Aftermarket overdrive/gear splitter questions

[Lonesome7.3]

I want to install an aftermarket over drive in my truck. First question is, is it an aftermarket over drive or a gear splitter? I have heard them called different things. Also, which one do you all recommend? The only two I know of are from Gear Venders and US Gear. I am leaning towards the Gear Venders model.

http://www.gearvendors.com/f2wd4s.html

http://www.usgear.com/dual_range.htm

Are there any other options out there I should consider? What should I know before entering into such an expense?

 

[argve]

I think gearvendors can be shifted under full power if I remember correctly. I know that my brother has on is motorhome and he said that it's got a button on the floor to turn it on and he said that he just drives with it on.

I drove Darrin's truck and it had one and if I remember correctly it just shifted like another gear when I drove it...

 

[Lonesome7.3]

I have heard good things about them. I would like to know more about the US gear version. There is not a lot out there about them.

 

[Darrin Tosh]

I think gearvendors can be shifted under full power if I remember correctly. I know that my brother has on is motorhome and he said that it's got a button on the floor to turn it on and he said that he just drives with it on.

I drove Darrin's truck and it had one and if I remember correctly it just shifted like another gear when I drove it...

Correct, It can be used either way, for just a Overdrive, Or for a Gear Splitter. It has an automatic setting where it will kick in at 45 MPH all by itself, or a manual setting where you kick it in when you want to.

For me the auto setting is just right for standard cruising, however when I am accelerating hard, or towing I like to kick it in myself at a little higher speed.

I have used it as a gear splitter as well and it does work however it works better with 5 speed. With my C6, B&M Floor Shifter and Eaton OD Switch it does work but can be a little tricky to split the gears.

Later!

 

[Lonesome7.3]

So are you saying you have a Gearvenders unit? Is there anything specific You can tell me? Like maintainence, feul savings, install.

 

[PackRat]

Basically, a Gearvendor's is like having a 2-speed automatic tranny, to split your main box. A USGear is like having a 2-speed rear axle, like a medium duty truck.

IMHO, the USGear takes more skill to use properly.

 

[VanBoy]

I have a GearVendor's unit on my C6. The unit can not be "shifted" below 20 MPH. As far as I know, the US Gear can be. Both the US Gear and GV unit have an auto mode for OD use.

The GV unit can be shifted under full load. I have not tried split shifting too much as of yet. Usually, you are in 2nd gear already by 20 MPH, so you could split shift to 2nd OVER. And then when up to speed a little more, drop to 3rd DIRECT and then to 3rd OVER. I just wanted to have OD and most tell me it was an expensive way to get it..... oh well.

The US Gear as stated shifts like a two speed axle. From experience of driving a two speed truck, you 'engage' the shift under throttle... then for a split second, you let up on the accelerator or depress the clutch. This unloads the drive line and the shift happens. Down shifting is the same way, but just make sure you are slow enough or you'll grind something.

I've seen a few US Gear units online on Ebay. The only issue is getting the correct speedo stuff if you buy used. Someone stated that the US Gear unit "maybe" getting pulled from the market..... so parts are getting less and less.

I'll come back and post on install and such stuff....gotta get for now.

 

[Lonesome7.3]

Thanks. What kind of hauling and fuel inprovements did you see?

 

[VanBoy]

Thanks. What kind of hauling and fuel inprovements did you see?

Well, I really don't haul that much. If you saw my signature, the GV is on an F150... an old one none the less. When I did haul something before the GV, I was going up a highway grade at about 45 MPH, 2nd gear & engine going 2500+RPMS. I'm sure if I split 2nd, I could have been going 45 at much less RPMS or going 50MPH at the same RPMS.

After install, I noticed a small improvement. Fuel economy went from about 15MPG to just under 17MPG highway. Both the GV and US Gear advertise between 10-25% depending on driving habits. Then my distributor went T/U (and I thought it was the carb)...so I messed w/ the carb fuel/air ratio. Right now, it's running WAY rich...... haven't had time to redo. Right now, my fuel economy sucks on my I6 300.

Hauling improvement you man see depends on your specific info, as in your axle ratio, which transmission and how much you plan to haul. If you have 4.10's, and an E4OD, you could actually run a double over drive and drop your final ratio to about 2.33. It would keep your RPM way down running at 75MPH empty. The 4th gear in a E4OD is a deeper reduction vs the GV unit. The E4OD is .78 ratio while the GV is a .73. Granted, not much, but you could in theory lock out your factory OD and tow w/ the GV unit (so the tranny doesn't hunt). But, there is two trains of thought on if you should or can tow using the factory OD. Some say you can, others say NO.

There was a member at the other Ford forum (thedieselstop) that had TWO GV OD's if I recall the pic right. I'm sure they belong to this one too, but I just can't recall the user name. It was on a Ford crew cab so there was enough frame. For some reason, I think it had the ZF tranny also.....not sure.

 

[RLDSL]

Or , you could install an old Spicer Brownie and have OD ,direct and under.
I just finished installing one of these, but I stiff have a few minor things to hookup to get it back on the road( exhaust pipe and clutch slave )
Definitely more work to install, but a much stronger box

Whatever setup you go with, I could strongly suggest keeping your old driveshafts and needed crossmembers intact and bagging them up and rigging a hanger to carry with you under the truck , and get new shafts made or get a set of boneyard shafts and have them modified for the new setup.
THis way if you are traveling and the OD units folds on you, you can just pay any shop to remove the dead box and slap your old shafts back on and be on your way.
There are some serious terror tales out there from GV owners who have had the things fold under warranty and then had to pay some insane tow bills to get their rig to an authorized service center for repairs. Those places do not grow on trees.

Personally, I'm not that fond of the GV setup, I used to work on european cars and I've rebuilt lots of Laycock OD units ( I have a couple laying around here collecting dust ), They came from the factory on many Volvo cars and they aren't all that bulletproof. Shifting the things at to slow a speed will really tear them up as they don't have enough internal pressure built up to fully engage the thing, and they go into a kind of limbo and try to tear themself up.
THen GV tries to keep all the parts proprietary where you have to send the thing to them for rebuild, they won't cut loose with a lot of things. The parts are available for both J and P type Laycocks, but very hard to find if you don't know the right people.

 

[Lonesome7.3]

That is some good advice.

Can ou tell me more about the Spicer Brownie OD?

Oh one more thing, I am running 4:10 gears but have 37 inch tall tires. I know that has to make a difference.

 

[RLDSL]

That is some good advice.

Can ou tell me more about the Spicer Brownie OD?

Oh one more thing, I am running 4:10 gears but have 37 inch tall tires. I know that has to make a difference.

These are the critters that used to go in semi trucks , dump trucks etc as an auxilliary transmission back when they had twin sticks ( they still make them, but the ones now are only the really heavy duty twin countershaft boxes which are way too heavy for a pickup ) But when you consider that these pickups have about the same or better HP than a lot of the semi trucks that were running cross country when they started making these boxes, the match is just right.

Rear end gears and tranny ratios have a lot to do with box selection. They came with different internal ratios and you would want to find one that gives you the most even splits between gears, meaning you have to get the formula ( which I can dig up ) and run the figures for each of the availabel ratios. I have all the factory manuals for I believe all of the spicer auxilliaries and the spec sheets which I can copy off that makes it fairly easy, then the hard part is waiting for one to come up on ebay, or there is a wrecking yard in Oregon Anderson Bros that has a bunch of the things and they even sell them rebuilt for very reasonaable ( in fact cheaper than the last used one i saw on ebay ) They have quite a few in stock right now
I was hoping to find an air split model so it would be easier for my wife to drive, but they didn't have any of those except in the large boxes and after about a year of searching, I finally went with a regular 5831b.
I'm just a few picky things from having it back on the road and will have some pictures up here soon. If it would ever stop raining, and the young'uns get over being sick, I might actually get the thing finished. I want to drive that thing so bad I can taste it

 

[Lonesome7.3]

Thanks man, I just learned something.

 

[VanBoy]

Speeking of twin sticks...... a local farm shop swapped out a tranny (5 or 6 speed) out of a late 60's KW logging truck. They put in a regular 10 or 13 speed tranny. BUT... they kept the brownie in place..... I get an evil grin from them everytime we talk about that truck.... something about it going like a bat out of heck when empty.


I wouldn't mind getting this formula for a brownie box calculations. Who knows, maybe it will come handy for projects.....

By the way... dumb question... how do you tell which is a brownie box on that web page you posted?

 

[RLDSL]

Speeking of twin sticks...... a local farm shop swapped out a tranny (5 or 6 speed) out of a late 60's KW logging truck. They put in a regular 10 or 13 speed tranny. BUT... they kept the brownie in place..... I get an evil grin from them everytime we talk about that truck.... something about it going like a bat out of heck when empty.


I wouldn't mind getting this formula for a brownie box calculations. Who knows, maybe it will come handy for projects.....

By the way... dumb question... how do you tell which is a brownie box on that web page you posted?

That used to be a VERY common mod up in WA and OR. I've seen log trucks with all kinds of interesting gear combinations. hottest rig I've ever seen was a short log rig ( one of those trucks that hauls the huge bottom sections of the old growth trees, they only had to be legal on one axle at that time, usually the steer ) KW with a 1693 cat with twin turbos and a 6x6 tranny arrangement. I was sailing up Cabbage hill in eastern OR at 75 ( loaded, I had a 72 KW with a 1693 TA turned up hot with a 13 speed, I'd never been passed on a hill before that day, and never after ) but that sucker went waltzing past me like I was standing still, and he had to be grossing well over 100k ( probably closer to 115 ) and I only had around 80k
you could tell he didn't like to spend too much time crawling through the woods

The auxilliaries on that page are listed under Spicer transmissions, auxiliaries
They may have some Fuller Aux boxes too, but I've never deciphered the codes on those. The ones marked P are air shift ( p for pneumatic ) but they only have the big boxes in that.

This page over at GV has the ratios of all the major trannys in the pickups. I'll have to find that formula and re scan that sheet later