OK im driving a 1984 chevy scottdale 4x4
its a half ton truck with a 3/4 ton suspension
it now has 31 inch bf goodwrench tires on it
and a after market edelbrock crate motor.
I bought this truck a few years back off a friend that I dont talk to anymore and ive been puzzled by one thing on this truck. From the factory the guy supposedly ordered the truck with a 2.72 rear end ratio. I know a good amount when it comes to motors and suspension and things like that but I don't know much about rear ends and rear end ratio.
Why did the guy order 2.72 gears instead of something like 3.10 gears or 3.70 gears? and if I was to change the rear end from 2.72 gearing up to 3.10 gearing what sort of changes should I expect to see?

 

if i were you i would go no less than 3.42 and personally i would go with 373 or 410s

272 to 310 wouldnt see much of a difference, but your rpm at highway speeds will go up a little and acceleration will improve

 

So im guessing then, 2.72 gears are a longer gear made higher speeds at low rpms? Which would explain why this full size truck gets 23 mpg on the highway and 17 mpg in the city

 

not quite... for every engine rpm your rear end is turning your wheels 2.72 times (your transmission gears it down some form the engine so figure driveshaft rpm) but if say you had a 3.73 or a 3.92 or a 4.10 then your rear end then it would be turning them that many times(3.73, 3.92, 4.10 times) a lower gear will net you better acceleration, worse gas mileage (higher rpms at highway speeds)... a higher gear ( lower number)will give you lower rpms at any speed - meant for gas mileage (damn EPA)

i dont know what your goals are for this truck (daily driver, street-strip, drag truck, etc.)

the ram srt10 has a 4.56 rear end gear which is how you get a heavy truck to do 0 to 60 in around 5 seconds and get 9 mpg.. and 500hp v10 doesnt hurt - just to put things in perspective

 

I agree, at least 3.73s with the 31" tires. You will lose a couple mpgs but your acceleration will be like night and day. Provided you're into acceleration like most of us nuts on here

 

I'll have to look into putting 373 gears in it once I get the money, right now though im working on fixing up my 84 regal, im still trying to decide whether to do a fi 6 cyl for it, or to go old school, and finish up this 350 ive got sitting in the garage that'll put out around 450 horses NA with a 9 to 1 compression ratio.