An
aluminum diff case is a very good idea. It will keep the gear mesh stable, unlike the stock plastic case.
Below are details on how I prep my diffs. I have approx 11 gal (
trx 2.5) on one set up this way. It is way past due for inspection, but it keeps working, and I don't care if it self destructs at this point. It's starting to get a little "loose". I'm using the stock cup and gears and the Al case from that link above.
I'm using lock lube in the cups for better traction and handling.
T-Maxx diff modification:
Here's the grease I use:
http://www2.towerhobbies.com/cgi-bin/WTI0091P?&C=CMH&V=YOK
I use the "hard" in the rear and the "medium" in the front.
You'll need shims too:
http://www.teamcrc.com/
6 mm and 10mm (the 10 mm are for the diff side brngs if you want to shim for better gear mesh)
-Remove and clean out diff cup
-Dry assemble spiders in cup and trial & error 6mm shims to remove excess endplay (should take 3-5 shims). You don't want it tight, so leave a little play (.010"-.020"). Keep the stock plastic washer against the cup. Split the shims side to side (equal # on each shaft).
-Apply lock lube to cup side gear and install into cup w/ shims. fill cup approx. 1/2 w/ lube and install spider/shaft assy. Fill rest of cup, leave a depression slightly smaller than ring gear side gear (try to leave no air). Apply lube to other side gear and install into ring gear w/ the rest of the shims. Assemble the ring gear to the cup (some grease will squirt out).
-If you want to improve ring gear/pinion mesh, now is the time.
-Dry assemble the cup assy. (carrier) into the case w/o the pinion. T & E the endplay w/ 10 mm shims (they go between the brng and the carrier) to .010" - .020". Keep track of # of shims (we'll call this the preload shim pack).
-Install pinion and adjust shims on ring gear side to move the mesh tighter. Put the rest of the preload shims on the other side and dry assemble the case to check. Some tight spots are fine, but you should be able to turn the pinion shaft w/ your fingers. Play w/ it till you get it right, might take a few tries.
-Disassemble and grease ring and pinion. I use this grease, you should be able to find it locally.
http://www.super-lube.com/index.html
-Final assemble diff
-Use a 3/16 id x 5/16 od x 1/16 thick o-ring between yoke and diff on the shaft during assembly. This will seal the diff and enhance the posi effect (w/o the o-ring you will get a glob of lock lube in your yoke). You will have to push HARD on the yokes to get the pins in.
-I also use foam body washers (p/n 4915) on the yoke to dust seal the brngs. Clean the yoke and stick it on. You will have to stretch it slightly to go over the raised area in the center. Apply some grease to the exposed areas of the foam before assembly. The foam will be tight at first, it will loosen up in a run or two.
The medium lube in the front doesn't hurt turn in.
The results holding the truck in the air are:
-spin 1 rear hard, spins whole driveline w/ little hesitation.
-spin 1 front hard, opposite side stays still a sec while rest of driveline turns, and then opp. side catches up
Sounds kinda dorky, but it's the best way I could describe it.
