Once you commit to portals, tire size comes next, and gearing follows. The ring and pinion ratio is only half the equation on a portal truck. Both the portals and gears in the differential can handle a gear reduction, and the two combine to give you your final output ratio.
When you find the perfect balance between your gear reduction at the hub and gear ratio in the diff, the performance both on and off road is on another level. It’s important that you get these ratios correct the first time, or you’re either leaving performance on the table or putting unnecessary strain on parts that didn’t need it.
I’m running 74Weld portals, which provide a 1.22 (22%) gear reduction at each hub. If you’re still deciding between portal setups, Brenan over at Trail4R.com put together a complete guide comparing 74Weld and Werewolf portal axles, a great reference to read, since the two are very different, and that decision should come before any of the gear math below.
To find your final output drive with 74Weld portals, take your ring and pinion ratio in the diff and multiply it by 1.22. For example, the factory 2nd Gen Tacoma ratio is 3.73; multiply that by 1.22, and you’ll get your final output drive.
Factory ratios aren’t the same across every Tacoma generation…
- 2nd Gen Tacoma (V6): Stock ring and pinion ratio is 3.73. With a 1.22 portal reduction, final output drive comes out to 4.55.
- 3rd Gen Tacoma: Stock ring and pinion ratio is 3.91. With the same 1.22 portal reduction, final output drive comes out to 4.77.
That gap between 4.55 and 4.77 might look small, but it’s important. Know your starting ratio before you decide whether a re-gear makes sense for your tire size.
We’re running Revolution Gears with REM finishing in our diffs.
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Table Of Contents
Do You Need To Re-Gear With Portals?
It depends on the tire size you plan on running.
- 35″ tires or smaller: No.
- 37″: No, unless your truck is a dedicated trail rig, seeing very little freeway driving. Stock gears handle 37s fine.
- 38″: Possible. A 4.88 starts making sense here, but still not needed.
- 40″: Yes, 4.88. This is the size where the re-gear actually makes sense on the trail and on the highway.
- 42″ or bigger: Yes.
That’s the short version.
Why I Chose A 4.88
A lot of people see bigger tires and assume portal axle gear reduction alone is enough to support them. At a certain point, a re-gear with portals is something you should consider. For me, that was a 4.88 ratio from Revolution Gear and Axle. With my portal reduction already handling the majority of the gear reduction at each hub, I didn’t need to push the diff any harder than that.
I started the build with 37″ tires because that’s the tire I was running before, but I knew I was eventually going to end up on 40″ Nitto Trail Grappler M/Ts… so 4.88s were the move.
Final Output Ratio
4.88 x 1.22 puts me at right around 5.95 at the wheel hubs. Most guys will run 5.29s on built Tacomas with 37-40″ tires, so not too far off.
Why Revolution Gear & Axle?
Revolution Gear’s sets are precision heat-treated to OEM specs, and the company’s been producing gear sets since 1984, so this isn’t their first rodeo with Tacoma applications.
Revolution Gear is also one of the only manufacturers running REM surface finishing on their gear sets, a process that smooths the contact surfaces at a microscopic level beyond what standard finishing achieves. Konrad covered what REM finishing is and why it matters for gears in detail, but the short version is it’s a big part of why these gear sets run quieter and hold up longer than a lot of what’s out there.
Re-Gearing With 37-38″ Tires?
37-38″ tires generally don’t need a re-gear at all with portals. Stock 3.73 or even the 3.91s in the manual transmission Tacoma perform great at highway speeds and in the rocks. The only reason to re-gear at a 37-38″ tire is if the truck is a dedicated trail rig, seeing very little, if any, highway driving. If you’re running a supercharger and splitting time between daily driving and trail use, 3.73 paired with 37-38″ tires is genuinely the sweet spot for an all-around build (both highway and off-road); there’s no reason to touch the gears.
Running a 4.88 ring and pinion with a 22% reduction puts you at 5.95, whereas the factory 3.73 gears would bring you to 4.55.
Dedicated Wheeling Rig?
If you’re building a dedicated wheeling rig, where you’re towing to the trail or even driving on the highway to the trail, and you want to drastically improve off-road performance, then re-gearing to 4.88s on 37-38″ tires might make sense. A lower ratio (numerically higher number) will multiply engine torque, which gives you better low-speed control, improves acceleration, and restores power if you’re running bigger tires.
Plenty of guys run 37-38″ tires on portals without re-gearing and have zero complaints. But if you’re looking to wheel hard consistently, then consider a re-gear at this size.
Re-Gearing With 40″ Tires?
The Revolution Gear and Axle 4.88 gear set with a 22% reduction put me at 5.95. It’s a little high, but I was willing to sacrifice some highway driving for better performance in the rocks. And at the end of the day, the 5.95 ratio does amazingly with the auto transmission on the highway.
After running this setup in the rocks and on the highway, I can say the 4.88 is the right call at 40 inches. It’s not such a low ratio that highway driving turns into a chore, RPMs stay reasonable at speed, and nothing feels like it’s screaming to keep up with traffic. But it’s got enough output to make a real difference the moment the trail gets technical. RPMs sit right around 2800 at 75 mph on the highway. I have found that from an in-cab perspective, some of the noise out there that they could be undrivable is a bit exaggerated.
What 5.95 Feels Like On 37″ Vs. 40″ Tires (With Portals)
On 37″ tires, I was slightly over-geared, and it showed up specifically on the highway. On the highway, RPMs sat noticeably higher than I wanted, somewhere in the 3,200 to 3,400 range at 75 miles per hour. Not terrible, but the 37″ tire just didn’t need that much final drive, so the truck felt like it was working a little harder than necessary every time I was just trying to cruise.
In the rocks, though, it was the opposite story; the truck was extremely composed at low speed, more controlled than the tire even required. I knew at the time I’d be stepping up to 40s eventually, so the highway tradeoff didn’t bother me.
With the 40″ tires, it’s a completely different story. The bigger tire is heavier and harder to turn, so that same 5.95 final drive was exactly what the truck needed, on both the highway and off-road. I’m extremely happy with the 4.88 on 40s paired with portals.
It handles extremely well on the highway, sitting right at 2,800 RPM at 75 miles per hour, no more of that eager, high-RPM feeling I had at 37″.
In the rocks, it’s just as composed as it was on the smaller tire, with noticeably better low-end torque control to match the bigger contact patch.
If you’re considering a re-gear at 37″ or 38″ with portals, just know what you’re signing up for. The rocks will feel great, arguably better than the tire size calls for, but you’ll be giving something up on the highway.
What’s the takeaway?Â
- 37″ highway: higher RPM (3,200–3,400 at 75), over-geared for highway.
- 37″ rocks: very composed, almost more controlled than necessary.
- 40″ highway: 2,800 RPM at 75, perfect.
- 40″ rocks: Just as composed as it was on the smaller tire, just better.
Final Thoughts
Portals and re-gearing usually don’t come up unless you’re running 40″ tires. It was kinda nice to test both tire sizes in the rocks and on the highway, though.
The 4.88s from Revolution Gear and Axle, paired with my portal reduction, were composed in the rocks on both 37s and 40s. On 37s, it was a bit over-geared for the freeway but good in the rocks. Once I went to the 40s, that same 4.88 finally made perfect sense, on the trail and on the highway.
If you’re at 37″ or 38″ and considering 4.88s, just know what you’re signing up for. The rocks will feel great, maybe even better than the tire size calls for, but you’ll be trading some highway manners for it.
