axle ratio
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Senior User
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axle ratio
If I'm missing something, please correct me. The only reason for towing with a 4.10 instead of a 3.55 (13K w/E4OD in OD/4.10= 2.91
= about 2350 at 70) is the lack of transmission gears to get moving & up to speed in the first place. Thanks, Bob:-)
= about 2350 at 70) is the lack of transmission gears to get moving & up to speed in the first place. Thanks, Bob:-)
Cargo Master
Joined: Mar 2001
Posts: 2,759
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From: Elk River, MN
axle ratio
Higher numerical ratio keeps your engine RPM's up where the power and torque are located so when you go up a grade, there is power to keep up your speed. Most people only tow in direct drive, but with an E4OD refer to the owners manual or try it both OD and OD lockout to see which works best for your load. I use OD for flat and downhill but use lock out for grades and downhill.
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axle ratio
My point was that I can tow nicely at 70 in OD at about 2350 which in OD is I believe equal to a 2.91 rear end. Therefore if I can tow at 70 with a 2.91 ratio, towing at 60 with a 3.55 at 2365 should be no problem. The problem is that no one makes a medium duty 6 or 7 speed
close ratio upper, with a low 1st, to get the load moving. Allison is starting to make auto's for the job, but I want manual. Bob
1990 E350 Cabriolet
460, E4OD, 4.10, 30.4" Diameter tires.
close ratio upper, with a low 1st, to get the load moving. Allison is starting to make auto's for the job, but I want manual. Bob
1990 E350 Cabriolet
460, E4OD, 4.10, 30.4" Diameter tires.
Sit. Stay.
Joined: Oct 2001
Posts: 18,308
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From: Washington State
axle ratio
>My point was that I can tow nicely at 70 in OD at about 2350
>which in OD is I believe equal to a 2.91 rear end. Therefore
>if I can tow at 70 with a 2.91 ratio, towing at 60 with a
>3.55 at 2365 should be no problem.
WHAT?!??! 2.91 rear-end?!?! Your rear-end gears don't change based on your gear position!
What is it that you are trying to accomplish with this excercise?
What is your truck rated to tow with the 460 & the 4.10's?
Going to 3.55's will really skew that figure! It'll lower it!
As stated before, your rear-end gears keep the engine within a certain RPM range to enable you to USE the available TQ properly and efficiently.
Go to[link:www.ring-pinion.com/calc-rpm.html|Randy's Calculator] to get your RPM for a given rear-end ratio. Make sure that you know the ratio of your OD!!
>which in OD is I believe equal to a 2.91 rear end. Therefore
>if I can tow at 70 with a 2.91 ratio, towing at 60 with a
>3.55 at 2365 should be no problem.
WHAT?!??! 2.91 rear-end?!?! Your rear-end gears don't change based on your gear position!
What is it that you are trying to accomplish with this excercise?
What is your truck rated to tow with the 460 & the 4.10's?
Going to 3.55's will really skew that figure! It'll lower it!
As stated before, your rear-end gears keep the engine within a certain RPM range to enable you to USE the available TQ properly and efficiently.
Go to[link:www.ring-pinion.com/calc-rpm.html|Randy's Calculator] to get your RPM for a given rear-end ratio. Make sure that you know the ratio of your OD!!
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Joined: Sep 2000
Posts: 7,298
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From: Southern California
axle ratio
Monsta, I think what elliott is saying is that in Overdrive his final drive ratio is currently 2.91
So with a 4.10 axle and if the OD gear ratio is .71, which I think it is, then the final drive ratio will be 2.91
4.10 x .71 = 2.91
So if he had a 3.55 axle, but didn't use OD, he would have the same rpm at 60 mph as he had with a 4.10 in OD at 70 mph.
But I agree with your point. Going to 3.55 axle ratio will lower the towing capability of the truck. It won't accelerate as fast and will be harder to maintain speed on hills even if he keeps it out of Overdrive. It may look okay on paper, but out on the road it doesn't work out quite the same.
So with a 4.10 axle and if the OD gear ratio is .71, which I think it is, then the final drive ratio will be 2.91
4.10 x .71 = 2.91
So if he had a 3.55 axle, but didn't use OD, he would have the same rpm at 60 mph as he had with a 4.10 in OD at 70 mph.
But I agree with your point. Going to 3.55 axle ratio will lower the towing capability of the truck. It won't accelerate as fast and will be harder to maintain speed on hills even if he keeps it out of Overdrive. It may look okay on paper, but out on the road it doesn't work out quite the same.
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axle ratio
I understand what you both are saying. My overall thought is that if I can get enough gear choices between 1st & direct, the 3.55 would not be a problem
Elliott
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