Upgrades, upgrades, upgrades...

[Megazone23]

Hey, guys -- just want to pick the collective brain here. I just bought a heavy duty Maxx drive train on eBay (well about a month ago, but I recently returned from a 5 month project in China, so I haven't been able to do anything until now). Included in the lot was center drive shafts, CVDs for each corner, and front and rear diffs (aluminum cases/collars with aluminum diff cup, 3mm screws, and modified gears) -- not sure what exactly is inside, though.

Anyway, one of the diffs has no play at all in the outdrives, and it seems to spin a little tight, but not necessarily overly tight. The other one spins a lot more freely, but there's probably about half a mm of play in the outdrives. If I hold it with the outdrives vertically, it almost feels like the teeth of the ring gear is buzzing against something else. If I flip it 180, it spins very smoothly. I'm pretty sure this one needs to be torn down and at the very least re-shimmed, if not just rebuilt and greased. Do you think the other one needs it as well?

The ultimate point of this is to go brushless one of these days. To that end, I've gone ahead and bought some Integy bulks (F/R) with braces to hold the new hardware. I don't know if I'll be able to pull off both a GMaxx frame and a brushless setup (thinking Warrior 9920 and Feigao 9L running on 12 cells, eventually 14), but I know I can pull off one or the other.

If I go brushless first, how long would the rest of the stock chassis hold up? I understand excessive wheelies and backflips may ensue, but like I said, I don't think I can get both major upgrades. I don't race; probably never will. I'm more interested in the lower maintenance/better efficiency of brushless for my bashing.

Then again, my bashing may force the frame upgrade if this weekend was any indication. Missed an approach and caught the edge of my driveway exiting the ditch. Somehow the wheel nut popped off, and the lower A-arm was ripped from the hinge pin. I only noticed it this morning as I was walking out the door, so I haven't had a chance to see if any damaged was incurred to the hinge pin itself or my Powerstrokes. :eek: So I'm thinking about replacing all four corners with RPMs.

Sorry for the ramble -- I look forward to your collective wisdom.

[Megazone23]

Looks like I got off easy. Only the lower A-arm seems to have suffered any damage. I guess I'll put off the RPM upgrade for the time being.

[coolhandcountry]

If you going to start running the 14 cells I would consider a 10L. If you going brushless you may consider a aluminum diff cups if the ones you got don't have them. Steel idlers is a must and cvds to. I am nost sure what all you have so. That would get you pretty set.

[squeeforever]

i would go for a xl motor. maybe a 8 or 9xl.

[Megazone23]

Thanks for the input. I did get carbon steel CVDs and center shafts as part of the deal, and the diff cups should be aluminum with the 3mm screws and upgraded gears, so I think I'm good there. I also have some UE idlers on the way from another auction. I'm hoping to be able to get a strobe slipper setup with spur and pinions from Mike when I'm ready to order the brushless motor and controller.

Sounds like you guys think I should go ahead and get the brushless even with the stock chassis. I figure I can always get a T-Maxx 3.3 wheelie bar until I can save up enough dosh to go Gorilla. As for L vs XL, am I correct in understanding the XL can will provide greater torque?

What about the play in the diff? The more I think about it, the more I think I'm just going to rebuild the diffs anyway so I can be sure that they're put together well. At least this way if they're not, I'll be the direct cause instead of it happening because I was too lazy to check!

[Megazone23]

Okay, got a quick question regarding shimming the diff. If I understand things clearly (which is likely suspect at this time), there is a shim inside the diff cup with the spider gears (Traxxas Part 3981). But in another thread re: rebuilding the diff, someone said it may be necessary to shim the diff assembly within the diff case as well, but I don't see any shims indicated in the Traxxas exploded diagram, so what size (inside and outside diam) shims should I get, and will it interfere with the bearings?

[Megazone23]

Here's another update. I took a closer look at the diff, and I'd be very surprised if there's a shim available to take that up. Even if there is, it's the action inside of the diff cup that seems to be the issue. It doesn't seem to be a problem with slop, because there's no play in the diff assembly itself if I hold it by one of the output shafts and try to move the ring gear/diff cup up and down.

When I turn one of the output shafts, though, it feels like the gears aren't meshing well, similar to the way a zipper feels when you zip it up. I've looked at the teeth on the output shafts and the spiders, but there doesn't seem to be any wear. On some teeth, it almost appears as if there's a very slight nick, but you really have to look closely to see it. It doesn't seem like what I would think you would find if the gears were grinding. I found no evidence of binding anywhere, either against the diff cup or the ring gear.

Should I just replace the output shafts (2) and spider gears (2) and see what happens? If so, is it okay to get the stock shafts/spiders or are there some better aftermarkets?

[coolhandcountry]

It sounds as if the bearings or something is the wrong size or wore out. The spyder gears may be meshing to tightly as well for the zipper feel.

[Megazone23]

The bearings in the diff case seem to be in good shape and the right size, but like I said, the issues seem to be inside the diff cup where there are no bearings. I just looked at it again, and if I push in and pull out on the output shafts, there's just the slightest bit of play there. I feel the zipper effect more if I'm pushing in on the output shafts but still slightly even if I'm pulling out on them, so perhaps you're right about the mesh being too tight.

So if I were to replace the spiders and outputs, would the stock gears hold up to the brushless power or do I need to find some tougher aftermarket gears?

[coolhandcountry]

The best thing I have used is the 1/8 diffs. The aluminum cups and stuff will last and hold up pretty good. If you start getting to 18 -20 cells you really need some strong diffs though.

[Megazone23]

Thanks for the input. Eventually I may upgrade to the 1/8 diffs, but right now the checkbook pretty much says I gotta stop at the brushless setup. Then the next step will be getting a G-Maxx chassis.

I doubt I'll ever go any higher than 14 cells since I'm sure that would only guarantee that I destroy my Maxx in a blaze of plastic/aluminum shrapnel glory.:036: As it is, I may not even venture past 12 for a while.

I went ahead and just got some stock spiders, and I think I may have discovered at least part of the problem. The spider gear rod that's installed is ground down on one end so it's not perfectly round. That may be what's providing the additional play and possibly getting the gears out of proper mesh. I'll put it all back together when I get home tonight and let you know how it goes.

I picked up some Traxxas 10K wt diff lube while I was there. I hope that will be adequate.

[coolhandcountry]

the emaxx cases are not sealed up. The diff lube needs to be used in a sealed diff if not it is going to make a big mess. If you just run like 14 cells. I wouldn't worry about it as much. The weight is lower and power so the diffs has a much better shot at surviving.

[Megazone23]

I only used enough of the lube to put a light coat on the teeth. I replaced the spider gears, spider shaft, and output shafts, and the action is really smooth now. Just for kicks, I put in one of the original output shafts, and the notchiness came back, so I think something was out of whack there.

I think the spider shaft is one of the other problems. The old one had one edge flattened at one end. When I tried installing the new one, it wouldn't fit into the slots, so I figure the previous owner ground it down to make it fit. I took another approach and put the shaft in my Dremel and ground down the corner edge of the ends so that it has a chamfered edge instead of square. That allowed the shaft to slide right in without allowing any lateral movement.

At any rate, the diff seems to be tip top now. Thanks for your input coolhandcountry. It really helped me think things through, and I ended up learning a lot!