I was looking at gear venders overdrive. i wanting to know if any body has had any experience with them. My truck is a 72 f-100 with a 390 and a c-6 tranny. Is this overdrive worth the money or should i look to other options like getting an Aod To fit the FE.

 

I'd also like to get an overdrive for my 390/C6 combo. I like the durability and current setup on my C6, so I'm less inclined to get an AOD. What are some opinions on the durability of the AOD vs C6? I believe either way we are looking at about $2000 for the fix. With a substantial improvemnt in mileage it would take 50-100K miles to pay for it. But I would like to keep the current load carrying capacity and acceleration but not be running 3500 RPM on the highway when not haulin stuff or trying to haul @#$! My truck is seriuosly humming at highway speed now. Has anyone seen these Gear Vendor units for sale used?

Greg

 

I , too , looked at the gear vendors unit , but if you study the fabrication that is necessary on their website you will come to the conclusion that unless you are really Good at fabrication ---you are going to spend Big Bucks just getting the unit installed muchless paying for the unit itself---you'll probably have around 4,000 tied up in the unit by the time you're finished----that's considerably more than I paid for my truck----for four K you can buy and install a 5 speed!!!!!!!!!!fd

 

Guys the cost of the gear venders has kept most of us from using them. The big motor homes and rigs like that are where you will find them in use.
The C6 in known as bullet proof, while the AOD didn't rate so good.

There is one thing that you have to get a grip on, Big Ford Iron, and good gas milage are not to be used in the same sentence. The 50s era design FE came along when gas was $.22 a gal and plentyful, AND we used our trucks for work only, not daily drivers.
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In the cool still quiet of night, you can hear chevies rusting away.

 

Many of us have considered the GV, but find it too expensive. For the automatic guys, the Lentech is cheaper, as are the NV4500 or Clark OD for the stick guys. You don't get the 6 or 7 ratios the GV gives, but those options solve the high rpm on the highway problem. I changed the final drive from 4.56 to 3.73, which was intended to do that, but now I just drive faster.
Eric

 

I hear what you are saying! But if all that's between us and a little better mileage, is a gear reduction, you'd think we could do it for less than $4000. I think I'll start Greg's Overdrive Units here in my shop :-) If somebody finds a decent solution let us know.

Greg

 

You cannot beat the Gear Vendor unit for shear strength and ease of use. There should not be any fabricating on a C-6 other than shortening the drive shaft. The tail shaft must be removed and replaced with the GV adapter and there is one clearance to set up. All in all not a hard job at all.
Mine has been in continuous use for at least 12 years including full power shifts at the strip behind a 400hp high torque motor. It changes my 4.11 to a 3.25.
It's hard to justify milage wise but it'll help the engine live longer and is a performance booster. You can also shift it in and out if towing to equal 6 speeds when you need them.

Bear Tracks

 

I have had one in my '69 F250 Camper Special 410FE/C6/3.73 for about half a year now. I rebuilt the C6 at the same time; installed the GV output shaft and tailhousing on the bench, so I am not sure how difficult it would be to install it with C6 in vehicle. It bolted to the crossmember exactly like the old 7 inch (shorty) cast iron tailhousing did.

Likes: Much quieter in the cab at hiway speeds; you forget how much it helps the noise level until you take it out of OD while doing 60.
Easier to keep up with the flow of traffic on the freeway. 60 MPH is now 2250 RPM in OD; 2750 in direct. I can now do about 75 at the same RPM that I could only do 60 before.
Gained about 1-1.5 MPG on the freeway; it probably would be better if I didn't drive faster now.
Can be shifted in/out at any speed above 25, under any load, in any forward gear in the C6. Don't even have to let-off the gas.
Unlike the AOD, you can tow with it in OD, and it won't be shifting in/out on you automatically when climbing a hill.

Dislikes: Had to dent-in the front corner of my gas tank for clearence, lost about a gallon capacity; never dented my truck on purpose before.
Requires 2qt. of GM or Mopar Synthetic Gear Lube at about $20 a quart. They also recommend oil change every 10,000 miles--there goes my fuel savings!
Too many electronic components with it. There is a brain box that sences your speed and keeps track of how many times the unit has shifted. There is a manual switch box with lights that allows you to choose between Autodrive and Overdrive. And finally a foot switch (similar to a dimmer switch) that engages/disengages the OD. All of this had to be mounted inside the cab. The foot switch alone would be just fine with me; easier to troubleshoot and much less clutter under the dash.
Not happy with the fit of the supplied slip yolk to the splines on the final output shaft. Too loose and sloppy especially for a 32-spline shaft IMHO. Since there is allready a slip-spline in my driveline, a simple 4-bolt output flange like what was on the original C6 shaft would be much more rigid and durable. However I do like the big 1350 series u-joint the GV slip yolk requires.
Driveshaft shortening was not cheap. Just a weld and balance alone cost $100 at a driveline shop. I did all the actual measuring, shortening, and trimming on a lathe myself. Plus a new 1350 weld-on yolk to match GV yolk, three new Spicer u-joints, a new carrier bearing, and 12" of 3" tube. Total driveline modification cost: almost $200.

Question for Beartracks: You purchased it about 12 years ago--how much did it cost back then? What gear lube are you required to use? Do you have all the electronic crap or a simple on/off switch? Does yours make a slight "houling" noise around 30-40 MPH while in OD?

 

I ordered mine from an RV place in Kansas for about$1,100. a long time ago. It doesn't make any noise except a slight whine sometimes when coasting. Fluid is Dexron II or III and I have the deep sump. I change it once a year or so but it doesn't really get very dirty. No heat to speak of. I only have the auto/man switch box and the dimmer style switch. What does the other electronic box do for you? I would dearly love to be able to down shift the OD while up shifting the C-6 under full power. The gear cut on the OD makes this hard to time without letting off the gas. I can shift it up at will.
Bear Tracks

 

The other box is what they call The Autodrive Control box. All the wires are connected to it using telephone style jacks. There is also a jack that disengages the lockup torque converter in newer vehicles when the GV shifts; and a jack that somehow prevents the OD from coming on when a vehicle is locked in 4X4. There is also a digital display that counts how many times the GV is shifted.

I haven't tried any serious six-speed gear splitting yet, but I understand what you mean about getting the timing right. My C6 shifts almost instantly when I select a gear; whereas the GV takes about a second delay to change after I hit the button. If I wait too long and the GV downshifts before the C6 upshifts, then there is a split second where the RPM jumps up even higher; almost as if I hit a neutral gear. Trying to make them shift exactily at the same time is going to take me some practice. Unfortunately, now that I have a company truck to drive to work (free gas) I don't drive my own truck very often to get any.

 

Ooops! I guess I do have the other box. I don't recomend trying the OD downshift/tranny up shift combo at the same time under full power. I think it led to the early demise of my last C-6. It's just really hard on the tranny internals if it doesn't happen at just the right time. I've tried to think of a way of automating the operation, maybe tying into tranny pressure or a delay switch, hmmmmmmm?

Bear

 

Gosh guys after reading your posts $100-150.00 for a rear gear change seems mighty cheap.
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John

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In the cool still quiet of night, you can hear chevies rusting away.

 

Heck, if I don't spend it the wife will!

 

I heard THAT!!
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John

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[link:www.ford-trucks.net/users/jowilker/NCFTE.html|NCFTO] North Carolina Ford Truck Owners Group

In the cool still quiet of night, you can hear chevies rusting away.

 

Leave the c-6 alone.If you want gas milage buy a 4-5spd economiser.When you drive a full size truck you don't worry about mpgs.