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Overdrive Options - 1930 DC8


stooy

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G'day Everyone, 

 

I have been toying with the idea of an overdrive for our 1930 Dodge DC8. 

 

I am aware what I am thinking is probably unrealistic, but please bear with me just in case I am not.  

 

Are there any period (30's or 40s) over drives out there that I could fit with my existing original 3 speed gearbox? 

 

I am not keen on the modern gear vendors etc.

 

Keen to hear your thoughts. 

 

Many Thanks 


Stewart 

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Hi Stooy  Twenty odd years ago I was on a big Rally and one of the entrants was a big Chrysler Roadster of around 28 or 29 and it went like the clappers The bloke that owned it had fitted the Transmission out of a Toyota Dyna light truck These are a 5 speed O/D box 

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The CD8 has two first gears, one low and one VERY low. 4th (top) gear is still 1:1. Not really an upgrade.

 

I would go with Gear Vendors. I put a Borg-Warner overdrive in my 1929 Cadillac, and it dates to the '40s, but its reliability has been spotty at best. Gear Vendors is bulletproof and doesn't use free-wheeling, which is the most dangerous feature I can imagine on an old car with ancient brakes. It doesn't look vintage, of course, but if you prefer one that works properly to one that looks old, Gear Vendors is the right choice. I wish I'd spent the $3000 I spent on my B-W unit and bought a Gear Vendors unit instead. Now there's no going back as I had to cut and modify my torque tube to accommodate it.

 

For me, it would be an easy choice.

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Later o/d gearboxes were quite a lot bigger than the DC box. I have a 1939 Studebaker Commander overdrive gearbox and it is a BIG bit of kit. The earlier ones were centrifugal only with freewheeling device included. Later in the '30s a solenoid was included to provide for a kick-down change out of o/d after about 1940 a governor was included to improve tractability further. The simplest thing might be (horrors) to fit a 5 speed out of a fairly modern heap. You would have to think about the hand brake too. The Studebaker o/d box was unusual in that the gearbox was on its side to allow a lower floor in the car.


I have been dreaming of a lower-number diff. for my DC but I imagine they are about as hard to find as rocking horse droppings. The other thing is larger tyres. I have removed 600x18 Continentals from mine (odometer read about 7% low) and put 550x18s on. Boy it goes now but fuel lack-of-economy is much more pronounced (maybe I enjoy too much the improved ability to climb our hills) and it is pretty noisy at 50 mph. The 600s were pretty old and very stiff, so a real pain to manipulate onto and off the locking ring rims.

 

I'll look through the 1942 Republic gear catalogue to see if the 41-10 option was available for anything else... back soon.

 

 

Edited by Spinneyhill (see edit history)
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The 41-10 OEM numbers are Set No. 308389, ring gear 309958, pinion 309959; Republic nos. H1059 and H1060. These are also listed for:

 

1931-2 Chry. CM, CI std ratio.

1931-2 Chry. CP, CD 8s, std ratio.

1930-2 DeSoto CF.

1931-2 Dodge DD, DI, DH, DL, DJ, DG, DK, DC

1930-1 Dodge DD, DB, DC

No Dodge trucks.

 

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I'm going through the same idea with my 30 Plymouth. I've got a '36 and a '39 Chrysler/Desoto floor shift overdrive transmissions. Biggest issue is that the input shafts are about 4 inches longer than my 30's. Plan B is to cut out a plate for the front of a 50's ford, Chevy, stude, or Kaiser overdrive unit, ditch the transmission part and fab up a bracket to mount it behind the stock transmission. All while not irreversibly altering the originality of the car too much. Simular idea that they do for model As.

 

As for the freewheeling concern you can wire up a governor override switch and keep it locked in overdrive till you stall.

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Consider using a Mitchell OD (Mitchell Mfg in Colusa, CA, originally developed for Model A Fords but beta-tested on Mr. Mitchell Chevy 454 dually). Remove original driveshaft and put it in a corner for the purist.  Buy two short shafts with modern, greaseable u-joints from your local driveline shop. These are mechanically operated and are synchro between direct and OD (see below). Mitchell sells cables to shift the OD in and out, but I think theirs are too robust, and smaller but good ones can probably be found at a boat shop.

 

I put a Mitchell in my 1925 Pierce 80 sedan with mountain and SF gearing, 4.88 to 1, and used Mitchell's 26% option (36% also available).  Comfortable cruising used to be 36-37, and engine was screaming at 40-41; now 49 is a comfortable cruising speed.

 

Upon request (no additional charge when I bought), they'll flip and drill the case so that the push-pull shifter at the transmission is on the right front rather than the left.  Our member GLong fabricated linkage which comes up thru the hand brake notch in the floorboard (only enlarged the notch 1/8 inch), adding a second floor mounted shift lever.  We used a 1-inch shift ball to differentiate it from the ~2-inch transmission ball.  The Pierce is a totally different car!  My linkage is fine for a driver, and I do drive it a lot.

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The Mitchell looks to be a good piece of kit, but I am wary of the double shift. I have owned a motorhome on a Mazda T4000 (a.k.a. Titan) truck with a double shifting arrangement. The gearbox was the usual floor mounted lever, the "overdrive" was a column mounted lever. Double shifting on hills was a real trial to get it done quick enough to keep up momentum. Reaching for the second lever was a pain. Shifts down had to be done early so there were some revs left to continue.

 

I like the way the Laycock overdrive (fitted to Triumphs etc.) was operated. It is just a wee push-pull knob fitted to the gear lever. it makes the second shift easy at the same time as changing gear.

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Spinney, in about 2,000 miles with the Mitchell, I haven't had a need to do a split shift (i.e., shifting both the crashbox factory trans and the synchromesh Mitchell OD at the same time).  Approaching an upgrade in 3rd OD, while my rpms are still up, I'll easily shift the Mitchell to 3rd direct at a spot most advantageous to 3rd-direct performance.  The Mitchell is synchronized, so double clutching is NOT required either up- or down-shifting.  After cresting the hill, I'll upshift to OD with the ease of synchromesh. 

 

There are conditions where 2nd-OD is just perfect.  Most of the time, however, I leave it in direct until 33 mph or so, then shift into OD.  On one corkscrew, dirt washboard, steep upgrade on the Modoc Tour (Fandango Pass, if you know the area), FIRST OD was just right! 

 

I loved the electrically-operated Laycock de Normanville OD on a friend's TR-3 more than 50 years ago.  As I remember, it was controlled by a toggle switch on the instrument panel to the left of the steering wheel.  I believe Gear Vendors has a similar control today, but it's significantly costlier than the Mitchell.

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Thanks guys for all the input. 

 

Firstly there is no way I am going to install a 5 speed box in the car, I have nothing against people who do, but I really enjoy the crash box experience. 

 

Thanks Grimey, I didn't know about Mitchell. Do you mind if I ask how much it roughly cost you? (there are no prices on their website). 

 

Cheers 

 

Stewart 

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Stewart, base price of the unit is about $1,800US, the last time I checked  They sell as options (but you should ask anyway).....

1.  Heavy steel plate to mount on your frame from which the OD box can be suspended. Problem with the plate is that whine in OD will be more noticeable below 35-40 mph.  My former 1939 Cad 75 is run in OD full time with such a plate, and you can hear the whine in OD only (not direct) until 40.  My 1925 Pierce 80 does NOT use the plate.  Have four brackets coming from the frame.

2.  Various bracket arrangements

3.  Heavy duty push-pull cables for remote control. (I think the latter are big-rig sized, that is, TOO HD, and that you can do better with locally-sourced boat/marine cables.

The push-pull actuator is on the left side of the OD, which is fine if you're in a RHD country like Oz; if you're in the U.S. or another LHD country.  The actuator needs 3 inches of movement on the driver's end.  It's easy to fab a bellcrank (or maybe they sell one) to mount on/near the OD unit.

 

Ask them if they've done any bracketing plans for a circa 1930 MoPaR.

 

George aka Grimy

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