Should I change gear ratio?

[Wtfan18]

yeah i made the plunge and bought a t-56 they are expensive to say the least look to spend over a grand on the tranny itself. let alone have to buy a 400$ clutch 150$ slave 190$shifter i will have close to 2grand into mine by the time it is installed but i will be worth it all day in my opinion after all its just money... if we were all uptight about it we wouldnt be modding our trucks now would we

[01blackerado]

Should top out well over 150+ but you wont makeit there by the 1/4 anyway unless you have 1000whp

[Botlfed]

Im just goin off of what my gears top out at and its the same with txakitekt, he also has 4:10s. mine is programmed to 130 but i never get there.

[LS1GMCTruck]

How much does an in inch of tire diameter change the final drive ratio, or rear end gearing?

[RedHeartbeat]

It depends on what gearing or tire size you started with.

28" tire has a rollout distance of 87.96"
29" tire has a rollout distance of 91.11"

you travel 3.15" further down the road per tire revolution if you travel at the same RPM/MPH. In 1:1 lockup such as 3rd gear in a 4L60e that's an increase of 3.6% distance traveled. On the flip side you reduce your engine RPM by about the same 4% if you maintained the same RPM from the 28" to 29" tire.

[derf]

How much does an in inch of tire diameter change the final drive ratio, or rear end gearing?

I know this is an old topic but I wrote a Java applet that lets you plug in all your information (tranny, t-case if you have one, gear ratio and tire size) and it will show you a pretty close approximation of what RPMs you'll run at different speeds in all the gears as well as what speed you'll be going at certain RPMs in all gears. There's two copies of the form so you can do a side-by-side comparison.

Gear Ratio Calculator

If you're running a 2wd truck, just pick (almost) any transfer case and ignore the stuff about low range and crawl speeds.

[HotRodV6]

one of the reason why is the trans wont shift into 4th under WOT, or atleast they never used to.

I went from 3.42 to 4.10 in my 2001 Blazer x and it shaved about .4 tenths off the 1/4 and i ran 3000 RPMS at 80 woth 26in tall tires with a 4l60E trans.

In these trucks the 4.10 is a popular choice, but with your 5 speed i think the 3.73 would be a better choice.

[zeake]

I bet you have to shift pretty quick quik.

I would love to have 4.88s in my truck for the weekend. I'd have to spend 2 times the money though.

[Timmer1]

thanks for all your inputs. Does anybody have any 3.73's in good condition they are willing to part with?

[NITROUS]

If you don't plan on any future performance mods like FI or some type of major HP increase go with the gear change. If you plan on a stall and some upgrades keep the 3.08. My 1st gear is no good with a 3200 stall 25.6" tire and 4.10 gears. I'm probably going to go back to a 3.42 or something close to it with the supercharger.