High gear ratios, 5 spd. manual W/ OD vs my 4 spd. auto W/ OD

I have a 2013 Tacoma 4X4 auto. W/ 2.7 eng. & orig. 4.11 rear end gears. From the ring gear & pinion calculators I'm seeing, in high gear, & both using the orig. 4.11 ring gear & pinion, the 5 spd manual W/ OD is turning appx. 300 rpm more at 60 mph than the 4 spd. auto W/ OD & a locking torque converter. Is this correct? My Taco seems to be struggling to just hold it's speed while cruising at appx. 60 mph. I'm thinking of changing my ring gear & pinion gears, to get the rpm up a little without going too far. From what I'm seeing if I change to 4.56 gearing, my auto. will then be running appx. the same rpm @ 60 mph. as a 5 spd. manual W/ OD & the orig. 4.11 gears. Any help appreciated.

 

That automatic has a 4th gear ratio of 0.705:1 whereas manual has a ratio of 0.81:1. That means that the engine will spin (0.81-0.705)/0.81 = 13% faster and it will deliver 13% more torque to the wheels.
The 300 rpm looks about close. Maybe a little higher than actual.

I personally wouldn't do it. If anything, I'd like the manual to be a higher ratio closer to the automatic, but I'm not willing to compromise 1st gear to achieve that.
Keep in mind that since you have a 4x4, you must re-gear BOTH differentials.

If anything, you'd probably be better off just by switching to a slightly shorter tire. That will get you more force to the ground, and slightly reduce your aerodynamic profile, which has the same benefit.

 

Thanks man, I know I've got a dilemma. I got rid of a "98" Taco 2.4, 5 spd., 4X4 that I loved, plenty of power, never a complaint. I now have this 2013 2.7, auto. that is a dog, especially in hi gear w/ converter locked, always straining & starts shifting at the first sight of any hill or upgrade. Yeah, having to change both ends will be not cheap, but I'm very dissatisfied. From what I've found, a tire appx. 2 3/4" shorter than I have now, would raise the rpm. appx. the same as going from the 4.11 to a 4.56. Maybe I can find two, 2 3/4" shorter, to put on the rear for a few days to see if the rpm change will make the difference I'm hoping for, without too many rpm for hwy. use. Oh shoot, if I hadn't traded, I wouldn't have this problem.

 

You don't necessarily have to go the full distance. Like I said, the manual is geared TOO LOW. Factory tires are 30.5 inch (245/75R16). So the tire size you probably want to look at is 245/65R16 which will reduce the diameter 2 inches, which will reduce the circumference by 6.28 inches. The factory tire circumference is 95.82 inches, so the smaller size will yield 6.28/95.82=6.6% reduction in distance traveled per tire revolution. Effectively gearing it down by 6.6%. That's less than the 11% difference you would get with 4.56 gears.

Also note that you won't be able to realize any aerodynamic improvements unless you try the smaller wheels on BOTH axles.

And understand of course, that that transmission will STILL make it a "dog" for a few reasons;
1) Its first gear ratio is still 2.8:1 compared to the MT with 3.95.
2) Its still automatic, which means that it WILL downshift long before the engine is allowed to make its maximum torque.

A manual transmission lets you floor it without downshifting, which ultimately means that it can make more torque. With an automatic, the engine will only be allowed to make its maximum torque in the LOWEST gear that it can safely operate in at that speed.


Since I gather that you recently acquired the vehicle and are therefore NOT the first owner, are you CERTAIN that the truck doesn't have bigger tires already installed? Check the sidewall. Factory tire size should read 245/75R16.

 

Yeah, my tires are 275/70/17 (32.16" dia.) appx. 1 2/3" taller than the orig. 245/75/16 @ 30.47" dia. No doubt, there's a lot to be considered. I keep thinking, if I keep my rpm., @ hwy. spd., in line with what a manual trans. will be turning at hwy. spd., I don't see why I won't be OK. From what I'm finding, a 5 spd W/ OD, my size tires, a 4.11 gear, @ 60 mph. will be turning appx. 2098 rpm. vs. my auto. 4 spd OD with converter locked is turning only 1835 rpm. that's a 263 rpm lower than the 5 spd. If I change my 4.11 to a 4.56 gear, my auto would then turn 2001 rpm @ 60 mph. still appx. 100 rpm. under what the 5 spd. is turning with the 4.11. If I change to a 4.88 gear, then my auto should be turning appx. 2141 rpm. @ 60 mph., that's only 43 rpm. more than the 5 spd. with the orig. 4.11 gear. Also, the 5 spd. with 4.11 gears, 60 mph. with the orig. 245/75/16 tires would be turning 2175 rpm. @ 60 mph., that's even 34 rpm. more than mine would be with the auto. & my size tires & 4.88 gears. The more I try to figure out, the more questions I come up with. Why would Toyota think two Taco's running down the hwy @ 60 mph. if one has a 5 spd trans., it would need to be turning 263 more rpm. than the same Taco, with an auto. trans. Heck, auto. trans. always seem more sluggish than manuals, looks like, if anything, the auto. would be turning more than the manual. Gosh, there's a lot to think about before doing something like this, but I am really disappointed with my Taco's performance. Shoot, I almost wish I'd just kept my old 1998 reg cab, 4X4, 2.4, 5spd. that I never had a complaint with. The guy that has my old "98" now drove my 2013 a couple of wks. ago & said "I see why you aren't happy with this 2013", "It ain't got no power". I should be able to find some tires small enough to be roughly equal to a 4.56 gear (225,75/16 @ 29.3 dia., 245/70/16 @ 29.5 dia.), just to try. To find tires to equal the 4.88 gears, would need to be appx. 26.5" dia. that'd be pretty small. Decisions decisions, maybe I'll figure something out, just don't want to make a "BIG" mistake, I can't afford that.

 

Do you really need those big wheels on it? In all honesty, try a set of factory sized tires on it. I think you'll find that it will perform quite well like that. IMO, the 4-speed AT really doesn't align well with the idea of "big wheels off road".

As for why they put different gear ratio on the MT and AT... its to compensate for the stupid people who will complain that they have to shift whenever they're pointed up a hill. The MT will pretty much hold highway speed while driving vertically.

 

May be correct, but from the gearing calibration chart I'm using, 60 mph. 4.11 gears & orig. tire dia. 30.47" = 1904 rpm @ 60 mph. if I punch in 60 mph. 4.11 gears & my actual tire dia. 32.16 = 1803 rpm @ 60 mph. That's only 101 rpm. difference. No doubt 100 more rpm. would be an improvement, but it just seems the 100 rpm may be a barely noticeable difference. While driving my Taco, at 60 mph. the tach is just under 2,000, if I press the gas just hard enough to get the converter to unlock, the tach goes up appx. 400 rpm., this 400 rpm is very noticeable, but it's still not a huge drastic difference that has the eng. running way out of range.

 

Its a 5% increase in torque.
Its also a reduction in your aerodynamic profile, which reduces the amount of torque you need to hold a speed.

So what are you trying to do, climb mount everest with the torque converter locked?