gear ratios

Lostnwalmart

Lostnwalmart

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Jul 19, 2006
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so with a diesel what are you opinion on the rear end ratio would you want a lower gear like a 4.10 or a gear like a 3.31? and this would be on say a 650+ hp truck built for dd and the strip? 4k+ rpm in the gasser world they like higher ratios to help get more tourqe and faster launches but they have more rpm to play with (compared to a stock truck) just wondering
 
Lower numerical numbers generally work better. It gives the motor something to spool against. Remeber these truck work best with heavy loads (something to spool against).
 
For what it's worth i've been told you want your gearing to put you crossing the traps at your hp peak. I don't see why this would be any different for a diesel then a gas motor, just that a diesel obviously has a lower rpm window so you generally want the taller gear for diesel apps. I have 4.10s in my truck and would definitely like to have 3.53s!
 
Well I have always believed that a numericall lower gear would help alot on MOST diesels when it comes to drag racing. All that torque is worth less unless you are using it to pull the gear. I think it is even more true with a manual trans. Gears are just torque multipliers. Make more torque and you need to multiply it less. Stretch those gears out and make that turbo cry and make all that torque work for you.
 
I agree that taller gears ( lower numerical #s) are better for any turbo charged application especially manual, like I have. The Turbo wants to be loaded to make boost. Hi strung N/A motors like short gears to stay at peak HP, but turbos need to stay loaded.

I have a 3.42 in my Dana 80 and would love to lower it even more. But 600.00 for a 3.31 is not worth the outlay.

Is anyone making 3.07's for Dana 80? I have searched and found them only for Dana 70 rearends. I checked U.S. Gear, Yukon, Richmond and the tallest gear I found was a genuine 3.31 Dana.
 
but say you had a built motor that could run 5k rpm and make power up high like that would the lower gears numerical still be keen or would you want a higher number to get you moving faster?
 
I'd still stay clear of 4.10 even with RPM. You're going to want to put the torgue down. Also remember unless you're running a powerglide everytime it shifts you're going to loose E.T.

Keep it at the minimum amount of shifts without running out the usable power.
 
ok that question was just running around in my head i knew the lower gears loaded the truck better but the higher gears would accelerate better just wondered if there was maybe a happy medium =D
 
Use the calculator and gear accordingly. 643 rwhp = 114 mph with a 6400 raceweight. A 3.33 gear with .69 ratio OD and 32" tire puts you through traps at 2750 which is probably a good hp peak for most common cummins builds.

I used comp d and richmond calculators to obtain these numbers. Adjust them as they suit your particular combination.
 
SlowCummin said:
I agree that taller gears ( lower numerical #s) are better for any turbo charged application especially manual, like I have. The Turbo wants to be loaded to make boost. Hi strung N/A motors like short gears to stay at peak HP, but turbos need to stay loaded.

I have a 3.42 in my Dana 80 and would love to lower it even more. But 600.00 for a 3.31 is not worth the outlay.

Is anyone making 3.07's for Dana 80? I have searched and found them only for Dana 70 rearends. I checked U.S. Gear, Yukon, Richmond and the tallest gear I found was a genuine 3.31 Dana.
Click to expand...


Where did you find 3.07's for a D70?? The lowest I have found is 3.54...which is what I currently have.
 
3.07's were in dana 71's and 61's. Different carrier offset. I dont think you can put 3.07's in a standard d70
 
Well not that i have a ton of power, but i am going to try the 275 gear i have and see what happens. I hope the converter does not hate me too bad.
 
it seems like 3.55's and 35" tires is probably close to making peak power at the traps! i shift into OD at around 60ft before the 1/4 and run .2 lower than stayin in drive! manual trans mind you!
 
9in2.jpg
 
:hehe:Is that a jacked up Camero in the back ground:rockwoot:That is :woohoo:awesome:umno:


HAHAHA:bow:


Farken :tree: D by JQMile on that one
 
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