I know this should probably go under transmissions or something but its already posted ha. When I raise my truck to 9 inches and put 38 inch tires on it, what size new gears do i need. My truck is a 2005 4x4 screw if you didnt know. And what company do you recomend: Genuine Gears, Auburn Gear, Precision Gear or what?

 

with 38" i recomend 4.88, i have done alot of ring and pinions, on lots of diffrent vehicles and the best gears IMO are the Precision Gears, the wormanship is outstanding, at the time i put my 4.88 in my F-150 only genuin gear was making them, they are a good gear i have had them and installed them in a few vehicles and they have done great, good luck

 

But you still recommend the Precision over Genuine? And thanks for the help!

 

What was the OEM gear and tire size?

 

What else is there besides price and size? Like what im using it for?

 

I'm asking...Did the truck come with 3.55 gears or 3.73 gears? Did it ORIGINALLY have 265/75/16s or 265/70/17s. If you give me these two peices of info, I can show you a quick equation that will show you what gear ratio to pick for you 38s.

Sidewinder

 

Uhm im guessing 3.73, haha sorry bout my last post that was supposed to go under a different Thread of mine under tires and i guess i got here on accident.

 

OK..lets shoot from the hip.

Let's say your truck has 265/75/16s and has 3.55 gears.

Your tire diameter is derived from its width, aspect ratio, and wheel size.
First, the width, 265mm=10.43"
The aspect ratio for this tire is 75. This means the sidewall height is 75% of the width. So, EACH sidewall is 10.43 x .75 = 7.82"

The diameter of the tire is (7.82" x 2) + 16(the wheel diameter) = 31.64"

The ratio increase of your old-to-new tire diameter is 38 divided by 31.64 = 1.20

Now, if the original equipment gearing was (is) 3.55, muliply this gear by the tire size increase ratio to get the new desired gear size.

3.55 x 1.2 = 4.26

Since there is no such ratio as 4.26:1, ALWAYS round UP to the next available ratio. For our trucks, I think it would be 4.56:1.

It is important to note that this ratio would bring THIS combination back close to stock. BigTruck311 may have had a different set-up to begin with or chose to go higher in ratio than the stock gearing.....It's all good.

The equations I just showed gives the MINIMUN ratio to bring your back to stock torque to the ground.

I hope I haven't confused anyone...It's been a long day!

Sidewinder

 

Thanks sidewinder, verry confusing but i think i got it! But jsut in case, which gears would you suggest?

 

4.56's will work just fine, but since you are putting bigger, HEAVIER tires, the higher ratio will give you better performance. Get the 4.88's

 

I agree with Bigtruck and Johngs. I would go with the 4.88s due to two things.

1. As johngs said, the new wheels and tires will be MUCH heavier than the stock set-up.
2. I wish sometimes that my truck had 4.11s in it NOW with stock tires.

Have a great holiday season guys!

Sidewinder

 

4.10's would have put my truck back to pretty close to stock with the 3.55's but i hated the way my truck drove stock so i went with 4.56's. i don't regret the decision one bit.

4.88 should be perfect for 38" tires. i might even consider going to the next step up just for the fun of it. if you're going up to 38" tires i don't think you're extremely concerned with economy and conservative driving.

i know that with the 8.8 diff you need to get a different carrier to go with anything bigger than 4.56 due to the thickness of the ring gear. i actually had to grind a little off a few of the teeth on the new ring gear to get the centre pin to work. i'm not really sure if you need to do this on the 9.75 rear end.

 

yes i do