The calculators don't lie but since you don't believe in math...

I run (roughly) 2800 RPM in 5th at 83 mph on worn 33s. Sometimes higher RPMs. Sometimes lower RPMs. Depends which way the wind is blowing. Literally. There's also no such thing as a flat road which will impact it as well even with the torque converter locked there will be variations.


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I believe in math, but I also know the difference between published (calulated) values and real world values...as you pointed out

Weird....calculator puts me at 2759. Glad I double checked that.


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Almost 2%, huge difference! This is why I asked.

Okay. I'll admit I LOL'd at this 🤣


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Yes, but there's more variables to account for if you're trying for "Real World" values. The only way you'd get accurate, repeatable real world results is to set up a couple test vehicles and consistently drive them the same way every time for a set period. That is of course you've controlled all other variables that could influence and exceed your error margins.

It's just the tire size that make a difference. The calculator can't know the exact diameter... When I put in the exact measured dimensions of my tires... it matches my gps perfectly. Don't forget your spedo might be off . Speed is overstated from the factory in my experience. 33s usually make it match real world. But we are taking about very minor differences here... 34s and 4.56 seem like a perfect match to me.

Absolutely correct on both accounts.

...but the RPM difference will have a big impact on highway fuel economy. My personal experience after the regear is a slight improvement in town and a slight drop on the highway.

That's exactly what you'd expect as well.



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It is very accurate to real world. Calculator says 74 mph at 2500 rpm and I show 75 mph with GPS. Speedo is showing approx. 71 mph, which I know is indicating slow due to tire size.

Did you end up getting yours done?

I work at @Fat Bobs Garage and am probably going to do mine in my 4runner this spring before I start hauling my trailer.

I am interested in seeing if you ended up doing this, or if we can help you get it done.

Let me know!

I'm running 4.56 gears from ECGS on 285/70 Nitto RG's. I took a trip from Atlanta, GA to Cincinnati, OH, and back. I averaged maybe 13.5 mpg running 70-80 mph.

The best part is the power it has going through the TN and KY mountains. It's a hit on MPG but worth every penny to gain the power back and then some.

The only regret is not going with a front locker when I did this upgrade. I'm a firm believer in having and not needing rather than needing and not having.

Here is a quick shot from the road trip to give you an idea of the mph vs rpm. I'd say this is about 70 mph at 2500 rpm.



Also, I ran 4.56 with 295/70 and 35x12.50 in this rig. The 295/70 is a perfect match between a bigger tire than 285 and good highway rpm's along with great power. I'm sure a 285/75 would have been great also.

The 35's felt stock if not still a bit better.

Hell, I ran 4.56's with stock wheels and tires to see what it was like. Not too bad. Definitely want to keep it under 70 mph or the mpg drops drastically.

How much difference is there really between 4.56 and 4.88 gears? I know on this thread a lot of people are saying go with the 4.56 gears, why did you choose them over 4.88? Just curious.

Thanks

So, if I'm reading this thread correctly, regearing and an air locker should cost around $2,500???

I have an SR5 that I plan to regear and add an air locker. A reputable shop in Jersey quoted me $4,000 to $4,500 including parts. I have an air compressor installed and would run the switch wires.

WTF???

My regear only(no locker add) with ECGS cost me almost $2400 2+ years ago. I'm not sure how much 2+ years would raise the cost or the cost of the locker install but it does seem high. Are you planning on using ECGS or having the shop do it?

I'm probably having a shop do it. new gears, bearing kit and air locker. I normally do my own work, but this shop is ARB certified and with potential seal issues, I'd rather have parts and labor warrantied.

most of the cost was supposedly the IFS gears. I expected around $3,500 start to finish, but $4,500... nope