Need center diff help…

[xcntrk]

Hey all, could use some advice about a center diff setup. I just converted a Ofna Hyper-7 over to electric using an RCM mount, Neu 1512/2.5d on 4s. I replaced the center fluid with 130k, new seals, and run 46/13 gearing.

First run out everything performed well for about 10min until I blew the center diff. Prior to the damage the front-end still seemed to unload a bit slipping the center diff nearly all the way up to top-speed before it seemed stopped unloading; even with the heavy 130k. Upon teardown, the entire diff gearing is shot. One bevel gear and all 4 spiders teeth are munched.

Is there a logical upgrade for the stock center diff? Something strong, perhaps a 6-spider, maybe a torsen-style? Or should I just replace/fix the damaged gears and give it another go? Is the center diff the same as the front/rear diffs? What fluid should I be running or is this dependent on number of spider-gears?

[lincpimp]

Interesting. Did you use a plastic spur or the stock steel one?

You may have too much clearance in the center diff, and the gears are not meshing up properly?

[xcntrk]

For whatever reason, when I did a dry test-fit of the RCM mount/bulkhead I had a bit of excess slop with the diff slightly moving from front-to-back. I did a little research and found this can be solved by stacking the diff gaskets between the spur and diff housing. I started off with 3 but feared the bevel gear was too far off the spiders and could jump. So I dropped down to 2 gaskets and sealed her up. May have been a contributor to the issue. I could rebuild and drop back down to a single gasket, but that won’t help my RCM bulkhead slop any.

[bdebde]

You can also use shims on the outside of the bearings.

[lincpimp]

One gasket worked for me, but the gaskets are different thickness depending on mfg. Do not use one and see if the diff is too tight. If not just use silicone sealant to prevent leaks. Or if it is too tight just use one gasket, and shim the bearings to get a good fit in the bulks like bdebde said.

[xcntrk]

Anybody got an easly link for the right size bearing shims? The lip (race) on the bulkheads has very small mounting surface where the bearing actually sits. I've hunted around and still come up empty handed trying to find a good fitting shim. Does ofna make one specifically for this purpose?

[BrianG]

I have a Hyper8 and have no trouble with stripping gears at all. I think using two gaskets is definitely what caused them to strip - only the tops of the gears were meshed. Do what linc said: use gaskets that will properly shim the diff internals and use large shims on the outside bearings (between the CD mount and CD) to take up the slack. Only two or three should need to be used.

[tc3_racer_001]

hi there, ive got a h8.5, will the hyper mount fit, and will i need to shim the cd or not (will there be any movement?) and what are these gasket things, never heard of them!

sorry for the random question, just seemed like a suitable place to get my question answered! (i went for the standard diff so thje kyosho plastic spur should fit...

[BrianG]

These: http://www3.towerhobbies.com/cgi-bin...?&I=LXCWN2&P=7

Thery're cardboard seals you put on the diff before you screw the end on. Keeps them from leaking.

[xcntrk]

^right; but as posted from my experiance (lessons-learned), these should not be used to address any diff movement within the bulkheads. Instead, looks like shimming the bearing is the proper approach. These are what I ordered to hopefully fix the slop.