4.30 gears in 8" clamshell and e-locker diffs with 255s

anyone running 4.30 gears with 255/85/16 or 255/80/17? Curious what RPMs I would be seeing on at 65 with an automatic.

 

4.30's will be nearly impossible to find for the front. Only the 3rd gens were offered in this config so you'd need to be hunting wrecking yards for something new and smashed. Here is a calculator to get you squared away on the rpms...http://www.crawlpedia.com/rpm_gear_calculator.htm I'd guess that combo would be sweet in an auto with some extra weight though. Keep in mind actual tire height though (my 255/80 coopers were 32" tall when brand new mounted at 40 psi).

 

I thought Yukon offers 4.30

 

4.56 with 255/85/16 i am about 2300 or so at 70

 

They do for the rear for sure but I was sure no one makes them for the clamshell yet other than oem toyota... May have to look back into this.

 

Yukon makes a 4.30

 

Well thats badass.

 

The Yukon 4.30 gears for the front are brand spankin new. They were not available in April when I was looking (and boy did I look). I went with 4.56 gears but I run a 34" tire and could potentially see myself going slightly larger in the distant future. With that said, 4.56 gears were right for me. 4.30 is really a perfect ratio though. It's the right mix of mechanical advantage AND fuel economy. As long as you aren't running a gigantic tire and or carrying a lot of weight due to bumpers or whatever I'd highly recommend the 4.30 ratio. But if you plan to go larger than a 33" tire at some point you should consider 4.56 gears. Think about this from a long term strategy considering the price to do gears is VERY expensive.

 

@ItalynStylion, I'm afraid I'll be overgeared if I'm only running 33's. I tow and running 65mph in 4th for a few hours with 4.56 gears and 33's would suck.

I'm hoping the 4.30 with 255/85/16 will be slightly lower than the stock 3.73 with 265/75/16.

 

So with those two tires, you're looking at 33.1" vs 31.6" diameter. With the 4.30 gears and the 33.1" tire you'll be turning 2200rpm at 70MPH on the highway. Stock gears and the 31.6" tires you will be turning 1999rpm at 70MPH. So even with the larger tires, 4.30 is still a good mechanical advantage over stock gears and stock tires. Which is good, because those larger tires are harder to turn from a weight/rotating mass perspective. With the 33.1" tire, 4.56 gears, you'll be turning 2333rpm on the highway at 70mph. That's going to feel a lot stronger.

Now, I'm not sure I totally understand your first statement about towing with 33" tires and 4.56 gears. Why would you have to run in 4th? Now, if you think you'll need to shift to 4th regardless of the rear end ratio you pick, that's a different story. 4th is a 1.00 ratio gear (5th is 0.72) so the calculations for engine RPM look like this. With 33.1" tires at 70mph, 3240rpm for 4.56 gears and 3055rpm for 4.30 gears. Now, on the stock 31.6" tires and stock 3.73 gears, in 4th gear at 70mph you're turning 2776rpm.

If I were you, 4.30 would be my gear ratio for sure as long as the towing you do is somewhat infrequent. Good mechanical advantage when you tow but still good fuel economy for the rest of your miles (which I'd imagine are the majority of your miles).

Here are the two links I used to calculate everything. They are very helpful. http://www.csgnetwork.com/multirpmcalc.html

 

I tow 4 to 6 times a month during the summer with trips between 2 and 5 hours. Towing is D is a good way to cook a transmission...dropping it down to 4 locks the torque converter and reduces transmission temps.

 

Yes, that's true....sounds like 4.30 is your ratio. It will help with a lot of what you need.

How heavy is the load you tow? And do you have the transmission cooler?

 

The trailer is about 5,500lbs loaded and I have a transmission cooler. I'm also running sliders, skids, a bumper/winch, and will have my HC rear bumper installed in a couple months.

This is my DD and I don't anticipate going larger that 255s.

Did you install you gears yourself @ItalynStylion?

 

Wow, I didn't realize you were that weighed down already. I'm betting you have about 600-700lbs of extra weight you carry around daily. And with a trailer of that weight that's a LOT of work on the truck. Larger tires are going to make that pretty tough. Knowing that now, 4.56 or go home.

I didn't install mine. Had a great local shop called Baertrax do the work. I did lockers at the same time because the labor was the exact same and because ARB was offering a free compressor if you bought lockers.

 

Just a heads up ecgs is offering the 4.30 complete clamshell regear now

 

AT or man trans?

 

I have been waiting for this!

 

Now you have me second guessing my setup. I was going to go 4.56's with 285/70-17. I'll have plate bumpers and full skids shortly after on a DCLB. My driving environment would be a mix of city and highway (No tow) with changing elevations like rolling hills and mountain passes.

 

I emailed ecgs yesterday about it and they updated their site this morning. I'm glad they have this option now, I will be ordering my setup this week

 

I have on AT