my friend who does transmission and diff rebuild is building my diff with OSG 1.5 way and 5.1 final drive. he's having a hard time sourcing shims to set the backlash. he said mazda only offer two size and neither of them are exact match needed. those who have after market FD, who built your diff and where did you get shims from.

thanks,

 

MazdaMotorsports.com offers all of the sizes

I went into the parts website, navigated to stock parts and then filtered in as follows: 2005 : RX-8 : CHASSIS AXLE SUSPENSION,BRAKE : REAR DIFFERENTIALS

I lost count but they have something like 20 or so different sizes listed there. We've ordered them from there so I know they exist.

 

Yes, my son and I rebuilt the diff on our XP RX-7 with the OSG and a RX-8 4.44 gearing with many shims from our dealer. The Parts manager, who we have known in his position for over 25 years, sent out several that we requested and then took back those that we didn't need.

 

the shims specs i need is not available from mazda, i just checked on mazdamotorsport. looks like i'll need to have custom shims made.

 

That would be very odd. Are you sure you measured correctly?

They carry all of the shims listed in the FSM. Sometimes their parts website doesn't list everything on the page, but you can put in the part number in the quick order form and it will come up anyway.

 

we need a 5.33mm and a 6.65mm but mazdamotorsports only show 5.5 for thinnest and 6.4 for thickest.

 

We've done 4 or 5 diffs now, including an OSG, and never encountered this.

I would suggest you double check that you got the ring gear seated properly, the pinion gear is adjusted properly, and the bearings are pressed on all the way. Also, that total shim stack up to case width is correct.

I assume you have an FSM you are following, but if not, here is the one we use: http://foxed.ca/rx7manual/manuals/RX...DriveTrain.pdf
Page 39 has the shims section.

 

Thanks for the info. We have double checked the ring gear is seated and the bearings pressed.
This is what it looks like right now with the backlash set to .004". What's your recommendation on which way to shim this.
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We are using 3mm pinion shim which is the thinnest one Mazda make. Also, to get the backlash to .004, we can't do it with the available oem shims. The 5.1 FD is not a Mazda unit, it's an aftermarket one.