New Gears? - 04 Ram 1500 4x4

I'm still working the problems from my last post reguarding the cruise, front end alignment and vibrations. I'm getting ther, but need advice on new
gear ratios. I went from stock 245/70 17s to 35x12.5 17s. This threw the computer way off in the truck and the dealer has been trying to aviod helping me out. The cruise issue apparantly can't be fixed with out new gears.They set the cruise to work up to 61 MPH. Whay this number I have no idea, I don't think the know - because no one can explain it to me.
Anyway, I was planning on installing 4.10 gears to help with big tires and towing, but now I'm being told that shorter gears may be better? It seems my only options are 4.10 and 4.56 - with aftermarket gears for this truck. Whic one will help me most..I pull a 3k # trailer on ocassion and would like to run at ~70-75 MPH with it.
Thanks
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HomeBrewer wrote:

That doesn't make sense. I set mine at 80 mph. I think your dealer is confused.

I would go with 4.56. That should put you into the power band while towing.
--
.boB
Arrived: 2006 FXDI, Red.
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On Thu, 27 Jul 2006 17:33:50 -0600, ".boB"
Lets put it this way, a 4.56 with 35's is not much better than a 3.73 with 30's and a 4.10 would be equal to about a 3.42 to 3.55 with stock tires. What does this mean? You want at least a 4.56 here especailly if you want to tow anything (there is more than just effective gear ratio here as extra lift and tire ad more drag too) A 4.88 would be better as it would about equal 4.10's with stock tires which is not deep at all (though some think it is) in a 4x4 truck with OD. Also, 4.88 gears are made for your axles by Yukon and you want to use Yukon or Precision gears here. ----------------- The SnoMan www.thesnoman.com
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I've searched and call about 10 vendors and no one has anything beyond the 4.56 gears. You have a source for 4.88's?
wrote:

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Not when used in a Dodge. There's a listing for 4.88's in a GM 9.25", but that's not going to help you.
4.56 is the best you're going to do, and it'll be fine. You'll have almost the same final drive ratio as you had with your 3.92's and stock tires (just a hair shorter, which means you'll be turning about 50 more RPMs at 65MPH with the 4.56/35" combo compared to the 3.92/30.5" combo)
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On Sat, 29 Jul 2006 01:50:27 GMT, "Tom Lawrence"

First a 1500 likely does not have a 9.25 front axle but even if it does, "Tom" should know the a 9.25 AAM front axle made for dodge uses the exact same ring and pinion as the GM 9.25IFS. (this was done to limit production costs for axle) so you can use GM gears in it. There are not two different sets or styles of 9.25 gears made as it would not be cost productive at all. Just like Dodge started using the AAM 11.5 in rear of some trucks that uses same ring and pinion as GM app. No different than D44's or D60's used in Fords, dodges or GM's, there are the same unless they are reverse rotation. ALso the D50 used by Ford in some apps uses D44 gears.
One more thing, while you comparison is close with gears, you leave out that truck does not work in a vacum on steel wheels and it will not give 3.92 like perfomance with 4.56's because of increased rolling resistance and drag from big tires and lifted truck. The RPM may match but performance will not yet so many like yourself seem stuck on the RPM thing as being the solution. If he wants 3.92 with stock tire like performance he needs at least a 4.88 becaice of extra drag that most ignore. with 4.56's it will feel like maybe a 3.73 at most performance wise and hurt towing at serious weight. ----------------- The SnoMan www.thesnoman.com
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Where did I say 'front'?

"Snoman" should know that in the 1500's, Dodge uses an 8" IFS differential up front, which ALSO only shows up to a 4.56 R&P.

Tell ya what, genius... why don't you post a source (and part numbers) for these mythical 4.88 gears you keep speaking of, and the rest of us will shut up.
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My truck uses the AAM 8" IFS and the 9.25 rear. There are NO 4.88s that will fit in the front. Also I have 3.55 gears now, and had 245/70s from the factory. That set up pulled my trailer just fine. I think with the added drag of 35's the 4.56 gears should be the ticket.
Now I am scared that the dealer can't program my computer to get the cruise and speedo correct after I change the gears. I have been there 3x since adding the tires and the cruise only works up to 61MPH and the speedo is off by 4 MPH once I get up to about 65. I assume this is due to the tire specs being slightly off and stating they rotate 598 times per mile.

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On Sat, 29 Jul 2006 20:16:46 GMT, "Tom Lawrence"

Guess again clueless. AAM does not make a 8.0 IFS axle. They make a 8.25 one that dodge uses too (they make a cast iron pig and alum pig version) Again dribble from you. The blind leading the blind. Dodge may call it a 8.0 but it is a 8.25 and uses the same gears as a GM 8.25 to keep costs down.

YG GM8.25-488R (same reverse roatation gearset as GM uses. You really are clueless aren't you? In the link below you will see it and AAM make a max of 4.78 themselves but Yukon makes them to 5.13. (AAM also makes a 7.25, and a 9.25 version)
http://www.aam.com/technology/tech_prod_dl_frontaxle825.html

----------------- The SnoMan www.thesnoman.com
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Amazing. So, the four service manuals I have, that ALL show the ring gear to be 8.0" in diameter, are wrong? Or are you saying GMs 8.25 uses an 8.0" ring gear? Strange that all their other differentials are named for the exact dimension of the ring gear, isn't it?
Let's see.... here's the Dodge specs (copied straight from the 2003 FSM):
http://home.earthlink.net/~tlawren349/diff_specs.JPG
And here's the ring gear spec. for the GM 8.25 (whaddaya know - they say it's 8.25"): http://www.differentials.com/pdfs/27.pdf
Now - you tell me how 8.0" = 8.25"
I know, I know.... the Dodge manual is wrong. It's really an 8.25" gear - they just felt like printing 8.0" for the last four years, just to confuse people. You've actually held one of these in your hand, and personally verified it to be 8.25", right?
Let's also remember that HomeBrewer called several different vendors and shops, and they all told him the same story: only 4.56 available for his axles. I guess they were all "clueless" too, huh?
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