Gear Vendor vs. US Gear

[DBaker]

I'm planning to add an auxilary transmission on my '98, 12 valve, NV4500. TST power, gauges and Pac brake are in the mail now.

I have 3:55 gears and pull a 34 ft 5th wheel camper. I would appreciate any input on pros and cons between Gear Vendor and

US Gear. Thanks for any info.

 

[RustyJC]

The GearVendor setup is a modification of the original Laycock overdrive design (ref. 50's Jags, Healeys, Triumphs, etc. ) The advantage of this design is that it can be shifted under power. The disadvantage of this design is that it must be in direct drive to use an exhaust brake - torque applications in opposite-than-normal direction (i. e. , engine braking using an exhaust brake) can cause slippage and failure when engaged. In general terms, the GearVendor is more suited to an automatic transmission application (keeping the exhaust brake restriction in mind. )



The U. S. Gear design is basically the original Doug Nash setup and achieves its under/overdrive through physical gearing. It doesn't lend itself to shifting under power (it's almost like one of the 1940's Wilson pre-selector transmissions where you flip the switch to select the shift, a light comes on when the unit is ready, and you dab the clutch [thus untorquing the unit] to make the shift. ) Since it's an all-gear unit, no restrictions on exhaust braking. The U. S. Gear unit is perhaps more suited to manual transmission applications. I plan on adding a U. S. Gear 20% overdrive to our 2002 ETH/DEE with 4. 10 axle for use when not towing as well as for gearsplitting.



JM2CW - Hope this helps.



Rusty

 

[MikeR]

The GV works much like an automatic trans,it has a fluid pump in it. You can't split gears until you're going faster than 30 mph,so the pump can operate.



If you're the kind of guy that must have a manual trans in your truck,then the US Gear unit is the only one that makes sense.

It is an all-gear operation just like the NV 4500 in your truck. You can split any gear.

 

[RobG]

I have the US Gear unit in my 2001 ETH/DEE and love it. I run it with the overdrive on when empty, and with it off when unloaded (I have 4. 10's also). The 4. 10's rock for towing.



Then when climbing hills, I select whatever gear will get me the RPMs I want for lowest EGTs (usually 2600-2800 given my mods), which is usually 5 or 5OD.



Shifting it isn't a problem... you flip the shifter-mounted switch, and they say to wait two seconds for pressure to build on the spring mechanism in the overdrive before flashing the clutch. I've learned to time it so that I flip the switch, and then move to the clutch pedal. By the time I reach it and flash the pedal, 2-3 seconds has passed.



The only "issue" I have with it is the CLUNK sound it makes 75% of the time when it shifts. This is normal from what I've been told by US Gear, Diesel Dynamics (who I bought it through), and others who have them. Oh well, what can you do?



All in all, I like it.



Oh let me add this... if you have a long-bed truck, I strongly recommend staying with a two-piece driveshaft. Many driveline shops will want to make you a one-piece one (like they did in my case). I wish like heck I'd stayed two piece and just shortened the one piece of it. My whole transmission/OD/xfer case flops around a lot on the rubber bushing now that there's nothing to support the aft end of the setup. But crap, I already spent $400 getting the two shafts done; I'm not about to switch back just yet.



Rob

 

[BPINE]

Nicely put Rusty, DBAKER you say you have an exhaust brake in the mail that means you have no choice US Gear. Don't worry about the clunk noise when shifting it is completly normal and they all do it, that's just the way it opperates.

 

[Paul]

If you have a 4X4 with a standard cab, you must alter the fuel tank to install a U S Gear OD.

 

[Bob Horrell]

One more consideration and the icebreaker for me is that should the unit fail, with the GV unit you still have your regular gears and can continue onward. You just don't have reverse. I often tow my 4 horse trailer full of horses and the thought of being stranded with the horses, should the unit fail, made my decision for me. If the US Gear unit fails you are stuck.

I have heard of both units failing. I am not sure of the cause of US Gear failures. The most common cause for GV unit failures is using it during deceleration. It won't last long if this is done, especially if equipped with an exhaust brake. Normal changes experienced while in cruise and in OD are not a problem, just when decending hills or coming to a stop. You can learn to live with this shortcoming.

I have had my GV for about 40,000 miles, most of it towing. I have over 400hp and have had no problems. Until you get used to shifting, there is the characteristic clunk, but with practice this can be eliminated both on upshifts and downshifts.

I know a number of people use it in drag racing applications with automatics. Lots of horsepower and hard shifts. It seems to do real well under these conditions.

Also, you can't use the GV unit while in 4X4, where you can use the US Gear. During my numerous times in 4X4 I haven't really encountered a situation where I needed to split the gears. the torque of the Cummins just pulls you on through.

Just some more things for you to think about. I know it is a tough decision and it took me 6 months to make mine. If it wasn't for the possibility of becoming stranded, I may have made a different decision - or then again I might still be trying to decide.

 

[BPINE]

Bob not to discount what you have said because it is all true, but there are many parts on these trucks that can leave you stranded. With proper maintenance it should be no more risk than anything else, at least that's what I keep telling myself.

 

[SixShooter]

How do you normally drive with the GV overdrive? Maybe you could rig up a monetary switch somewhere on the brake pedal so that when it is depressed it shuts off the overdrive unit, and when it is released the unit comes back on. I think for the ones of use with a US gear brake this would be easy because there is already a brake pedal switch, you could just have one for it to operate the brake and one for the O/D unit. Lets get are brains stormin here, any help from people with the dcelerator would be great- mine will sone be on the way.

 

[Bob Horrell]

BPine, you are correct. There are many things that could go wrong and leave you stranded. I am a maintenance nut and do all I can to minimize potential failures. So far I have been very lucky with all my machines. I even raced motocross for many years without ever having a DNF - at least not for mechanical reasons - injuries don't count.

Jacob082, I have contemplated the very thing you are talking about only you would need to do it off the throttle and not the brake. I thought about using one of the switches used for actuating an exhaust brake. I just haven't had time to do it yet and I have really developed a habit switching out of OD when decelerating. Nobody else drives my truck, so it hasn't been a real high priority. I don't think it would be that hard to do. There is already a circuit that disables the OD when in 4X4 so all you would have to do is actuate that circuit with a switch off the throttle assembly (either the old cable stop switch or the new throttle pedal one).

 

[SixShooter]

Seeing how Bill K has already got a Smart Controller for he transmission, Maybe he could adat it to add on the GV unit and so then the exhaust brke will only work in direct drive. Bill K if you are there will it be possible to use a US Gear D-Celerator and a GV Overdrive with your TC smart controller?

 

[DBaker]

Thanks for all the input! Based on what I've heard I think I'll probably go with the US Gear unit. The Pac brake arrived today along with The Auto Meter gauges. I know what I'll be doing tomorrow! The Pac brake directions seem to indicate that if I don't have the heavy exhaust springs in yet I can operate the unit but just don't insert the "performance" plug in the butterfly.

Any risk in this? I realize the brake would not work at optimal performance.

 

[JJW_ND]

Might not need more gears w/ more power?

You should pull your trailer a few times after the TST upgrade. You might find that your stock gearing is fine with the extra power.



Even the 230hp upgrade should dramatically improve power. A few extra RPMs on top of the power would far sure eliminate the need for more gears.



jjw

ND

 

[Turbo Thom]

For my part , I've had my US Gear unit for about 2 1/2 years. Up to now it has worked pretty well but with clunk when shifting. The problem I have is the lack of service available for these splitters. Now it has started acting like it is searching when it shifts. I just got back from driving in the Tenn. mountians and had a time waiting for it to shift. It would shift, then seem to jump out of gear, then try to shift back in then out again with no input from me except for the first shift. It seems the help from US Gear service is minimuil at best. I've been treated better from a number af places. With the shorter shafts it has to be in place for the drive shaft. I'm looking for another unit to replace this one and have it looked at for possible rebuild.

Don't think I'm complaining, I'm not. When it works right in the mountians it can't be beat. I turning around 280 HP and the splitter is still great in keeping it in the RPM range.

Good unit.

Preston

 

[Paul]

I have a circuit, with 2 relays, wired into my GearVendor harness. One atomatically resets the GV power when shifting out of 4X4, and the other locks out the exh. brake when the GV is energized.

 

[rob10858]

we had a six gv units and two us gear set ups in our 97 thru 96 dodge ctds v10's and chevy gassers basically because we loved the idea of shifting into high fifth and the lower rpms and fuel savings that we saw. the us gear units were clunky and hard to shift vs the gv that shifted like a dream. we instructed all of our drivers about the proper maint and use of these od units, and for about 50000 miles they all performed perfectly. after that , well dont ask me. i will say this, the drive shaft has to be cut to accomodate both units and when we converted back to the stock transmission[all manual] its wound up costing us about $800 per truck, not to mention the original cost of the units, now scrap metal. great idea, great results, but no longevity. if any of you guys sell these things e mail me and try to sell me on the new units. and by the way both will leave you stranded if a seal or gear tooth fails, unless you have 4wd. the way the us gear units lasted longer and we still have one on one of our chevys. i loved these things more than any other mods that we did to our trucks , but in the end they were a costly mistake. i still wish i had a gv on our 6 speed's that would be awesome, but it aint going to happen. my opinion, both companies were very good to work with but in the end, we took the hit in the wallet.

 

[Shooter]

The G V for the 24v have 2 inputs ( passive ) for locking out the od. When you put it into 4x the GV controler shifts it out of od and locks it out untill you shift back into 2x. It has a seperate input for an exhaust brake that connects to the e brakes solenoid to automaticly shift into direct each time the e-brake solenoid engages the e-brake. You can also hook up a lock out input to keep it from double od, or for many other acessories, plows or what ever.



EDIT: I forgot you have a manual. You will just have the manual mode



The GV has 2 modes: manual or auto. Auto will split 2nd thru od with no driver input or manual where the driver will use the foot switch to to shift the GV at his pleasure but can not over ride the lock out functions ( 4x, e-brake, etc. ). It is pretty idiot proof, as u can see even I can use one. I have over 10k towing miles on mine and it still works flawlessly. I have found no need to use it while m/t except on the drag strip where it got me . 5 sec over no 3rd od split.

 

[SixShooter]

Excellent post Shooter. I thought that you couldn't use an e brake with the GV but I guess I am wrong. Thanks for the info-yourpost made my decision on which one to get thanks again.

 

[C Schomer]

Turbo Tom, I've worked on 2 sp rear ends and the Eatons were the best(US Gear is the Eaton design). The clunking isn't a big deal - at least to the box. You are shifting gears without syncros or clutch packs so clunking is normal unless you get REALLY good at it! The only problems I've seen is worn brushes in the motor or a broken shift spring - both inexpensive repairs if you do it yourself. When you flip the button(under power) - the motor runs just enough to preload the spring. Then when you hit the clutch and throttle, the power is off the box and the spring slams the gears. With the engine off and the truck not moving, you should hear quick, positive operation of the motor in the box when you hit the button. It doesn't matter to the motor and spring if you're moving or not and you can hear what's going on with the engine off. Craig