Re-gearing from 3.73 to 4.10?

[Luuuke]

Can someone who has done the 3.73 to 4.10 swap who has 285s post there RPMs vs. true GPS speed as the previous post for.the 4.55 setup with 35s

"- Rpms vs. true GPS speed:
77 mph --> 2.500
72 mph --> 2.400
68 mph --> 2.300
59 mph --> 2.000"

I have 285s/r17 on my 2013 e350 with the 5.4L V8. When I bought the van it already had 285s on it so I never experienced what it was like before with smaller tires. But it drives like a dog. This is especially apparent when pulling a small 2000lb trailer in the mountains when we are only able to go 40-50mph uphill.

Debating what regear to do 4.10 or 4.30?

Boy Wonder are you happy with the 4.10 or do you think you would like the 4.30 better?

I appreciate anyone's thoughts or recommendations.

Thanks!

[Twoxentrix]

If you do a google search you can find several calculators that will give you answers to your question - nice part is you can play with it to see how much each variable in gear & tire size impact RPM’s and Speed...this is just one:
https://spicerparts.com/calculators/...rpm-calculator

[1der]

make sure to use .70 as the transmission top gear ratio for the 5.4 tranny. Tire diam will be 32.7 if those are KO2's

Not sure if 5 Star Tuning has a solution for your year/engine but might be worth a call.

[carringb]

Luuke - 4.10 gears would be barely noticeable. For 285s, the 4.30 ratio should be the minimum you consider. 4.56 would be even better, but the 4.30s would basically replicate the stock gear and tire combo so you wouldn't have to worry doing any speedometer corrections.

[boywonder]

Originally Posted by Luuuke

Boy Wonder are you happy with the 4.10 or do you think you would like the 4.30 better?

I'm very happy with 4.10's......speedo was reading 10% low with 3.73s and now reads around 4% low. For me it's a good trade off between mileage (I hope! haven't checked it yet..been too giddy with my 4.10s ) and climbing performance. The performance on grades is noticable. It went from pathetic to acceptable.



I'm running 5.4L 285/70-17s.....


As carringB mentioned.....4.30's may be better....would likely get the speedo right on and further increase climbing performance..I'm too lazy to do the math right now and don't know how much it would impact mileage.