Help with gear and tire MATH
 

Can someone start me in the right direction with this subject. I have an 88 truck with 22RE, If I run different size tires than factory how do I develop the correct gear ratios for the axles to compensate? I am not talking about anything major, just maybe 31's when the factory was 225/75's. I want to maintain my torque curves on the low end and keep my GAS MILEAGE!

Do larger tires of similar tread design automatically mean lower fuel mileage if you keep the gear ratio constant?

Thanks for any help!

Do a simple equation.

4.10 are for 29 what X are for 31's. For example.

But as general rule for you gasers is:

31 - 4.56
33 - 4.88
35 - 5.29

David

X2 on what he said.

How will 33's with 4.56 gears work with a V6? What about gas mileage?

x3 - the rigs that came with 31's stock had 4.56 with the manual tranny and 4.88 with the auto.

My truck was V6/MT/4.56/31 stock - my opinions of the different combos:

4.56/31 - too low. First was about worthless - by the time you got moving, you were tached out.

4.56/33 - too high. First had some "legs" now, but there was a noticeable loss of pep in 5th. Had to downshift A LOT more. Speedo was DEAD ON to the GPS (<1 MPH difference at 70MPH)

4.88/33 - JUST RIGHT. First has some usefulness, and it will hold 5th on rolling terrain.

33's will work with 4.56's i just put some on my truck and i agree with what tc said. I can still use 5th gear in mine though Haven't tried 33's with 4.88's in my rig though.

(i think my 33's are on the smaller size though, maybe 32's)

Most of the opinions seem to be pretty close but here's something a little more technical for you.
The formula has all the info you need except your gearing ratios. Note: the numbers will be a little off with a non-lock-up auto tranny.

I am going to go 33' and 4.56, until i find an already locked geared front third, then i would regear the rear.

That's kinda what I was thinking...4.56 for now with the 33's, and when I find an elocker from a salvage yard with 4.88's, I'll get that and break down and get the 4.88's for the front then. How will that affect gas mileage though?

My 33's run fine with 4.56. 1st and 2nd are a lot nicer on the street, rpm's are a bit lower on the hiway, gas milage after checking the "real" speed hasn't changed.

I ran 33's for about two years on the stock 4.10s. My new 5.29s are much better though. Pretty wound out on the highway but I think it likes it.

My truck came with 225/75 15's. I put 31X10.50 15's on it. With the 22RE 5-speed it was a dog with 4:10's in it. I had dumptrucks passing me while going up hills. I recently put 4:56's in it and immediate power increase.It's no longer a dog, but I haven't did a fuel mileage check yet.

I was looking at the Marlin site and their 3rd members only come in either 4.88 or 5.26 would that be overkill for my 81 4cyl w/31's?

4.88's might not be too bad, especially if you use it offroad. Having the RPM's up will help the carburetor at angles.

Gonna be taching somewhere around 3500 RPM at 70 on the highway though ... no problem for the engine, hell it will love it, but takes some time getting used to the noise!

Plus then you're ready to go to 33's ...

I ran 31's and 4.10's for a couple years. I actually really liked that combo. Now I'm running 33's and the stock 4.10's until I have the money to re gear. It's definitely a DOG at the moment. But it Looks good! lol

If you run 31's you are running about 10% over stock gearing, if you are still running stock 4.10's. Personally, like I mentioned, I really liked that combo. It still had most of the bottom end of stock, but tached a little lower at speed. And it still climbed hills decent. I'm looking at going to 4.88s with my 33's. But now that it's not my daily driver, I'm thinking 5.29's make more sense. :)

Good Luck!
Grant

maybe I'll just go with the 33's....the main thing is I want to leave it stock height...I wonder if 33's will fit....

they fit REAL NICE!!http://i290.photobucket.com/albums/l...a/DSC00216.jpg

man, I have stock 3:73 gears in my 94 with 5in of lift. I push 32/11.50s without a problem. i dont know what yall are talkin about:think:

Um, no, you obviously don't know what a properly geared vehicle runs like...