Yes, that's correct, about 2100 at 75.

Gerry

 

the increase in truck height is exactly equal to the increase in tire radius. And we already know the radius of each tire from the previous exercise:

radius of the big tire = 17.2"
radius of the little tire = 15.8"

so the increase in height is 17.2 - 15.8 = 1.4"

Nope, it's not. 1.4 is your increase in tire height. Tires are round, and the axle is in the center line. If one tire is 1.4 taller than the short tire, half of that tire is above the centerline and does nothing for overall truck height. The other half is below the centerline, and that's where the overall height is changed, which is .7"

 

The radius is half the diameter. If the radius increases an inch and a half, the diameter increases 3 inches.

The truck will rise almost an inch and a half. RTFQ & RTFA.

 

Exactly ;D

 

[quote author=Doug link=board=20;threadid=17922;start=30#msg169930 date=1060355317]
yea, the 6 speed is wonderful. and I agree that for running empty, the 3.54 gears are very nice, and allow you to run low rpms. Except that in your case, somebody must have slipped in a different gear in there for you or your tach is a couple hundred rpm off. 6-speeds run about ~1850 at that speed with the tire size you have.
[/quote]

I was just guessing the rpm at 65 mph was about 1600. I really couldn't remember for sure. Today I checked and it appears to be about 1750....like you said. And I actually have (to the best of my knowledge) 3.55's..at least that's what the window sticker says. ;D

 

[quote author=erics76 link=board=20;threadid=17922;start=60#msg170179 date=1060383714]

the increase in truck height is exactly equal to the increase in tire radius. And we already know the radius of each tire from the previous exercise:

radius of the big tire = 17.2"
radius of the little tire = 15.8"

so the increase in height is 17.2 - 15.8 = 1.4"

Nope, it's not. 1.4 is your increase in tire height. Tires are round, and the axle is in the center line. If one tire is 1.4 taller than the short tire, half of that tire is above the centerline and does nothing for overall truck height. The other half is below the centerline, and that's where the overall height is changed, which is .7"

[/quote]
uh. re-read my post again. 1.4" is the tire radius, not the diameter, and the increase in vehicle height is indeed 1.4". ;D

 

Something doesn't sound right me here....my HO with a 6 speed and 3.73's runs right at 2100 rpm @ 70 mph on a flat grade, shouldn't this be the rpm for a 4.10 rear truck???

 

2100 is about right for a 6 speed with 265/70-17 and 3.73s, depending on what tire is actually on there. the theoretical rpm using BFGs data for that size tires is 2079.

the same source of data (BFG) predicts that the 4.10 6-speeds will run at 2286 and the autos at 2160.

 

[quote author=turbov6joe link=board=20;threadid=17922;start=60#msg179501 date=1062504015]
Something doesn't sound right me here....my HO with a 6 speed and 3.73's runs right at 2100 rpm @ 70 mph on a flat grade, shouldn't this be the rpm for a 4.10 rear truck???
[/quote]My truck runs ~2300 rpm @70 mph.

 

Trying to do some research on 3.73 vs 4.10 gear ratio...

Ran across a question about where to find what gear ratio one has and the person called DC to find out.

I found the sticker that listed mine by accident...it's pasted in the glove compartment or whatever you choose to call it.

Now, if one is pulling 14,000 pounds, which is the best gear? I know that 4.10 will cost more gas mileage unloaded, but the 3.73 will not pull that weight will it? At least it won't according to Dodge...

I was told I had a 4.10 and found out I had a 3.73. It is a HO Turbo Diesel but according to the Dodge website, it is not rated to pull but 13,950. The 14,000 pound I questioned above is a 'guessimate.' The fiver, fully loaded, has a capacity of 14,660. Since we want to fulltime, I want to be comfortable that we're not going to be overweight.

Soooo...I'm bugging dealership to make it right. Am I being overcautious? I don't want to be one of those RVers who pull overweight just because the truck will pull it....

Thanks!

 

[quote author=BIGCUMMINZ link=board=20;threadid=17922;start=60#msg199057 date=1066696148]just put 315's on ....
[/quote]geeez, I said that in the 4th post 2.5 months ago.

Hey Dodge HO 03, if you're gonna leave it stock, get the 4.10's; you'll love'em. & you won't have much, if any fuel mileage penalty.

 

I've had both sets of gears in various trucks....with the new 03 and beyond I dont think the higher rpm is a big deal...I had 4:10 in an old 12 valve and at 70 mph was around 2300 rpm which was very noisy in that truck..mileage was still respecatable though...i would suggest that if your present rear end is not causing any problems or making noises..to consider going to a taller tire..get more clearance and drop your ratio at the same time..then if you dont like it..its simple to change back..

 

[quote author=DodgeHO03 link=board=20;threadid=17922;start=60#msg199049 date=1066695374]
I was told I had a 4.10 and found out I had a
[/quote]


Did you guys miss that he has 3.73's, I really don't think he wants taller tires on it. Guess you could put shorter tires on to make your 3.73's like 4.10's

But any way I think your truck will pull it fine with the 3.73's. What you migh notice is that you are going to be down shifting for hills that you wouldn't be with the 4.10's. But on the up side you can run faster in direct gear than you can with 4.10's. Meaning that on a steep hill you can down shift at say 60 instead of at 55 like you would have to with 4.10's.

I would just try it first and see how it goes for you, swaping gears gets to be expensive in a 4X4. If you have an automatic the 4.10's are of more benifit.

 

The truck is an automatic - 48RE. Dealership Operations Mgr told me today that the truck can really pull more than Dodge says--they rate it low to play CYA.

They obviously don't want to admit that their salesman goofed. But then I guess we goofed by not getting it in writing--just didn't think we needed to because we made it very clear that we wanted to pull a heavy fiver and that we wanted a 4.10 to do the job!

Now, I wonder if the Ops Mgr would be willing to sign a statement to the fact that pulling heavy is OK...ya' know...to use in case of a breakdown???