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Larger Tires?

2006 Dodge 3500 diesel (unlike the gas engine, the power band tapers off rapidly as the rpms go up) with a 4.10 rear axle. I should have got a 3.73. I could go to a salvage yard and try and find the gearing I want or get a whole new axle and change it out, but that is beyond my mechanical ability- also could be very expensive. Short of that though, since I do need to get new tires soon, if I buy a set with a larger diameter but same width, will I reduce the engine rpms at a steady speed of 65 mph? It has LT235/80 R17’s on it now. Will it improve my fuel efficiency?

Thanbks in advance

Of course. You would want to, still, use 80 series tires. Are there any larger diameter 80 series tires available? Have you calculated the difference a larger diameter tire would make in the final drive ratio?

AFAIK, larger tires will confuse your speedometer. The reason for this is that your vehicle is used to a certain circumference. Say it’s 36", and you’re increasing the circumference to 40". Your car will think it’s going 36"/revolution, when it is in reality going 40".

You have contradictory goals here.

On the one side, using larger diameter tires is going to reduce your power to the ground. And on the other side it is going to improve your fuel efficiancy.

You can’t get one without sacrificing the other.

I think you are trying to do it the hard way.  Yea hard because what you are going to do will not likely do any measurable improvement and you will end up with less than desirable tyres and still no improvement in the power end.

In regards to the axel swap,not so great technically,some issues dealing with heavy pieces,check out the expense maybe not so bad.Do make a comparison about just changing just the gears (this will be a pro job)you won’t get to where you want to be with the tire swap idea.

Get some firm figures together and then decide.Your engine should pull the 3.73’s with no problem the 4.10’s are overkill (what I am talking about is, your off the line performance should still be adaquate).

Where does he say he is trying to increase power to the ground?

Keep in mind that if this truck is a 4x4, you’ll have to change the front gear ratio as well. That spells big bucks.

You are correct,the OP did not post a 4X4 description.

I think larger tires would do what you want, however it would reduce your power, do you have power to spare? Also it would throw your speedometer off some. If it is automatic, it might confuse the shifting points, I don’t know.

I hope it is not a duelly, that means 4 tires.

Just take it in and have it re-geared and have someone reprogram the ECM to correct your speedometer and transmission shiftpoints.

You can change tire sizes, but it’d have to be a pretty dramatic change to bump your engine RPM down to a satisfactory point.

Did you order a 4.10 specially for this thing, or was it part of a package? I can’t imagine it being standard issue with the diesel.

If it is a 4X4, which you never said it was, you would need to replace the front tires also.

You are right.

According to Cars .com research link, his 3500 series comes with the 3.73 and the 4.10 is an option.

Joe, why would the tires be “less than desirable”? Do you mean that they would be taller and less stable?