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overdrive/underdrive?

6866 Views 8 Replies 5 Participants Last post by  Torque Daddy
okay so my buddy has a 2000 one ton 4x4 with the six speed, shes hopped up pretty good, dyno'd around 800. He wants an overdrive/underdrive.. after some researdh im lookin at gear vendors. anyone else know of any good brands, hints, tips, secrets? Thanks in advance guys.
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· Kansas Chapter VP
Big Red. 1993 W350. NV 4500. HX35.
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Hey,

Well I think Gear Vendors is about the only one that is still around and being made...:confused013:

The other one was US Gear, but I don't think they make it any more!:confused013:

I've heard some stories about them not really being strong enough to handle the power of the Cummins, but I've never had one myself!:S:

Later,
Winslow
 

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seems like on there web site they are rated up to 1200h.p. they are cool>>>overdrive for every gear:thumbsup::thumbsup::thumbsup:
 

· Kansas Chapter VP
Big Red. 1993 W350. NV 4500. HX35.
Joined
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5,411 Posts
seems like on there web site they are rated up to 1200h.p. they are cool>>>overdrive for every gear:thumbsup::thumbsup::thumbsup:
Hey,

That's very possible!:thumbsup:

But you don't get overdrive in 4x4 or under 10-20 mph... at least that's what I was told on a different thread!!:thumbsup::S:

Later,
Winslow
 

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Discussion Starter · #5 ·
I actually found one at a local dealer today in a 98 with the 5 speed and a PacBrake. It was pretty sweet :)

I do see it being a downfall not having it in 4x4 and below 20mph.. but how much of a granny gear do you really need? a 9 speed is just fine with me :)

Im currently lookin at a 2001 with the 6speed and an H.O. and I think I might have to find one for it :) that and a pacbrake for sure, that thing is mint!
 

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a local guy around here (lives in Casper, and has a family shop up here) has a 96 Cummins 4x4, big turbo, injectors, intake and some other goodies on his 5spd with 3:55 gears, he paid near $4k for his Gear Vendors and has toasted it a couple of times, he tows a MotorCross trailer around up and down the Front range and Montana some, as well as a Tri axle Desert Fox Toy hauler. He really likes being able to have a Double Overdrive for the long flats. (5th gear, and the GV O/D) but if he hits any kindof hill he usually drops the Trans back to 4th which equals the ratio of 5th gear byitself. I wish I had a double OD as my RPMs @ 70 are at 2300..... but I cant justify another 2.5 ft of leverage hanging off my drivetrain, and $4k before this dumb schmuck gets to go put it in. He said that he has never needed to use the GV in 4x4 and it is to much of a hassle to split 1st and 2nd (the under 20mph deal) as the ratios start canceling each other out and your shifting for nothing, untill you get up to 3rd. I had a Ranger Torque Splitter in an old 6.2 that I had Turbo'd. It made a world of Differance on that old 4spd, but I wouldnt trust it behind a Cummins. That being said, there is a guy over in Pirate4x4 that put one behind a 12v and mated it to a SM420 granny tranny and put it in an old Scout, he reports to have blown up 2 clutches but never had any problems out of the Ranger.... I personally wouldnt trust it as a Scout with the 12v still probly weighs in at 4k,,, where I weigh in at 9k.....
 

· Kansas Chapter VP
Big Red. 1993 W350. NV 4500. HX35.
Joined
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5,411 Posts
a local guy around here (lives in Casper, and has a family shop up here) has a 96 Cummins 4x4, big turbo, injectors, intake and some other goodies on his 5spd with 3:55 gears, he paid near $4k for his Gear Vendors and has toasted it a couple of times, he tows a MotorCross trailer around up and down the Front range and Montana some, as well as a Tri axle Desert Fox Toy hauler. He really likes being able to have a Double Overdrive for the long flats. (5th gear, and the GV O/D) but if he hits any kindof hill he usually drops the Trans back to 4th which equals the ratio of 5th gear byitself. I wish I had a double OD as my RPMs @ 70 are at 2300..... but I cant justify another 2.5 ft of leverage hanging off my drivetrain, and $4k before this dumb schmuck gets to go put it in. He said that he has never needed to use the GV in 4x4 and it is to much of a hassle to split 1st and 2nd (the under 20mph deal) as the ratios start canceling each other out and your shifting for nothing, untill you get up to 3rd. I had a Ranger Torque Splitter in an old 6.2 that I had Turbo'd. It made a world of Differance on that old 4spd, but I wouldnt trust it behind a Cummins. That being said, there is a guy over in Pirate4x4 that put one behind a 12v and mated it to a SM420 granny tranny and put it in an old Scout, he reports to have blown up 2 clutches but never had any problems out of the Ranger.... I personally wouldnt trust it as a Scout with the 12v still probly weighs in at 4k,,, where I weigh in at 9k.....
Hey,

It would be REALLY cool to be able to split gears and have a double overdrive, but the breaking part I don't like!!!:shock:

Later,
Winslow
 

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I've have a U.S. Gear underdrive. It was on the truck when I bought it, and it didn't work. I called U.S. Gear and they were very helpful. The cost was reasonable to get it working again. That has been about a year ago, so I don't know if they're still selling new units. Their website is still up though...

They say it has a GCVW of 35,000lbs, so I'm not worried about breaking it. However, it can be damaged by trying to engage the underdrive too quickly. There is an electric motor that drives a worm gear that "pre-loads" the gear you've selected. You're supposed to wait 2 seconds before flashing the clutch to engage. Trying to engage too soon can damage the motor (one of the things I had to replace).

I'm not sure if the gear vendors products work in similar fashion, but the 2 second wait time can make it a little awkward if you're trying to run through consecutive gears (3u, 3, 4u, 4, 5u, 5). I don't think it's meant to be used that way. Its convenient if you start up a long grade to gain three or four hundred RPMS when a full downshift would have been too much. My underdrive is 20%. They make overdrives too. You might check them out.
 
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