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My Gear Vendor overdrive drives me nuts.

When it is working, it performs magnificently - increasing MPG by at least 1.5 MPG by itself and enabling aero improvements to the truck to bear fruit,.

But it is not very reliable. It has more bugs than coastal Guatemala and now it is leaking fluid.

Maybe I would have been smarter to have had an adapter made and installed a Tremec 6060 instead. I would have lost only 30 ft-lb torque rating (my old 444 doesn't make that much torque anyway - it dynos out at 560 ft-lb peak) and I would have gotten a better overall overdrive ratio(0.5:1 instead of 0.562:1) with only a single overdrive gear and the reliability of a manual shift transmission.
 

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Bump

these never took off like I anticipated

I don't know anyone who runs one now
I just knew a few that did but since removed them

I wanted to try one on my 5r 4x4 but the 4 grand and not knowing anyone to endorse them changed my mid

https://www.gearvendors.com/4x4f4s.html
 

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Dave, what kind of mileage does the Gear Vendor unit give you, and at what RPM and speed? An overdrive as steep as you are quoting is remarkable to me.

It's too bad the Gear Vendor isn't more reliable. It would be nice to have one, but not at the cost of being driven to a condition of even more nuttiness than I already am.
 

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Discussion Starter #4
1325 RPM at 70 MPH
1050 RPM at 55 MPH

The truck cruises nicely at those RPMs.
 

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Owning a GV is like owning a race horse.

When it's right, it's sooo good.

I really cannot even find a better setup. A granny to get a load going up a hill with a super-tall overdrive for MPG.

When it's wrong, it's just more useless weight to haul around.
 

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When i did the cummins conversion on my 99' gmc 3500hd, it never even hit the road before i installed a gearvendor in it.. With a 4.63 ratio, the 6.5 diesel that was in it, was fairly happy.. I knew however the 5.9 wasnt gonna like those gears.. I dont load this truck ultra heavy like i do my other trucks, frankly because i dont have any real faith in the strength of the gearvendor unit.. My original unit went a bit over a year, and less then 10k miles, before pukeing.. When it went out i was coasting up to a redlight and it down shifted at about 35mph, by itself.. the tires actually barked and it spooked the piss outa me.. No more unit workie! Lucky gearvendor stood by it, and i got another unit free.. That was 4 years ago, and i have had zero issues since.. Really nice unit to have, but like i say i keep my combined loads on this truck to under about 20k lbs, and dont back up hills with much more then about 15k total weight.. I do what i can to keep it reliable..
 

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Discussion Starter #8
I've been looking at alternatives.

There is a version of the Tremec 6060 that has plenty of torque rating but it is a car transmission. The ratios are too close and biased to the "high" end.

The Tremec 6060 has a top ratio of 0.5:1 and its low gear ratio is 2.26:1
The ZF6-650 has a top gear of 0.72:1 and with the GV its 0.562:1
The granny gear on the ZF6-650 is 5.79:1.

The 2.26: low gear of the Tremec 6060 would be like starting out in second on the ZF6-650 (2.10:1). Not enough reduction to start a trailer against a hill.

2.26:1 is A-OK even for a relatively heavy car like the old "B" body GMs or Ford Panthers. No-go on a truck.

A Spicer 6+1 is non-syncro and I don't want to double clutch every shift.

Automatics are too frail and inefficient for my liking.

So I keep trying to make the thing work.
 

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The spicer 6+1 will likely be what i put into my f450/dt360 conversion.. That or a allison 2000.. I have both on my shop floor.. The zf6 in my 02' has seen some major loads, [30,000 gcwr] for many a mile.. With a bit over 100k on it, i have had no issues, but i know it's the weak link[ the clutch]..
 

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1325 RPM at 70 MPH
1050 RPM at 55 MPH

The truck cruises nicely at those RPMs.
Wow. Those are incredible numbers. They remind me of the old slow-rev marine diesels that seem to run forever.

Since I use my F250 strictly for towing, I guess an overdrive that steep wouldn't work for me anyway. With my E4OD and 3.55 gears, I'm turning about 1500RPM at 55MPH and can achieve about 14MPG on long-distance trips towing a 28-foot Jayco.

I don't think my old 96 could pull much at 1050RPM, especially in the hills. Peak torque is rated at 2000RPM for my engine.

Best of luck in your neverending quest to squeeze every mile possible out of a gallon of diesel. You da man!
 

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A Spicer 6+1 is non-syncro and I don't want to double clutch every shift.
6+1 is synchronized...and shifts much like any pickup manual transmission. But the OD is .74, so I don't#think it would be worth the effort for what you seem to want to accomplish.
 

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Is it crazy or is it me...I was doing 80-85 today in my stock 2000 F350 7.3 6 speed?
2000 RPM+....so I stumbled across this thread. I wasn't hauling anything and I just got this truck 2 months ago. It is bone stock.
 

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Discussion Starter #13
I'm afraid it's just you.

For dead-stock F350 7.3 6 speed and OEM-sized tires 2000 RPM = 70 MPH.

2000 RPM giving 85 MPH is 21% too high. Even if you had 3.55 gears and 27 inch outside diameter tires that would only account for half of that.

Don't trust the analog tach. Use the digital tach on an auxiliary idle control or a ScanGauge.
 
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