CAUTION! BOOK AHEAD:
I finally rebuilt my front diff a couple days ago after running for a month or more as a 2wd. I wanted to try rock rey gears in both ends, but since they are out of stock everywhere, I settled on another set of baja rey gears and a new front housing/bulkhead. Again, I used an entire tube of super glue to seal up the seam of the housing after I test assembled and shimmed a few times (ended up with .1mm between the gear and inner bearing, and .1mm between the outer bearing and dogbone drive cup this time) and packed it full of marine grease including the cavity between the pinion bearings. I also installed a hot racing twin hammers aluminum diff cup while I was in there (stock cup still looked fine, but I had already shredded the rear, and the front is a pain to get to, so it was more as a preventative measure) and new traxxas rubber sealed bearings (for no other reason than they were readily available) so both front and rear diffs are about as beefed up as can be with what's currently available.
I went out to the Pismo dunes on Sunday morning with my usual buddy, my two son's, and his son. I didn't borrow his paddles this time since the baja rey was now 4wd. It did not disappoint! I'm starting to question why I even built my other sand car since the baja rey does so well... as long as there is a little run-in leading to the climbs. I've got some Panther short course paddles and another pair of axial yeti score wheels in my shopping cart at tower hobbies right now, I can't wait to see how this truck does with tall paddles and 4wd.
I had two bad crashes out there though. We were mostly running near a very tall (for Pismo) dune that stood right around 100' tall. After going up a few times, I intended to barely jump off the lip and continue back down to the bottom, but what ended up happening was a 20' lawn dart followed by more rollovers than I could count. All I could do was watch. As it reached the bottom of the dune, it did one last slow motion roll back onto its wheels and it drove right out! Nothing damaged at all! Not 10 minutes later, my 4 year old was driving and I was shouting "slow down! Slow down!" and he proceeded to huck the baja rey off the top of the same big dune, but it dropped more like 30' down before starting it's roll overs all the way to the bottom. Again, it ended on its wheels, and he drove it up out of the bowl! Quite a spectacular show, and no damage at all!
I went to a dirt lot around the corner from my house this evening so my buddy could test out his slash, and my baja rey was getting awefully loud. He burnt up his brushed motor anyway, so I had no complaints about cutting our run short. When we got back to my house, I had my fingers crossed that it wasn't my front diff already, so I started inspection with the easy stuff by pulling the motor out. The problem was immediately positively identified, the 10mm trans bearings had exploded. I have new bearings here, but it sure would have been nice to have noticed a couple days ago when I already had the whole truck apart. I had given them the "wiggle test" and a quick shot of lube the other day, but of all the times I've had the diffs apart, I'd never changed the trans bearings. I think I'll see if there's anything to be gained by shimming while I have the transmission apart, but I think it was just those bearing's time to go.
I'm trying to decide if I should bite the bullet and throw another hot racing diff cup in the center diff too since the center diff is almost as big of a pain to get to as the front. I don't really want to just because it hasn't given me trouble, nor have I heard of anyone else breaking the center diff, and it doesn't see as much torque as the front/rear diffs since they have one more step of gear reduction. What would you do?
