Need some help here fellas. I have read back into the forum and found some info on rpm's with new gears. Someone had posted to turn the o/d off on your truck and that would be what the new gears would feel like to a degree. I did this today and noticed that my rpm's with o/d on was 1500 @ 55 mph, with it off 2200. At 70 mph, rpm's went from 2000 to 2800. I'm running 255/70 tires (30") with the factory 3.55 gears. Do these figures seem right to you guys who are running the 4.10 gears? I'm thinking of going with the 4.56 gears and a 285/75 tire. I have a feeling that my highway mileage will take a big dump with this. I tow often. Usually around 4,000 lbs. and thought the 4.56 might be a good gear. What do ya'll think?

 

I think you should spend some time playing with the gear calculator on this site;
http://www.accuautoparts.com/

 

The calculator link was pretty nice. However, I'm wanting to hear the real-world rpm range with 285/75's with 4.10 and 4.56. The 4.10 would get back a little better than stock according to the charts. I'd like to go a little more than that due to the towing I do. I know some of you run 4.56's with 33" tires. I mainly need to know the driveability on the highway running around 65-70 with this combination. I could always run the 4.10 with a 265/75, but I like the look of the 285 better.
Rich

 

I have 4.10's in my truck with manual tranny, Factory 265/70/17's i'm spinning around 2100 rpm around 65 mph

 

bump

 

to high of a gear for 33's consider 4.10's i have 4.56's on my 35's and she is very torq'ey little girl and very minor rpm increase on highway very minor very nice soild shifting to which is nice

4.56 with 33's would be a waste and higher rpm's for all daily driving not always a good thing you want to keep your truck kinda in the normal rpm range gear down a little is fine but thats way to much if you want those gear least do 35's im gonna go to a 37 next she will handle them just fine to

 

Thanks for the response. I'm not sure what I want to go with yet. If the highway mileage won't fall out, I think the 4.56 and 285 would work considering the towing I do. Real-world numbers are what I'm looking for. I appreciate your help.
Rich

 

4.56 are over kill for 33's unless you planing on a tire change to 35 or so later on go 4:10's or most 4:30's

 

Thanks for the posts. I talked with my mechanic bud who owns the shop and we decided the 4.10 285 would be a nice bump. I was worried the 4.56 would be too much gear, but I don't want to spend the money and say "what if". I still may decide to run a good 265 tire instead of the 285. I can keep my same drop-hitch and also I have a 265 spare I can swap over pretty easy. Thanks again. I'm going with the Yukon gears and probably the master rebuild kit. He's going to check everything out for me and let me know. With 96,000 on the clock, I think everything needs to be looked at pretty close. We're doing both axles and the gears for $1000. Best bid I've received and the guy owns a shop that deals in a lot of off-road trucks including building his own. I'll let everyone know how it all works out.
Rich

 

very nice choice of brand it will be a great setup