Re-gear 2023 SR 2.7 2WD. I have questions...

Counting revs is not super accurate - gets you in the ballpark but it would be easy to mistake 3.91 for 3.73. Toyota says 3.73 is not a factory auto for 3rd gen and that your truck would have 3.91.

Most accurate is to just use GPS to determine speed, document the RPM in a certain gear at that speed and back calculate it to figure out what you have. Of course you need to use an accurate tire dimension for that. 4.30 and 3.91 would be pretty far off in the calcs to get wrong, I’m sure he has 4.30 especially since that’s what Toyota says he has.

but yeah he can just count it once it’s out.

 

If I get to the point of pulling the diff out, it won't matter and I won't care...

 

Missed this with the page break...

I’m comfortable with strength and durability, for any task I have for it. I won't be pulling stumps, but the occasional low-stacked load of oak could need to be hauled 15 miles to my brother (55 mph two-lane blacktop), or 40 to my aunt (70mph 4 lane). 5.71's could be handy, although any kick down to 4th would be somewhat angry.

There is a downside to being stuck to Hwy 50 instead of I 70 (unless you want to ride in the slow lane with the semis). With 5.71s, the limiter should be hitting at 75mph or so - which is not an insignificant thing to consider. If I'm going to manipulate the engine or ECU to get around that, I'd just supercharge it and achieve a similar purpose with a different set of costs and downsides.

It would be a way awesome 6th gear, and have the /75 aspect option as a fine-tune if needed. Adds about 3lbs per corner.

Worst case is I live with it like it is, or maybe just give it a little tweak with some 4.56's. It likes to annoying explore 6th, but it spends most of its time in 4th or 5th. A couple-hundred RPM gain there is useful, and doesn't have any drawbacks other than it's not very much bang for buck.

 

It's hard to have these discussions without knowing the absolutes. Truth is, without you finding some open road and accelerating until it won't pick up speed anymore, we don't know what your current potential top speed is. So it's hard to estimate where the top speed would be with any different gearset. It's really not a big deal to tune out the speed governor, so I would not let that be a hindrance. Any tuner can do it, there is no licensing or locking of the stock tune. You would need around $80 to crack your ECM so that it could be flashed, and then anyone with VFTuner should be able to hook up and load an edited stock file onto the truck. Make friends with someone here, there's bound to be someone that can help you out nearby with that specific issue.

One thing is for sure, I would not spend the money for the rear diff only to choose 4.56. That simply would not return near enough for the investment for me to consider that worth it. Even 4.88 is a pretty small improvement over 4.30.

If you're this concerned about driveshaft speeds, I would do 5.29 (a known safe ratio) and step up the tires 1". You will hardly notice the 3 lbs per corner. Hell, do the tires first, you might notice the difference with stock gears and then the 5.29s would fix it and feel like a huge improvement. The reality is you're not going to be cruising 100mph, you will still be in the safe zone of the driveshaft for reasonable speeds. If the critical speed is around 6K rpm, you would be below that up to around 102 mph. Again though, we don't know the critical speed to the exact number. We do know tons of people have 5.29s here and many of them are not on large tires and they don't have problems, me included. Your driveshaft critical speed shouldn't be much if any lower than the rest of them despite being around a foot longer, because it should be the short/front portion of your driveshaft that is longer than the short/front portion on other trucks. The rear half is the longer portion that would have less critical speed, and you should have the same or similar length there as the rest of us.

 

Why should this be any different than sitting in the barbershop jaw-jacking about it? We're not solving nuclear fission.

I'll of course verify anything I decide to do, this is just an internet forum. Doesn't mean it's a bad place to brainstorm within reasonable and realistic limits. I think we're well within those.

Top speed the truck is capable of isn't really a question. It's a truck and maybe I would hit 90 or 100 in an emergency. Tire speed rating is 112. I don't want to drive that wobbly, thin-framed, bloated sheet metal truck that fast. Dear god, look how skinny the spindles are.

Speed becomes an issue when you consider real interstate driving. Driveshaft speed aside, the cutoffs are still there. 5.29 limits you to the 85mph ballpark. You can pass on the interstate at that speed. 5.71 puts you below 80. That's a serious consideration to take into account - for a really, really usable 6 gears in rural Missouri Ozarks. It's tempting.

A smaller increase (4.56) adds a couple hundred rpm to 5th gear, getting it out of a lugging zone and more into its power band. It starts to be more useful and 6th is still useless. Right now it's almost as useless as 6th, and the downshifting to 4th is inevitable with any sort of headwind on flat road. MPG stays the same. Easy to do as well. If that prevents 50% of the downshifting to 4th, it might be worth it.

For those that know what CAS3 is, I'm basically filling out my DECMAT for the Cosby brief. Shaft speeds and ECU cuts are screening criteria. Useful power band in different scenarios are evaluation criteria.

 

Just tune it and get whatever gears you want, I have 5.29 3rd members on order and already have a tune. A tune helps a lot with the responsiveness, shifting and how it well it holds a gear under load. As well as fixing the speed limiter with changing gears and bumping the voltage if you switch to a agm battery. A tune is a must for me it fixed a lot of the issues just not all because of the lack of rpm in 5-6th at highway speeds. My truck with a size up AT a mid rise topper and some gear drives better with a tune. Then it did completely stock with the factory all seasons. You could probably get away with 4.88s and a tune. I also have an LCE header which I would recommend for the 2.7. My thought for going with 5.29s was yeah my day to day driving would probably benefit more with 4.88s from a mpg standpoint. I just did not want to put a load or some camping gear in the bed, basically do truck stuff with the truck and have it still do that 4-5th dance.

 

Determining what those gears are is kind of the question, because there are tradeoffs. I'm not interesting in chip tuning, but I have considered a header. The factory pipe is more than sufficient, tbh...

 

My best guess, w/o running the numbers, is 4.88. Don’t forget, the higher axle ratio will also multiply the torque, so the loss for each up shift won’t be as great.

 

That's exactly the line of thinking. 6th might be a little gutless still but 5th is strong.

Here's my chart (the italics below 6th are drive-shaft speeds).