Help me pick my gears

[99TanHoe]

Haven't seen too much discussion on gears so I wasn't sure where to put this. I just picked up the 99 Hoe in my Sig last week. The previous owner installed the lift, rims and tires but didn't regear it. Right now the truck has 315/70R17's on it. It looks pretty good but I may go up to 325's to get a full 35" tire.

The tire to gear charts tell me at 65mph I'll be turning the following RPM's with 4.56 Gears:
315 - (3rd gear 2898rpm) (OD 2017rpm)
325 - (3rd gear 2852rpm) (OD 1985rpm)

Right now with the 3.42 gears and 315's I'm turning about 2173 in 3rd gear and 1513 in OD. With the 3.42 gears its having trouble getting out of its own way. Its getting about 14 - 14.5 mpg with mixed driving.

If I stay with the 315's is 4.56 going to be the best gear or should I consider 4.11? 4.11 would put me at 2612 in 3rd gear and 1818 in OD. I noticed most of you running 35" tires are using the 4.56 gears.

What kind of gas mileage can I expect with the 4.56 gears compared to what I'm getting now. The drivetrain is totally stock right now and will probably stay that way for a while yet.

I read somewhere on a forum that these trucks reach their peak torque at 2800rpm so you should run a gear that puts you near 2800 in 3rd gear. Is that just taking power into consideration or would that be the best for fuel mileage also? This truck will be a daily driver.

Whats confusing me is the stock tire size on the door of the truck is 245/75R16. With 3.43 gears it would have been turning 2451 in 3rd gear and 1706 in OD. Thats alot closer to how the 315's would perform with 4.11 gears.

 

[99TanHoe]

Bump for an answer

Come on, somebody has to have some information on this. There's too many of you on here with 35's and 4.56 gears.

 

[ch4d]

here is some more info for you to read up on and it has a chart.

http://www.tahoeyukonforum.com/forum/showthread.php?t=23591

 

[bowtiefreak]

run a 4.56 or 4.88. I wish I would have gotten 4.88 in my rigs.

 

[Gzes]

im gonna do a 4.56 in my 2dr eventually when i get my lift and whatnot

 

[99TanHoe]

Bowtie

If you knew you weren't going to go with a larger tire than a 325 would you still want the 4.88. I'm denfinately not disagreeing with you, just trying to understand so I can get the best gears for my truck and my use of the truck. I'm trying to get the best mpg I can and still have a truck that performs well.

 

[purple 'hoe]

IMO, Don't fear the gear. 35's and 4.88's.

 

[Monzter Mike]

Considering the stock 3.42 gears & stock 245/75/16 size tires that came on your truck 4.10 gears would get you the closest to stock gearing if you run 325/70/17 tires. I put 4.10 gears in my 2wd 4 door Tahoe with 305/40/22 tires (31.6" tall) & it's just right for my truck, my Tahoe came with 235/75/15 tires & 3.73 gears from the factory.

But some 4.56 gears would be a good gear for all around performance on 325/70/17 tires if you pull lots of hills, drive up to the mountains or wheel your truck.

 

[99TanHoe]

Chad

Thanks for the link to Bowtie's thread. I just saw on that thread that Bowtie is running 315/70R17 which is the same size I'll probably stay with on my Tahoe. I like the empty wheel well look above the tire. Kind of makes the truck look higher than it really is.

But, that makes me wonder even more, what specifically makes you want the 4.88 gears if your running the 315's Bowtie? I thought you were running 325's.

 

[retorq]

You do realize 315 and 325 is the WIDTH of the tire, right??