So i'm tossing around the idea of swapping out my gears when I go up to 35's. I currently run 4.10's with 285/70/17's (32.8" diameter). I feel like they are ok, but with the weight of these trucks, and the overdrive on these auto trans, I think I could have easily gone deeper for better low end without any real downside at highway miles. Maybe like a 4.27 or so (which no one makes for the 9.25), or even 4.56 would probably have been doable in my opinion.

So, now that i'm moving up to 35's, everyone is quick to say 4.56. But, my experience with the 4.10's tells me that 4.88 would probably be a better choice to bolster my low end a little more (escpecially with the added weight of the 35's), and probably wouldn't impact the top end that much.

Here's the numbers I got using a good online rpm calculator:
---4.10's with 32.8" tire at 65 mph: RPM = 1911 (this is my current set-up, aka my baseline)
---4.10's with 35" tire at 65 mph: RPM = 1791 (difference of -120 rpm over baseline)
---4.56's with 35" tire at 65 mph: RPM = 1992 (difference of 81 rpm over baseline)
---4.88's with 35" tire at 65 mph: RPM = 2132 (difference of 221 rpm over baseline)

So, based on these results, it seems that 4.56 would put me back to about what I have today from a top end standpoint. I think the low end would be ok, but could probably be better (probably be about like what I have today). So this makes me think that the obvious choice for performance would be the 4.88's. But.......

Here is my concern. I like to plan ahead, so i'm worried about what might happen if I decide I don't like the 35's anymore, and want to go back to 285's. I would be stuck with this:
---4.88's with 32.8" tire at 65 mph: RPM = 2275 (difference of 364 rpm over baseline)
But if I went with 4.56, and had to go back for some reason, i'd be at this instead:
---4.56's with 32.8" tire at 65 mph: RPM = 2125 (difference of 214 rpm over baseline)

So this would seem to indicate that 4.56 would be the best choice in this scenario. It would work ok with the 35's (not the best, probably pretty much like what I have today), but would still be pretty good on the low end and acceptable on the top end in the event that I needed to go back to 285's. I think the 4.88's would be to much run with the 285's in this scenario, but not sure. Is 364 rpm that big of a deal? Low end would kick *** though.

Of course, the last option is to do nothing, and just run the 35's with my current 4.10's. Not my favorite option, but definetly the cheapest.

So, just looking for some opinions from folks that have tried these combos.
Thanks.

 

Holly hell dude with the 35s i have on with the stock gear (what ever that is) i hit around 1700 doing 65 .. i say try it with the gears you have then take it from there , hell if i listen to what people said on this forum1. i be broke 2. be pissed .. hell i droped the 3" pipe and flowmaster and went back to stock got my low end back ..I love my 35s they grab like hell i will be going with a wider rim maybe 9" wide. but thats after i finish my dewalt collection..lol... good luck dude but it all comes down to you and what you want and what you do with your road queen..lol...

 

I definatly plan to run them with my current gears first to see if I can live with it. Just looking for some opinion is all. Funny you should say that, but i'm thinking about downsizing from the cat out too (currently is 3" all the way).

 

but you will be happy down sizing the pipe .. what a difference

 

I ran 4:56 in my older ford with 35" BFG M/T it was fantastic! 'till the truck was stolen [sm=smiley19.gif][sm=smiley19.gif]
4:88 will give you a bit more low end and better acceleration but I think the RPM is getting up there a bit much.
I say get if you do a fair bit of highway driving get the 4:56. If mostly city driving and foolin around off road go for 4:88. If you really are torn between the 2 get the 4:88.

 

im runnin 35's with my 4.10's. i like em just fine, lemme know when u change ill be curious to see.

 

go with 4.56
i have 4.56 in mine with 38"s - 15.5" wide - very heavy tire


i am going to run 4.88's when i get around to ordering them
u will be happy with 4.56 with 35's
without affecting your gas-milage TOO much

 

Silver,

I think you'll hate the 35's with the 4.11 gears. It'll be like going to back to stock 3.55 with your current tires. I think you'll want to go bigger ratio.

On Monday I'm getting the stock 3.55's replaced with 4.11 yukons running a 265x70x16 which I believe is 31.6". According to the RichmondRPM calculator at drivetraindirect.com I'm currently going 1693RPMs at 65MPH. The new gears will run me 1960RPMs at 65MPH. I just filled the tank 30 min ago (drovethe 3 min straighthome)and willwrite down the mileage just before the gears get swapped thenrefill right after they put the gears inand notethegallons used.After that, I'll drive the same number of miles and refill again to note the differences in gallons and what my mileage is. It'll give you a rough estimate of what the gear swap (~270rpms difference) does to the mileage.It's not exact mind you, butI think sometimes real world situations prove the best litmus test of all. I don't have any unusualtrips in my near future, so it'll be roughly the same as an average two week span for me. I won't be able to lay into it with the new gears until they're broken in anyway, so I won't have to worry about the new lead foot.

 

I have 4.56s. I run 35s in summer and 33s in winter. It seems to be a good match I think. I was debating between 4.10 and 4.56 before I got mine and am glad I went with 4.56. The only reason I'd say 4.88 is if you ever think you might go bigger than 35s.

 

4.56's
Gain in lower end and still decent mileage. I ran 35's for two years with 3.55's. Cried over my power range the whole time. Around town it was OK, But on the highway it sucked.Then again you are running 4.10's so it shouldn't be too bad. When running 33's with 3.55's it was OK. The 35's killed mine with 3.55.
At 70MPH most of the timeI hada choice of letting the O/D kick in and have no power to pick up without kicking it out or leave it off and run 3000RPM's to be able to get off ofmy ownway. The O/D button on the dash was my pick up speed button, or I just left it off for the normal "I'm on my way to work get the he!! out of my way" driving.
Put the 4.56's in and it was like a shift kit and motor rebuild all at once. Awesome to drive again. RPM's in a usable range again.Wanted to install a posi and while I was in there do it all.
Since you have 4.10's which are in the middle, you might want to see how it runs before putting a grand in it. The front carrier will need to get switched out for the higher gear, Two gear sets, Two install kits, Labor.
If money isn't a concern, switch them.