What are my overdrive options?

BandidoLenny

BandidoLenny

Junior Member
I have a 53 with a Flathead and a non-overdrive 3 speed. Can my current ****** be modified for overdrive or do I have to find a completely different transmission?
The car will do 80mph on the highway but it prefers 70... I am looking to lower my RPM's at these speeds. I am currently running 205/75-15's with a 4:10 rearend. Maybe taller tires or a higher rear end gear?
 
Pretty tough just to add it on to the 3-speed as the mainshaft is different too, you need to look for an OD from a '52 and up Ford or Merc so it has the right length and the mount will be in the right place. Stock rear for your 3-speed should be 3.78, the 4.11 is in the OD equipped cars. ..B.
 
The forward gear case should be similar but it likely won't have the provision for the reverse lock out mechanism. The input shaft, countershaft, syncronizers, 2nd gear, 1st gear, and reverse idler gear may interchange with the overdrive stuff but I can't be certain without checking first.

The earlier Mercury overdrives through early 51 won't interchange with Ford. 1951 was a cross over year for the Ford transmissions too so like Barlea mentioned, look for 52 53 types. Some of the early Y-block stuff might work too. Mercurys usually had the 3.92:1 rear but 4.27:1 & 4.54:1 were available.

Kerby
 
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With all the parts you need it is easiest to just get another transmission. You will need a relay and kickdown switch plus the wiring harness for a stock installation. Also the operating cable. Make sure the governor and solenoid are on the transmission or you will need to look for them too. If you read up a little on them you will find this to be a neat little addition to your car. Though unsafe I like the freewheeling at low speeds. Another option is an automatic od conversion. I am not too familiar with them but there are installation kits.
 
The Mitchell is for cars with a torque tube, it won't fit any 49 and later Ford passenger cars.

52, 53, and I think 54 are all the same side loaded transmission.

55, 56, and maybe 57 are the same top loaded transmission. Somewhere around 57 the input shaft switched from course to fine spline. The trick is to measure the total transmission length and distance from the front of the transmission to the rear motor mount. Get an overdrive from a Ford with the same measurements and it will bolt into your car. Check for fine spline vs coarse spline at the input and output shafts. You may need to switch clutch disk and/or drive shaft yoke.

I recently bolted, with no modifications, a 56 overdrive transmission into a 52 sedan. Make sure to get a working solenoid in whichever voltage, 6 or 12, your car is.

I have installed 5 Borg-Warner overdrives. I never bother will all the factory controls. You can install them if you find them and you want them, but you don't need most of them. All that you have to have is the lock out cable, a good working solenoid, an on-off switch capable of a few amps, and two wires. I take the governor off, remove the gear on the bottom, and put them back in to fill the hole. Then I run a wire from the "on" post on the ignition switch to my on-off switch, and another wire from the other side of the on-off switch to the solenoid. The solenoid has two wire connections, only one of these is needed. Put power to each one separately while grounding the housing and you will find out which one is necessary.

To get into overdrive with the switch set up you: push the lock out cable in, drive up to the speed where you want overdrive (typically 40-50 m.p.h.), turn the switch on, let off the gas, and you are in overdrive. To drop out of overdrive, turn off the switch and let off the gas a little. You can go into and out of overdrive at almost any speed this way.

With either full factory control or switch setup, never pull out on the cable unless you are accelerating while out of overdrive, or you are at a dead stop.

If this is all a bit confusing, PM me and I'll try to clarify.
 
BandidoLenny said:
I have a 53 with a Flathead and a non-overdrive 3 speed. Can my current ****** be modified for overdrive or do I have to find a completely different transmission?
The car will do 80mph on the highway but it prefers 70... I am looking to lower my RPM's at these speeds. I am currently running 205/75-15's with a 4:10 rearend. Maybe taller tires or a higher rear end gear?
Click to expand...

If you really are running a 4.10, your engine is spinning about 3500 rpm at 70, and about 4000 rpm at 80! :eek: I suspect either a speedo error, higher rear ratio, or a VERY well built flatmotor! (with a short lifespan :() RPMs in the 1800-2500 range on the highway will be much better for miliage, and that flathead! You really need an OD with those 4.10 gears to run the speeds you want. A .7 OD would bring the rpms down to about 2500 @ 70 mph. JMO :)
 
Talk to Sue Mitchell. The Mitchell Overdrive is adaptable to open drive line cars.
I'm using 3:54s, 235/75-15 (29.5 inch tall) with 26% overdrive and am spinning
2150 rpms at 70 mph.
 
Thanks for the info everyone!
Yes, I do have a 4.10 rear end... not sure if this car had overdrive originally or not but my speedo is correct. Maybe someone swapped in the 4:10 gears at some point? ...and corrected the speedo somehow?
I want to keep my car original with 3 on the tree so I am going to start hunting for a donor car with a complete overdrive set-up. If no luck then maybe the Mitchell Overdrive is worth looking into.
 
I would not be surprised if you could find a 54-56 Ford rear from a Ford-O-Matic car cheap as a lot of guys swap them for an 8" or 9" rear end when doing a 5.0 or 351W swap, it would be a bolt-in as compared to adding the overdrive, the 7.5 or 8" from an early Mustang or Maverick is an EZ fit also with 3.00 or 3.23 gear ratio's common.
 
JeffB2 said:
I would not be surprised if you could find a 54-56 Ford rear from a Ford-O-Matic car cheap as a lot of guys swap them for an 8" or 9" rear end when doing a 5.0 or 351W swap, it would be a bolt-in as compared to adding the overdrive, the 7.5 or 8" from an early Mustang or Maverick is an EZ fit also with 3.00 or 3.23 gear ratio's common.
Click to expand...

I thought about and may go that route but... What about correcting the speedometer?
 
Change out the little nylon gear in your trans tailshaft that drives the speedo cable to match the rear ratio after the change, but the ODs must be pretty common in Texas, and the wiring harness is simple. I'm sure I have one here, but it's at the bottom of a pile in my cold garage or I could tell you what numbers to expect on the tailshaft housing of a '52 up OD. Anyone else have one handy? ..B.
 
All the 1952-54 Ford three speed overdrive transmissions were the same. The tail housings will measure 17-29/32" long. This is measured from the OD adapter casting flange to the tail end at the seal. The support mount will have two bolt holes that measure 6-9/32" center-to-center. The housing had the part number AB-7650-B or B2AZ-7A039-B.

The gearbox was similar to the 49-53 but there were differences in the side cover, plus the overdrive gearbox had the provision for the reverse lockout rail. All Ford gears changed in 1951 and will not intermix with the 49-50 gears.
 
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