I was helping a friend freshen up his transmission last weekend since we have a few months before our next race and noticed something odd with his transmission (JDM GSR tranny with an ITR 5th gear).
Upon removal of the 5th gear from the mainshaft, I checked the tooth count: 33 teeth.
I then checked the tooth count on the countershaft 5th gear: 28 teeth, the correct tooth count for an ITR matching 5th gear set.

He ordered a new (mainshaft) ITR 5th gear from Acura. Part #23581-P80-F00
A week later he comes over to watch the reinstallation process and as I'm comparing the new gear to the old gear I noticed that the identifying tick marks on the new 5th gear do not match up with those on the old 5th gear.


new ITR 5th gear on the left, old ITR 5th gear on the right

This concerned me, so I counted the teeth on the new gear: 33 teeth. I then referenced my spreadsheet of gear diameters to ensure that it was in fact an ITR 5th gear. I don't have the measurements in front of me (since I'm at work right now) but the diameter of the new gear matched up with what I have on my spreadsheet down to a tenth of a millimeter. I measured the old ITR 5th gear and it also had the same diameter (to the tenth of a millimeter) as the new ITR 5th gear, and my spreadsheet.

Did Honda/Acura revise the 5th gear and give it different identifying tick marks??

 

It will be fine. The JDM GSR uses the same shaft gears as the B16 Hydro which is the same ratio as an early ITR but with different ID marking. Honda has superseded the B16/JDM GSR M/S 5th gear (3 id marks 33 teeth) to the ITR 5th gear (1 ID mark 33 teeth)

 

Thank you so much! You guys are such a great asset to this forum.
In addition to the 5th gear refresh, we also dropped in a new MFactory 4.7 final drive in there. Cool to see your business card on the inside of the box as we opened it.