Blown diff (again), here's a pic

[Chevy-SS]

I keep blowing this diff out. It's the rear on a T-Maxx racer with Picco .26. Check out this pic. Look close, you can see metal pinion gear teeth all over the place, lol.

This is how I set ring and pinion: I put whole diff together and then look for about 1mm of in/out on pinion gear. I am looking for smoothness, with no ratcheting or clicking. Am I doing it right?

I think the problem is the diff case. I ordered aluminum case with screws on all four corners. That should stop flexing.

 

[El Pirata]

You should add shims to stop that play. 1mm is a lot of play for something that should have very little play.

Also the diff itself might need some shims to keep it from moving in the diff case.

 

[ImBroken]

With a .26, you might want to look into some hardened Diff gears... The stock pot metal gears will not hold up to that monster...
Check RRP, Maximizer, Kippster, Unlimited Engineering if your loaded... lol

 

[Rolex]

You definately need to shim the pinion for minimum play. When the gears are in, slide the pinion in and out and see how much the pinion moves away from the ring gear. If it moves out too far, only the tips of the teeth are engaging, and it won't last long.
You need good bite without pressing them together too much.

 

[olds97_lss]

Originally posted by ImBroken
With a .26, you might want to look into some hardened Diff gears... The stock pot metal gears will not hold up to that monster...
Check RRP, Maximizer, Kippster, Unlimited Engineering if your loaded... lol

In addition to replacing gears, I'd suggest getting aluminum diff cups. Kipster and maximizer both make them. You can find both at http://www.stormerhobbies.com/

These also have bigger screws in the cup itself.

Personally, I went with maximizers and used the modified stock ring gear and stock everything else. I also used aluminum diff cases like your about to do. Changing out the diff cups to aluminum makes a big difference in life.

 

[Chevy-SS]

I think I found biggest part of the problem. If you look closely, you can see 3mm threaded inserts have been installed for the two screws. (note: I bought this truck used. The guy used them all over the truck) You can also see that they have pulled out a few thousandths, which would certainly be enough to allow case flexing, which would then allow gear mesh to vary, and KA-BOOM!

This truck came with an OS .21, which I promptly blew up. A spare engine was included, which I installed and also promptly blew up (connecting rods in both engines). After that, I put in the Picco .26 and started blowing drive train parts (tranny and three diffs, lol).

My new aluminum diff case should stop flexing. I think I will try another set of standard 2.5 gears, since I have three brand new diffs already. This time I will carefully shim everything for minimum movement with smooth operation. If they blow, I will definitely move up to RRP or one of the others for hardened gears.

Thanks for comments.

btw - ImBroken, yer startin' to resemble El Pirata. Have you guys been hangin' out together? :trashed:

 

[akmadmaxx]

These would do the trick!

https://www.ssl-stormerhobbies.com/cgi-bin/seekpart.pl?pn=UE13540B

 

[Chevy-SS]

Wow, $285 for the two diffs. That's almost as much as the whole truck. LOL

 

[ImBroken]

Here's a nice price for what you may be looking for....
Maximizer Diff

 

[Chevy-SS]

ImBroken,

Thanks for link. Would I be better off with this?: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=44028&item=5902856041&rd=1

What's the advantage of the Maximizer diff?

 

[ImBroken]

To tell ya the truth, I run the RRP gears with the Maximizer cups. I just noticed that Maximizer started selling a complete kit that includes the pinion gears & cup. Seemed like a better deal to me... I'm sure there both of equal quality...

 

[Chevy-SS]

Thanks. What purpose does the "upgraded" cup serve?

 

[olds97_lss]

It makes for a stronger spider gear setup. Less likely to sheer off the little screws that hold the cup on the gear and also the rails that hold the pin for the spider gears doesn't wear like it does with the plastic cup. It just makes for a stronger setup that lasts a lot longer.

 

[Chevy-SS]

I figured the answer was something like that.

gracias

 

[olds97_lss]

I've been running mine in a 21 maxx for about 3 gallons. The gears and cups show no wear, but I have had to replace the out drive bearings to each axle since they crap out in about a gallon. I've tried stock bearings, duratrax teflon sealed bearings and boca green seals. All of them wear out about the same.

 

[StrechM]

These will also work very well. http://www.kippster-racing.com/
The problem is with the smaller Traxxas machine screws shearing on impact. The 3mm replacements seem to hold up better when shimmed correctly. From what I have gathered, the correct tolerances are more important than the replacement products.