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Anyone here run a Gear Vendors overdrive and can tell me what you think of it. I am thinking of putting one on my 1979 Ford f250 with 3.73 gearing and C6, 3 speed auto with stock style 31 inch tires. I think it runs a little over 3,000 rpm at 70 mph, I don't have a tach though. Not too concerned about gas mileage, I have put over 60 thousand miles on this truck between 2004 and now and I drive it on the interstate allmost daily so I would like to slow the rpms down a bit and make it a little quieter on the highway.
Last edited by 73-79 ford fan; 06-13-2009 at 01:57 AM..
I would check into an overdrive automatic from a later model truck or van. The cost of a rebuilt transmission plus installation would probably be less or the same as a Gear Vendors overdrive unit plus installation.
I've foolishly let a Gear Vendors unit go with a vehicle. They are well worth it in my opinion. They also can split the gears when hauling a load. I had an older 7.3 with that absolutely wrong geared ovedrive ford trans and with the Gearvendors unit, I could pull a 10,000 pound mini dozer as quick as I could foot on the floor just the truck before the gear vendors. The other advantage was the over/under drive option allowed me to always be in a good power but fuel saving range at nearly any speed. I miss that thing, because the truck i have now could certainly use it! A later model trans will cost more and still not have the gear options for your needs.
I've foolishly let a Gear Vendors unit go with a vehicle. They are well worth it in my opinion. They also can split the gears when hauling a load. I had an older 7.3 with that absolutely wrong geared ovedrive ford trans and with the Gearvendors unit, I could pull a 10,000 pound mini dozer as quick as I could foot on the floor just the truck before the gear vendors. The other advantage was the over/under drive option allowed me to always be in a good power but fuel saving range at nearly any speed. I miss that thing, because the truck i have now could certainly use it! A later model trans will cost more and still not have the gear options for your needs.
According to the OP all they want is to reduce the RPM at highway speeds, not pull 10,000 mini dozers.
The cost of a rebuilt 4spd auto installed should be the same or less than the gear vendors unit installed. The gear vendors unit alone is over $3k and installation would be at least another $700.
Well I recently did pull a very heavy 20 foot bat wing brush hog about 50 miles, but the main thing I want is lower on highway rpms like what an overdrive gear would do. The Ford E4OD auto from a 460 would work and they have a lock-up clutch torque converter which might increase gas millage a bit, but that transmission does not have a very good reputation especially when compared to the C6. I don't want to go to the trouble of swapping in a manual like the ZF 5 speed.
According to the OP all they want is to reduce the RPM at highway speeds, not pull 10,000 mini dozers.
The cost of a rebuilt 4spd auto installed should be the same or less than the gear vendors unit installed. The gear vendors unit alone is over $3k and installation would be at least another $700.
He also wanted to know if anyone had experience with them, which I have. That was my point in my reply. Yes, the E4OD can be put into his truck, but it has poor gearing and the overdrive isn't that much of an overdrive. It is just an added on gear to an old C6 and a messed up valvebody/computer controled transmission. .85 is not that much of a hiway speed rpm drop. The avalible choices with a Gear Vendors set up you can go all the way to a .54 overdrive gear. That's a 46 percent drop in rpm.
Surprised no one has suggested the OP get a tach, not that hard to install, and also what engine he's running. The size/model of the engine is going to make a lot of difference, regarding the target RPM for 70 MPH cruise.
I have had bad luck with aux. overdrive transmissions that hooked up to the trans output with a u-joint and mount "hard" to a fabricated cross-member - the old Hone. I think the Gear Vendors is different.
With the C6, can he shift the overdrive just by putting the C6 into neutral, or does he have to be moving slow/be stopped to shift the O/D?
Offhand I am thinking putting a transmission with overdrive (which has the advantage that you are getting a rebuilt trans) is a better move.
Or, just do the old school thing and change the rear-end gears. Depending, you might find an axle with the gearset you want in a junkyard, prep it up with new seals and brakes, then do the swap.
You will need to change the speedo drive or at least driven gear if you want the speedo to be right, IIRC the '79 has a mechanical speedo.
I work for Gear Vendors and have owned a few myself. The overdrive ratio is a conservative .78 to 1. This ratio was chosen because it creates a real nice split (half gear upshift) on most all three speed automatics and four speed manuals. Other transmissions can also benefit from certain gear splits and the 22% overdrive (.78 to 1) is just the right amount of overdrive for most heavy vehicles or vehicles that haul or tow. As an example: a vehicle with a 4.10 axle ratio will go down the highway as if it had a 3.20 axle ratio when the Gear Vendors unit is engaged. By the way, when installed in an automatic equipped vehicle, the gears vendors can be shifted under load and even under full throttle, they really are worth the investment and in most cases can be moved to your next vehicle with a simple adaptor exchange. Mitch Yow
RPM X 60 X [1/(Transmission gear ratio)] X [1/(Differential gear ratio)] X [ { ( [ {tire width in mm} x {aspect ratio} x 2 ] + {rim diameter in mm} ) X 3.14 } / 1609344 ] = MPH
1/RPM = ( 60 X [1/(Transmission gear ratio)] X [1/(Differential gear ratio)] X [ { (Tire dia. in mm) X 3.14 } / 1609344 ] ) / MPH
( 60 X [1/(1)] X [1/(3.73)] X [ { 787.4 X 3.14 } / 1609344 ] ) / 70 = 1 / RPM
could you run a ZF-5 speed?. I got one in my 91 F250 and it is pretty solid if you don't mind stick shift. you could pull it out of any junked 87-96 F250/F350
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I've foolishly let a Gear Vendors unit go with a vehicle. They are well worth it in my opinion. They also can split the gears when hauling a load. I had an older 7.3 with that absolutely wrong geared ovedrive ford trans and with the Gearvendors unit, I could pull a 10,000 pound mini dozer as quick as I could foot on the floor just the truck before the gear vendors. The other advantage was the over/under drive option allowed me to always be in a good power but fuel saving range at nearly any speed. I miss that thing, because the truck i have now could certainly use it! A later model trans will cost more and still not have the gear options for your needs.
