After searching both the Trailvoy and this forum, I haven't found a good mathematical explaination for the numbers here. It also seems that some of the calculations for H0104 and B0205 shown on my readout from my TB are off just bit, which could be why when I had the stock tires my speedo was a little off from my GPS. So, I tried to understand from a math standpoint what was going on, starting with H0101, which you should be then able to calculate H0104 and in theory, B0205.

Just some quick background info, my blazer is an 03 SWB, 4wd, 3.73 open diff and came with BFG Long Trail T/As from the factory.

The factory readout for my blazer shows H0101 = 65199.

Using the equation H0101 = P*D*1000000/(T*pi)

Where P = 40 (which seems to make sense, 40 pulses per revolution of the output shaft)
Where D = 3.73 (in my case, since it uses 3.73 gears)
1000000 = the number of milimeters in a kilometer
Where T = 727.656mm

Before I start, let me explain "T", as one might quickly point out that a 245/70/16 tire, measures 29.5" in diameter. That may be true in theory, however, if you look at the BFG website for the LongTrail T/A, you'll see that it is 704 revolutions per mile, which I as I understand is a measured distance with a given load on the tire.

So to find out "T",
Divide 5280 feet per mile, by 704 revolutions per mile. That gives you 1 revolution is equal to 7.5 feet.
5280/704 = 7.5

7.5 feet, times 12 inches per foot, gives you 90 inches per revolution.
7.5*12 = 90

Take 90 inches, divide by pi, and you get 28.6479 inches in diameter
90/3.1415926 = 28.6479

Multiply 28.6479 inches by 25.4mm per inch, and you get 727.656399mm
28.6479*25.4 = 727.656

I included the math for anyone that would like to check and ensure it was done correctly.

Now back to H0101
40*3.73*1000000/(T*pi) = 65266

I know, not quite the 65199 number, but close.
Rewriting the equation and solving for "T", using H0101 = 65199, I ended up with T being equal to 28.6776".

So, that is a difference of my calculated diameter of 28.6776" - 28.6479" (from above) = .0298" in diameter!
It would be safe to assume a little bit of rounding was used when BFG arrived at the 704 revolutions/mile number.

The reason for the math was to simply understand where the number of 65199 came from. And I figured that if I could indeed calculate it out, that I could then properly calculate H0104 and B0205.

Based on my math above, it is my belief that H0104 in the table listed in EFILive should not be labeled as "Trans Output Shaft Revs/Kilometer", but as in "Trans Output Shaft Revs/Mile".

My table shows H0104 = 2637.4

Here is the math.

If H0101 = H0102*H0104,
then H0104 = H0101/H0102.

But 65199/40 = 1629.975, not the 2637.4 value shown in my table for H0104.

However, multiplying 1629.975 by 1.609344 (which is the number of kilometers in 1 mile) is equal to 2622.63. Hmm, so 2637 - 2622 = 15. This is a difference of 15 revolutions of the driveshaft in one mile, which is 600 pulses. 600 pulses in a mile seems like it would be a huge amount of error. We'll look at that issue in a moment.

15 revolutions of the driveshaft, divided by the 3.73 gear ratio, is 4 revolutions of the rear wheel. With a roll out distance of 7.5 feet per revolution of the rear wheel, this is equal to 30 feet. (7.5*4) in 1 mile.

So according to this, the percent error is 1/2%. I'm not going to show how to calculate percent error.

B0205 should also be able to be calculated the same way.

Taking the 65199 * 1.609344 = 104927, which should be a good value to use for the B0205. I believe that this math is what EFILive is using to calculate the numbers for what they call "TOS" for H0104 and B0205.

NOTE: This is all assuming that the transmission is using a 40 tooth reluctor, which is an assumption. I have not been able to confirm this, thats just what comes up when I do a search for replacement reluctors for the 4l60e trans.

Also note, to calculate the H0101 number, you need to start with the revolutions per mile from your tire manufacturer's website and calculate back the diameter.

This math also explains what goldbergv95 was showing in his chart with the circled numbers. I believe he means miles, not meters, otherwise the numbers would not match up.

If all of this has been explained before, sorry, I couldn't find it. Woohoo, post number 1 for me!