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2

2k4mach

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san antonio, tx
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  1. Bashing
hey guys i did a search and didnt find anything regarding this and its starting to get frustrating.

i keep tearing up the seal on the left output gear in my rear diff thus slinging my diff oil all over the place. all the gears look great its just that 1 seal that keeps getting torn up.

the last time i took the time to shim everything real nicely and within a minute of running there was oil dripping off the bottom of the truck.

oh yeah its a 4907 with the sealed diffs in it.

I'm at a loss as to what is causing this.

I'm running 100k fluid in it.

and also what has got me really confused is the back half of the chassis will be covered in oil in what i assumed was the diff fluid as it poured out past the bearing but I'm beginning to question that as the oil film seems very thin compared to what 100k diff fluid feels like.

i checked my motor and dont see any signs of oil/gas leaking. i dont see any crack on the gas tank or pin holes in my fuel lines.


EDIT: the tank does have a leak in it. guess ill pick up a proline tank as soon as LHS opens
 
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I'm not sure I'd take the time to shim my diff, unless I was running a real hot engine. You could also be over-filling it too, but I doubt it. Where are you shimming it? Inside the diff? If it needs any shimming at all I would only shim the pinion. You have to be very careful tightening the ring gear as well. You want to tighten it in a cris-cross pattern a little at a time, without over-tightening it. If you think it is a fuel leak then check the tank by blowing in the pressure line under water. T-maxx tanks will leak from the screw holes sometimes. 100k seems a bit stiff, but to each his own.:D
 
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i just shimmed the pinion.

i was thinking maybe i had my slipper too tight but i dunno. torn it down 3 times now since friday afternoon, I'm getting aggravated quickly as all i wanna do is go out and finish tuning the picco and have some fun.
 
I would try not shimming any thing, the pinion may seem ok when spun by hand, but under load it could be putting alot of side pressure on the output gear or diff carrier. I didn't notice you had a picco. I have a sirio 27 on my revo and so far the gears are fine, but I did break a carrier. Check inside the ring gear too, there could be a metal burr that is toasting the seal.

I would not suspect the slipper at all, but it should be allowed to slip just a foot or two on take-off.
 
check the edges of your diff cup....replce it if you have to....use new diff seals (cup rin seal AND the little o-rings inside the cup) and internal bearings, sometimes when they blow it will allow oil to seep though and out that little outer carrier where your diff case bearings sit.....also check that your diff case is snug when you bolt it down...if it's able to flex at all that Picco will twist it pretty hard and cause some leaking.....if that doesn't work then you my friend have a gremlin that is sneaking in and eating your seals at night and you need to seek help from a forum specializing in Monster Extermination.....

it's easy to overlook the small parts in the diff...I'm not saying this in a negative way but Double check ALL the parts you are replacing with an exploded view and when you are sure you got them all....check it again.....

I wouldshim your diffs IF they need it...alot of the maxx stuff (if you use stock parts) will fit pretty freaking close already....only shim them if you feel slop in the carriers for each bearing....also tryto keep the diff centered when you shim them...don't stack up allyour spacers on one side to just take up slop.....

good luck
 
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bout to make a trip to the LHS to get a few parts. is it worth going to the emaxx gear set? i notice it has a small carrier support bar included in it.

its funny as ill tear it open, gears and everything look great but that 1 seal/xring whatever you wanna call it looks like it was sitting next to a bomb. its in about 30 pieces spread all over the diff cup.

oh 1 more quick ?

how full should i be filling that diff cup with fluid. I've been filling it like it was a shock as i never really saw the level from the factory as the seals were leaking and by the time i got it apart the cups were pretty close to being empty.
 
Usually, fill just up to the top of the cross bar that holds the spider gears.

Sounds like the shaft the o-ring sits on may be roughed up or the case itself where the o-ring seals may be damaged. Might want to inpect those as well before making the trip to the LHS. Or, your possibly missing a teflon shim in there.

Or just say to heck with it and pickup a new diff (or two) on ebay. They are fairly cheap. $17 shipped for a complete diff. Cheaper than the $30-$35 shipped I pay for savage diffs. ;)

EDIT:
Wait a minute... when did traxxas start running sealed diffs on the t-maxx?

I just downloaded the manuals for the 4908 3.3 maxx and 4909 3.3 maxx. Up until the 4908 came out, the maxx didn't run sealed diffs. The 4908 did, but the others didn't (including the 4909). They had run revo'esque diffs, but they weren't sealed. They only had a teflon washer behind the output gear on both sides of the diff. You were forced to use grease of some sort and not oil as it would ooze it's way out.

Which side is it that's getting tore up? The ring gear side or the spider gear cup side? Is there a groove in the cup or gear for the seal? You may have the wrong cup/gear to support running a sealed diff. This would smash and tear the o-ring within minutes if it were the case...

This is the non-sealed diff cup/gear:
http://www3.towerhobbies.com/cgi-bin/WTI0095P?FVSEARCH=4981&search=Go&sourceid=Mozilla-search

The sealed diff cup:
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXHGF4&P=7

And gear:
http://www3.towerhobbies.com/cgi-bin/wti0095p?FVPROFIL=&FVSEARCH=5379X+&search=Go
 
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the spider gear side was getting tore up.


i went and got my parts. rebuilt it and proceeded to go bashing for a couple hours. so far doesn't look like the seal blew apart. everything is nice and dry.

i used a 50/50 mix of 120k and 50k oil.


i wiped my LHS of the 5381 seal kits haha. they had 3 on friday and i grabbed 2 then picked up the last today.

my slipper pads were kinda worn so i did replace them and dont have the slipper as tight as i did before so maybe its that theres less shock hitting the diff now. this whole ordeal had me so confused.
 

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