I have a 1956 ford f350 v8 312 (yes, verified 312) and would like to attain freeway speeds. A place called gearvendors,com says they have an overdrive that would increase my top speed by 22% or 20 miles .... here is what they say "
We have a remote mount overdrive that you can place in the center of the driveshaft, this requires you to fabricate a crossmember to hang the unit from.

Overdrive will drop your highway RPM by 22% (around 800rpm drop), or allow you to run 20mph faster."

Has anyone done this or used this vendor for an overdrive ?

 

OD is mandatory in any car/truck I'd build up. Better mpg, and easier to talk to your passengers.
I'm curious to see what their box looks like... sounds just like an old Brownie style box. I cut the crossmember and removed mine from my F500 frame before I scrapped it. At some point, I'm going to try to clean it up and sell it.

 

Rather than going with a gear vendors unit, you might consider putting an AOD behind your Y block (that is what I am going to do with mine). Below is a weblink to Bendtsen's who makes an adapter to connect a Y block to an AOD.

Ford Y-Block Transmission Adapters

My father's neighbor used Bendtsen's unit in his 1957 Ford Thunderbird (312/AOD) and is very happy with it.

 

Yeah. I agree.

Although, I don't know if I would put an AOD in an F-350 though. It's sort of a light duty transmission.


I would put an E4OD in .......... just like the one going in my 55 F-600!

It's behind a 292 though...... 20 cu-in LESS than a 312. You can clearly see the Bendtsen adapter.

I also wouldn't do it without changing to SIDE-type engine mounts. This will distribute the weight more evenly. (you have to shorten the driveshaft (front one, if you have 2))

You'll also have to add a rear transmission mount.

If you use an AODE, then you'll require a transmission control unit. I am using this one There's several on the market.







The gear vendors aux trans is well designed and works well (they shift like an automatic) . They generally bolt on the back of an existing transmission using an adapter.

If there's no adapter for your transmission, then they split the driveshaft and put them between the trans and the rear axle.

Because there's better rear axle ratios available for your truck, you might be better off changing your rear axle ratio and going to an over-drive type trans.

The (right-size) gear vendors unit is VERY strong and would even work well in my F-600 fully loaded (but cost a fortune!!). But with my original 6.80:1 axle ratio, and original (38") tire size, my rear axle and drive shaft RPM would have been about 3600 RPM at a comfortable 60 mph cruising speed........

I went to 40" tires and a 2 speed axle (with a 5.83:1 high range)

40" tires and 5.83:1 will give me about 2950 (driveshaft) RPM at 60 MPH and with the 0.71:1 OD in the E4OD, approx 2100 (eng RPM) at a comfortable 60mph (empty) cruising speed.



Yeah.....they cost a LOT!


That adapter above is the one Bendtsen sells for the AOD.


Cheers,


Rick

 

and GearVendors is a tad on the expensive side.. >$3k usually..

an adapter and AOD are lots cheaper..

sam

 

Many 292/312 came with a 3 speed with overdrive as stock on cars and pickups. It would be easy to put one in your truck and will reduce your RPM about 20% to 25%.

 

For the most part, I completely agree with the others. The unit sold by Gear Vendors is an option, but by the time you tie up 3 G's in the unit, have two new drivelines built, fab and install the crossmember and OD unit, and get your driveline angles dialed in, you're going to have probably $4000 total and many hours of your time tied up in it. IMHO, that's just too much of an investment in a truck that you likely won't ever be driving enough to realize a good return. I've also heard more than one story about GV units that have failed prematurely.

There are better, less expensive, and less complicated options. With a 312, you've got enough power on tap that I'd suggest an axle swap first. You'll get the biggest bang for your buck here. If you've got single rear wheels, look for a Dana 60 with a 3.73 ratio out of a '67-'72 Ford F-250. These axles are easy to find in salvage yards, shouldn't cost more than $250 at the most, and will basically be a bolt-in to your truck. Worst case, the rear driveline will need to be shortened a bit and the pinion angle will need adjusted.

If that still doesn't get your cruising speed up where you want it, there are several options for both automatic and manual transmissions with an OD gear that can be adapted to your y-block. They are obviously more expensive and complicated than the axle swap, but the investment would be a fraction of the cost of a GV OD unit. Just a few things to think about!

 

A 3.73:1 axle might be a little high if you want to do any towing or driving around fully loaded but would be pretty much perfect depending on what tires you have.

If you have 33-12.50/16.5 tires, (33inch dia)

A 3.73:1 ratio will give you around 610 rear wheel RPM (at 60 mph)

[just take the rear tire circumference <feet> and divide 5280 by IT ] 5280/circ = rear wheel RPM <at 60 mph only>


circumference can be found by multiplying rolling diameter in FEET by Pi (3.142)

610 x 3.73 is approx 2275 RPM

610 x 4.11 = approx 2500 RPM


If you have an AOD <0.67 OD> in front of that..................2275 x 0.67= approx 1525 rpm.


It would be great if you had a Cummins under the hood. It might be a little "tall" for a Y-block.


2500 x 0.67 = 1680. Still pretty "tall" with an OD for a Y....... Great for a 6.9/7.3L Diesel, Cummins 6BT , 6.5L GM diesel etc......


My F-600 weighs around 7000 lbs empty. An F-350 might be close to 6000lbs? Any cruising RPM less than 2000 might be problematic for a Y

 

A '56 312 was rated in the neighborhood of 215 HP - pretty close to the rated output of many later model engines in trucks with gear ratios that are even numerically lower than a 3.73. And a long stroke 312 is likely going to be a lot torquier to boot. I don't have a chart of curb weights for the '53-'56 trucks but an F-350 is going to tip the scales at closer to 3500 lbs. than 6000. Bottom line - a 200 and something HP engine should have no trouble at all pushing a 3500 or so lb. truck down the road at less than 2000 RPM. If it does, there's something wrong with it.

 

Yeah. I don't have any idea what an empty F-350 would weigh. Mine has a scale wt of 5600 without the flat bed on it......so I exaggerated a bit for the F-350!


3500 sounds a LOT better but I still think 1500 RPM might be a tad low for any pickup other than maybe a 1/2 T

 

https://www.ford-trucks.com/forums/1...w-0-a-bed.html

WITHOUT any bed, 3650 - 3750 lbs.

I agree, you want at least 2000 RPM at cruise speed or you'll be downshifting all the time.

 

Do you mind column shift and a non-synchronized first gear? If these are not a problem, find and install a T85 / R11 Borg-Warner transmission / overdrive combination. This is what was installed in 312 equipped Fords back in the 50s and it is very tough.

What transmission do you currently have?

 

I have a 56 with a 292 original Borg Warner 3spd with O/D and a 3.73 rear end and my gas mileage is approx 12.3 and that is with a Holley 94 2bbl #55 jets in it.

 

"wellcraft"-

I'm new to this forum, so bear with me. You said that you have, "a 56 with a 292 original Borg Warner 3spd with O/D and a 3.73 rear end and my gas mileage is approx 12.3 and that is with a Holley 94 2bbl #55 jets in it."

Is that a ford f600?

Tom

 

Tom, you can click on a member's username in the left side of his post, and go to "View Public Profile", then click on the tab for "About Me" or whatever. That will show you that Wellcraft has a F-100.

Offhand, I'd be amazed if an F-600 was getting 12 mpg, overdrive or not.