im getting a supercharger put on in about a year, but right now i need new tires, so i thought i would upgrade to 37's or 38's. but im concerned about what gears i should get with tires that big. i was going to go with 4.88's since i was on a stock motor, but now that im going to get a supercharger, i dont want my highway RPM's to be too much with the 4.88's.

so i was thinking about gettting 4.56's so that when i get the supercharger, it will be enough power to push the truck and not have alot of RPM's at highway speeds.


what do you guys think.

 

I am running 38's with 4.56s. Also have a Lightning motor in the truck. The difference in 4.56 and 4.88s are small. I'd do 4.88s if i could do it again. Only reason i don't have 4.88s now is cause when i geared 4.88s weren't released.

With the 38s and 4.56s its at 2kish at 70mph.

Wayne

 

well for me i have always looked at it like this
31=3.73
33=4.10
35=4.56
37=4.88
40=5.13 or better, lol but i have 32s on my jeep with a 5-speed and 4.56s and i love it .
when i regear my truck ill go with 4.56 for 33-36 but i dont do alot of highway stuff just stump pulling

 

so with 4.88's my rpms would be about 2200 or so?

i just dont want to kill my mpg when i go down the highway. or rev the engine more than i have to for long periods of time.



i have a question, how much boost do you have when you are just cruising down the highway?

 

Don't worry about the supercharger till you get it. You will not be in boost when you are cruising the highway anyways. 90% of the time I am not in boost when I drive. So if I gear my truck for economy it will run like a dog.

4.30:1 gears will almost get you back to stock gearing based on a tire size of 255/70 R16 and 37 inch replacement tires. With 38s you will need a 4.56:1 gear. Re gearing to get you back to stock rpm doesn't account for the extra weight of the bigger tires. You have to allow for that too. So as was suggested you should consider 4.88s just to get you back to stock power to the wheels. You are going to need all the gear you got with those tires unless you want to continuously drop a gear just to climb an over pass. Once you get the blower your gas mileage will go out the window till you get over the initial "WOW this thing hauls ****" syndrome.

 

Im at about 10inches of vacuum while cruising on the interstate.

Wayne

 

ok. i guess ill go with the 4.88's then, thanks guys