Yukon Xl 8.1l 4.10 - Motor Revolution ?

georgesdelajungle007 · May 26, 2008

Hi,

I have a Yukon XL 2500 2005 with the 8.1L and the 4.10 Gear Ratio.

Actually, like many of you, I'm a little bit concerned with the gaz price, so I started to make some driving test.

I found out that if I keep the revolution of the motor under 2000RPM, it takes a lot less gaz than if I keep it over 2000RPM. (on a similar road, going 50MPH instead of 65MPH makes a difference of 4 to 6 MPG according to the internal computer)

With the 4.10 Gear Ratio, 2000RPM is about 55 - 60 MPH. No need to say that is not really possible to think about going 1500 RPM on the highway!!!

So I'm now considering the possibility to change the Gear Ratio for a 3.73, but I'd like to know what revolution can I expect to have at 60MPH?

Does anybody have that combination? a 8.1L with the 3.73 Gear Ratio?

Thanks for your info!

ksiesel · May 26, 2008

You can do the math for this very easily. Since it is a ratio and you know your RPM at say 60 mph with the 4.10's, you can just take your current RPM and multiply by (3.73 / 4.10).

The result is about 1819 RPM at 60 MPH with the 3.73's.

svensk · May 26, 2008

gears won't matter with an 8.1L. The cost of doing the swap isn't worth any tiny gains you will get.

BigJayDogg3 · May 26, 2008

You can do the math for this very easily. Since it is a ratio and you know your RPM at say 60 mph with the 4.10's, you can just take your current RPM and multiply by (3.73 / 4.10).

The result is about 1819 RPM at 60 MPH with the 3.73's.

I knew there was some kind of formula for it, but never knew it, nor wanted to know it enough to look for it. Thanks.

2004GMC1500CC · May 26, 2008

Hi,

I have a Yukon XL 2500 2005 with the 8.1L and the 4.10 Gear Ratio.

Actually, like many of you, I'm a little bit concerned with the gaz price, so I started to make some driving test.

I found out that if I keep the revolution of the motor under 2000RPM, it takes a lot less gaz than if I keep it over 2000RPM. (on a similar road, going 50MPH instead of 65MPH makes a difference of 4 to 6 MPG according to the internal computer)

With the 4.10 Gear Ratio, 2000RPM is about 55 - 60 MPH. No need to say that is not really possible to think about going 1500 RPM on the highway!!!

So I'm now considering the possibility to change the Gear Ratio for a 3.73, but I'd like to know what revolution can I expect to have at 60MPH?

Does anybody have that combination? a 8.1L with the 3.73 Gear Ratio?

Thanks for your info!

More likely you are getting better mileage from driving slower and having less wind resistance.

C & A s Dad · May 27, 2008

I think Troy has answered your question. I do not think the RPMs are what is hurting your MPG, it is the wind.

georgesdelajungle007 · May 27, 2008

I think Troy has answered your question. I do not think the RPMs are what is hurting your MPG, it is the wind.

I never thought about that (wind instead of RPM...). I was probably just searching for the magical touch to get better MPG...

I love my truck, but when I bought it, gaz price was a lot lower.

Thanks everybody, I will just try to be carefull with my right foot

C & A s Dad · May 27, 2008

Also, I hate to state the obvious but when using Litre to state engine size, it kind of hides the fact that you are talking about 496 cubic inches producing enough gut wrenching torque to drag a 5,000 sq ft house off it's foundation.

I am assuming you are towing something of significance with your truck. If so I can only pass along a quote from my Dad. "If you are gonna dance, you have to pay the fiddler".

From my time on a Camping forum, your truck is thought of very highly in the towing community.

georgesdelajungle007 · May 27, 2008

Also, I hate to state the obvious but when using Litre to state engine size, it kind of hides the fact that you are talking about 496 cubic inches producing enough gut wrenching torque to drag a 5,000 sq ft house off it's foundation.

I am assuming you are towing something of significance with your truck. If so I can only pass along a quote from my Dad. "If you are gonna dance, you have to pay the fiddler".

From my time on a Camping forum, your truck is thought of very highly in the towing community.

You are wright, I'm towing a 30' travel trailer of 6500 lbs. (pretty easy to tow since the truck can handle something up to 12 000lbs)

When I was searching for a truck, I found this one used and the previous owner was trying to sell it for about 6 months. So i got a great deal for it.

I thought at that time that the money saved to buy it will compensate for the gaz for a while and by the way I will be able to have a truck that's not borderline to pull my TT.

But I still always have a little tears that comes up everytime I fill it up.

When I will be tired of speding that much money on it, I will sell it and will go back to a tent and a bicycle