All this is trial and error and takes time to complete but you will be rewarded with a transmission that will last much longer than if you had not done this If you have a brushless model or plan to upgrade to a brushless system I consider the differential shimming manditory.
- Remove your transmission from the car an remove one side cover.(If you still have bushing's install bearings now).
- Then remove the differential and idler gears from the case.
- Place one shim on the input shaft.
- temporarily reinstall the side cover with a few screws tightened snugly try to slide the input in and out to test for play if it doesn't move rotate to test for binding.
- If rotation is stiff dissemble and try a thinner shim . If shaft slides in in out freely add a additional shim . experiment with different thicknesses till shaft rotates freely but doesn't move in and out of the case..
- Re install idler gear with one shim re install side cover as before but with a few more screws and test for binding . If binding is present try a thinner shim . If no binding is present try a thicker shim or install a second shim .
- Well after you remove the 4 screws on the side you will be greeted with this .
- remove the center bevel gears and proceed to remove the e clips from the out-drives.
- Pull the out drives from the case halves and add a 5 mm shim to one as seen in picture number 2
- Add and remove shims as necessary there should be just a light bit of resistance to rotation and installation of the e-clip should not be difficult .
- With slop removed from the out-drives the only thing left is the play between the gears themselves .
- Start by installing one 3mm shim behind each gear as in picture number 3 , both shims must be of the same thickness.
- Reassemble with just a pair of screw to test for play . If binding is felt remove shims and try a thinner shim or no shim at all .