Adding an extra gear

[96DieselBurb]

Hi guys! Ok, I bought a 96 2500 Suburban with the 4 speed tranny and 4.10 gears about a month ago and its great and everything but Im pushing about 2350-2400 RPM going down the highway @ 65 mph. this is not so good for my mileage when Im not towing anything (which is most of the time) I am curious, without swaping the tranny, is it possible to add a gear or an overdrive or something to it? I mean, I guess if I have to I will swap the tranny but that doesnt really make much sense if Im only going to see a 3-4 mpg increase.

[grancito]

put some bigger tires on it, just remember the speed will be higher than the speedo reads. Your Tach should be reading 2283 at 65mph, 265-75x16 tires will bring the revs down to 2221. My burb has this size, I think 285's will rub without modifications.

[96DieselBurb]

Yeah, I was thinking about just slapping on some bigger tires but you dont think that Ill get a bigger drop in RPM with some kind of overdrive like gear vendors or something? Im only asking because Ive read several posts of folks getting upwards of 20 mpg with the overdrive trannys and to me, thats great! How did you know what the tach should be reading at 65 mph bye the way?

[Garth J]

Go to gearvendors website they have a chart there the gives you all the info on speed, tire size and gear ratios and what your RPM will be.
I had one on my 85 6.2 with the 3 speed auto and 4:10 gears it was the best thing for highway driving. I should have kept it when I sold the truck and put it on my 94

[Craig]

Went to gearvedors.com. Could not find the chart. I am very interesed in the chart to make some calculations.

Thanks

[grancito]

To 96DIESELBURB, in answer to how I got the reves for 65mph I was using the diff ratio the overdrive ratio(0.75) and the distance traveled for one turn of the tire (measured) it is a little different from the theoretical as tire pressure and weight change it a bit, also tire sizes are not always as they say. I do not agree with other opinions on this site of gear ratios saving fuel, only saves ware on moving parts. I have made many experiments and found that improving engine efficiency is where you will improve fuel economy. My 10 cents worth. Sorry opponents.
Grant

[96DieselBurb]

Hmmm.....Well then. That gives me something to think about then. Thanks!! BTW what else would you reccomend as far as saving fuel/improving engine efficiency? I am very interested in this! Im guessing that starting with new tires as you stated before would be good huh?

[grancito]

tape an egg to the accelerator pedal and don't break it while driving! Make the engine breath well, if it blows black smoke, thats fuel wasted, there are many mods to exhaust and intake, weigh up cost and how long to recoupe. Work an extra half hour, blow black smoke and have fun.