i was wondering if there was any way you can decrease rpms while going faster on the highway i mean it seems like its just so wastful having it tack at2300 rpms/2600 rpms going 70mph and deisels make so much low end torque when your not even hauling anything.is there a way like a different rear end or tranny thats just as strong/reliable as a e4od tranny any ideas??????????

 

Gears... Or a gear vendor unit to ad another overdrive.

 

ZF-5 and 2.73 gears... Now that'd be an interesting combo... On the highway it'd probly cruise about 1700 rpm at 70.

 

Sounds like you have 4.10 gears in the axles so a switch to 3.55's or larger tires would help.

 

simplest solution would be to slow down :-) Bu seriously, how much of a difference gas mileage wise would any of this really make? Doubt any gear swaps or larger tires are going to pay enough dividends mileage wise to offset the install costs to be worthwhile unless you drive it a lot. I say drive it and enjoy it.

 

I have a '97 F-350 XLT reg cab 7.3L PSD 5spd 3.55 gears I go about 65-70 everywhere 1900-2100 rpm's and was getting 19.5-19.8 mpg every tank until I did the ICP mod now I'm at 16.5-17.3 the last 5 tanks of fuel I'm about to undo the mod no difference in performance and loss fuel economy. Anyhow that's the best I got and there is no way to get any better

 

Keep in mind that if the rpms get too low the engine falls out of its power band and you run the risk of lugging it. More throttle may be required to maintain speed, especially on hills. Worst case scenario you'll end up downshifting more and defeating the purpose.

 

i agree,
and cheaper yet would be to simply buy a used sterling 10.25 full float axle with 3.55's already.they can generally be sourced for around a couple Benjamin's plus the cost of new u-bolts.
the issue is when you have a 4wd.the front would need to be swapped as well making it much more costly.
swapping from 4.10's to 3.55 should yield an all around average of a couple mpg.nothing to sneeze at with these fuel prices.
the only reason you wouldn't make the swap would be if you tow heavy and often.
with my truck i haul heavy but tow light so the 3.55 R&P (with shorter tires for 3.84 effective gearing) serves me nicely.
when i do also tow heavy (fill my dump trailer and dump bed with wood) she still gets along ok.

 

i am not a diesel guy and dont claim to be. but arent diesels made to lug? what is wrong with lugging down a little bit? like i said i am not a diesel guy so if someone could explain that would be awesome

 

Lugging down just a little bit shouldn't hurt. The problem is when the engine lugs too much. Think of trying to drive around town in a high gear while driving slow... the engine is at or near idle RPM but with a load on it, and might even be noticeably chugging. This is hard on bearings due to the low volume of oil being pumped at that engine speed.

Most diesels make their torque right off idle, which is great if you have a stubborn load you need to get moving, but I wouldn't continuously operate one too close to idle speed while having any appreciable load on it. That's what low gears are for, let the engine rev and get things moving. You need to get some RPM up to ensure good oil circulation.

Same goes for any engine regardless of fuel type. Low RPM = Low oil flow.
Low oil flow + high engine load = more bearing/valvetrain wear.

 

Changing gears will slow down your engine and give you better mileage (although maybe not enough to be worth the cost and probably not at all if it gets too low, as others have already stated).

Larger tires will also slow down the engine and MAY give you better mileage. But larger tires often have more rolling resistance (especially if they are wider as well as taller). And they usually hurt the wind resistance of the truck. So they will hurt your mileage too, and the question ends up being whether the help outweighs the hurt. Gears are a more reliable (but more expensive) route to go.

 

would ATS have anything with a 5 or 6 speed automatic tranny?? or someone ...just wondering