The Mystery of the B07A 4.30/4.56 PreRunner Gear Ratio

So I've been doing some research to do the PreRunner 4x4 conversion on my truck (1998 PreRunner Ext. Cab 2.7l AUTO). My VIN sticker on the driver's side door pillar indicates I have a gear ratio of B07A.

When I looked up this gear code, several threads and charts online point out I have 4.30 gearing. But here's the thing, several sources say the '07' in my gearing code has some exceptions. According to LC Engineering "The '07' code was introduced in 2000 and it's actual ratio has not been confirmed, however, Toyota did reintroduce the 4.30 ratio to the Tacomas in 2000, so I assume the mysterious "07" code indicates 4.30, but this is not confirmed."

What makes it even more confusing is when looking up a front differential/carrier for my truck in my assumed gear code of 4.30, a front carrier with this gearing does not exist. Front carriers with the 'Front Axle, w/o automatic disconnecting differential; 4 cylinder, AUTO' configuration only exist in the 3.58/4.10/4.56 and nothing else. Even for the other configurations of engine and drivetrain there is no such thing as a front carrier with 4.30 gearing. I got all this information from car-part as well as other various scrappers who use the same parts database system.

I'm stumped. Yeah yeah yeah I know I can just go outside, mark the driveshaft, and count the revolutions but I wanT to know what your guys' experience is. This seems to only be a problem on PreRunners of '98-'00.

 

So, to add more confusion to this, my 99 3RZ TRD pre runner has B04A B07A door code, but it has 4.30 gears. I verified this by jacking up the rear axle and spinning the driver side wheel 10 complete rotations. I put a piece of tape on the driveshaft and counted the revolutions and it spun 21.5 times. You take this number and multiply by 2 (since the passenger wheel is not turning during this) and divide by 10 (number of tire revolutions). This comes out to be exactly 4.30 and there is no possibility that it is any other ratio. I even took a video of it just incase I miscounted.

I also further verified this by installing a elocker axle with 4.56 gears. I reinstalled my stock speed sensor gear in the transmission and my speed is correct on my speedometer. (I have 255/85 tires and put a different speed gear in to correct the speedometer previously with the stock 4.30s).

Edit: I suggest you lift the rear axle off the ground (you actually only need to get one wheel up) and rotate the wheel like I did. This will tell you exactly what ratio you have. Your truck needs to be in neutral btw.

 

Jeez Toyota. If somehow my truck actually has 4.30 gearing, I'm a little boned. I called up a Toyota scrapper and they told me they have never seen a Tacoma with a front carrier geared at 4.30. They said they did have a 4Runner front carrier with 4.30 gearing I can use. I still have a suspicion I have 4.56.

 

Lift the rear end and spin the driveshaft 10 times. Count how many times the wheel spins and divid by ten.

You can do one spin of the driveshaft, but if you're trying to decifer between 4.10 4.30 and 4.56 it may be worth going the longer route.

 

So I did what you said. I jacked up the driver's side tire off the ground, put the truck into neutral, and spun the tire 10 times. I did this test 3 times and 2 out of the three tests resulted in 21, with the last one being 22. I counted 21 rotations of the driveshaft. Doing the math 21 x 2 = 42 / 10 = 4.2

So rounding it up I guess I have the 4.30 gear ratio as the VIN sticker gear code of 4.30 states.

 

Yep that sounds right. If you had 4.10s it would be 20.5 rotations, if you had 4.56s it would be 22.5.

I wrapped some painters tape around the shaft with a tab sticking off, that way it would be really obvious as it rotated.

 

I just tested this again but with the passenger tire. This time I rotated the tire 20 times. I counted exactly 43 rotations. Am I crazy or does that mean 4.30?

 

Another test I did was spin the drive shaft 10 times. I counted about 4 rotations of the tire.

 

Well I guess the only way to be sure is to count the teeth on the gears. I needed to change the rear differential oil anyway.

 

Another way to confirm would be to drop the rear driveline and look at the color of the pinion nut.

 

Can you elaborate?

 

Not sure if they continued it on the tacos, but the mini trucks, 79-95 had, along with the door codes, a color on the pinion nut of the third member itself. You could double check the door code with the pinion color. Pink was 4.10, red was 4.11, blue was 4.30, white was 4.56. If the thirds had ever been replaced or worked on, the color code was inaccurate.

Edit : Just found the info, apparently it was only to 1995 so don't go chasing that idea.
http://www.4crawler.com/4x4/4R_TechInfo.shtml#Differentials

 

Yes that means 4.30s

 

Huh, wow. Guess I will be using the ADD 4Runner carrier with 4.30 then.

I'm going to be opening up the rear differential tonight to make sure. I needed to change the oil anyway.

 

Unless your pulling the 3rd member out you can't count the teeth.

 

Yeah that's what I just realized. I've done it on a Mazda B3000 where the back of the housing comes off.

 

I thought the manuals came with 4:56 and the autos 4:30?

I remember something about my grandfathers 2003 4wd 3RZ auto having 4:30

 

@BartMaster1234 I just realized that I was wrong about my axle code. My truck has the B07A code just like yours, and it had 4.30s stock. I will edit my previous post as well so it is less confusing for people looking at this.

 

Interesting. My truck had 4.30 gears after counting the revolutions of the driveshaft/tire.

 

@BartMaster1234 did you ever figure this out? I am selling the diff from my last part out and I want to make sure it is the 4.30 it has the mystery B07a code.