Gear Vendors Question

[Sinister]

To those few guys who are running Gear Vendors overdives, how much rpm drop do you get in OD? I'm looking at some GV units on Fleabay and they're saying 400-500 rpm drop.

[69GMCLonghorn]

It is a .78 overdrive. So here's the formula:

RPM= MPH x Gear Ratio x 336, divided by tire diameter.

So if you're running 31/32" tires and a 4.10 rear end, this is where you'd be at when doing 70 MPH:

Top gear 1:1, non O/D: 3050 rpm
Top gear 1:1, with O/D: 2350 rpm

The other advantage that they seldome talk about is that you can split all the other gears, too. So on the highway, you could have 3 gears, instead of one like I do. You'd have 3rd O/D, 4th, 4th O/D.

[Sinister]

That's the kind of drop in rpm I need. I just don't know what the OD ratio is on the Fleabay ones. Listing says it's a P type of Gear Vendors.

[69GMCLonghorn]

In talking with Gear Vendors, they are all .78. I guess someone could probably find a way to mess with it and change the gearing, but I don't know why you'd want to.

A little history on my truck: I actually ordered a Gear Vendors and started installing it. That is when I realized I had an NP435 trans instead of an SM465. The adaptor didn't fit. GV had never heard of a GM version of the NP435 and could not provide me with an adaptor that would work. So here I sit, with the pistons swapping holes at 70 MPH, burning gas like there was no tomorrow.

[Sinister]

Some of the e-bay vendors say they have aftermarket adapters. Might want to ask if they have what you need.

[69GMCLonghorn]

Yeah, not a bad idea, but I've pretty much written it off at this point. Money's been spent on vacations and house projects.

[dazza]

So Longhorn,

Is your adapter being used as a door stop or did they take it back? If you're using the door stop option and decided to sell, what would you be asking for it?

Thanks,
daz

[mtdave2]

im starting to REALLY think about one of these units.....wish i could find a deal on one. the 3k price tag is a bit much.

i think i would pull the trigger right now, if the unit would give me 1/2 gear UNDER first. it really isnt an underdrive imho.

[mtdave2]

to the guys who have installed one of these, did you leave the drive line carrier or just make on long drive shaft? once the unit is on the front shaft will be only a foot or so long... why bother?

[WorkinLonghorn]

A .78 overdrive will make your RPMs .78 of what they were before regardless of tire size etc.
Unless I'm missing something.

Hey Sinister,What rear gears/tires you running now?

[69GMCLonghorn]

Originally Posted by dazza

So Longhorn,

Is your adapter being used as a door stop or did they take it back? If you're using the door stop option and decided to sell, what would you be asking for it?

Thanks,
daz

Actually, I was fortunate enough that they took the whole shootin' match back and refunded my money. Customer service is FANTASTIC over there. I just found it hard to believe that they couldn't come up with an adaptor that would work. Oh well, such is life.

I have a cousin with a 3/4 ton F**D with a 460, O/D tranny and a gear vendors. Tires are average, about 31/32". He's taching about 1800 RPM at 70 MPH, which is fine when empty. He runs one gear lower when he's towing his fifth wheel. He said the ability to split the gears is awesome when he starts up a hill... There's no point where he has to wrap it out or lug it. He can ALWAYS keep it in the torque band.

Even though I never got mine installed, I would think anybody who can swing the price would not be disappoiinted in adding one of these to their truck.

[WorkinLonghorn]

I used to drive a 16' flatbed from Hollywood to Fontana and it had a 4spd with a 2-spd rear and it was really nice splitting the gears going up that grade.
I imagine that GV would be just the ticket for towing.
For regilar driving maybe a higher rear ratio would do.

[hotrodhomi]

I thought about buying a used one, but I've heard that GV is less than helpful if you didn't purchase from them directly.

[Sinister]

Originally Posted by WorkinLonghorn

A .78 overdrive will make your RPMs .78 of what they were before regardless of tire size etc.
Unless I'm missing something.

Hey Sinister,What rear gears/tires you running now?

4:10, 265/70R16. I'm right around 3000 rpm doing 65/70 mph.

[69GMCLonghorn]

Originally Posted by Sinister

4:10, 265/70R16. I'm right around 3000 rpm doing 65/70 mph.

DO IT, man, do it!!! Let us know how it goes. The install actually looks to be really straightforward. I'm about half stupid and I am pretty sure I would have had it running in a couple days.

BTW, for you LA boys, I'll probably be at the Early Rodders meet in Montrose this Saturday morning. Hope to see some trucks there!

[WorkinLonghorn]

Sounds like you need to lose that 4.10 and get a 3.07. Or a 3.54. I've got 3.73 with 31" tires and still turn 3000 at 72MPH.
How much is a used GV? I wonder if any ever slip by the guys at Pick-your part and make it into the yard.

[69GMCLonghorn]

Originally Posted by WorkinLonghorn

Sounds like you need to lose that 4.10 and get a 3.07. Or a 3.54. I've got 3.73 with 31" tires and still turn 3000 at 72MPH.
How much is a used GV? I wonder if any ever slip by the guys at Pick-your part and make it into the yard.

Most likely Sinister has the same rear end that my truck had, which is an Eaton. You can't get anything higher (numerically lower) than 4.10's for it. Trust me; I'd have gone that route on mine if possible.

[dazza]

You guys are right there with those voices in my head... "go ahead do it.. it's already torn down... nows the time... think of the fuel savings... it's only numbers on a credit card!"

I do think I can justify it, after all it will be my dd.
Currently I'm running 31's with a 3.07p rear, about 2600@70mph with a 350/sm465/np205.

So, is it just a bolt on with the drive shaft needing to be shortened? What about the speedo gearing?

[Sinister]

Originally Posted by WorkinLonghorn

Sounds like you need to lose that 4.10 and get a 3.07. Or a 3.54. I've got 3.73 with 31" tires and still turn 3000 at 72MPH.
How much is a used GV? I wonder if any ever slip by the guys at Pick-your part and make it into the yard.

69GMCLonghorn is right I have an Eaton. I've seen used Gear Vendors units on Fleabay for around $1600 with adapter and electronics. Rebuilt ones slightly more.

[WorkinLonghorn]

You guys are right there with those voices in my head... "go ahead do it.. it's already torn down... nows the time... think of the fuel savings... it's only numbers on a credit card!"

LOL that's pretty funny.

Currently I'm running 31's with a 3.07p rear, about 2600@70mph with a 350/sm465/np205.

\]

That doesn't compute unless I svrewed up. In my notes I figured a 3.07 with 31" tires would be 2500= 75.1 MPH

69GMCLonghorn is right I have an Eaton.

OK. I don't know squat about these things.Just that my last '69 (1500) had 3.07 gears and 33" tires and ran ridiculously low RPMs and got 10MPG on the freeway!

I've seen used Gear Vendors units on Fleabay for around $1600 with adapter and electronics. Rebuilt ones slightly more.

WOW. Sure would be nice though.

[dazza]

That doesn't compute unless I svrewed up. In my notes I figured a 3.07 with 31" tires would be 2500= 75.1 MPH

You're probably right, it may have been around 2300, if my "couple of days to fix a leak" repair job hadn't takin' the last year or so of my life, I might be able to remember!

[Judoman]

Originally Posted by hotrodhomi

I thought about buying a used one, but I've heard that GV is less than helpful if you didn't purchase from them directly.

I can only relate my personal experience with Gear Vendors. I had one installed in my 82 Suburban, with a 6.2 diesel,w/ Gale Banks turbo. I bought the unit from a GV dealer, who installed it with a 2 piece driveshaft. Had vibration on takeoff, which they tried to remedy by shimming the rearend, to change driveshaft angle. After multiple attempts, they said I would have to get used to it. I drove directly to Gear Vendors (only 100 mi. from my house), and asked them to check it out. They said the installers should have gone with a one piece driveshaft, and if I wanted them to build one, I could pick the burb up the next day. I was pissed, because I had paid for two driveshafts on the initial installation, and now I have to pay for another? I just wanted it fixed, so I said go ahead. I pick up the truck the next day, vibration is gone-good, where`s my bill? NO CHARGE. I could not believe it. I fully expected to pay for another driveshaft, always assuming you don`t get something for nothing. After that, I always drove the 100 mi to Gear Vendors to get the OD unit serviced. After installing the OD, my mileage was 18-20mpg, in a 3/4 Suburban, with 4.10 gears. Sold the burb to a friend, who replaced the diesel with a 350, but kept the turbo 400 and OD- probably 80,000 mi on GV now, with no problems whatsoever.

[toddtheodd]

Originally Posted by mtdave2

to the guys who have installed one of these, did you leave the drive line carrier or just make on long drive shaft? once the unit is on the front shaft will be only a foot or so long... why bother?

I don't have a GV, but I do have a long bed. And when the carrier bearing and ujoints were going out, it was actually cheaper to have a custom one piece drive shaft built and put in than it was to replace 3 ujoints and the carrier bearing.
It is one HELL of a long piece of metal, but it runs smooth.

[BCOWANWHEELS]

i,d find me a sm465 if i was you. there cheap

[Longhorn Man]

dazza, your MPG will probably drop if you do it