I use my truck for hauling a tractor to the woods for food plots, it's only about 14,000 trailer and all. Its got 4.30 gears, gets 15 mpg with me driving and 17 mpg with my pops driving. My question is what would be a good gear ratio for it. Most of the time im not hauling anything and drive 45 min to get anywhere from here in southern middle TN.
With that MPG's I wouldn't change a thing. But I'm no expert though. With 37's on mine and 9" of lift I get 13.5-14 with 3.73 rears. But the in the winter It goes down about 1MPG because of fuel blends and more idle time. Seems with the pulling you do and the 305's it would be worth the cost of swapping gears out to anything lower.
OK so you have 34" tires. Honestly 3.73 are plenty and the best deal if you are not towing heavy loads long distances and or regularly. Ideally for best mpg and in general best use of your entire RPM band they work best. You want to keep your cruising RPMs under 2000 RPM if possible for best mpg. It sounds like most all your driving is like mine. I am about 20-30 miles to anything other than a couple fuel stations. Most all my driving is hwy type. Very little stop and go or city stuff at all. You will likely pick up 2 mpg. I would suggest you get a chip and add a striaght thru muffler and a open air intake you may pick up a bit more with better trans strategy. I think you will then find the new gearing very agreeable.
As you can see from the diff between your pops and you; how you drive is the most critical to getting better mpg.
I bet your pop would see 20 and you 17-18. That is if you can keep your foot out of it.
Figure:
Speed: Gears 3.73/4.30 RPM in OD 4r100 trans
75 MPH: 1950/2262
70 MPH: 1825/2111
65 MPH: 1700/1980
But there is one big thing you have to decide is this really worth the cost of swapping the gears out? That is a very small amount of towing it sounds like make that the primary gearing but not sure how much you drive it other times. If that was your DD or you really do see a good a ton of miles I would think the swap could be worth it. There is no question you will be turning lower RPMs and that will save fuel. The other consideration is what is the topography of the roads there? Are you always going up and down fairly good grades/hill etc of is it not to bad.
Thank you for the input/info. I think it is time to save up and install a set of 3.73's. Most of the driving is on small rolling hills, nothing to steep. Pops can always get getter mpg's than i can in anything, but hey im 34 and he is 55, (i think its the whole grey hair thing). I did pick up a couple more mpg when i put an edge tuner in it. I guess it is time for an air box as well. Again thank you for all the input/info, very helpful.sn:
It had a 6in lift on it with 35's, mpg's were about the same. i know 34's and 35's dont have enough difference to change anything. The mileage check was by hand, i check it on every fill up. 15.8-17.4 depending on how many cobras and ss cars i play with in a week. As far as swamping axles im not sure i could find an 80 for the rear with a LS diff for under 1500, these rock crawler guys have ran the price out of site. A junkyard 60 for the front is still about 800 with out knowing if it needs to be rebuilt, and chances are real good it would be an open carrier. Im just goin to sell some play toys and put some cash back and cange the gears. Does anyone know what the deal is with the thick cut gears for the 4.10 and up carrier?
If you tow more than rarely, then 4.10s are the tallest I'd suggest. I just went to 4.10s with 37s from 3.73s with 35s and the drop in EGT was substantial. Now for the winter I run 33s and have no complaints about engine RPM.
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