I need to know who has gears with bigger tires, and what gear and tire combo your running, i am thinking about buying a 4.56 setup, with 36's soon, and need to know if this is too low, thanks guys

I'm still on the fence about re-gearing or not. If/when I do re-gear it will be with a set of 4.56's.

Never thought of 4.56 but I was informed that anything 37 and up, you should throw in 4.10.

As for my truck, running stock (3.73) with 315's (35's).

LATER!

I have 35's on my truck with a 6 inch lift. I went to 4.10's (apparently, 4.11 & 4.10 are synonymous because I ordered the 4.11 gear set that AAM makes for GM and it says 4.11 on the box, but when you count teeth, its 4.10).

The reason I went to 4.10's is because after lifting and going to 35's, my final ratio was 3.29. The original ratio, as you know, was 3.73. Bumping up to 4.10's brought it back to about 3.62 final. The truck felt more like itself again.

Some people "chip up" to make up the difference, but I thought doing this would only mask the problem and I wanted to be able to get the most out of any performance adder rather than just bring it back to stock performance levels.

Going 4.56 with 36's and a 16 inch wheel will put your final at about 3.86. In fifth gear at 75MPH in stock trim, you would be pulling about 2188 RPMs. With the 36's and 4.56 gears, you will be pulling about 2266. If you went with 37's and the 4.56 you'd only be pulling about 2205 RPMs. Still a bit high, but not as bad. If you can give me the actual tire and wheel combo I can recompute it.

I'm still running 3.73 gears on 37's

37's with 3.73 here going on 23K miles now

Chisuzu, Can you show your math? How are you computing this? When I go to those sites that sell gears and rears, they have converters where you enter your tire and gear ratio, then offer an answer for what new ratio you should run. Others have lookup charts to get there. Either way, they say that a 35 - 36 inch tire should be running with 4.56 to 4.88's. Help us out here, please.

BB

I'll be right back. I got something for you guys.....

This was written a while back. "Ok, I did a few calculations and came up with this: My stock tire height was 30.0" and my present tires are 36.8" So 30.0 divided by 36.8 multiply by 3.73 gives me an effective ratio of 3.04. Damn, that is wayyyy to high!!

Now lets try this: The tires on now are 36.8" divided by the original size of 30.0" multiply by 3.73 would tell me that I need a ratio of 4.56. Wow, I did that myself??? And my math teacher failed me in math. Lol."

When I was getting ready to do the lift, I collected all the formulas and built an excel spreadsheet that shows stock ratio and RPM at a given MPH. Then I have all ratios from 3.73 to 4.88 to see what the ratio and RPM difference is.

That's why I said I could recompute if I had the proper tire and wheel size. I just assumed a 16 inch wheel.

Don't worry about regearing unless you plan on pulling heavy trailers.. I had 39's and it actually did a better mph in the quarter than with smaller ones.. On the other hand, pulling a heavy trailer would make the truck feel much weaker.. Kind of a Dr. Jeckel and Mr. Hyde type thing..

I agree, if you live in a place that is relatively flat and don't really tow anything. I would probably have left it alone too if I still lived in Florida. Up here in the mountains though it really does make difference and you can feel it. The tranny does more down shifting than it did when it was stock and all that is working the drivetrain harder.

I looked at it from the perspective that I could add more power to compensate, but what would it do to my tranny? I noticed significant power lost on long grade climbs and downshifting that didn't exist prior. It took a lot more pedal to get up to and stay at speed, etc.

These Allisons get pretty hot as it is, working them harder is only going to exacerbate the problem, so I decided to go ahead and regear. It may not be for everyone, but I think it was the correct decision for me.

ok my tires now are a set of 36x14.5x16 inch pj's, which are a pretty heavy tire. Also, i did loose power, and i live in wv, so there is a lot of mountains, but dont tow much. But when i added the edge, in level one i can pull a hill in od, and not come out of it, and i have it set on the corrected tire height, and it said that i pulled a 15.4@88 mph and a 0-60 time of 6.9 sec's, if i regear, will it hurt these times, or better them, and yes the temp goes up with bigger tires, i put the b&m super cooler with fan, that helped a lot, but i am going to a bigger pan also, or just a built tranny evenutally, thanks guys for all the help, i really dont know what to do.

I ran my other truck 35 on 18 in rims 4:56 Honestly I wasnt impressed 8.1/allison 2k for the everything.Gas mileage didnt change much either.The only major thing I notced is I could power break easier...Rpms came up a little quicker..didnt pull my trailer any faster up the hill,Throttle response was bettter but I was looking for pulling power...never felt like staock again

ok my tires now are a set of 36x14.5x16 inch pj's, which are a pretty heavy tire. Also, i did loose power, and i live in wv, so there is a lot of mountains, but dont tow much. But when i added the edge, in level one i can pull a hill in od, and not come out of it, and i have it set on the corrected tire height, and it said that i pulled a 15.4@88 mph and a 0-60 time of 6.9 sec's, if i regear, will it hurt these times, or better them, and yes the temp goes up with bigger tires, i put the b&m super cooler with fan, that helped a lot, but i am going to a bigger pan also, or just a built tranny evenutally, thanks guys for all the help, i really dont know what to do.
Its up to you. As I mentioned before, you can "chip up" to compensate or regear. I think if you regear you will see an improvement in power with your Edge. Like I said, I wanted the most from a power adder, not just to compensate for the lack of power my lift and tires made.

Regearing will definitely make it easier on your engine and tranny to get that rolling stock moving.

You need a chip even if you regear. Why? More rolling resistance and weight.

The 4.11 or 4.10 might have been because the front is 4.10 and the rear is 4.11. Did you count the rear gear or the front gear?

The fronts are usually a little taller so when in 4wd the front pulls just a tiny tiny bit. This keeps the front down when going up hills and keeps the front straight when on slippery surfaces. Nothing like a little front wheel drive when the going gets tough.

I ran my other truck 35 on 18 in rims 4:56 Honestly I wasnt impressed 8.1/allison 2k for the everything.Gas mileage didnt change much either.The only major thing I notced is I could power break easier...Rpms came up a little quicker..didnt pull my trailer any faster up the hill,Throttle response was bettter but I was looking for pulling power...never felt like staock again
Figuring a 325/65R18 (35x13.50R18) with a 4.56, in OD at 75MPH you would be pulling about 2358 RPMs versus 2188 stock. I can see how your mileage would suffer. Seems like a little too much gear. With a 4.10, you would have been pulling only about 2120 versus 2188 stock at the same speed, so your mileage should have been close to stock even with the heavier rolling stock.

so what did the 4.10's and 37's pull on rpm's at 70mph?

You need a chip even if you regear. Why? More rolling resistance and weight.

The 4.11 or 4.10 might have been because the front is 4.10 and the rear is 4.11. Did you count the rear gear or the front gear?

I've been running without one. I have a Predator, but I haven't loaded it yet. The truck still goes pretty good, but I have done the intake and exhaust and they did help.

Honestly, I can't remember if I counted both. I remember asking the rep I bought the gears from and he told me they're the same thing. He also said that AAM was the only company making the gears. Who knows?

so what did the 4.10's and 37's pull on rpm's at 70mph?Please bear in mind, these numbers are based on formulas and may vary slightly from real world application, but should be close enough to judge with.

That being said, a 37x13.50 tire with 4.10s should pull about 1850 RPM versus 2042 stock. A 4.56 would pull about 2058, so I would say the 4.56 for that tire, though it pulls more RPMs, would be a better match.
This is for 70MPH as requested.

thanks alot chisuzu, i am still thinking about it, who knows yet

I was thinking about re-gearing my truck as well I have a 2005 Duramax with 305-55-20 tires and I think mine runs a little high on the rpm's for what is being posted, I have a predator tuner and i have eliminated the cat, blocked the EGR, and Finger-Sticked the truck, I Love the way it performs on the 85 HP setting but I guess I am addicted cause I keep reading and searching for more power, can someone tell me if 4.10's are too much for my truck the tires according to the manufacturer's site are supposed to be 33.2' inches in diameter, what kind of RPM's would i be turning at 70 MPH ?? Thanks for any help...

I was thinking about re-gearing my truck as well I have a 2005 Duramax with 305-55-20 tires and I think mine runs a little high on the rpm's for what is being posted, I have a predator tuner and i have eliminated the cat, blocked the EGR, and Finger-Sticked the truck, I Love the way it performs on the 85 HP setting but I guess I am addicted cause I keep reading and searching for more power, can someone tell me if 4.10's are too much for my truck the tires according to the manufacturer's site are supposed to be 33.2' inches in diameter, what kind of RPM's would i be turning at 70 MPH ?? Thanks for any help...If you regeared to 4.10, you would be pushing the RPMs upward, not downward. With those tires, you dropped your final ratio from 3.73 to 3.43. RPMs stock at 75MPH would have been about 2188, with the new tire/wheel combo should be around 2010.

If you went to 4.10, your final would be 3.77. You would be pulling about 2210 RPMs at 75. That's about 22 more than stock or 200 more than you're doing now.

I would leave it alone.

I have 37x13.50 and I regeared to 4.56 and I noticed less pedal to get up to speed. RPM's are a little higher but it's easier on the drivetrain when I tow up long hills.

Just got rid of a 2001 Tahoe, 6" RCD lift, and 33's. Was pulling a 25' Toybox, and unable to hold 20 mph throught the mountains, to the desert. Loaded weight (too heavy for the Tahoe) was approx. 8,000 lbs. I had exhaust, and K&N. Spoke to the speed shop I deal with, and they initially recommended 4.11 gears, but, after double checking stock tire size, settled on 4.56's. Even though I sold the truck shortly after the gear change out (It just wasn't the right tow vehicle), the performance difference was unbelievable. Not a very technical answer, just real world stuff. I would do it again in an instant, no regrets. Hope this helps your decision...........