Odd Question Regarding Gears

[toeheadskater]

Everyone keeps saying to use 4.88s with 33's
So i did some digging, and my truck came stock with 3.90s
I have a 3.4/5 speed combo
I run 31's just fine. I even climb steep hills at 60 in 5th just fine
I just purchased some 33x12.5x15s and want to run them
Would regearing be totally necessary?
I used Expert Advice - Expert Advice - SummitRacing.com to calculate 33s with 4.88s and at 70 I'd be doing 3500+ RPM
Thoughts?

p.s. love this forum/live on it

 

[toeheadskater]

Before grilling me...
I don't the tranny gear ratios
So if 5th is over 1:1 thats my bad

 

[benedict1337]

I'm running 35's with stock 4.10 gears. My accelation took a loss but I'm at about 2200 rpms at 70 mph. I ran 33's for a while and didn't notice much of a difference at all. I honestly don't think a re-gear is neccisary with 33's

 

[toeheadskater]

Right, but yours came stock with 4.10
Mine came stock with 3.90
So I'm curious as to whether it's still a good idea to run 33's on my stock (3.90) gear ratio

 

[fluffeh]

3.90 and 4.10 is a very small difference. You probably wouldn't notice it. 3.90 to 4.88 you definitely would notice a difference. That said, if he was okay with 4.10, you should be fine with 3.90. It may be a bit BETTER with a different ratio, but you should be fine with 3.90.

 

[benedict1337]

Yea I know quite a few people with zr2 blazers running 33's and 3.73 gears. But I think you really only would need to re-gear if you decide to run 35's or larger. I'm still getting 18+ mpg on highway trips with 35's and 4.10's

 

[toeheadskater]

So after doing the spin test I can see that I HAVE true 3.90s like the door jam sticker suggests. But then when I look at the "axle code" which is A02A according to http://toyota.off-road.com/trucks-4x4/tech/toyota-differential-identification-18588.html I should have a 138mm diameter ring and 3.36 gear ratio? I'm beginning to wonder what the hell this sticker could even mean. I look at the rear end and it's clearly a 10 bolt 8" rear end. And that's supposedly the only thing that 3rd gen runners even came with...
Thoughts?

 

[white_n_slow]

One thing people don't take into consideration when asking this question is location. Someone could be perfectly happy with 35's and stock gears if they live in Florida. Take the same truck up I-70 through the mountains and you will want to get out and walk.

4:88's and 33's will bring the gearing considerably lower (e.i. higher RPM at the same speed) than stock. 4:56 and 33's or 4:88 and 35's is actually a closer to stock match, numerically speaking, but then you have to think about rotating mass (heavier tires) and if you ever want to tow anything, etc, etc etc.

As for what gears you have, the spin test is the best way to figure it out aside from opening up the diff and counting teeth. I'd go with the results of the spin test and ignore the sticker.

And finally, you can just answer your own question by running the tires and seeing how annoying it is to you. Re-gearing is never strictly necessary, but it's definitely a good investment depending on your needs. But really, if you can live with the new tires, it's your call.

 

[toeheadskater]

Thank you for the response. I'm more curious though on how to know what I have in the event that I want to change anything. I don't understand the reference code that's in my door jam. A02A doesn't make sense on any of the decoder deals. I'm under the assumption that I have a standard 8" rear end. But but according the the code.