Gearing question? Need Help

[evldsl]

I am going to order a 3500 diesel shortbed p/u in the near future. I need to know the next two answers to the questions. I haven't made a decision on the auto or standard yet. I will be adding horsepower mods and controlers.

#1. automatic with on the fly 4x4 and will put larger tires 305's ,what rear gearing 4. 10 or 3. 73 for best rpm range.

#2. standard 6 speed with on the floor manual 4x4 shift with 305 tires, what gearing 4. 10 or 3. 73 for best rpm range.

I will tow moderate weight trailer's part of the time. I may purchase a slide in in the future.

I will send the auto trans out for a build up so it will handle the engine mod's.

Thanks for the help,I guess the guy's who tow a lot would know the answers.

 

[SRadke]

With the increased power and realtively little towing I'd opt for the 3. 73's with the 6'er and be on the fence with the auto. You'll get many opinons on this but I always figure you're better off to be geared too high and use a lower gear than to need another gear you don't have.



-Scott

 

[Bertram65]

The 4. 10s with the auto work out to roughly the same final drive ratio as the 3. 73s with the 6 speed, those seem to be the ideal for each. With the auto the drop from OD to 3rd is a big one so if you are planning on putting on larger tires and towing the 4. 10s are the way to go to keep you in the power at highway speeds. There is very little difference in fuel mileage assuming the trans is the same on both, I can run 1900 RPMs for a tank or 2500 RPMs, the difference is less than 2MPG.

 

[evldsl]

no help out there?.

 

[BigEasy]

go with the 6er

I agree with Scott. 3. 73s and the 6pack. That's what I'm ordering from Tomeygun shortly... only because the 3. 54s are no longer available.



Like he said, it's better to have to shift down, than to not be able to shift up. The 6er is cheaper, more durable, and you can use a Jake/Pac brake too!

 

[BHolm]

Bertram65, You might be able to run 2500 rpm all day in a 305/555 and only lose 2 mpg but the 600 is different, plan on losing 4-5 mpg. I have run my '03 QC at a fairly steady 85 mph and done 18+ mpg, the '05 is in the 13-14 mpg range at that speed.



All of my trucks are stock autos with 3. 73s, the '03s pull heavy all the time, nothing more than rolling hills. I haven't found the need for deeper gears even grossing over 27k lbs in the mountains. If my wife wasn't usning the truck a lot I think I would go 3. 73s and the 6 speed. Adding an exhaust brake would be high on my list and the 6 speed makes that easier. I am very pleased with the 48re though. I'm not sure you can go wrong

 

[JHardwick]

I like my 6 speed and 4:10's. I don't really see that 3:73's would provide any fuel economy ... ... ... I tow heavy and don't need to go 100mph all the time though.



When your towing heavy, and running state or county routes, that extra gearing stresses everything a lot less. Now, on the freeway, I've caught myself trying to grab a gear that wasn't there, but I don't have to downshift coming to the next hill and again, I doubt I'm losing much fuel mileage.



Just my opinion based on my usage.

 

[SRadke]

..... but I don't have to downshift coming to the next hill... ...

High gears, tall tires, and a PMCR = no downshifting here Oo.



-Scott