Why do I keep busting the bevel gear in the diff?

[RevoS]

[shadow=red]I keep on busting these gears[/shadow]
1. http://www.hpiracing.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=86030&Category_Code=

2. http://http://www.hpiracing.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=86031&Category_Code==

Any reasons why this will keep on hapening?

 

[Da Hellion]

Need more info! Does the gear look like it has a normal ware pattern ? What are you doing when this happens.A picture of the broken gear would be a big help

 

[bustedgears]

did you have the 4 spider diff mod?

 

[.21Rc10GT]

What kind of engine are you running? is there a lot of slop in the pinion gear (can you move it in and out)?

 

[rossb]

I've never broken that gear.

 

[RevoS]

Well can not move it in or out and yes I have the 4 diff spider mod, 2 gears off the 13 tooth bevel gear broke of in the front diff and the rear. I am running the standard S-25 motor. I do not have photos now or the technology to get photos.

 

[olds97_lss]

Are your cup screws staying tight? I had that problem once because the screws on the cup backed out a little bit which completely messed up the gear mesh.

I just recently replaced my rear diff case with an aluminum one so I could shim it better. It doesn't take much slop to make for bad gear alignment.

Out of 12 gallons of running (prior to the new diff case) I ruined 5 sets of the gears your ruining (ring/pinion). I'm pretty sure it's because with the stock diff case, the gear mesh isn't all that great. Even with brand new parts, you can turn the pinion gear 1/16th of a turn before the ring gear moves. Now, with the aluminum case and shims, I have almost no slop between the ring/pinion. I'm only on gallon one, so I'm not sure if it's helping yet... I know before, I was only lasting a few gallons before one of the diffs would fry the ring and/or pinion gear.

 

[RevoS]

Thanks, That was the problem! When I took it out I noticed that the screw was very loose. Thank you for the help

 

[olds97_lss]

What screws are you using? Machine thread type screws are best. I think the stock screws are course threaded plastic type screws which are more prone to coming loose.

Try some 3mmX16mm machine thread screws like these: http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXFRK6&P=7

Included in the 4 bevel upgrade from HPI are 3mmX18mm, but I couldn't find a link for any: http://www2.towerhobbies.com/cgi-bin/wti0001p?&W=000426515&I=LXJLH6&P=K