Stock N/A 3.4 Powerband for Regear

[Diagram14]

I apologize for asking about my Tacoma on a 4runner forum but I can't ignore the resource...

I am on the tail end of doing my research for differential regearing, having lost too much torque after a lift and tires. My 04 DC TRD auto Tacoma is lifted ~3" and wearing Cooper Discover ST/Maxx 255/85R16s. Cooper has the true tire diameter listed at 32.8".

Maybe my search terminology is terrible but I have googled my brains out for the stock powerband for the 3.4 with zero success. I am hoping to use the numbers to help me decide between the 4.56:1 and the 4.88:1 gears. The only thing I have found is a generic statement about the powerband being narrow but I want to pick the gear ratio that lands an average cruising speed in that RPM window. If anyone has that information in any form I would appreciate the share.

I used the gearing-RPM calculator at csgnetwork.com that includes a final-drive input so I could compare RPMs in 3rd and OD between the gearing options. I also verified the accuracy to my current setup by noting GPS speed and RPM and inputting those values to confirm. I found the calculator to be around 20 RPMs different from what I could eyeball from the in-dash tachometer. See those numbers in the attachment.

I know there are a lot of opinions out there on which gear set to choose and each has their own merits. I hope to let the numbers decide this debate for me. Just like the old saying goes, "Happy motor happy life."

 

[UnderFire]

Presumably you had factory 30-31" diameter tires, going up to a 33" tire, I'd say you'll want to go up 2 steps to be as close to factory as possible.

So it depends what gears you started with.

3.90 or 4.10 I'd go 4.56, or 4.30 I'd step up to a 4.88. The cruising RPM's at highway speeds are going to be in your sweet spot of 2k-2600ish with either set of gears, so you're fine there, just depends what you're used to.

Any further thinking than that, and you're definitely over-thinking it, you only have a few options, and you just want it to be close to what the stock ratio was.

 

[cashmoney]

I've always chosen gears based on the percent of change in tire size. Tire size goes up 10% then gears need to change by 10% and I always choose the lowest (numerically higher).

 

[Diagram14]

Overthinking it is what I do best.

Yes, factory tires are the 265/70R16, same as the 16" wheeled 4runners I believe. Stock gear ratio is 4.10 which puts the theoretical ratio to restore stock torque at ~4.39:1.

If I was living somewhere in the midwest I wouldnt bother with regearing because the flat highway performance is sufficient. However, there are some hills I drive often that I cannot hold 50 MPH in 3rd. I also occasionally tow a drift boat which was a struggle with the stock tire and is pretty much a joke with the 33s.

The 2000-2600 RPM window pretty much covers a 65-85 MPH window in OD with factory gears and tires. Are you aware of any dyno curves that support the effectiveness of that RPM band?

 

[02SE]

Here's an engine dyno chart of a stock 5VZ-FE as compared to the old 3VZ-E.

Peak torque of the 5VZ-FE, is at 3600 RPM, peak HP is at 4800 RPM.

 

[KidVermicious]

Check out grimmjeepr.com/gearcalc. Plug in the numbers for a stock truck, then bump the tires to your new size and screw with the gear ratio until you've found what you like.

 

[cashmoney]

Here's an engine dyno chart of a stock 5VZ-FE as compared to the old 3VZ-E.

Peak torque of the 5VZ-FE, is at 3600 RPM, peak HP is at 4800 RPM.

That's probably the crappiest power band I've ever seen. Explains why I have to drive the highway in 3rd gear to maintain 70mph on flat ground.

 

[Diagram14]

02SE - Great info. Thanks

KidVermicious - I've actually used that calculator and others and they are all very similar.

Like many others I've narrowed it down to the 4.56s and 4.88s and have no problem going either way. I realize at this point it is only a game of +/-200ish RPMs but if the efficiency window for cruising speed is only 600ish RPMs wide the difference in ratios is 33% of that window. I'm still looking for the technical information to make that decision.