Model A drive line

[Gerald cook]

I need advice on my drive line I have a 1929 Tudor with a newly rebuilt engine with up grades it is a very strong 4 cylinder. I would like it to be more streetable. I need advice on hoe to proceed. I've been looking at Mitchell transmissions and overdrive. I currently have a rebuilt stock transmission. This combination has limited my driving 50-60 mph range. I have Babbitt rods and mains and a balanced crank. My rear end has stock gear ratio. Any advice would be appreciated. Thanks Jerry

[Tom Wesenberg]

50 to 60 is a good top driving speed, but to do that speed I'd want an overdrive or at least a 3.27 rear end ratio.

[Brentwood Bob]

A Mitchell comes in 2 ratios. Call mitchell and discuss with them.
Bob

[Dave in MN]

JMO: The Mitchell overdrive is expensive but it makes such a difference if you plan to drive between 50-60 or faster. The overdrive allows you to shift effortlessly when needed due to the synchromesh feature. I do lots of travel at the speeds you mention and find myself in and out of overdrive as the hills require to keep the engine rpm in a suitable range. I have had a 26% Mitchell overdrive installed with 4:11 rear ratio for the last 75,000 miles we have put on our '29 Phaeton.
The Mitchell transmission will not give you any higher third gear and that means you need to over-rev your engine when traveling fast.
Safety first: Before you speed up make sure you can slow down. Brakes!
Good Day!

[Dick Steinkamp]

If you want to go faster than 50-60 MPH, I suggest upgrades to the braking system. At a minimum, adjust the brakes so that the fronts come on first and do most of the stopping (like "modern" cars do). Also consider Flathead Ted's self centering/self energizing kit or self energizing hydraulics.

Try a panic stop from 60 (give yourself plenty of traffic free road!). If it is much over 200 feet, you are really not safe at 60 without some brake changes.

http://www.government-fleet.com/cont...-distance.aspx

[jfreddie]

Sponsored Links (Register now to hide all advertisements)

The F-150 overdrive, 4 spd transmission conversion is hands down best IMHO. The kit is spendy, $3000, but all inclusive and you can order the overdrive ratio you want.

I helped Carl G. with his and it was very straightforward.

If I had an extra $3000 I'd have one.

Thanks,

[Tom Wesenberg]

I agree with the F-150 being the best for improved drivability and added speed.
Due to cost and liking to stay as original as possible, I'll probably settle for the 3.27 ring and pinion.

[jfreddie]

I like that combo, too.

Takes a nice strong motor to do hills without lugging, but definitely enhances cruise speed.

Using 16" wheels and slightly smaller diameter radial tires gets around the lugging issue and gives a huge drivability improvement.

Good luck...

[Charlie Stephens]

Originally Posted by Gerald cook

I need advice on my drive line I have a 1929 Tudor with a newly rebuilt engine with up grades it is a very strong 4 cylinder. I would like it to be more streetable. I need advice on hoe to proceed. I've been looking at Mitchell transmissions and overdrive. I currently have a rebuilt stock transmission. This combination has limited my driving 50-60 mph range. I have Babbitt rods and mains and a balanced crank. My rear end has stock gear ratio. Any advice would be appreciated. Thanks Jerry

"My rear end has stock gear ratio." leaves a lot of room for speculation. Check the number on the speedometer gear on the drive shaft, post it and that will give you the real ratio. Alternatively push the car forward one revolution of the wheels while counting the revolutions of the engine in 3rd gear that will give you the ratio. 3.54 or 3.27 gears make a world of difference. Another thing is that the Model A lacks aerodynamics. At high speeds a gust of wind on the large side areas will cause you an uncomfortable feeling. Semi trucks and canyons crossing the highway are the main problem. My '31 RDPU with 3.54 gears is comfortable at 55 MPH but that is about it.

Charlie Stephens

[Jason in TX]

I think overdrive is the way to go.

I have the Laycock (Volvo) overdrive, and I love it. I thought I wanted an F150 four speed in my next car, but after driving in Colorado in my torque tube installed overdrive with a group of cars with F150 overdrives, I'm now ALL for the torque tube overdrive.

You can split every gear with a torque tube overdrive. I was driving in 2nd gear with the OD on and passing the other cars with F150 because their 1st, 2nd, and 3rd are similar to a stock vehicle. They bogged in 3rd, but 2nd was too slow going up the hills.

So, for that, I would say torque tube overdrive is superior.

- Mitchell is mechanically activated by second shifter lever next to stock lever on the floor

- Borg Warner is electric switch and a T handle attached to a cable mounted near the steering column. two things to mess with and remember

- Volvo overdrive is just an on and off switch. I have a lock out switch drilled into my shifter tower, so I can't accidentally operate the overdrive in reverse. (they break if engaged and go in reverse.)

[1931 flamingo]

There's a Mitchell o'drive for sale now on the ahooga site. FWIW
Paul in CT

[Tom Endy]

In my opinion and experience a Mitchell overdrive is the way to go. They are a factory made overdrive and made very well, and the gear ratio of 26% is properly sized for a 1:378 ring & pinion ratio. Other overdrives on the market are cottage industry modifications taken from era modern cars. The Mitchell overdrive has a simple gear shift lever on the floor that shifts either in or out of overdrive. The Mitchell is considered a gear splitter in that it gives you six speed forward and two in reverse. The two in reverse are usually never used, but second gear overdrive is beneficial climbing a steep grade and coming down one for engine braking. High gear overdrive is perfect for cruising along at 55 or 60 mph on a fast highway with the engine turning over at a nominal 2,000 RPM and thinking it is doing about 45 mph.

The overdrive is not that difficult to install if you know how and have the proper tools. You need tall jack stands, a safe and proper spring spreader and a drive shaft removal tool (Mitchell can supply the drive shaft tool). Keep in mind there is usually a 6-weeks to three month lead time when you place an order.

Mitchell also supplies a replacement syncro-mesh transmission that is well built and provides a number of modern advantages. If you have the money to spend, go for it. For my money I will stick with an original Model A transmission because they are reliable and easy to repair and after 30 years of driving a Model A I know how to double clutch without even thinking about it.

The majority of Model A's were delivered with a 1:378 ring & pinion gear set. A lower gearing of a 1:411 R&P was installed in pick ups, station wagons and such and in some town sedans delivered to dealers in hilly locations. A 1:354 higher gearing came along later when the countries roads improved. It is found today in some Model A's. A 26% Mitchell will also support this gear set. The 1:327 gear set is a recent option. I would not run them with a 26% Mitchell, nor with the 1:411.

There are numerous methods to determine which gear set is installed in your car. It involves counting the rotation of the engine pulley in high gear and counting the rotation of one wheel jacked up. You then do a mathematical calculation and hope you got it right.

The easiest way to tell is have the ring & pinion laying on a work bench and count the number of teeth on the pinion and the number of teeth on the ring. If there are 9-teeth on the pinion and 34-teeth on the ring. The smaller number divides into the larger and it equals 3.78 (3.777777777).

Do a search on this forum and there are posts that describe all the option of determination the gear ratio and also the R&P count of the other R&P ratios.

Tom Endy

[larrys40]

I agree with Jason and Tom Endy that the overdrive is the way to go. Have had my '30 Tudor out to Colorado 5 times in the high country and I'm running an older produced "Ryan Overdrive" unit with a 3:54 rear. It is an excellent highway cruiser and hill climber when needed as Jason said, you can "split" the gears when desired for the best range.
I have installed a number of Mitchells for guys and they are an excellent upgrade, best mated with the stock 3.78 in my opinion with the 26% unit.
The best thing you can do to make your car more easily driveable on today's roads.

All of this said.. the rest of your mechanicals, brakes, steering, front end, ,etc must be in top notch shape, able to stop on a dime... and be good and tight. If it's not fix it.

All of that done you should have a fine driving "A". One unit done a number of years ago had one of AER's touring engines and a Mitchell... I had rebuilt everything else on the chassis and it was a flawless driving car all day long on the freeway at 62 + .

Larry Shepard

Originally Posted by Jason in TX

I think overdrive is the way to go.

I have the Laycock (Volvo) overdrive, and I love it. I thought I wanted an F150 four speed in my next car, but after driving in Colorado in my torque tube installed overdrive with a group of cars with F150 overdrives, I'm now ALL for the torque tube overdrive.

You can split every gear with a torque tube overdrive. I was driving in 2nd gear with the OD on and passing the other cars with F150 because their 1st, 2nd, and 3rd are similar to a stock vehicle. They bogged in 3rd, but 2nd was too slow going up the hills.

So, for that, I would say torque tube overdrive is superior.

- Mitchell is mechanically activated by second shifter lever next to stock lever on the floor

- Borg Warner is electric switch and a T handle attached to a cable mounted near the steering column. two things to mess with and remember

- Volvo overdrive is just an on and off switch. I have a lock out switch drilled into my shifter tower, so I can't accidentally operate the overdrive in reverse. (they break if engaged and go in reverse.)

[JohnLaVoy]

I like the Mitchell overdrive and the stock transmission.

[Smitty]

I have been running Mitchel Overdrive with 3:54 rear end gears in my coupe for several years. Mitchell is excellent and smooths the car out quite a bit. Running a Snyder 5.5.1 head and touring cam. Really runs nice since I installed FSI ignition.

Steve

[Jason in TX]

This is a volvo overdrive in a Model A Chassis



A borg warner in a Model A chassis




A mitchell overdrive in a Model A chassis



Extra shifter for Mitchell Overdrive:



Here is the early 1980s F150 4 speed OD transmission installed in Model A chassis.




Volvo overdrive install "How To"

http://www.thelmasgarage.com/volvo.htm

[Synchro909]

I have 3 Model As - all of them with a Mitchell O/D and one with one of their gearboxes as well. I find that with the standard gearbox, the big gap between 2nd and 3rd gears is not so much of a problem. High second is a very handy gear and you will soon get used to changing up to ordinary 3rd and down shifting. I've just installed a cable shift on one of the cars which I will be testing tomorrow. I think it will be another improvement.
In the car with both Mitchell gearbox and O/D, I can change both with the one motion. All cars have 3.78 diff ratios but I'm going to put a 3.54 in the P/U. With the Mitchell coghouse and O/D, I've towed a camper weighing about the same as the car around the outback for about 30-35,000 miles at 80 kph (50 mph) I can't see me changing anything any time soon.

[Kevin in NJ]

Define what you mean by streetable?

A properly rebuilt to factory spec chassis is good for 10's of thousands of miles running at 55 MPH. You can have all the overdrives you want. You need a very well balanced engine and know how to run the spark lever to keep from tearing up the babbitt.

My brothers coupe has been on the road since 1970. It has always been run 55 to 60 MPH. Even with the bad babbitt put in by the shop. We ran it out to Wisconsin and were passing small cars going up the PA mountains.

I think too many guys are wasting their $$$$ and really do not need the over drive. If you are not putting many thousands of miles of years going all over the place you probably really do not need to spend your $$$ on an overdrive. Spend your $$$$ on getting the chassis as close to Ford factory specs. Then just drive the car hard and enjoy it. If you did it right your grand children will still be driving the car years down the line.

[Jason in TX]

Agree with Kevin. A stock Model A is an enjoyable vehicle. If you are going to drive it around your immediate 50 square miles, don't bother with any modifications.

If you are going to go on long 6-8 hour sustained driving days for a week at a time with a group of other touring cars, The OD is a miracle. Engine isn't screaming and you can keep up with them.

[Gerald cook]

To all the Ford Barn members who took the time to give me advice on my post thank you very much. Every reply gave me information on my car I needed. I have a lot to think about. Thanks again Jerry