I have a 3.91 '741 in my coupe at the moment, I picked up a Richmond Gear 4.10 gearset that I'm going to install and need some recommendations and a check of my calculations.

The new gearset is for a '742 case, which previously had a 3.55 factory ratio.

OK, so I measured all the parts and am looking for some recommendations regarding the starting point for the pinion head bearing shim.

Here is what I have so far:

1) Pinion head thickness dimension (from end flat face to where the bearing and/or shim sit on the other side)
OEM - 2.575"
RICHMOND - 2.627"

2) OEM pinion shim
0.090"

3) OEM gear marking
'-1'

4) RICHMOND gear marking
CROWN markings => 'I57 BL007'
PINION markings => 'I57 CD 2.720'

OK, so I understand the Richmond markings, set backlash to 0.007" and measure the pinion installed in the case to centerline of the cap of 2.720". Great...but I do not have the tools, so another method is needed.

To simplify things I have purchased another NEW Timken pinion bearing which I will hone out a tad so it's a slip-fit onto the new pinion. That will ease the trial-end-error gearset mesh pattern reading. Before I get there though I would like to start as close as possible to what the ideal spot may be.

OK, so the stock gears were using a 0.090" shim and given the difference in pinion head thickness between the two (0.052) that gives me a left-over thickness of 0.038" (0.090-0.052) needed to get the new pinion into roughly the same operating spot as the previous OEM install.

Does the above make sense?

Oh, I am no pro at this...ha ha, you can tell for sure, but I did successfully setup my previous 3.91 gearset for the '741 case and it's been holding up pretty well, no noise, no problems that I can report. I remember measuring things repeatedly back then, but it's been a few years so I am practically re-starting the learning effort on this topic.

Thanks!