Gear upgraded, 3.08 to 4.10

[EnzoColorado]

I just upgraded the gear in my Suburban from 3.08 to 4.10! Still need to go to a speedo shop to get the speedometer calibrated. First drive today, it's feels quite a bit more responsive though it's funny to see 95 mph on the speedo while still on the freeway entrance ramp. Can't wait until next camping trip in September to New Mexico to see how much better it tows.

[bfourman]

EnzoColorado wrote:

OP here. I created a spreadsheet to calculate RPM at different speed (40 to 70 mph, increment of 10 mph) in different tranny gears with all the possible axle upgrade. That helped me to decide which one to upgrade. I'm coming from 3.08 so I had many options. If you want to PM me your email, I can email you my spreadsheet and you can change the numbers to match your vehicle.

If your Yukon is 4x4 you'll have to change from rear and front gear. That may affect the decision.

I can only use OD on flat ground, any grade and I'm pulling it down to 3rd. It seems happiest around 2800-3000 RPM and that is accomplished easiest in 3rd with the TC locked.

I used a calculator at Randy's Ring & Pinion to ballpark it, but I'll PM you my email.

It will be a junkyard axle swap for a couple of reasons. Cost is a factor, but in the process I can upgrade my semi-float rear 14 bolt to a full-float 14 bolt, which will carry the weight better. I am right at the line weight wise with my current setup and bigger is always better. It is 4x4, I'm aware of needing to change both. That won't be a issue, but I'll have to get with Blackbear for a re-tune.

[dodge_guy]

bfourman wrote:
I have been milling around in my head whether or not it would be more effective to change gear ratio from 3.73 to 4.10 in my Yukon XL 2500 or to work on improving engine torque and HP at the RPMs I'm currently at. It would only be a 2-300 RPM change and I'm not sure that would be enough for my 4 speed trans to make a difference.

It made a huge difference in my V-10. I went from 3.73 to 4.30. 3rd gear runs about 400rpm higher but closer to where it's making its power. I never really could run in OD with the 3.73's. With the 4.30 I am able to run in OD with no issues. It only kicks into 3rd on the bigger hills. Worth every penny!

[EnzoColorado]

bfourman wrote:
I have been milling around in my head whether or not it would be more effective to change gear ratio from 3.73 to 4.10 in my Yukon XL 2500 or to work on improving engine torque and HP at the RPMs I'm currently at. It would only be a 2-300 RPM change and I'm not sure that would be enough for my 4 speed trans to make a difference.

OP here. I created a spreadsheet to calculate RPM at different speed (40 to 70 mph, increment of 10 mph) in different tranny gears with all the possible axle upgrade. That helped me to decide which one to upgrade. I'm coming from 3.08 so I had many options. If you want to PM me your email, I can email you my spreadsheet and you can change the numbers to match your vehicle.

If your Yukon is 4x4 you'll have to change from rear and front gear. That may affect the decision.

[skothari]

shabbir.kothari@gmail.com

please pm me your spreadsheet and thank you so much for putting this together. i'm looking to move from 3.08 to 4.10 and dont know where to start my research

[MORSNOW]

The post you are replying to is over seven years old from the old RV.Net days, you may want to PM the poster in hopes they are still around occasionally.  

[wnjj]

bfourman wrote:
I have been milling around in my head whether or not it would be more effective to change gear ratio from 3.73 to 4.10 in my Yukon XL 2500 or to work on improving engine torque and HP at the RPMs I'm currently at. It would only be a 2-300 RPM change and I'm not sure that would be enough for my 4 speed trans to make a difference.

It depends upon where you find you are lacking. For example, if your vehicle shifts in and out of overdrive on rolling hills or with a light headwind, that 2-300rpm may be the difference in keeping it in the higher gear. If you're looking to accelerate quicker onto the freeway, improving the engine may be the better option.

[bfourman]

I have been milling around in my head whether or not it would be more effective to change gear ratio from 3.73 to 4.10 in my Yukon XL 2500 or to work on improving engine torque and HP at the RPMs I'm currently at. It would only be a 2-300 RPM change and I'm not sure that would be enough for my 4 speed trans to make a difference.

[dodge_guy]

wnjj wrote:
While there are some ratios that are similar after the gear swap, it matters which transmission gears you're talking about.

For example, using the numbers from the 3.08 column above, the jump from 2nd to 3rd is 50% a increase in road speed for a given RPM. The jump from 3rd to 4th is only 33%.

This means 3.08, 3rd gear is like 4.10, 4th gear (both ~4.84:1 overall ratio).

So if you're pulling a hill in 3rd with 3.08 and need to shift down to 2nd, your engine rev's 50% higher after the shift. With the 4.10 it's 33% shifting from 4th to 3rd. That's a closer spread for the same road speed and more desirable.


In short, it's not the same to simply "run a gear lower" because reality means there's only 1 or 2 transmission gears that actually matter when pulling a grade for a given speed with a given rear end gear ratio. What this also means is that lower rear gears may not automatically be better if it changes you to a shift point that is wider than where you were at before.

Exactly my point. a 200-300 jump in rpm can mean the difference in running in a higher gear but a lower rpm. everything works in harmony. the easier you make it work, the better everything works together. even the 6 speed autos.

[wnjj]

While there are some ratios that are similar after the gear swap, it matters which transmission gears you're talking about.

For example, using the numbers from the 3.08 column above, the jump from 2nd to 3rd is 50% a increase in road speed for a given RPM. The jump from 3rd to 4th is only 33%.

This means 3.08, 3rd gear is like 4.10, 4th gear (both ~4.84:1 overall ratio).

So if you're pulling a hill in 3rd with 3.08 and need to shift down to 2nd, your engine rev's 50% higher after the shift. With the 4.10 it's 33% shifting from 4th to 3rd. That's a closer spread for the same road speed and more desirable.


In short, it's not the same to simply "run a gear lower" because reality means there's only 1 or 2 transmission gears that actually matter when pulling a grade for a given speed with a given rear end gear ratio. What this also means is that lower rear gears may not automatically be better if it changes you to a shift point that is wider than where you were at before.

[time2roll]

larry barnhart wrote:
two brothers stopping at the alpenlite factory on their trip south. Both had the same fifths and trucks but one had the 4.10 and one had the 3.73.
The 4.10 always used 5 more gallons of gas at every fill up.

chevman

Something is wrong with one of the trucks.
Assuming they filled up at 25 gallon intervals that is a 20 percent difference.
No way normal between 4.10 & 3.73 towing.

[RCMAN46]

TurnThePage wrote:

RCMAN46 wrote:

TurnThePage wrote:
I took my old F150 4.6L from 3.55 to 4.10. It made a HUGE difference. Unloaded highway mileage took a 1 mpg hit, but city driving and towing both had improved mileage. Not only that, I could suddenly maintain speeds towing in the mountains, and not have to worry about the truck grinding to a halt on long, steep climbs, which nearly did happen previously. It could suddenly cruise on the highway without dropping out of overdrive because a slight headwind or incline. The truck was so much more enjoyable to drive too. In short, it's the best mod I ever did to that truck, and I did a lot of them.

What transmission did the old Ford have?

I believe it was the 4R70...

My original comment to the OP changing from a 3.08 to a 4.1 gear may make very little difference because of the gear spread in the GM 6 speed transmission.

If you compare the overall ratios you will find the ratios with the 3.08 are very close to the 4.1 if you compare ratios with the 3.08 down one gear in each case.

Thus after first gear there is very little change as you go up in gears until 6 th gear which is rarely used when towing with the 3.08.

With your change of gears and the Ford 4 speed that is not the case.

[TurnThePage]

RCMAN46 wrote:

TurnThePage wrote:
I took my old F150 4.6L from 3.55 to 4.10. It made a HUGE difference. Unloaded highway mileage took a 1 mpg hit, but city driving and towing both had improved mileage. Not only that, I could suddenly maintain speeds towing in the mountains, and not have to worry about the truck grinding to a halt on long, steep climbs, which nearly did happen previously. It could suddenly cruise on the highway without dropping out of overdrive because a slight headwind or incline. The truck was so much more enjoyable to drive too. In short, it's the best mod I ever did to that truck, and I did a lot of them.

What transmission did the old Ford have?

I believe it was the 4R70...

[BenK]

Check out the Ford 2017 towing guide. Look up any, but this seems to be focused on F150

Note that these are all close ratio automatics

Then check out the exact same truck with different diff ratios and the max trailer weights and GCWR's all increase with a higher numeric diff ratio...

2017 Ford towing guide

Older charts did show 4.1's and IMO due to the older non double OD automatics

[RCMAN46]

TurnThePage wrote:
I took my old F150 4.6L from 3.55 to 4.10. It made a HUGE difference. Unloaded highway mileage took a 1 mpg hit, but city driving and towing both had improved mileage. Not only that, I could suddenly maintain speeds towing in the mountains, and not have to worry about the truck grinding to a halt on long, steep climbs, which nearly did happen previously. It could suddenly cruise on the highway without dropping out of overdrive because a slight headwind or incline. The truck was so much more enjoyable to drive too. In short, it's the best mod I ever did to that truck, and I did a lot of them.

What transmission did the old Ford have?