Determining the right regear

Wondering how people decide which regear to go with. I currently have a 3.91, and there are a few options (~4.5, 4.9, 5.2) I see commonly available.

I will be going from the stock tire size to 33s, and that increases my circumference by 7%. Thus, I would want to increase my gear ratio by the same, to recover "factory gearing" (ie so that my RPMS at 70mph will be the same, both before and after the tires+regear):

1.07 x 3.91 = 4.2

So 4.2? That's lower than anything I see available. I guess the other part of the equation is that adding extra weight in the form of larger heavier tires calls for a higher gear ratio, and maybe that's what pushes it from needing a 4.2 to, let's say, 4.5. Total speculation on my part there.

Thoughts?

 

Not a pro. Flamers will get flamed back for simply stating my opinion.

Thoughts?

If you regear it seems the 4.56 is a great ratio for the 33” tires. Some have had remorse going bigger ratio (she said).

With that said, your highway MPG will suck more than it sucks now.

Disclaimer: I am on 285/75/r16 on stock 3.91 gears since 2004. This is the equivalent of close to 33”. Low end could use some help, but is the cost worth it? Maybe it is for a 2WD?

Those are my thoughts.

 

Lol, from now on instead of "thoughts" I'll have to ask "facts?"

I think I've read you say that you've had that size tire for ~10 yrs, but do you recall what kind of a hit your mpg took when you switched to 33s?

I am pretty sure that, counter to what you said about MPGs getting worse, regearing to compensate for bigger tires will increase your mpg by returning you to the efficient part of your power band at cruise. Now of course I don't mean that the MPGs will be better compared to stock tire size and stock gearing, but rather that it will be more efficient than 10% taller tires with stock gearing.

 

The truck did take a hit in the MPG when going to bigger tires in City Driving. Highway stayed the same. Right now I’m in the 14-18 range still at almost 20 years old on 33”. I calculate the MPG every fill up. Not bad.

Your RPM’s will be affected with the re-gearing and will effect your MPG at higher gears/speeds. Its all a trade off. Like I said, most really like the balance of 4.56 ratio at the 33” tire. Some have gone higher ratio usually in non-daily drivers and off road type purpose trucks. Slow and crawling type driving.

Its an easy job for 2wd. Go for it.

 

Gear calculators are almost garbage in my opinion. They account only for diameter and not for weight.

If you want the closest possible match for your speedo 4.30 is almost perfect. Its expensive, more than any other gear set last I checked.

If you want real return and a little extra torque then go 4.56

I've had 4.56 since 2010, your mpg won't suffer like people think, it might even get better.

 

Yeah, I'm thinking it's 4.2 to match exactly to the factory final drive ratio, but the practical solution will be the 4.56, as inevitably the extra weight of the bigger tires and future add ons (winch, heavier bumpers) will eat up the difference.

 

Actually, looks like JustDiffs has Toyota 4.30 for a reasonable price now. They used to be over $600 back when i was looking for gears.

https://www.justdifferentials.com/Toyota-8-4-s/2021.htm

I would still go 4.56 though. Call the guys at JustDiffs and they'll give you sound advice, a lot of them are Toyota guys. Go with Nitro gears and a new bearing kit, pay a little extra for a solid collar too. I have over 100k miles on mine and thats the setup I got.

If you want an LSD or locker, no better time to get that while you're at it. Doesn't add labor.

 

Right on, I'll check them out. I have also been thinking about slapping in an ARB. Good to know it's worked well for you

 

Survey says: 4.56!

 

You'll need onboard air if you're going to do that, just fyi.

 

On board air is good to have if you're planning to drive through deserts. Its a very slippery slope but its fun.

 

I've been using a dewalt battery powered unit to air back up after I go out, but it takes around 10 mins to get all 4 tires from 20->~30 psi. A proper setup with a tank would be nice...

 

Sorry, to more clear. The ARB locker is an air actuated locker, you must run an air line to the diff and have an ARB onboard compressor. Like you said though, when offroading especially when it comes to tires, redundancy is best. I run a CO2 powertank for ease and speed but I have my compressor as a backup or should I run out of CO2 on a long trip.

 

Yup, I know. I've heard some people manage without even using a tank to actuate the locker, if they have a sufficient length of pressurized line running from the compressor to the locker to act as a mini-tank.

I imagine, though, that you'd probably want a tank if you're also running it to fill up your tires?

 

I personally don't run a tank connected to the compressor at the moment. Never had issues with the locker. Every now and then the compressor motor will run for just a few seconds but haven't had any failures yet.

 

Do you use that to air up tires too?

 

An arb single or dual compressor will activate lockers and air up tires. No need for a tank unless you want to run air tools.

 

Its my backup. I run a Powertank mounted in the bed for routine air up after airing down. It takes about 15-20 seconds a tire. Whereas the compressor takes 2-3 min x 4 tires. I dont have a multi-tire simultaneous set up yet.

 

You mean you don't use air tools when you're out in the wilderness?

 

18v son, so I can charge it with my solar panel.

 

See this is where I get confused so maybe you guys can help me.

As you guys know from my other threads, I am going TRD supercharger and the Kazuma LSD.
So I've been looking at gears, and like you guys said in this thread, that most guys like bigger gears for crawling.
But in my case, I drive from OC to San Diego weekly as well as all over SoCal for work and family stuff.
200+ miles on the freeway in one trip usually.

So I'm looking at more of freeway speed and MPG.

I have the 4.10 rear gear fro mmy Sequoia rear end and thinking about just getting a Sequoia front diff and dropping that matching gear in.

I'm 3.9 and 4x4 BTW.

So what do you guys think?

I have to remove the axles and everything anyway to install the LSD so just buying gears is what I'm looking at.

I'm running 285/70/17, basically a 33" tire, and plan on keeping close to this setup.

cost effective+ quality+ money+ power+ MPG = 4.10 ??

Best Bang for the buck option.

Thanks guys!

 

For 33s I’ve been torn between 4.10 or 4.30. 4.10 would be cheapest since well.. I have a used gear set that ratio. Just hoping a TRD LSD pops up eventually and I’ll build my spare pig

 

If I find another one I'll send you the link.
There have been a few of the LSD's poop up randomly lately.

So just to clarify what do you think I should do?

OH yeah, and you were right about the sequoia backing plates.
Trying to figure out my options on that one too...
Thanks for your help on that!

 

I think 4.10s would be the cheaper choice and should be “enough” for 33s. But 4.30s will feel even quicker. At the cost of minimal mpg possibly

 

Big thing with 4.10s is the easily available used front diffs so you don’t need to drop coin on new gears for the front diffs

(there some super rare 4.56 gear taco front diffs if you wanted that aggressive of a ratio.)

 

Your speculation is correct as per a discussion I had with Matt, MCM Fab.