Does anyone else remember that thread??
Needless to say the fellow was hasseled pretty bad about his claim and left (I think?)

In it there was a fellow chatting up how his truck was getting in the 30's as far as fuel economy goes. according to him there were two basic things done to his truck, a "gear" in the motor was adjusted for the timing and his rear end was set up.

Looking back on it the "gear" this fellow was talking about was more than likely the tone ring as he was saying it increased pollution, special exemption etc (all contributed to the hasseling the fellow got). This was all before the tone ring mod became popular. (true enough, the tone ring mod does increase fuel economy)

This brings me to the second item that fellow was talking about, the rear end setup.
How much of a negative impact could a poorly set up rear end make on fuel economy? I am under no illusion I would gain 8 mpg out of it but it does make sense if it is not quite set up it could make a dent in the overall performance of the truck.

Anyone ever had a rear end changed and noticed the fuel needle move faster or slower?

Edited to add: The fellow I am talking about had a third gen truck. '03 or '04.

 

That happened to a guy at dsmtuners.com(a site about turbo Eclipses/Talons/Lasers) He posted claiming he had a Holset turbo installed on his car. Everybody laughed at him and said it was too big and impossible. They chased him away before letting him prove himself and he never returned. Now it has become a relatively common turbo upgrade for those cars as well as some other imports.

For your question about gearing, speed kills mileage. You have a brick, the faster you go, the more drag and lower economy. The other factor is RPM. Your gearing must be set up to keep you at the engine speed where fuel consumption is lowest at the speed you travel. I have not seen a fuel consumption graph for the common rail, but many Cummins engines have lowest fuel consumtion around 1700-1800rpm.
As for actual mileage numbers, I have none as I have no experience.

 

Don't remember the thread, and don't know about the gear in the engine. Thought I'd heard that the tone ring mod was more for cool factor than performance or economy. But as to the rear end, I disagree that there would be much, if any benefit from reworking the setup. This assumes that the backlash is set to tolerances (.004-.010") and the pinion is wearing in the approximate middle of the ring (correct pinion depth). There could possibly be some small gains available in the design of the differential. As an example, in drag racing, we usually consider the GM 12 bolt to be most efficient, with the Ford 9" being the easiest to repair and replace with a small tradeoff in efficiency. Something to do with the relative centerlines between the ring and pinion. The dana 60 is supposedly as good as the 12 bolt, but with so much more unsprung weight, it still slows the car down compared to either. I've never seen any efficiency data on the AAM, but would suspect that it's not worse than a dana 60 and therefore pretty good. It's probably not even worth measuring, since you're only talking about thousandths of a second on the quarter mile anyway. That means a lot to the class racers, but nothing to us truck owners.

 

The title caught my eye. I wish there was a way to get 35mpg, hope that guy comes back. I'm not familiar with a ring tone gear? Is that a 3rd gen thing? I had another 94 CTD with a 3.50 gear and it would run around 1750 rpms at 65 mph and get about 23 mpg. The truck I have now has 4.10 gears and it runs 1750 rpms at 55 mph and gets 17 mpg. Thats quite a difference. I try to drive by rpms because there is a sweet spot for efficiency with these engines. I just can't seem to find it with this truck. You would think that driving the same engine in two different trucks the same way would show similiar results. I have no idea of the previous owner mods on either of these trucks so that might be where the difference is.

 

If you are talking about the guy in the northwest that had the work done there was a lot more involved than simple changes.

The one I have info on was an early 3rd gen. The "gear" in the engine was the cam gear. The engine mods consisted of retiming the cam and reworking the injection sequence for timing, duration, and pulse width.

All the fluids were replaced with synthetics and the drive train was reset to optimal clearances in the diffs and trans/tcase. Thats just what was posted so am sure there were lots of little tweaks going on from one endof the truck to the other.

You would be surprised at how much an out of spec diff will contribute to drag and efficiency reduction. Multiply that by 2 and factor in 7k of weight and it can be significant. Small changes alone may not make an impact but adding many together will eventually show results.

Is 35 mpg realistic? Possibly, if the conditions are right and the driver is well versed in techniques, but, thats a long way from a daily driver for the masses. I am familiar with the guy that did this work and if he says it will help you can bank on it.

 

negative people suck!!!!

 

The "gear mesh" on the ring and pinion I don't feel that would change any noticable amount between different rears. But the bearing preload that is a different story. I could see a slight chance of a noticable improvement by reducing the bearing preload on the pinion gears and the differential gears as well as the outer wheel bearings, but all those items need to be a little on the tight side when pulling any heavy loads. Due to the FACT that rear end housings(like all types of steel) grows when it gets hot, causing the "cold" preload to deminish. If it goes completely away the bearings will "waller around". The term "waller" is a highly technical term I use, thus causing premature bearing failure. A person would be better off finding a way to free up the brakes so there is absolutely no drag on the rotors when the brakes were not applied, that may require shimming calipers one way or another or even milling caliper mount to fit exactly centered on rotor. And I think some aftermarket racing brakes for cars have some sort of valving that allowes the caliper piston to retract slightly more than a stock caliper to reduce drag. Maybe someone can figure out how to do this on our heavy duty trucks.

 

I don't remember where the fellow was from nor do I remember all the details as to what was done to his truck. This post I am talking about was a couple years ago (tried the search, didn't dig it up) so it is very likely we are talking about the same thing.

The reason I dragged this up now was my recent tone ring mod. For me, there has been a noticable difference in the very short time I have had it done. (leading me to believe there was something way out of spec to begin with)
Like yourself, I do believe that several small changes can add up.

While I am not quite looking at changing the cam nor the programming for the computer I am looking for a couple more of the small things that add up. It just seamed to make sense to me the rear was the next place to look as it is where all the power changes direction and is applied to the ground.

Any info on what his overall economy numbers have been?

 

When you say you have noticed improvement, define improvement MPG, temp.....?

 

The info was met with such disdain that the original poster never returned, on several forums. It was for the most part a lot of unsubstantiated opinions that lacked any basis so it was not well met.

The only credence I can place in the claims is the individual that did the work posted several rebuttals that clarified what had been done. He made no claims to mpg gains only pointed out the changes will increase mileage.

 

Yes, I recall the rough ride he received. Part of his problem was he didn't appear to be mechanically inclined enough to clearly articulate the steps taken (from what little I recall)
I didn't know the individual that actually performed the work posted in the thread. By that time I probably lost interest and stopped watching it....

Would you have any idea what either of the user names were so I can do a search that way? (PM if you like)




Much like the posts we are discussing here I have nothing to substantiate my claims. so I do need to be careful in my "cheerleading"
With the one tank I have run through I am at the 900Km mark on the trip meter (560 miles) and I need to fill up. I don't recall getting that kind of range before. The overhead is displaying 19+ mpg where previously it would be displaying 17-18. The exhaust isn't as acidic (perhaps the wrong term but it doesn't make your eyes water as fast when your around that corner of the truck) and it also seams the valve rattle on 2nd gear launch is gone.

Once again, this is seat of the pants. If you do a search on "tone ring" or Rokktech sensor (both will do the same thing) you will see what others have noticed by advancing the timing.

 

There was a lot of posts on one of the sites in the last few mths. talking about why the Rams are getting the millage they are as compaired to semi's , a lot of off the cuff about the bigger loads , more resistance [ 18 wheels ] ect. , thinking that there should be better millage in the RAMs .
A lot of good thories . Never did reach a conclusion .