Question For US Gear owners

[Dkevdog]

I am considering the addition of the US Gear overdrive to my 01' HO 6speed dually. It is 2wd and I have the 4:10. Great for towing, not so great for freeway driving.



My questions to those of you who have the setup, especially those with similar (6sp) is: What kind of mileage improvements have you seen with it? Do you find yourself gearsplitting or do you leave it one way or another depending on your load? And, given the steep expense, was it worth it and would you do it again???





Thanks in advance





Kev

 

[RustyJC]

Kev,



Hurry up and do it and report the results. I'm considering the same thing.



The last time I checked, the 2WD NV5600 application wasn't listed on U. S. Gear's website - but it's been awhile since I checked. If you need them, I have the part numbers for the 2WD adapters, etc. Let me know.



Rusty

 

[Dkevdog]

Rusty, you can check here they are available, and have been for some time from what I understand. I spoke with one guy who has a 4wd 2001 6 speed and he's had it for quite a while.



I'm more on the fence about justification of price vs perfomrance and economy- this certainly isn't a cheap mod... ...





Kev

 

[illflem]

Kev, I'll bet if you pencil it out you'll come out cheaper changing out the rear end to 3. 54 and driving in 5th while towing.

 

[jrobinson1]

I have 3. 5's and us gear. 2250rpm at 100+mph.



Use it constantly empty I go 1 over, 2 over, 3, 3 over, 4, 4over, 5 over and cruise 1750 @ 80mph Great for empty cruising. Love the choice of gears for climbing grades.



Runs hot but they say thats normal. I have about 40K on mine w no problems. Still playing w/ oil choices. ATF running now.



With a 24v and 6spd I don't know. I got it cause our 12v RPM band is so narrow. With Gov springs it seems sorta extra but nice to have. Because I have it I don't use all the RPM the gov springs give me. If I had the springs 1st I prolly wouldn't have got the US gear.



Fuel maybe 1mpg better just cause I can stay in effiecient RPM more often. Don't get it for that. 1mpg takes like 400k to pay for the unit.



I do like mine. I feel more for the driving pleasure then anything. I never have to climb grades at RPM I don't like no matter the speed of traffic or my load etc.



HTH



james

 

[illflem]

James, member LarryB figured out that the same stuff recommended for your transmission, Castrol Syntorx, made his US Gearbox run 50° cooler. US Gear now recommends it.

 

[jrobinson1]

Thanks illflem. I was thinking of trying it. Sounds positive. I only have had the temp guage since ATF was in it, so well see the change.

 

[LarryB]

Kev

I think if I were You I would change rear gears only. The 6sp 24v is a pretty good gear setup as is. Going with a 2sp really is a lot of monkeying around and expensive for no real gain. I have a good friend with a 2002 HO/6sp w 3. 55s or close, and he is very happy pulling his 10K 5th wheel.



After I have gone through all the stuff I wish I had just gone with the taller rear gears and the 4K spring set. I have gone back to the 3K gov springs and find that the 2sp is necessary when pulling heavy because the 3k springs make a narrower power band. With the 4K springs I don't even split gears. I just use 5th-over for flats.



The only real plus I can see is that its fun to play "trucker" when running through all those gears. I have not noticed any real mileage increase.



I have also noticed lower oil temps as the miles have added up and the oil was changed to Castrol Syntorq as illflem mentioned.

 

[Dkevdog]

OK- Try and follow me here and explain why I'm wrong

I guess maybe I'm a little confused then. I was hoping for a significant increase in mileage. I guess you guys aren't seeing it though. Both of you are talking 12valves. Would a 24 V make a difference?



I have been told that the 24Valve "sweet spot" is in around 2100 RPM. For me, that is about 62MPH. I like to go 75, and that puts me up around 2300 to 2400. I have noticed that according to the OH console computer my best MPG is around the 1700-1800RPM, where I have seen the computer report 17 - 19 MPG. I would LOVE to actual get that MPG, and I thought the US Gear would keep me down in that range which would equal the higher MPG.



Why does this theory not work??



Taller gears are an option, but I don't think I want to drop down to the 3:55 gears and give up the gearing

all the time - which is the other reason I thought the gear splitter would be the way to go. I don't tow too heavy now (about 9K) but plan on pulling a Jeep behind the Fiver soon and that will kick the wieghts up some.



I know Garrett (Big White Beast) stepped in between to 3:73 gears, but I don't what (if anything) it did to him for mileage.



Kev

 

[LarryB]

I think the reason you see better mileage at lower RPM is due to lower speed/wind drag rather than RPM. Also you loose energy in the 2sp due to efficiency loss. All that heat coming out of the gearbox is energy coming from fuel. My experience seems to be that the energy saved by not spinning the engine as fast is lost on turning the extra gears & oil, resulting in questionable net gain. It still seems to take the same amount of fuel to push the rig through the air.



I may be wrong but with the 6sp, 4. 11s don't seem necessary. 1st is plenty low and all 6 gears seem evenly spaced with 3. 55s



Just my opinions.

 

[RustyJC]

Originally posted by LarryB's Super Starter Contacts

I may be wrong but with the 6sp, 4. 11s don't seem necessary. 1st is plenty low and all 6 gears seem evenly spaced with 3. 55s



Just my opinions.

The 4. 10 rear axle increased the GCWR on my truck from 20,000 lbs to 21,500 lbs. Since we're running 21,180 lbs GCW towing our 13,500 lb 5ver, we went with the 4. 10's.



From an engineering perspective, the 4. 10's reduce torque loading on everything from the pinion gear back to the engine for a given BHP or torque output at the rear wheels. Thus the increased GCWR.



Rusty

 

[Dkevdog]

Larry- Very Interesting. I would have never thought about it this way, but when you bring it up like that, it does make sense. Extra force required to turn additional friction laden (Gears) parts.



The guy I spoke of early with the 4x4 01 6speed 4:10 brags of mileage in the high teens, not too bad for a dually. I have no reason to doubt him, but I can't seem to find anyone else doing that with the US Gear setup.



Rusty, seeing as you are equipped with a similar drivetrain, I assume that you were thinking about the splitter for the same reasons as I was. I hadn't thought too much about about getting away from the taller gears before to increase economy- primarily because It was highly sugested that I stay with the 4:10 for towing.



Maybe the 3:73 is the compromise I need, or maybe I don't really need the taller gears and could get away with a 3:54.



Kev

 

[RustyJC]

Kev,



The 4. 10's are great for towing heavy - I'm running right in the sweet spot insofar as power is concerned at about 2350 in 6th at 70 MPH. For running the freeway empty (which I very seldom do), a taller gear would be nice. That's why I'm considering the U. S. Gear overdrive unit.



Yes, one can tow with a 3. 73 or a 3. 54, but for equivalent rear wheel torques, drivetrain torque loadings will be 9. 0% higher with the 3. 73 or 13. 7% higher with the 3. 54 than it is with the 4. 10's.



Ya pays yore money and ya takes yore choice!



Rusty

 

[Loren]

Kev,



My thoughts on the subject:



1.

If you are thinking of installing the overdrive for fuel mileage alone, it is absolutely not worth it. I haven't done the math, but I suspect that James is correct that it would take 400,000 miles to pay for itself, and that assumes that you will actually see better mileage.



I have also done some informal testing with my computer. I agree with Larry that the reason you see better mileage at lower RPM's is due to the lower speed, not the lower RPM's. Check it out for yourself. Drive at 45 or 50 in fifth gear and note the mileage. Then shift to sixth and drive the same speed. You will be turning lower RPM's, of course, but your mileage will not differ by any significant amount.



In my own experience, the largest (by far) single factor in fuel mileage is the speed I drive. (Assuming the same load on the truck. ) I don't think that the unit will save even 1 mpg.



I just intstalled my U. S. Gear overdrive, so I don't have fuel mileage figures yet, but before the installation it I was getting anywhere from 16. 5 to 19. 0 mpg. The average was probably closer to 18. 0 to 18. 5 mpg. I doubt that the overdrive will improve on this.



2.

You say you are towing about 9000 pounds now. I have towed a 14,000 pound fifth-wheel with my 1995 truck with 3. 54 gears and automatic transmission. I don't like to do it, but it tows it.



That truck, however, is a 12 valve. I haven't towed the fifth-wheel any great distance with my 2000 ISB six-speed, but I am positive that it would have no difficulty with that load. It also has 3. 54 axles.



If you are really after higher gears, I think you can safely go with a 3. 54 axle for a lot less money than the U. S. Gear unit will cost you, especially since you have to switch just one axle.



It's true that you will increase the torque load on all the upstream components as Rusty states, but my truck seems to handle similar loads just fine. Note that although the loads will be lower with your stock 4. 10 ratio, the parts will turn about 6% more revolutions per mile. This may increase wear on those parts to more than what would be experienced at lower torque.



3.

The 24 valve engines have a much wider power band than the 12 valves. This means that you don't need such close gears to be able to accelerate with a heavy load or uphill. Add to this the six-speed transmission, with its excellent gear ratios, and you have a very good combination right from the factory.



If you want to split gears and can afford the overdrive unit, by all means get one. Whether or not you NEED it is another issue.



4.

I installed mine because I enjoy accessorizing my truck and because I can afford it. That is not the same as saying that I can justify it.



I am looking forward to cruising empty at 70 mph with RPM's of about 1700. Mostly, though, I wanted to be able to split the gears. There are occasions when I needed a gear between 3rd and 4th, or between 4th and 5th while pulling a trailer uphill. There are other times, even empty, when it would be nice to have a half-gear to get to a more comfortable RPM.



These are convenience issues, however, not necessities.



5.

There is a lot more to the installation than meets the eye. If you are good at solving your own mechanical problems, possibly including shortening your plastic fuel tank, and drive shaft modifications, you can do this yourself. Otherwise, consider having the installation done. Realize that even a professional installer may not get it right the first time.



6.

I haven't driven with my unit long enough to give very meaningful comments beyond those above, but I think that the overdrive ratio could be better, especially for our six-speeds. The ratios are more suitable for the five-speed transmission.



By this I mean that the U. S. Gear overdrive will split gears pretty well up to fifth. Fifth-over (Fifth gear on the transmission with the U. S. Gear unit in overdrive) is too close to sixth-direct. The step from sixth-direct to sixth-over is a large one, almost the equivalent to a full gear change rather than a half.



7.

On my truck, cruise control will not work in sixth-over.



8.

Rusty hit the nail on the head: "Ya pays yore money and ya takes yore choice. "



If you get it you'll like it. Whether it's worth the money or not is entirely up to you.



Loren

 

[Dkevdog]

Loren-

Thank you for your thoughts and opinions, very informative and I appreciate it.



I am still considering the unit, although exploring other options along the way. I would not even think of attempting the installation myself, I have been quoted around $600 for the install, NOT including driveline rebalance. US Gear does not reccomend the 6speed unit be installed by a DIYer.



A question for you Loren (and Larry Too. . )

Is the shifting in and out of OD unit harsh or smooth?

I have heard that it "bangs" in/out of gear, and was wondering what kind of driveline shock and wear this creates??



Another finding- The pricing on these units seems to be pretty well fixed ? No difference in price between dealers??



Kev

 

[illflem]

Kev, had a talk with a guy who has an stock '02 6 speed with 3. 54, tows a 14k trailer. This was his third CTD, he installed the USG overdrive on the other two but said the 6 speed didn't need it...

 

[LarryB]

Originally posted by Dkevdog

Is the shifting in and out of OD unit harsh or smooth?

I have heard that it "bangs" in/out of gear, and was wondering what kind of driveline shock and wear this creates??

I too wonder about the stress and wear on the driveline components. Sometimes the shift is so smooth it sounds like an auto. Sometimes it bangs so bad you would swear the whole drivetrain will be laying on the ground in a smoking pile. My thinking is maybe the electric shift actuator inside the 2sp is a little too strong as it seems to shove it into gear before the mesh is correct. The 2sp rear axels will grind a little if you don't have everything right but my USGear just goes ahead a shoves it right into gear. Shifting up is usually quite smooth. It's the split down-shifts that are hard to do. This has to do with the inertia of the gears and shafts in the main box needing to speed up or slow down to match the driveline speeds before the shift can occur. As I get more miles I learn how and when to shift for smother shifts, varying throttle, switch timing and clutch. Then, just when I think I have it figured out "BANG", it scares the crap out of me. I'm expecting that something will break one of these days. Maybe once the gear-dogs get rounded off a little it will shift smoother.

 

[randyn]

3.73 or 4.10 ?

Looks like a good place to ask this question. I'm about to order an '03 (first diesel for me), and am trying to decide on ratios. Will be getting HO auto, 4x4 quad, and will probably end up putting 305x70x17 or 315x70 tires on it when avaliable. Want some tires to keep front end from sinking in Louisiana mud. With the 315x70 and 4. 10 the effective ratio is almost same as 265x70 w/ 3. 73. Will pull only occationaly, but will be heavy (max) when I do and some of which will be off road. Same 305 or 315 tires w/ 3. 73 is about like a 3. 54 w/ 265x75x16. Any advise/discussion will be big help.

 

[Dkevdog]

Originally posted by illflem

Kev, had a talk with a guy who has an stock '02 6 speed with 3. 54, tows a 14k trailer. This was his third CTD, he installed the USG overdrive on the other two but said the 6 speed didn't need it...

I need to find someone with this type of a setup and pull a grade with it to see how it goes.



Randy- I hear the 3:73 is a nice setup, although if yopu plan on going with the taller wheels from the getgo, you might be better off with the 4:10.



My problem is I just feel like I need a NV5700- you know, a 7th gear for when I get it going over 65mph. I always feel like I'm running out of engine.





Kev

 

[FM]

This is a great thread for me. I was going to install the overdrive for higher mpg alone. You all really opened my eyes. I'm still trying to get my head wrapped around the physics though. On the one hand I can see it takes the same amount of energy (fuel) to overcome the same force (wind drag) but my thinking had been lower rpm at same mph is less fuel. Hey, thanks a million... ... actually it's closer to $2600.