4:10 vs 3:73

[Marky Dissod]

I just picked up a wrecked '05 burb to use for parts for LS swapping my '84 Jeep Wagoneer.
I see RPO GT5 = 4.10. My '03 z71 burb has 3.73. Anyone swap from 3.73 to 4.10?
I run the stock tire size 265/70R17 31.6" for now but may go to 32.5" or 33" soon.

We do a lot of highway driving and have pulled down great mpg with 3.73, especially if I drive 65-70MpH.
Thoughts on if the swap is worth it? Seems rear is straightforward to swap, front diff would be the most work.

Highway MpG will go down from great to pretty good, possibly good if you drive too assertively.
Stop'n'go MpG will improve, might even make up the difference.

4L60E will last longer with 4.10, unless you abuse it.
You'll need a pcm tune to take full advantage and correct the speedo, which will help the 4L60E last even longer.

 

[Burban22]

Highway MpG will go down from great to pretty good, possibly good if you drive too assertively.
Stop'n'go MpG will improve, might even make up the difference.

4L60E will last longer with 4.10, unless you abuse it.
You'll need a pcm tune to take full advantage and correct the speedo, which will help the 4L60E last even longer.

My 03 burb is blackbear tuned. I would need to send off the computer to get the speedo corrected. Guess I should look for a handheld tuner so they can just send me the file for speedometer corrections. Will see if I end up swapping but I may run 295/70/17 ~ 33" tire all the time instead of just in the winter so should be a wash going to 4:10. I can pull down really good highway mpg with 3:73 and stock tire size 18-20 if I go 65 - 70.

 

[Marky Dissod]

My 03 burb is blackbear tuned. I'd need to send off the computer to get the speedo corrected. Guess I should look for a handheld tuner so they can just send me the file for speedometer corrections.

You wouldn't rather send it to BlackBear, get your money's worth?

Or, if you pick your tire size carefully enough, you won't need any speedo correction for 4.10.
(By the way, 4.10 to 1 is NOT the same as 4 to 10).

 

[strutaeng]

Great thread revival!

Are either one of those differentials G80? Would that matter to you? Are you doing any towing? That's probably what that boils down to.

Compare what towing capacities are with those 2 different ratios according to your owners manual, and see if that's worth it. Again, if you do any towing. We don't know. MPG will likely go down a bit, but wouldn't be huge. Especially if you drive at the same speed. I think it's like a 200-ish RPM difference cruising?

 

[Burban22]

Looks like 1,000 lbs difference between 3:73 and 4:10 gears.

https://www.jnauto.com/pdf/04towingguide.pdf

My burb rarely tows. I have a 3500lb enclosed 16' trailer I tow a few times a year but usually use my newer truck. More get up and go with 4.10 would be great but we put alot of interstate miles on the burb and want the most mpg possible.

 

[Burban22]

Stepping up from stock tire size to my 33.3" BFG k02's would nearly cancel out the 4:10. hmmmm, I'll save the front and rear axle out of the '05 and if I get motivated enough can swap with my 3:73. Bearing the front diff on the totaled '05 burb is still usable. The PO slid off the road into a drainage ditch. Hit so hard the front frame rails are bent upward. No air bags deployed somehow.

Gear Ratio Calculator

Easy to use gear ratio calculator. Use our gear ratio calculator to find the correct gear ratio to run when changing tire sizes to keep your stock gearing.

tiresize.com

 

[Burban22]

Great thread revival!

Are either one of those differentials G80? Would that matter to you? Are you doing any towing? That's probably what that boils down to.

Compare what towing capacities are with those 2 different ratios according to your owners manual, and see if that's worth it. Again, if you do any towing. We don't know. MPG will likely go down a bit, but wouldn't be huge. Especially if you drive at the same speed. I think it's like a 200-ish RPM difference cruising?

lol! Hey, at least I searched! Both are G80.

 

[Burban22]

You wouldn't rather send it to BlackBear, get your money's worth?

Or, if you pick your tire size carefully enough, you won't need any speedo correction for 4.10.
(By the way, 4.10 to 1 is NOT the same as 4 to 10).

I thought they started charging now for any modification to the tune. I was trying to say it would be easier if I had an auto cal they could just send me the file and save me the shipping cost. Hopefully they don’t charge for just a tire size or gearing change

 

[Marky Dissod]

3.73:1 axle ... 265/70R17 tires are 31.60" tall ... 4L60E's 4th gear = 1800RpM @ 65MpH, 2000RpM @ 72MpH, 2200RpM @ 79MpH
4.10:1 axle ... you want tires 34.7" tall to avoid reprogramming the speedometer altogether.

Tires shorter than 34.7" tall will make the speedo read faster than actual with 4.10:1.
Tires taller than 34.7" will make the speedo read SLOWER than actual with 4.10:1.

If your tires go wider than 265mm, your highway MpG will get worse due to more drag area, even with 4.10:1.

 

[S33k3r]

I'll just place this here for your amusement...

Tire Size and Gear Ratio Chart