OD gurus

[greg g]

I ran into a guy who has the tail piece of an OD perhaps from a MOPAR. His contention is that the business end of the OD is housed in that piece and it will bolt up to any of the earlier transmissions. Any thought or opinions on this? He also say he has a 3.7 something rear end from a 50/51 plymouth. Are these narrower than the P and D rear axles, as are the 49's? I have checked the three charts I have but can't find any info on the measurments for the 49 - 52 series.

[Jim Yergin]

Greg,

Some where along the line I was told that while the OD assembly may bolt up to the regular transmission case, those cases lack a hole on the back that a lock out rod moves through to prevent the car from being shifted into reverse when in OD.

Jim Yergin

[Plymouthy Adams]

According to the BOOK...

rear axle track (ceter to center of tread)

46-48 60 1/8 ratio 3.9

1949 56 (shortest of all, single year item only) ratios 3.73, 3.9 or 4.1

1950-1954 58 7/16 ratios 3.73, 3.9 or 4.1

I do not have backing plate to backing plate measurements...

[Merle Coggins]

You could always just swap out the diff. It would probably be easier that swaping the whole axle anyway. Especially if you have to redo the brakes on the donor axle.

Merle

[blueskies]

His contention is that the business end of the OD is housed in that piece and it will bolt up to any of the earlier transmissions. Any thought or opinions on this?

Unfortunately, this is not the case, pardon the pun...

I assume we are talking about the R-10 overdrive, and not the R-7. There are internal differences between the regular three speed and the transmissions that have the OD. The reverse shift rail is longer, it extends from the transmission into the OD case, and acts as the manual control for the lockout cable, and reverse lock out switch when the transmission is shifted into reverse, preventing the OD from free-wheeling. Without this shift rail, there would be no reverse as the clutch would freewheel, and the lockout cable would not function.

The OD case can not be simply bolted in place of the regular tail shaft of the standard three speed. I don't remember now if the main shaft of the tranny is different from the regular three speed, but it holds the freewheeling clutch and sun gear at the OD side of the blocker ring and adapter plate.

Here's a pic of the adapter plate with the main shaft assembled with the clutch, sun gear, and pin type synchro. The other piece is the output shaft with the ring gear and clutch drum.

Sun gear and freewheeling clutch-

In this shot you can see the reverse shift rail that extends into the OD case from the transmission case.

Here's the exploded view of all the guts of the R-10.

Pete

[blueskies]

Greg,

Some where along the line I was told that while the OD assembly may bolt up to the regular transmission case, those cases lack a hole on the back that a lock out rod moves through to prevent the car from being shifted into reverse when in OD.

Jim Yergin

Jim-

It's the other way 'round... The reverse shift rail prevents the OD from enguaging when in reverse. If the OD were to enguage when in reverse, the freewheeling clutch would just spin inside it's drum, and the driveline wouldn't rotate.

Pete

[builtfercomfort]

Does anyone know if the same is true for the older R-7 OD (i.e. requires a different tranny, can't be swapped to a non-OD tranny?

(I seem to have an R-7 in my 39 Chrysler. Don't know if it works or not, car is not driveable yet)

[De Soto Frank]

'39 thru '41 OD cars had the R-7. The R-7 has only one "can" on it: the kick-down solenoid, on the driver's side. The later OD's (R-9 & R-10) have two "cans", the solenoid, and a governor.

Don't know if if the R-7 set-up uses a special tranny case or not; George Asche would be the man to ask.

De Soto Frank