Reading about 33" and 35" tires, the subject of re-gearing comes up. I understand that I will certainly "want" to re-gear if I put 35" tires on.
Other places on the internet suggest a 4.65 (rather than 4.88) ratio for 33"s as a compromise between recouping power and higher RPMs.
My questions are:
- Will I suffer adverse mechanical side-effects or damage anything if I re-gear to 4.65 while I still have 31" tires?
- My FJ feels a bit sluggish on-road and up steep inclines as-is. In your opinions, will I feel a power boost that justifies the price of re-gearing if I re-gear to 4.65 while I still have 31" tires?
- In your opinions, will re-gearing to 4.65 be sufficient for 33" tires? (Internet says "yes," just want to double-check).
- If you believe I should skip 4.65 and go straight to 4.88, please answer question #1 for 4.88.
Thanks in advance!
Up here in Colorado, at elevation so we're losing ~20% of our horsepower over your truck breathing at close to sea level, I've never even heard of a truck on 33's regearing. 35's, yeah regear. But 33's? Nobody does it, and with all due respect our hills are a bit steeper than yours in Texas
What year is your truck, how many miles? You should figure out if the sluggishness is something else -- needs new spark plugs etc -- or if it's just the nature of driving a brick at highway speeds. In flat / level down where you live our trucks aren't great highway vehicles anyway. If your truck feels sluggish just with 31's it's either "there's another big problem here" or "that's just how our trucks drive, get used to it". Assume the first one until you prove that's not the case. Go to an FJ meet and have another FJ owner ride with you, or even better, let them drive your truck. My '99 Wrangler had no power but I just thought "it's a Wrangler" until my brother drove it, said something was wrong and we found out the catalytic converter had rusted almost shut.
If your truck is an '07-'09, it was designed to run on premium gas. If you aren't putting premium in it, it's detuning (costing you ~20-30 HP) to keep from knocking. If your truck is a '10+ the stock HP/Torque specs are for regular gas but it can take advantage of premium gas, another 20-30 HP over stock. But again, most of those HP gains are at the top of our RPM range where our trucks don't typically live anyway.
To answer your specific questions: no, regearing for such small tires won't hurt anything, but it will limit your top speed. How much? One of the more technical guys can speak to that. Will regearing give you enough of a power gain feeling to justify the cost? No, because you've got some other problem that isn't being addressed, or the problem is how you think the truck should drive. The only improvement that you can do where you'll feel a big power boost is a supercharger, which are hard to find (the TRD one) for the '07-'09 and the '10+ trucks never got one from Toyota.
Maybe I'm a bit of a purist, but the only highway miles I like on my FJ are when it's taking me to / from a trail. If you're putting a lot of highway miles on your FJ, and you love your FJ and want to keep it forever, stop doing that. Go buy a cheap efficient highway car, the MPG savings will pay for the car in a couple of years. My highway car is an '11 Lexus GS460 that gets 30 MPG highway, it's like riding in a sporty couch with a great sound system that can do triple-digit speeds all day long. But you can start at used Civic / Corolla and work your way up from there based on your price range.