4.56 or 4.88

I have an automatic trans. Central California, where I live the elevation is 400 feet. Traveling out of the valley, using the I5 (Grapevine) or Hwy58 (Tehachapi) I would hit 4000-5000 feet but only for a short time. Most of where I would off road is Eastern Kern (Jawbone, Randsburg, Cal City Inyo Kern) which is roughly 2000-3500 feet and then the occasional beach trip to Pismo which is sea level.

 

Automatic trans

 

I know, that's why I recommended 4.88.

 

If anything see if there's anyone near you with 4.56 and 4.88 gearing in their truck that would let you test drive. See how you like em

 

To the OP........will 171 rpm at 75 mph be a deal breaker for you?

 

I’m running 4.56 on 35’s and am very happy with my choice, fwiw.

 

How is the speed control descending the steeps in 4low?

 

I have 4.56 on 32's. When I initially put on the 32's (2015 v5 4wd) it was sluggish. However, if you put in 4th a bit less sluggish on take off, can switch when cruising on interstate. I regeared before I realized that little trick. I do tow a light trailer (3,500#) and use 4th when towing. And I'm singing along at 3,000 rpms at around 60'ish when towing. When I got the 32's my mileage went down (adjusting for odometer variance) and regearing had no notable impact on mileage, at least when not towing.

Above being said the regearing has helped me tow up a couple of hills with my little trailer, that I may have had some difficulty with otherwise... I probably shouldn't have been towing up those hills anyway...

 

I’ll get back to you on that.

 

Just seems like 2600 rpms is too high to travel for any length of time, maybe I'm overthinking this!

 

Go 4.56

 

The calculator I'm using, West Coast Differentials gear ratio calculator, shows the auto. W/OD will run appx. 300 rpm higher at 75 mph., than the MT W/OD. Way more than going from 4.56 to 4.88. That's why I've always wondered why Toyota uses the same rear gear for all the Reg., cab 4X4, (later yrs.), Tacos? Auto. or MT, all got 4.10, way too hi for the 2.7 4X4 auto.

 

It seems like some of this is personal preference, maybe go drive your rig and achieve 2600 rpm at a reasonably high speed and and compare how it feels to 2450 RPM, then you could decide from there.

 

Might not be great for mileage and will put strain on seals and bearings. That being said older cars ran fairly high rpms. I run my Tacoma at about 3000 rpms when towing--more than I would prefer, but don't want to run in drive.

 

I've been running in 3rd., instead of "D". That's appx. 2500rpm @ 60, a little higher than I like, but way better than in "D" at appx. 1800 rpm. @ 60. I'm still trying to figure how to disable the locking converter & see what "D" feels like without the converter locked. I'm thinking about 2050 to 2150 rpm. @ 60. That may work well. I've heard just unplug one plug on the trans. I just don't know what plug.

 

On the highway I cruise for hours on end at 3000 rpm thanks to me being overgeared. Truck doesn’t give two shits. It’ll do 2600 all day.

 

So I'm also working on a regear in the near future as I'm running 33's and usually carry a fair amount of weight around (RTT, shell, camping & recovery gear) and just got some new steel in the front . I have a 2015 V6 MT and based on that calculation the 4.56 would be the one to go for (even when I eventually upgrade to 35's). Anyone running 4.56 on their 2.5 gen MT's and have any thoughts?

Thanks!

 

If you’re planning on jumping to 35s then that’d be the perfect gearing.

 

Cool. yeah, I'd like my next set of tires to be 35's. Also going to go long travel at some point as well. Would that in any way affect which gears I should be considering?

 

Not in any way that I can think of