Re-Gearing a 2018

[DasKeyserSoze]

Apparently regearing a 2018 is not as straightforward as I had hoped. The rear in the 2018 won't accept aftermarket gears, so I need to find a 9.5" 3rd member from a 2015 (or older) Tundra or LC with 3.91s or 4.30s. The center section of my front clamshell needs to be subbed out as well. Ken at Gear Installs has the center section, but I'll need to send him my front as well as find the rear 9.5" (ideally one with the larger heavy-duty pinions w/ 32 splines). Anyone have ideas/suggestions on where I could look to source this rear? Thanks!

 

[CharlieS]

I just did this to my '16, and you need the earlier front and rear diff carriers (or as you say, from certain year and option Tundras). I got mine from another 'mud member that had them from when he regeared his earlier LX. Another benefit is that if you are going to 3.91:1, the earler LC and LX came with this gear set. Not sure what you mean by a center carrier, but there are no changes to the transfer case or axles, just the front and rear differential housings.

 

[Tex68w]

I am so confused. do we not have 3.91 gears stock on 2018+ Cruisers?

*Edit- looks like 3.31 is standard.

 

[CharlieS]

Your edit is correct. They had 3.91 from 08 to 15 on the 6 speed and 3:31 starting in 16 with the 8 speed.

 

[TeCKis300]

As others have said, the easy button is to get the full front and rear carriers from a pre '16 200-series. 3.9 is what you'll want anyway. Ratios above that are going to be way too much gearing for the 8-speed tranny. Yes, there's such a thing as too much.

Once you get the carriers, it's just a question of what lockers you want to drop in.

 

[CharlieS]

Also, Ken (Zuk) told me (and posted on his website) recently that he'a taking 2022 off to camp and fish, so unless you've already confirmed with him, you might want to double check.

 

[DasKeyserSoze]

As others have said, the easy button is to get the full front and rear carriers from a pre '16 200-series.

Agreed...thought that getting them off a Tundra might make it lighter on the wallet, but don't really know where to start looking.

3.9 is what you'll want anyway. Ratios above that are going to be way too much gearing for the 8-speed tranny. Yes, there's such a thing as too much.

Contemplating between the 3.9 and 4.88 - I am regularly hauling 6 PAX as well as a trailer.

 

[bloc]

OP any diff housing/chunk from a 100-series will work too. Correct spline count, 4-spider case, and will bolt up to the axle housing. Teckis did just that. Lots of those on car-part.com The only negative I can find for the 100-series part vs 200 is a lower spline count to the pinion flange. I don't know whether this has any functional impact.

The front diff chunk from a tundra will work as well, available in a few ratios. 4.1 and 4.3 definitely. You'll just need to remove a needle bearing from one side of the housing to make your passenger side axle tube work, again Teckis did this in his gear thread.

I'd caution against going too deep with your gears. Stock 3.3 to the 4.56 or 4.88 range is a huge change. You can bolt in the 3.90s or 4.1/4.3 from a 100/tundra combination and with your low first and second gear be in great shape.

AND.. have OEM toyota gears, which are higher quality than anything aftermarket.

I just did this to my '16, and you need the earlier front and rear diff carriers (or as you say, from certain year and option Tundras). I got mine from another 'mud member that had them from when he regeared his earlier LX. Another benefit is that if you are going to 3.91:1, the earler LC and LX came with this gear set. Not sure what you mean by a center carrier, but there are no changes to the transfer case or axles, just the front and rear differential housings.

I'm also confused by OP's use of "center carrier".

 

[bloc]

For the record, stock gearing and tires needs 1769rpm to do 75mph.

assuming 33" tires, stock gears only need 1688rpm to cruise at the same speed

4.88s would push that to 2497rpm (!!!)

3.9s would ask 1995rpm.. much more in the ballpark of where most would want to be, assuming a bit more rpm for additional power to make up for increased aero and tire losses, but not so much that the engine is spinning like a top on the freeway in your tallest gear. And they can bolt right in from a 2008-2015.

You can play with the math yourself here: Engine RPM / Engine Speed Calculator - https://www.crawlpedia.com/rpm_gear_calculator.htm

Note that info you read about gears on earlier cruisers might not apply to yours. Folks with the 6-spd have a 0.588 top gear, to your 8-spd 0.67. This is a major reason yours has 3.3 axle ratios in the first place.

 

[TeCKis300]

Agreed...thought that getting them off a Tundra might make it lighter on the wallet, but don't really know where to start looking.


Contemplating between the 3.9 and 4.88 - I am regularly hauling 6 PAX as well as a trailer.

Yup, I used a front carrier off a Sequoia which shares part numbers with the Tundra. You might get lucky with someone having one on these boards. Try car-part.com. eBay. Shipping can be prohibitive for these heavy parts.

I'd still caution the want for too much gear. Gears don't make power. They multiply torque. Yet too much will feel like you can't ever get out of low gear.

My car alone isn't heavy but I arguably tow one of the heaviest trailers regularly beyond 15k combined rig weight. I'm at effectively stock gearing with 6-speed, 4.3s, and 35s and it works great because the 5.7 is plenty torquey. The 8-speed low end gearing stock is better still than my setup.

There's an open question if too much gearing over stock messes with torque converter lockup logic. There's at least one owner of the 8-speed that went 4.3s and found it was too much of a good thing. Did it all over with 3.9s.

 

[DasKeyserSoze]

Not sure what you mean by a center carrier

I'm also confused by OP's use of "center carrier".

Sorry, but thanks for pointing out the confusion...I edited my original post for clarity - I meant the center section of the front carrier if I am to re-use mine, but I would rather just source a new front and rear that way I am still up and running in the meantime.

 

[bloc]

Sorry, but thanks for pointing out the confusion...I edited my original post for clarity - I meant the center section of the front carrier if I am to re-use mine, but I would rather just source a new front and rear that way I am still up and running in the meantime.

So just to iron out some terminology because I think a few of us (and Zuk) are speaking about the same things different ways.. "carrier" can mean a couple things. Toyota considers the whole housing assembly including ring and pinion the "differential carrier sub-assembly." Then the diff itself, inside that sub assembly, is the case sub-assembly.

Elsewhere in the industry only the diff case without R&P is called the carrier. Possibly because what on a toyota is a sub-assembly carrying the final drive and diff, is an integral part of the axle housing in many other solid axle vehicles.

So... no clue if this helped.

I think you are on the right track though. Your housings work, but the diff case "center" portion must be sourced from a different vehicle. Your desire to drop the chunks in means that isn't as relevant.

I did a little digging in my parts program and the rear center case for my 2013 is PN 41301-60080. This was the same part number from the start of the 100-series to 2015 200s. It does not cross reference to a Tundra application. Now that doesn't necessarily mean a tundra case won't bolt in, but as you eluded to there are differences.. like the fact that I can't find a tundra diff with 4 spider gears in it.

Also tundra AND 200 front diffs all seem to have 2-spider diffs. So that isn't really a loss.

From prior research I know 100-series rear housings are the same part number as 2008-2015 200-series.

So one option is get a 100-series rear housing and tundra 5.7 front, find some 3.90s (and a rear pinion flange if possible.. the 100-series part won't work with 200-series pinion) from a regeared early 200, and have them all installed. This would give you ready-to-install housings to minimize downtime. From my pricing things in the past the tundra front can be found in most large population centers for about $150. The 100-series rear will go for about $400. With new bearings when you have your 3.90s or whatever gears installed the mileage on the unit shouldn't matter. Toyota gears wear extremely well so as long as the used R&P aren't ticking over 300k they should be fine for a long time too.

Or try and find 2008-2015 complete housings. I doubt there are many of these around.

 

[linuxgod]

Agreed...thought that getting them off a Tundra might make it lighter on the wallet, but don't really know where to start looking.


Contemplating between the 3.9 and 4.88 - I am regularly hauling 6 PAX as well as a trailer.

If you have a 2016+, you want either the 3.9 or maybe possibly 4.3 gears.

• 3.9 with the 8 speed is roughly equivalent to 4.30 gears on the earlier 6 speed, which is really the right gear for tire sizes up to 35". This ratio is just fine for loading up your overlanding rig with gear and people and still towing 6000-7000#.
• 4.3 with the 8 speed is roughly equivalent to 4.88 gears on the earlier 6 speed. These are good for low speed rock crawling. They're fun for giving passengers off-the-line whiplash. They can improve your MPG slightly when towing if you carefully manage what gear you drive in (i.e. they will often let you hold 5th gear with your torque converter locked despite pulling a big heavy trailer). They're an unnecessarily high gear ratio if you care about MPG when not towing unless you're going to drive 45-50mph.
• 4.88 with the 8 speed would be serious overkill unless you're planning to largely spend your days rock crawling. It will almost certainly hurt MPG in all scenarios. Also with the extra low 1st gear in the 8 speed I believe you run a higher risk of breaking something

 

[JohnJB]

FWIW, I know 2 16+ trucks that re-geared to 3.90s... only to later re-gear to 4.88s. And yes, they paid a shop to do the work both times so it cost them dearly.

So why did they do this? In both cases they were people who spent a lot of time on the highway in heavy trucks ("built" and running 34" tires) while also regularly towing trailers in excess of 4k to 6k lbs. They simply got sick of the trans still hunting (perhaps a byproduct of simply having two more non OD gears with shorter spreads?) at highway speed when they visited the hilly parts of the country. That's not to say the trucks struggled or it was unbearable, but they ultimately decided they rather go slightly over geared for their purposes than slightly under.

For this reason, I caution folks always saying oh the 8spd would be perfect with 3.90s, the 4.88s will be too much. Maybe that statement is true for you, but perhaps not for someone else. It depends on a variety factors and always comes down to personable preference. Heck, I don't doubt there's someone who has also already made the reverse decision and went down numerically after finding they didn't like so much gear. I just cringe when the forum gets so axiomatic about decisions, especially if folks don't have direct experience they can relay. It's okay for it not to be a black/white decision.

 

[bloc]

Whether it’s the 8 spd or 6, we shouldn’t be towing heavy in the top two gears anyway.

4.3 in a 6spd or 3.9 in the 8 puts us a hundred or two rpm’s above stock at most cruising speeds on 33s, and we still have all those other gears to use in S mode while towing to avoid hunting.

If the math doesn’t work out, there are OE toyota 4.3 and 4.1 options (100-series rear, tundra front)… and it is easy to see how someone that didn’t go far enough initially may overshoot on the redo. Even 4.56 but like 4.88s these aren’t easily available in OE toyota quality.

OP, you can use the calculator above to find different final drive cruising rpm results and spend extended periods in various gears on the freeway to see whether it would bug you.

I know for a fact 700rpm above stock would be too much for me to be happy driving an unloaded rig.

 

[grinchy]

Another downside of gearing up is it limits your tire size choices. Example: I have a 6 speed with 4.88s. I will never be able to run stock size 31" tires. While it feels like a go-cart and is super fun to drive (I ran 32" for a short while), the high freeway RPM is noticeable. I'm effectively 'limited' to 33"+ tire sizes. Of course I'd want to run these sizes anyhow for my overland style build, but someone adding gears just for towing use may want to stay with a stock tire size, and thus should factor that in to the gear ratio choice.
At 35" tire sizes my freeway rpms are unnoticeably higher than stock (200 rpm or so, if I recall), while I still get that fun off the line feel and maintain overall drivability (hill climbing, descending engine braking, better low speed gearing especially in 1st).

 

[Tex68w]

I feel like the stock gearing on 33's is more than adequate if not towing heavy. Now, should I move up to a 34-35" tire then I'd seriously consider regearing.

 

[linuxgod]

FWIW, I know 2 16+ trucks that re-geared to 3.90s... only to later re-gear to 4.88s. And yes, they paid a shop to do the work both times so it cost them dearly.

So why did they do this? In both cases they were people who spent a lot of time on the highway in heavy trucks ("built" and running 34" tires) while also regularly towing trailers in excess of 4k to 6k lbs. They simply got sick of the trans still hunting (perhaps a byproduct of simply having two more non OD gears with shorter spreads?) at highway speed when they visited the hilly parts of the country. That's not to say the trucks struggled or it was unbearable, but they ultimately decided they rather go slightly over geared for their purposes than slightly under.

For this reason, I caution folks always saying oh the 8spd would be perfect with 3.90s, the 4.88s will be too much. Maybe that statement is true for you, but perhaps not for someone else. It depends on a variety factors and always comes down to personable preference. Heck, I don't doubt there's someone who has also already made the reverse decision and went down numerically after finding they didn't like so much gear. I just cringe when the forum gets so axiomatic about decisions, especially if folks don't have direct experience they can relay. It's okay for it not to be a black/white decision.

That seems crazy to me. I have 4.88's on the 6 speed, I run right at GWVR with the truck loaded without the trailer, and then add 6000# of trailer and I'm nearing GCWR - and 4.88s are more than sufficient to tow. To a certain extent I wish I'd just bought 4.30s as 4.88 is a bit much around town without the load. Either way I can't imagine going to a higher ratio on the 6 speed, nor can I envision running the 8 speed with 4.88s.

 

[empty80]

@DasKeyserSoze, when I went down this path, I called Cruiser Outfitters. Kurt was able to talk me into the best solution for my truck, and they had the OEM and aftermarket parts on the shelf.

Cruiser Outfitters continue to impress me every time I call them.

 

[TeCKis300]

I whipped up a couple tables to perhaps convey what type of gearing we're talking about. Hopefully I didn't make too many errors here.

This contrasts overall gearing for different 3rd members against common tire spec diameter. i.e. 33.7" is what a 285/70r18 diameter commonly specs out to, or 34.6" is what a common 35x12.5 specs to.