What speed?

[Big_Daddy_T]

Im doin some figurin and need some input. I need to know when the six speed hits the rev limiter in 1st gear and second gear. did a quick search with no good hits.

 

[bighammer]

Well, if you figure 3000 RPM into 1st gear (5. 63:1) you get 532. 86 driveshaft RPM. Put that into the rear axle (3. 73:1) you get 142. 86 wheel RPM.



Assuming a 31. 4" dia, (couldn't find revs/mi number for a 265/70x17) it should be 98. 65" circumference. (pi * dia)



A mile is 5280' or 63360" so that tire should be turning 642. 27 revs/mi. (divide 63360 by 98. 65)



142. 86/min = 8571. 6/hr divided by 642. 27 = 13. 36 MPH





OK, somebody go out and check my math

 

[Summit]

dont know about 1st, but 2nd is 24. 5 mph governed out 03 3. 73

 

[Big_Daddy_T]

Ok guys I did alot of assuming and speculation and I think I figured out why the almighty cummins lost in the pickup truck article on the 15% grade. I do not believe any of the trucks made it out of second and into third. If you have two trucks with 3. 73s and one with 410s and you run em up the hill in second you got a big fat loser. The dodge never broke 20 mph.

I read that one of the drivers missed a shift. who misses a first to second shift. No one. So im figuring he went for third and wiped it. The truck lost forward momentum and scared the poo outta everyone involved. My thinking is the truck with the 410s is way more likely to entice a driver to shoot for 3rd than a truck with 373s. Especially a known good hill performer. Since the torque comes on earlier than the competition you got a chance of making it into third. Well if someone missed and it turned into an extremely dangerous condition. The other drivers are alot less likely to make the same attempt. All speculation. But a solid line of thought.

 

[Elite1]

Originally posted by Big_Daddy_T

Ok guys I did alot of assuming and speculation and I think I figured out why the almighty cummins lost in the pickup truck article on the 15% grade. I do not believe any of the trucks made it out of second and into third. If you have two trucks with 3. 73s and one with 410s and you run em up the hill in second you got a big fat loser. The dodge never broke 20 mph.

I read that one of the drivers missed a shift. who misses a first to second shift. No one. So im figuring he went for third and wiped it. The truck lost forward momentum and scared the poo outta everyone involved. My thinking is the truck with the 410s is way more likely to entice a driver to shoot for 3rd than a truck with 373s. Especially a known good hill performer. Since the torque comes on earlier than the competition you got a chance of making it into third. Well if someone missed and it turned into an extremely dangerous condition. The other drivers are alot less likely to make the same attempt. All speculation. But a solid line of thought.

Big daddy, I was looking at that competition as well... . I thought it was unfair for many reasons. They weren't comparing apples to apples... . They ran 2 fords, 2 chevys, and only 1 Dodge... the Dodge was a dually with a 410 gears, while all 4 of the other trucks had 373's..... Both fords and 1 chevy were single rear wheels... which makes them a little faster. One thing I found interesting was the ford & chevy autos were faster than the sticks, another thing was the weight difference, the Dodge was quite a bit heavier, not sure why... heavier duty body/frame? hmmm... .

 

[Summit]

bighammer

how much coffee did that take this morning????

i drank the whole pot and you still lost me

my numbers are from my speedo.

big daddy if i remember to check tomorrow ill let ya know.

 

[bmoeller]

Originally posted by Big_Daddy_T

Im doin some figurin and need some input. I need to know when the six speed hits the rev limiter in 1st gear and second gear. did a quick search with no good hits.

These should help-



http://dodgeram.org/tech/specs/axle/rpm_vs_mph.htm



http://www.f-body.org/gears/

 

[bighammer]

Right on the money. (had to check it out It just didn't sound right to me)







BTW Summit, 'bout a cup and a half

 

[Big_Daddy_T]

20-21 mph is when it defuels. So I think Im right on the money. The torque drop off is pretty mean after 2700 isnt it. 20 mph is like 3100 rpm. So the higher revving trucks with lower gears would have a distinct advantage in the steep hill climb.



Did anyone else notice that they mentioned they stalled a vehicle. And started it from a dead stop. Im willing to bet it was the cummins and a 2nd to 3rd missed shift. Could we write them and ask?

 

[Elite1]

With a 373 rearend and the six speed manual, HO motor, what do you think the optimum RPM's are for fuel mileage, flat ground?

 

[91W350]

I do not know about rpm, but mine does best between 55 and 60, not long after the torque converter locks up. I love the 20 plus mileage there, but it bores me to death to drive that slow. So I settle for a little over 17 at 73 mph. Mine is an 4X4 auto with 3. 73 axles.