I have 3.55 gears in my truck now and I get about 15-16 mpg. If I were to regear to say 4.56 or 4.88 what would that change to? I do about an equal amount of highway, aroundtown driving.Thanks.

 

it really depends on what you do with your tires. you can do all the math to percentage it out, but if you change gears only, and keep factory size tires, your acceleration will drastically improve, but your cruising rpm's will go way up and your mpg will come down. this is usually only done when you want to race or tow. generally people will regear in order to compensate for larger tires. so if you put on tires that were 15% bigger, and you changed gears by 15%, then you are getting back to factory acceleration, cruising rpm's, and probably not hurting you mpg any. 4.10 is a good change. 4.56 is huge. 4.88 is um, probably too much unless you want to turn some really fast 1/4 miles and see the rpm's hit big numbers.

 

How do your 285/75/16s run with your 3.55s? I've got 265s (they're bald) and I've been thinking about 285/75/16s or 305/70/16 if they'll fit my stock rims till I have some money for my little project. Do the big tires bog it down much?

Anyways I'm sort of thinking about Regearing/lifting/new tires/rims at the same time since it all seems to go together. Could I run 42 inch tires with 4.56s pretty good with like a 6 inch suspension lift?

 

How do your 285/75/16s run with your 3.55s?
sluggish, lack of torque and get up and go. this size tire needs a 4.11

Do the big tires bog it down much?
yes.

Could I run 42 inch tires with 4.56s pretty good with like a 6 inch suspension lift?
42's ? wow. you'd need 4.88 you'd also need a lot more lift than 6in.
my opinion is that's too big a tire for a daily driver. see what other people think.

 

Could not agree more. Although I have not had any other size tire on my truck, I have driven my friends truck with 265's, all the same except his is a 5.2L, I can't imagine that much of a difference in acceleration because of that. There is a noticable difference between the two tire sizes to me, with the 3.55's as we both have. Next tire change, unfortunately most likely a couple of years from now unless I just get fed up with it enough, I'm probably going to drop down to some mean looking 265's. Its honestly embarrasing driving on highways and such with lights because it takes a considerably longer time to get up to speed without making the truck shift to get that extra boost. (15-16mpg on a 5.9 4x4? wow).

 

42's even with 4.88's are going to be very sluggish. For a daily driver this is huge and i wouldn't recommend it....38's are pretty big but better then 42's for a dd. Also with 42's your going to be putting your axles through alot of stress, and you going to be looking into having to upgrade your brakes, and replace u joints and ball joints and bearings like no other. to fit 38's you can get away with a 5 inch susp and a 3in body lift. to fit 42's you'll probably have to go with skyjacker (or superlift..i get them mixed up) 7" with a 3" bodylift. That's pretty tall and you probably won't be able to go through the local mcdonalds drive thru....i would recommend steering clear of the 42's if your going to keep this a dd.

 

a friend of mines wife (yes, wife) has a ford with 44's. its a trail only truck. its got some huge amount of lift, maybe 16". i can barely climb up in it. they break axles on a regular basis, it drives worse than anything you can image. a complete headache. but boy will it rip up a mud hole.

 

Do a 3" lift keep the 265 ..and you will still keep the mpg.... my inlaws have theBFs tires on for over 5 years.... that will be my next tire BFs ..Im still getting 15.1 mpg city...

 

Found these neat calculators out on the Randys Ring & Gear Site. They might help with some of your questions.

http://www.ringpinion.com/Default.aspx

 

I have a 99' short box reg. cab with the 5.2L with 3.55 gears. the truck came with 225's. I have put 285's on it. The performance is very sluggish. What kindof gears would be good to bringit back to stock?