Should you Supercharge or Re-Gear Your 5th Gen 4Runner?

Magnuson Supercharger or Gearing to 4.10, 4.56 or 4.88 on the Toyota 4Runner (overview on gearing)

We had a question come in about the Supercharger Vs. Gearing. Both of these additions are great but understanding how they affect your RPMs and speed is important.

The question:

I hear some guys local (Phoenix) saying don’t waste your $ on a Magnuson SC. Get a 488 gear set up instead. Really? I mean I raced 5.0 mustangs and I know gears and SC’s… but is the SC that weak? or the gears that good?

It depends if you are running short on gears due to oversized tires and weight or short on actual horsepower, which is where the SC would come in. Whether you decide on the SC or the gears will depend on tire size, load weight, how you drive on and off-road use, etc.

Are you asking what to invest in… 4.88s or a SC? It depends how you use your truck on highway vs local roads/ off-road and what that power is used for. Either way, we would focus on the force. How much force does the SC provide to the wheel vs force with gears to the wheel?

In a perfect world, you would probably want both. With 33-34″ tires and a SC, you would probably want 4.56 gears. With 35″ tires and no SC, you might want to go with 4.88s.

That is just my personal opinion and hopefully, a ring and pinon head will chime in below.

Crawl Ratio and Gearing

Basically, we’re looking at the crawl ratio. The ratio of torque at the wheels to the torque at your flywheel (read more on your crankshaft and flywheel). This is how much your engine torque is multiplied before it gets to a place where power matters; your wheels. Both the SC and the gears will affect your crawl ratio in different ways.

Power goes through your engine into your transmission and then to your transfer case, and finally through your differential (your gearing), and lastly applied to the wheels, which is the last step in power.

Power is torque x RPM. The formula is… torque x RPM divided by 5252 = horsepower. If you go through a reduction in your gearing, you have to decrease your RPMs by the same ratio to keep your power constant.

So it depends on how much high-end/ low-end torque and power you want. Do you want more low-end torque at low RPMs (rock crawling) or would you prefer more high-end torque at high RPMs (towing a boat on the freeway)? Or, do you just want to keep everything as close as possible to stock RPMs when going up in tire size? By going with a lower gear like the 4.56s or 4.88s (generally speaking with larger tires) you will have lower RPMs compared to the factory gearing.

By going with 4.88 gears, you are creating better initial acceleration (from the 3.73 factory gearing) with larger tires. You may want to consider 4.56 gearing, not the 4.88 depending on your tire size and specific application.

With lower gears and larger tires, you will create better low-end torque compared to the factory 3.73 gears. There’s a really good article on gearing here. If you want to understand gearing in depth, read that article.

Gear Ratio, Tire Size, Speed and RPM Examples

There are handy gear ratio calculators out there, but here is one that I use and then here is another one.

Factory gearing is 3.73 running 31″ tires

• Gearing Ratio: 3.73
• Tire Height (Stock): 31″
• Speed: 70mph
• RPMS: 2906

Factory gearing with 33″ tires

• Gearing Ratio: 3.73
• Tire Height (Stock): 33″
• Speed: 70mph
• RPMS: 2730

Factory gearing with 34″ tires

• Gearing Ratio: 3.73
• Tire Height (Stock): 34″
• Speed: 70mph
• RPMS: 2649

Gearing down to 4.10 with 34″ tires (4.10 gears are not available for us)

• Gearing Ratio: 4.10
• Tire Height: 34″
• Speed: 70mph
• RPMS: 2912

Gearing down to 4.56 with 33″ tires

• Gearing Ratio: 4.56
• Tire Height (Stock): 34″
• Speed: 70mph
• RPMS: 3337

Gearing down to 4.88 with 33″ tires

• Gearing Ratio: 4.56
• Tire Height (Stock): 34″
• Speed: 70 MPH
• RPMS: 3571

Gearing down to 4.56 with 34″ tires

• Gearing Ratio: 4.56
• Tire Height (Stock): 34″
• Speed: 70 MPH
• RPMS: 3239

Gearing down to 4.88 with 34″ tires

• Gearing Ratio: 4.88
• Tire Height (Stock): 34″
• Speed: 70 MPH
• RPMS: 3466

Gearing down to 4.88 with 35″ tires

• Gearing Ratio: 4.88
• Tire Height (Stock): 35″
• Speed: 70 MPH
• RPMS: 3367

Gearing down to 4.88 with 36″ tires

• Gearing Ratio: 4.88
• Tire Height (Stock): 36″
• Speed: 70 MPH
• RPMS: 3274

Gearing down to 4.88 with 37″ tires

• Gearing Ratio: 4.88
• Tire Height (Stock): 37″
• Speed: 70 MPH
• RPMS: 3185

The difference between 4.56 and 4.88 is about 227 RPM at 70 MPH with the 34″ tires.

Your best bet would be to use a ratio calculator on any website to see what your RPM’s will be at a given speed.

For example: If you like to cruise on the highway at 70 MPH, use the calculator to see what your RPM would be at that speed with either ratio. Using that information, determine which RPM range makes you and your truck happier.

Do you anticipate going to a larger tire? Lean toward the 4.88. Serious about the supercharger? Probably opt for the 4.56.

With 4.56 and 4.88 gearing, you will have quicker acceleration, and higher RPM’s at speed.

The only drawback to higher numerical ratio gearsets (lower gears) is that the lower you go, there are fewer teeth on the pinion (less tooth contact = weaker). But this is usually not an issue until you get into really big tires and hardcore trails.

This really depends on how you intend on using the 4Runner.

The Supercharger

The sc is going to push more high-end and low-end torque which produces real power.

In another post on the SC, we jotted down these details below.

So we mentioned a 30% increase in power. Let’s get into more detail on what this actually breaks down to. It is actually more like 80-100. The 5th gen 4R is 270hp at the crank, Magnuson tested theirs at 250hp at the wheels (probably generous as drivetrain loss is normally 15-25%). The Magnuson SC tested 336hp (But, expect to see 330 on yours) at the wheels, 86rwhp (Rear Wheel Horse Power) increase from pre-install values. 336rwhp would be more like 386hp at the crank (vs 270hp listed stock). Basically, at the wheels, you are looking at 250hp stock compared to 336hp supercharged. At the crank (estimated) 270hp stock to 370-390hp supercharged (if you multiply 336 by 1.15 to account for drivetrain loss). We stayed conservative with the latter given the high RWHP pretest by Magnuson. 

The supercharger is going to give you even more initial acceleration and speed than gearing. I don’t think the supercharger needs a ton of explaining but it will really help with many areas of the 4Runner power problem. At low RPMs and high RPMs, you can expect to see actual HP gains with the SC.

The power increase will absolutely help. Whoever told you the SC was was a waste of money may have their own mind made up about gearing and the SC, but it is still a product you should consider depending on your daily and off-road driving needs.

With an SC, you will see less sluggishness, you will downshift less, and your MPG will likely be better under lighter loads as opposed to running gears like the 4.88s.

At the end of the day, you should consider them both but if you had to choose one, it really depends on tire size and how you use your 4Runner.

I am not a gearing or SC expert but I hope this helps answer the question.

Questions or Comment? Leave them below