I've been contemplating changing my rear end gears for a while now, but based on bits and pieces I've picked up along the way, I'm in the typical "do I want 3.73's or 4.10's" dilemma that most guys face (or will eventually). I do a lot of highway driving at 75-80 mph to and from work (I turned 30,000 miles on the way to work today in < 9 mos of ownership), so mpg is "pretty" important to me. Obviously (I would assume), I'm getting better mpg with the 3.55's, but how much worse would I be (could it get)if I went with the 73's or 4.10's? It seems that many people here feel that it isn't worth the time or money to change from the 55's to the 73's. Has anyone run their truck with whatever mods you got and 55's, then ONLY changed the gears (to either size) and run again at the same 1/4 mile track in similar conditions? What difference did you see (60' time, ET and mph)? What's it like to launch on the street with 4.10's and F1's? (i.e. I might break down at some point and buy ET Streets, but right now I'm 90% concerned with how its demeanor is going to change around town). And this is the last one, I promise: What do you guys typically run rpm-wise on the highway? I think I'm about 2300-2400 or so now at ~80mph. Thanks, later...

 

4.10 divided by 3.55 = 1.15 times 2400 = 2760 ..
Is that about right ?

 

...Is it that simple of a ratio to figure out what my new rpm compared to old rpm would be if I changed the rear end gears? I wasn't sure if the gear ratio in the tranny somehow played a part in it (i.e. isn't 3rd gear a 1:1 ratio, and overdrive something like ~0.7)? I'm not trying to make this into a math lesson, I'm just looking for input to see if my 60', ET and mph gain in the 1/4 and around town are worth the $ for parts, installation, and lower mpg. Thanks, later...

 

We use 3.73's in our L. They are great on the street and strip. Though we put drag shocks on the truck at the sametime as the gears, we did improve our 1/8mile E/T by 2 tenths. Our Fuel economy has also improved some. We get 17MPG on the Highway if we dont get into the boost to much. At 70MPH we are turning about 2300RPM in OD.

hope this could help some.


Im sorry I ment 17MPG on the highway, not in the City.

 

MXRACER I have a set of 4.10's in my truck. They're fun on the street, but a pain in the *** on the highway. you will always be pulling anoter 400 rpms. The best mpg I have ever gotten was 12.2 that was highway driving with a chip. If i were you
I would keep the 3.55's and install a lower blower pulley. A fast e.t. is possible with 3.55's look at Sal