 MPH corresponds to 2800 RPM. At 2800 RPM you have fallen way off peak HP and torque, meaning the engine has to really labor to make 60 mph happen. If I drove any Model A I have ever come across at 2800 RPM I would vibrate the teeth right out of my skull. I have run a temporary tach in many of these cars so I can know exactly what the RPMs are doing. However Ford did the original factory crank/flywheel balance no one seems to be able to duplicate it today. Plus the universal joint is a single joint, not one on each end of the drive shaft as was done later. Thus there is a constant fast/slow component to the rotation of the driveshaft and thus the tranny components and crank. This, too, sets up an oscillation. Plus there were few roads where you could actually accomplish 60 mph back then, unless you were on a track, so to me the 60 mph was a lot of hot air to accomplish some nifty advertising.

Remember, these are long-stroke motors, very unlike the short stroke high-revving engines of today. A long stroke motor has all its torque at the low end. Study the HP and torque curves, and study them again, and get your head around what those curves are trying to tell you.

If there are any Barners who have driven stock Model As out there at 60 mph for thousands of miles without engine damage let them come forward. To me, a stock A redlines at 2000, maybe 2200 rpm. I never run mine over 2000. (I have a full time tach).

IMO anything over this and you are shortening the life of your babbitt, especially the center main, which gets the most wear anyway.

I had a 3.54 gearset, but if you do the math, this is only 6% OD. The Mitchell is 26% OD and gears can be split depending on the road conditions, such as using high second in the mountains. I switched to the Mitchell and back to 3.78 and I am much happier I never need to go over 2000 and I can do about 65 mph at that rev. on level ground. I don't like to go that fast in an A but those of us who live in metropolitan areas sometimes have to use the interstate to get out to the more rural areas.

I want my babbitt to last a good long time. Choose your priorities, do your research, and make your choices accordingly.

And Terry has a great suggestion about riding with others who have the various forms of OD to see what they are about.

[Dusty]

Originally Posted by CarlG

I guess we can put "Best Overdrive" on the list with:

What kind of oil
Which Radiator
Alternator vs generator
12 volt vs 6 volt
Anitfreeze or water
etc vs etc

Well you forgot green fenders

[QGolden]

Originally Posted by w0ivb

] What is the best way to obtain near hiway speed; overdrive or overdrive transmission for a model A ?

Originally Posted by tbirdtbird

On page 102 of Schild's "Restorer's Model A Shop Manual" it shows a chart with multiple torque, HP, compression, and speed curves, from a 1930 factory catalogue. 60 MPH corresponds to 2800 RPM. At 2800 RPM you have fallen way off peak HP and torque,

Plus there were few roads where you could actually accomplish 60 mph back then,

IMO anything over this and you are shortening the life of your babbitt, especially the center main, which gets the most wear anyway.

And Terry has a great suggestion about riding with others who have the various forms of OD to see what they are about.

I have Jim's book and it has some good info in it. I read his charts with interest. Only published chart I have found. I completely agree, as soon as you know what the torque and HP curve is of a motor, there is no point in exceeding that RPM, it accomplishes nothing but engine wear. Today's "average" road speed is different than the "average" speed of the 30's. Higher, and a lot longer distance at a given RPM, much less need to slow down for other cars, horses, etc.

It is personal choice, your comfort level, it's your car, keeping them original is a great goal. But there is a lot to be said for overdrive, synchromesh transmission shifting, the ability to coast without engine brake if wanted. Etc.

[modelAtony]

Originally Posted by w0ivb

] What is the best way to obtain near hiway speed; overdrive or overdrive transmission for a model A ?

I like the Mitchell best. Really bolt on unit and after you have driven a short time you will realize it makes your car operate like it is fully syncro trans. F 150 unit like Gary Bernard and MR ken parker install are great but 1st gear is lower than orig. trans . You can replace the car bell housing and use the AA bellhousing and not cut the small gap in brake unit. I am originally from Dallas,TX area and in 2003 talked to Gary about his unit because I didn't want the extra shifter that the Mitchell had. Told Gary I was going to have car in GREAT RACE and that stopped everything cold. Gary had been trying to get the 4 speed ok'd for 3 years in the race and owner of race Tom MC rea [sp] always said no. This is the reason I went with Mitchell , I was also running 3.27 gear since 2001. Mr Mitchell thought it would be to high of gear but I knew my car and it's great wouldn't change anything. You can also get different gearing use just ask for it. Check out my avatar info for car performance. have fun modelAtony Lafayette,la

[larrys40]

I concur with Tom Endy that the Mitchell is the preferred way to go, 26%. You essentially have 6 forward speeds if needed for various driving conditions..... and it is a well built unit that will give years of service. It gets the engine RPM's down to a comfortable level for highway cruising. My '30 Tudor has an older Ryan ( Mitchell was just coming out then) and at 23% plus I kept my 3:54 it does well on the highways with a HC head. I have driven Pikes Peak with it and many mountain passes in Colorado.... and the additional gearing makes it nice.

As with any car... you have to know your car, gearing/load/when to shift... do not lug... etc

As Tom says the cost of the overdrive adds value to the car as a tour car if a sale is desired. I have installed Mitchells and all have gone well. They are a bolt up install except for the floorboard cut.

Larry Shepard

[Jim Huseby]

With a Mitchell, you don't have to have an extra shift lever coming through the floor, as there is a sturdy cable operated option. If you're gonna run this set up in a speedster or a severely lowered car you will have to turn the cable lever on the O'D unit upside down and mount the cable from the rear to get clearance to the floor.

[Tiny]

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Originally Posted by Dusty

Well you forgot green fenders

And unsightly Whitewalls

[Dick M]

I know many happy Model Aers who have the Mitchell OD. They are very well made and are good units. However, I have the Laycock (Volvo) OD in my coupe. I love it for two reasons. First, the price is less expensive the Micthell. And second, the ease of shifting the unit in and out of overdrive. It can be shifted without engaging the clutch and it is operated with a toggle switch located under the gearshift knob. It also does not take up any valuable floor space. JMO

[apbright]

I installed a Mitchell on my own as a Rookie (with only a little help from the local shop to get the pinion gear onto the Mitchell shaft). It was undoubtedly the best modification I made to the car. I drive about 300 mi / week, about half of them having to be on the Interstate. Before I had the Mitchell, I rarely could stay above 55, and was revving the engine so hard it was painful and embarrassing to listen to.

Also, when climbing hills here in Northern California, the 2 1/2 gear is essential - there is just too much gear ratio space between 2nd and 3rd when climbing these hills.

[Duffy1]

Lots of folks run f-150 and love um . Me for one .

[Jordan]

I have the 4-speed from Gary Bernard. I absolutely love it. It's fully syncro so no worries about grinding gears. I had a worn out transmission anyways, so when going for an overdrive it was a no brainer to just get the 4 speed. I do however miss the whine of the Model A transmission. If the transmission is good in my next car, I'll get a mitchell so I can have the best of both worlds.

[modelAsteve]

I love my Volvo!

[bettlesr]

I made up a chart of engine RPM vs car speed before I changed my trans to a f150 trans. I used the small V8 gearing to 1st gear as low numerically (3.01:1) as possible. Trans code AK.This is based on using 16" radials on my car. With a .100 over engine and 7.5:1 head, there is no problems in using OD even at 35 mph. This is a full pressure inserted engine. And no, I don't try to climb steep hills in OD!

[Kurt in NJ]

. However Ford did the original factory crank/flywheel balance no one seems to be able to duplicate it today. ---when many machine shops have the attitude that it is just an old car, it won't matter it's hard to get anything done to oe specs

Plus the universal joint is a single joint, not one on each end of the drive shaft as was done later. Thus there is a constant fast/slow component to the rotation of the driveshaft The angle of the engine nearly matches the angle of the driveshaft, not enough of an angle to be a factor.

Plus there were few roads where you could actually accomplish 60 mph back then, unless you were on a track, so to me the 60 mph was a lot of hot air to accomplish some nifty advertising. --from the may-june Model A News -in 1933 a model a with 62,000 miles averaged 62 mph traveling from LA to Phoenix, and on the return trip averaged 60, previous to this they did 500 miles on the salt flats at 66.66 mph average speed (It must have been a wild ride for the observer in the back seat)

If there are any Barners who have driven stock Model As out there at 60 mph for thousands of miles without engine damage let them come forward. To me, a stock A redlines at 2000, maybe 2200 rpm. I never run mine over 2000. (I have a full time tach). --- On the 3rd day of driving the freshly done babbitt I knew that the car would show 67 on the speedo, but I tried to keep it under 60 for the next 1000 miles, on the way home I tried to break it, rarely under 60, PA turnpike at 65(averaging 23 mpg), 2000 miles more ----I don't know how many more miles. I used to unhook the cable so my parents didn't know how far I drove


I want my babbitt to last a good long time. Choose your priorities, do your research, and make your choices accordingly. -- When my car was first restored with a professionally rebuilt engine I rarely got over 50,drove it easy-- that job only lasted 3000 miles before the babbitt crumbled ---so I figured that I couldn't do worse doing it myself, I have spent the last 25 years trying to break it, even though I know that I have a flywheel/crankshaft balance problem ---the only thing I have broke is the babbitt on 1 rod, one I shouldn't have used when I put the engine togewther, but it was closest to the other 3 in weight---and yes I was going above 65 when it came apart--but being babbit it did no damage to the crankshaft, and i drove it home after it happened.


And all this in responce to a first time post by someone that just wants to go "near highway speeds "---over 30 posts about overdrive.

I think I am getting closer to breaking my engine, the flywheel vibration is getting a little more pronounced, from the beginning the car would move in a circular motion going through 8-900 rpm, I know the crankshaft was ground .003 off center, it was the first time I poured babbitt and I have figured how can I know how good I did if i didn't try to break it, I have run the car in a circle for over 1 hour at idle in 3rd on a 95 degree day, lugged it through deep sand, left it at full advance for most driving, some of the oil changes were done with used oil, and I have come to the conclusion that there is not much you can do to save bad babbitt, and conversly that there isn't much you can do to hurt good babbitt.
I also feel that proper restoration to original specifications and tolerances will eliminate the need for most modifications in normal use

If I was to install an overdrive I will use a Columbia because it is the cheapest option for me