Question For US Gear owners

[LarryB]

Originally posted by Dkevdog

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.

I definitely feel that with this engine taller gears are the way to go. Especially if you have 4wd/6sp. If 1st isn't low enough then tray 4w low. Even pulling heavy with my setup in double-over I sometimes could use another gear up top and first is always low enough on the bottom.



I'm curious, Is there anyone out there that thinks they're geared too tall??

 

[Loren]

Kev,



More information:



1.

Yes, the shifting is harsh. I don't have the experience with my unit that Larry does, so he can probably shift his better. Mine still clunks into gear most of the time. My wife told me that she couldn't believe I would install something on my truck that made such a noise.



2.

The procedure for shifting with a manual transmission is as follows:

a) While the drivetrain is under a load (accelerating or decelerating), select the push-pull switch to the new selection.

b) Wait two seconds.

c) Push in the clutch to unload the drivetrain. The overdrive will shift when the drivetrain is unloaded.

d) Release the clutch.



One thing I’ve discovered already is that you don’t have to push the clutch in to unload the drivetrain, but you’d better. For example, if you are accelerating and you select overdrive, the unit will shift if you release pressure from the accelerator. This will result in a really big clunk, and, I suspect, serious shock loads to the drivetrain. Sometimes it is enough that I am afraid something will break.



3.

Pricing: Call Brent Barr at 866-794-6496 (toll-free). I got an excellent price from him. You might also try a local dealer. My local guy was in line, but couldn’t quite match Brent’s price. You can find bargains. Keep hunting.



4.

I agree with Bill’s acquaintance. I don’t think the overdrive is necessary, especially with the six-speed. That doesn’t mean that you won’t like it, though.



5.

Randy: Get the 3. 73 axles. The diesels are always geared too low from the factory. Remember, these ratios were developed mostly for the gasoline engines.



6.

Kev: If you can get to Indiana, I’ll let you drive my truck. We’ll have some difficulty pulling a grade, though. There is nothing like the Grapevine out here. To be fair, I’m in southern Indiana, and we do have some steep hills. They just aren’t too long.



7.

Before installing the overdrive, I found myself reaching for the shift lever trying to shift one more gear after I was already in sixth. That was one of the reasons for my buying the overdrive. Sixth-over, however, is a really high gear. I have Rickson 19. 5" wheels on my truck, so I have raised the gearing about 4% from those. The result is that I can’t really shift into sixth-over until I’m doing about 60-65 mph. The slightest hill will result in a shift down to sixth-direct. Also, as I said, my cruise control will not work in sixth-over. If I want to use that feature I’m stuck in sixth-direct. (Back where I started. )



8.

I’m with Larry. Now that I have the 3. 54 axles, and the 19. 5" wheels, and the U. S. Gear overdrive, I FINALLY feel that I am geared too tall. I think it would be perfect if I had 4. 10 axles and kept the overdrive and the Rickson wheels. I also have a 4WD, so I have the option of low range if I need lower gears. The overdrive allows a top speed in low range of about 30 mph or so.



9.

I was trying to justify the time to submit an article to Robert for TDR magazine publication. Maybe this thread will convince him that there is enough interest that he should publish it.



Loren

 

[FM]

I must confess, after sleeping on it and having my eyes opened but glazed over, I still don't see why mileage doesn't improve.



When I drive my current truck (see sig) in 4th @ 65 I get much worse mileage than in 5th. I don't see why this would not be the case with 6th over?



When you come to a hill in order to maintain your rpms and mph you dump more fuel hence poorer mpg. If you're running flat land in 6th over does the engine produce enough hp with less or equal throttle than the amount of throtle running in 6th, mph being equal? If so I'd think the gear splitter would have to be grossly inefficent to cancel mpg gains. Or is it a "hill" senerio where you have to increase throttle in 6th over to maintain the same mph due to decreased torque?



Would another benifit to being able to run higher mph at lower rpms be less engine wear? Or would these gains be minimal to the degree of pointlessness?



Like others, I hoped for the best of both worlds, highway mileage and low end pull/offroad creep. I can't dispute the emperical data, not trying to. Perhaps I'm all wet (in daNile).

 

[Dkevdog]

Originally posted by LarryB's Super Starter Contacts

I'm curious, Is there anyone out there that thinks they're geared too tall??

Yeah- Garrett (Big Wgite Beast) did. He changes his 01 3500 factory 4:10 setup to a 3:54, and said it was lugging all too much, so he pulled out his wallet again and went up to 3:73.



Here is the oddity that makes no sense to me at all: He claims there was ZERO difference in mileage between ANY of the the three combos.



Maybe I'm missing something because I'm not a physicist, but that doesn't make any sense at all.



I was *told* that your best and most fuel efficient range was UNDER 2000rpm. If that is the case (and even if it isn't for that matter) how can running 70mph at 2300rpm net the same mileage as running 70mph at 1900rpm?? (just as an example).



It was earlier suggested in this thread that I try to run at 50Mph in 6th gear, and then at 50mph in 5th. See what the OH computer thinks about it. I did. The results support my arguement. In 6th, at 1750rpm, I saw the OH read between 18-20mpg. In High rpm 5th, say about 2100rpm, it dropped to 15.



Granted- I know the OH computer is NOT that accurate at best, it still gave me the results I expected to see.

If you're running flat land in 6th over does the engine produce enough hp with less or equal throttle than the amount of throtle running in 6th, mph being equal? If so I'd think the gear splitter would have to be grossly inefficent to cancel mpg gains.

FM- You are thinking along the lines that I am. I am not doubting Larry or Bill (Illflem), I happen to have great deal of respect for both of them. It just that the more I try to make sense out of this, the less sense it makes.



Right now I'm steering at swapping out to 3:54's. I'm sure I can find someone interested in a swap. I want to find an HO 6speed I can try before I buy though.



BUT- If switching to 3:54's won't net me any mileage (as Garrett reports) what's th point?



Kev

 

[illflem]

Kev, it sure seems like the majority of folks here that complain of poor mileage often have 4. 10s. I know my mileage takes a considerable dump over 2000 rpm, but once had to run my five speed several hundred miles in 4th about 45-50 mph on curving ups and downs in S. Utah, tach was almost always over 2k but it was about the best mileage I ever got. I thought for sure it was going to be the worst. Maybe it is just speed and not rpm or a complicated combination of the two.

 

[FM]

Dkevdog

"I am not doubting Larry or Bill (Illflem)"



Me either. How do you argue with " this is my rig, this is how its set up, this is what it does. " I mean, it is what it is. I just wanted to mileage sooooo bad. You know cake and eat it too.



I understand the concept of energy loss due to more gears. I had just assumed (we know what that does) that going from a final drive of 2. 99 6th to 2. 39 6th over would be huge.



Hey guys I know you can led a horse to water but... if you can make me understand this I'd be grateful. I'd love to have a 12spd but can't spend the coin without getting a big payoff in return. Looks like I have to settle with airtabs and 315s. My 4. 10 is non-negotiable.

 

[jtisdale]

Excellent, informative thread...

I have been kicking around the idea of a US gear unit in the next year or so also. However, with my plans of going with 33" tires, I was leaning towards the underdrive unit. It seems, given the winding, hilly county roads in my area and the fact that I have 3. 54's, I feel my truck (in its mostly stock configuration) is too "long-legged". I seldom have to use 6th. I am sure going with slightly taller tires, will only compound the small "problem" I already have. I figured an underdrive unit would be more user friendly, especially while towing in my area, with my set up.

Maybe I shoud just keep driving around in 4th and 5th. I cant see how that would be any harder on the transmission than crusing flat out for miles in 6th.

Thanks for the info.

 

[Dkevdog]

Originally posted by FM

I'd love to have a 12spd but can't spend the coin without getting a big payoff in return. Looks like I have to settle with airtabs and 315s. My 4. 10 is non-negotiable.

FM- My point exactly! I am willing to spend the money if the payback is there, But I have not seen any proof or heck... even evidence of any real mileage gains. I still can not believe that the unit is that inefficient and I still am trying to make sense out of it.



I'm trying to remember who in our local chapter has a 3:54 HO six speed that is geared for towing a fifth wheel (if there even is one). I want to actually feel how it runs before running out and doing any gear switching. Couple that thought with the fact that I am looking in to towing a jeep behind the fifth wheel and the wieght factor goes up even more. I do feel that the 4:10 and the 6 speed make 1st useless unless you're pulling. And even then I can start it in 2nd without any trouble. Of course I'm only at 9K right now.



I'm also still waiting for the mechanical genius' to jump in and explain (in terms us uneducated can understrand) why this whole thing is the way it is.



Kev

 

[CumminsAholic]

I also have one on a 96 5 speed 4:10 gears. It makes a pretty loud clunk when you shift it. I use the truck for my cabinet business , it has an enclosed box (van body) on it that sticks up and over the cab. The truck has 180K on it and I think it's had the OD unit pretty much all of them miles, so they are pretty durable. I usually always leave it in high, unless I'm pulling a trailer and am going under 75. As far as mileage gains, I dunno, I never ran it in low for a full tank. It is better with the od, I just don't know how much for sure. If I had to guess, I'd say 2-3 mpg. But that's with a 12v that has a lower reving power band than a 24v. I believe at 70mph it makes about a 200 rpm difference, next time I drive it I'll pay closer attention to it.

On my 98. 5 I also have 4:10 gears, but an auto. By going to a 33" tire I gained over a mile and a half a gallon, almost 2 mpg. When I bought it it was stock and I was getting 15mpg at the best. Now with all of my mods I usually get 17 -18 and can sometimes squeak out a 20 if I'm really nice to it. The tires helped out the most with mileage, next probably the edge EZ because of the timing change.

If I were you I'd either go to a different gear ratio (I'd say 3:73) or get taller tires. With a 6 speed you can always drop to 5th if you need more power and run in 6th when you're empty for the mileage. I don't think you'd split shift very much and for the amount of money an OD costs you can buy a lot of fuel. Just my opinion. If you have any questions feel free to PM me.

Corey

 

[CFAR]

Ah what a good thread.



The faster you go the more wind resistance, hence worse mileage.

The slower your engine turns over (within limits) the better your mileage.

There will be parasitic losses associated with any additional gearing + weight + wind resistance (if it sticks down at all)



I was only getting about 15-18 mpg for the first 18000 miles. I changed the way I drive, mainly the shift points, on level or small inclines I never rev above about 1750 rpm. Mileage increased to between 20-22.



Bully Dog III's, If I baby it I will still get the same mileage. Winter fuel, I'm lucky if I get 15mpg.



On the road I try to stay below 67 mph, above that my mileage drops like a rock.



If you installed a OD you will get better mileage, the question remains, how much?

 

[jrobinson1]

I installed the OD with only a small gain in MPG. Seems to be due to staying in "efficient rpm zone" Another gear box adds weight and friction which generates heat. Heat = Energy lost But it does changes driving characteristics.



Cruising mpg is same but RPMs are down at 65. Granted there is a high speed improvement around 80 - 85mph I don't fall into the gas guzzler hole as quick because of effiecient RPM's at that speed. The mpg does decrease due to wind over 67 but not like it used to. That is all I have found that improved (besides drive pleasure of a proper gear for all speeds). Our trucks have a wind resistance barrier around 65 - 67 for efficiency.



I feel it moved the mpg curve a little: the beginning of the curve is the same all the way to peak efficiency at 65 then it doesn't fall as fast as it used to but no more then 1 mpg better, if that. My 85 MPG is 18 - 19. Before us gear 85 was down around 16-17mpg.



I think the lower cruising rpm's will help in the long run for engine longevity. Hours of freeway cruising at 1600 - 1700 vs 2000+. I like to stay a little behind the peak power then sit over the other side of it. I may be wrong but I feel its better for the motor. Over revving just shakes things apart and wears things out. IMO



HTI (Hope that imformative)



james

 

[GiesJ]

Dkevdog-

what size tires you runnin on that 2wd 3500?

I think it's been mentioned but maybe a tire size increase would help you out some? good luck, if nothing else, the over drive is just cool.

jason

 

[Dkevdog]

Jason- Funny you should mention that, I am hoping to upgrade my worn stock tires (235's) to the 255/85LT16. I can't find anything in an E Rated tire, someone suggested Cooper, but nothing yet, including cooper.



I know, I know, I don't need an E rated tire, but would certainly prefer one if it were available.





James- Interesting that you went with the OD unit and a 3:54 rear. I'm thinking more that a 3:54 rear (or possibly 3:73) is all I need with the 6 speed.





Kev

 

[crawler]

Its up to you in the end. If fuel mileage is the main concern then just go with a gear swap. On my rig I consistently weigh in at a gross weight of 30,000. I've even been stupid and run over 40,000lbs before. With the 3. 54s you CAN get it and keep it moving. I know the weights I pull are stupid, but thats how I have to do it some times. Of course with that much weight you need to run vacuum over hydraulic brakes on your trailer or something similar. If I'm not in school then my truck is hooked up to a 36' flatbed with tandem dual axles and compound disc brakes. By the way I run 3. 54 gears. I wouldn't mind having 3. 73s, but I would probably want the gear splitter then just so I could run a little faster when I'm empty.

 

[jrobinson1]

If I had a 24v and 6spd I wouldn't have. Our Rpms powerband is narrower and lower then 24 valves to do 70 empty on a freeway I was around 2000 rpm and didn't like it. Also out 2nd to 3rd shift is really wide and I like to cut it in half. I run alot freeway miles flatland much is not very heavy. I felt like I was topping out. 2200 rpm I felt it start defueling and that only had me around 85 if I recall. If/when I run that fast I want to care for the motor a little more.



I got the OD after a 9 hour run CA - AZ at 80-85 and the truck seemed like it was pushed too hard. I was pushin the clock as we many times do. Thought I would help er out. Many days no the OD isn't needed but having it there is nice. Even if I don't get the mileage economy at least I aint killing her (or it doesn't sound like it)



Had the gov springs been in first it probably wouldn't be necessary because I could raise my shift point and not "lug" into the next gear. Except for highspeed cruising.



On a side note.

For the NV4500 I have seen a higher 5th. came out of a chevy nv4500. a Friend has one. not quite to double OD but better then stock. Just a thought. 6sp maybe a custom gear? $$$ who knows. I don't even know if a shop would do it. That give you more top and not lose your low end towing.



Sorry for the long ones. just you as much to think of as possible. Took me 6 mos to decide. got a good deal that clinched it. I still can argue either way.



james

 

[GiesJ]

Kev -

my buddy and TDR member just put on some load E's on his 2500. I think you would have an issue with the rear duals if you ran the same tire as him but I'm going to forward this thread to him and see if he has any further comments. He's got 4. 10s and wants to be able to cruise a bit faster empty too - more than likely he'll be swapping to 3. 55s. The 255's should fit without a spacer on your rears and the height increase should help some.



Jason

 

[mschoenheider]

I could not find 255/85/16s in an E, so I went with 265/75/16E Michelins. I have the 3. 55s sitting in the garage, ready to swap in once I order a shim kit. My goal is lower cruising rpms when empty. The most I will normally tow is my gooseneck with two jeeps on it (13k), which I have no problem with right now, so I don't think the 3. 55s will hurt me too much. If they do, I know a set of 370s will fix the problem.



Mark

 

[FM]

Thanks James, informative just not what I wanted to hear. What's you mpg at 60 - 65?



I like the lower rpms at higher mph but I'm not sure I'll spend the coinage for that right now. Without a big mileage boost it moves to the want list.



Hey Mark have you thought about going to 19. 5" wheels. You can get F or G rated tires and what ever OD you want. Checkout



http://www.ricksontruck.com/home.html



That's another item on my wish list. It's hard to justify doing much to my new truck (when I get it) because I have no doubt it will out preform my current truck which does almost anything I ask. I'm just looking for ways to lower operation cost and make it last longer.

 

[Dkevdog]

This has really become a very informative thread. Thanks to everyone for their contributions. With the cost of fuel becoming simply ubsurd , we all begin to look for ways to squeeze out a few more MPG's.



Crawler- how do those heavy loads do with your setup when it comes to pulling a grade??



My only concern with dropping from a 4:10 to a 3:54 is that It would be too much of a drop the other direction. I tend to pull alot in the mountains, which is why I thought about the 3:73.



I'm gonna end up beating this thing to death before I deciede .



As for tires- Mark- remember I have a 3500- 265's won't fit and I don't want spacers. Jason- if your friend is talking 255/85's in an E- find out what he's running please.



Kev

 

[jrobinson1]

My mpg hand calc at every fill no additives

90% freeway

20 -21 @ 65

18 - 19 @ 75

mid to upper 19 @ 80-85 (this is the only change w/ OD, used to be 17 -18)



I drive light foot. Have 285/65 3. 55 and 12v From stock till now hardly any change in MPG.



Having one towing hills and freeways empty it is great otherwise a large hole in the wallet. Only benefits I see is less wear and tear on the motor and driver pleasure.



james