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Discussion Starter #1
Anyone have any idea what the RPM change would be in changing out a set of 3.55 to 3.90 i was told around 200 rpm I have a 18913a trany on 24.5 tall rubber thanks
 

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I curious WHY you would want to change it. My trans is a 14609B with a .73 OD. Ive got 3.58 rears on low 24.5s. I ADDED a splitter to make it a 13 speed which gives me a final OD of .63. Im pulling a grain trailer now at around 80K and in the fall they let us go to 88K. And yes there have been times its gotten up to 92K which is legal as long as you dont get caught. Ive been loading in the fields and running the highways with no trouble at all. If Im good and heavy Im in and out of that top OD more often since Ive only got 400hp to deal with. Since you have tall rubber we should be geared very close to the same.

Im one that likes to use ODs to keep the rpms down on the highway. I believe that is one reason I get half way decent mileage.
 

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Wish I could find someone to trade me some 3:55-3:70 gears for my 3:90. Right now it's 1500rpm at 65...wouldn't mind a 1350 at 65.
 

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Discussion Starter #6
The front rear just let go a bolt out of the ring gear must have come loose and broke 3 teeth off the pinnion gear.:fan I ended up replacing both rears i switched over to 3.90s. I had to turn the rear rear in for a core. The front was replaced with a new one from eaton but had to order the rear they had reman in stock so thats what i did. my caculations show i should have about a 175 rpm change i haul a bucket in upstate ny so any local work is at 102000 i hope the 3.90 will make it alittle easyer on the truck will see on monday:
 

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3.55's :rock
After I did the roadranger calculator thingamabob that's what I came up with.....22.5, 16918b, yada yada.

What I've got now works fine for construction season, but this time of the year it's more highway time and leg stretchin...

But I spose it's 'spensive and switching them is most likely far out of my area of expertise.
 

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After I did the roadranger calculator thingamabob that's what I came up with.....22.5, 16918b, yada yada.

What I've got now works fine for construction season, but this time of the year it's more highway time and leg stretchin...

But I spose it's 'spensive and switching them is most likely far out of my area of expertise.
Switchin em is easy and takes almost no tools. I know guys that change their gears back and forth once a year with new fluid for whatever hauling. Bout 4 hours for both and good time to check ujoints. :)
 

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Switchin em is easy and takes almost no tools. I know guys that change their gears back and forth once a year with new fluid for whatever hauling. Bout 4 hours for both and good time to check ujoints. :)
I'll bring it over to yer backyard this summer with a case of Keystone...:toytruck
 

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Discussion Starter #12
taking them in and out is a simple job the hardest part can be trying to get the nuts off the yokes they go back together much easier with the through shaft out of the housing
the 3.55 worked well just hard to get moving off pavment with permit loads
 

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After I did the roadranger calculator thingamabob that's what I came up with.....22.5, 16918b, yada yada.

What I've got now works fine for construction season, but this time of the year it's more highway time and leg stretchin...

But I spose it's 'spensive and switching them is most likely far out of my area of expertise.
If by chance you're running a 430hp C12 and a 13 RR in that Pete, 3.70's would be good gears. Get 6.4-6.6mpg out of our '99 T-8. Bullrack or hopper. Hangs with our ISX500 pretty good in TN and KY. :toytruck But, I gotta weight 15k or more than that '99 for it to keep up with me in my W9. ;)

But, if you really only pull that short bucket, 3.55's would be perfect. :D
 

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If by chance you're running a 430hp C12 and a 13 RR in that Pete, 3.70's would be good gears. Get 6.4-6.6mpg out of our '99 T-8. Bullrack or hopper. Hangs with our ISX500 pretty good in TN and KY. :toytruck But, I gotta weight 15k or more than that '99 for it to keep up with me in my W9. ;)

But, if you really only pull that short bucket, 3.55's would be perfect. :D
Nah...525hp N14. With the short bucket I can gross only 73,280 so I shouldn't have much problem pulling that with 3:55's. There's a lot more stop 'n go and what not in the summer on construction. During the winter it's either a long dump or hopper trailer on the highway more, so to knock down the rpm's a bit would be nice....13xx rpm at 65 or so would be good.
 

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Well I know Iowa is right next door to Wisconsin and Minnesota and every bar I see up there has an old Pabst Blue Ribbon sign outside.

If I may, I'd suggest some PBRs for the CAT Man. :happymugs:D
 
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