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A few questions here dealing with a 92 five speed 354 rears 4x4.

1. With stock size tires what is your rpm @ 60 mph?

2. You guys with 410 gears and stock tires what is your rpm @ 60 mph?

Now you guys with 410's and 33 inch tires what are your rpm's @ 60mph

I am tryin to figure with my 33 inch tires and 354 rears in 4th gear am I about the same gearing as 410's in fifth and if I change back to stock height tires will it make that much difference pulling a fifth wheel.

Also with stock size tires you you feel the milage will differ much from my 33's.

I am lookin for real world exp and not conjecture. I know some of you guys tow for a liveing, what are your thoughts?

thanks guys

gomerpile

well if its any constalation you can get a good idea at this website www.grimmjeeper.com/gears.html

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Ya know I forgot all about that site. Yep that will help with the rpm. Now the question is the difference in pullin power. The reason for this is I am at least contemplating going to a larger fifthwheel. The question is if I go back to the original tires will it compensate for the extra weight, 3000lbs or a total of 10k dry weight, I will be pulling. This weight could go as high at 15k total. If my fourth gear is like fifth with 410's I probably gain nothing with a gearing change. To expensive anyway.

BearKiller

Tire size = 235-85-16

Ratio = 3:55

RPM at 65 MPH in fifth gear = app. 1600

RPM at 55 MPH in Fourth (direct) gear = app. 1600

c = pi x diameter, I think??

5280 feet in a mile.

I figured all this out, mathematically, many years ago, when I ditched a set of 3:08 gears and L-78-15 tires, in favor of 4:10 gears and 15-38.5-15 tires.

It worked out, both on paper, and in real practice, that the speedometer, and odometer, were dead-on after the swap, with no other alterations.

Mileage-wise, empty truck, no trailer, with either gear option, you will experience better fuel mileage with the taller tires; the kicker is that this increased mileage will not show on the odometer, as it will not allow for the extra distance the tires travel with each turn of the wheels.

In fact, it may show a drop in mileage, although you are getting more.

Does any of this make any sense??

Another point to consider is the weight of the tire/wheel combination that you are having to rotate.

I assume that your truck is single-rear-wheel, as I can't envision 33" tires not rubbing against each other on a DRW.

My thinking is that it would consume less of the trucks energy to keep a single 33" tire/wheel rolling, than it would to turn two 30" tire/wheels.

There is also the unsprung weight, which is a big power-eater, to factor in the equation.

Micaiahfied

i pull an 8,000# 5ver with my wife's 92 2wd auto 3.54... over the winter i swapped on some big 33x12.5 in plave of the stock approx 31.8 tires. didn't really make a bit of difference. i wouldn't bother switching back just cause of the extra weight. if you're gonna spend money upgrade your air (like HTT housing) so you can add a little more fuel to pull the extra weight.

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Yeah I really didn't want to change gearing just to get an idea as where my 4th gear was compaired to high gear in a 410 setup.

Hey ran into a bit of a problem this morning. I will post on the forum but since we are talkin drivetrain here.

I think my original clutch is done. I have 150k on it. Now the question. What does a job like that cost? I mean to have it done. To old for that now. Also is the best clutch and pressure plate setup the stock one or is there a better one priced reasonably?