desperate for xxt mf diff help

[worm2559]

I am having the hardest time keeping diffs in my truck. This last time was one day. I think I over tightened it this time. Any tips on rebuilding them or alternative parts. Does the CR have the same diff.

[JeromeK99]

I am assuming you are talking about a XXX-T MF... there wasn't a XX-T version..

What is exactly happening... You say you cant keep a diff in your truck. Over tightening will more than likely just make the truck handle horrible... shouldn't cause it to go bad... perhaps the balls will wear out faster... What is going bad? What are you replacing.

Need a little more information, including, motor and battery... tires and what you are running it on.. street... track.. loose dirt.. clay..

The Losi ball diff has been pretty much the same since the XX days... very minor changes other than the diff gears.

Let us know exactly what is happening and I'm sure we can help!

Jerome :cool:

[obzelite]

xxxt rtr mf1 mf2 and cr all use the same ball diff.
i'm guessing you're having the common problem I've seen almost everyone, bar the rtr ppl, have of melting the centre right out it.
your diff is slipping too much, the bearings heat up and then the centre of the gear just rips right out.
the rtr of course is set correctly from the factory so is a allot harder to kill

grab the manual and read the section very carefully about setting up slip in the diff. its a pain to get it right and when you get it wrong and run a big motor you can guarantee to melt it.
i've run a whole meet in stock, stuck a mod motor in and melted the gear in less than a lap.

a metal gear would be awesome, but you can only find them for the xxx-nt which uses a different box and a much larger gear.

if your bashing and keep destroying them, just buy the diff centre from the desert truck or speed-t, the speed-t replaces the bearing with two special washers, and the desert truck runs a geared diff designed for abuse of bashing.
The desert one can also be used to race as its not locked like the speed-t one.

[worm2559]

i am running a novak SS5800 brushless system. I seems the main thing I keep ruining is the washers that are on each side of the balls near the outside of the diff. i think it is called the throw-out bearing? The washers usually end up in pieces. It also seems to happen everywhere, this last time was in the backyard, pretty loose surface, and it was only one battery.

[Briguy]

Wow , breaking the washers :confused:. You must really be cranking on that screw , or something isn`t put back together correctly . I don`t think I ever broke the washers and I`ve been racing a long time .

[Matt Sunderlage]

When building the diff you have to take your time and initally tighten it one-two turns at a time while rotating the outdrives to be sure the parts seat properly. I've had diffs last almost an entire season. Slipper setting is also very important to having a good diff last.

[smedly]

Actually, Robinson Racing makes a hardened aluminum diff gear for the xxx-t also as well as the xxx-nt. I have hard aluminum diff gears in both my trucks, and hard aluminum idlers also. The tranny case for the rtr is the same as the cr, but different than the Gen-2.

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXXGM1

I see that his real problem is the steel washers breaking, which sounds unusual, those are pretty stout pieces. Make sure you are using ball diff grease, and don't overtighten it. I adjust mine by holding the rear tires down firmly to the ground and goosing the throttle (with the slipper tight) until it picks up the front tires, then back off the slipper. any more than that and you it will handle like crap...not enough diff action.

I have also put a small amount of blue locktight on the screw that goes through the diff to make sure it stays there, but just a little.


[QUOTE=obzelite;5591]xxxt rtr mf1 mf2 and cr all use the same ball diff
a metal gear would be awesome, but you can only find them for the xxx-nt which uses a different box and a much larger gear.

[JeromeK99]

Sounds like he's talking about the diff rings... its somewhat rare to bust them.. but it's been done.. even running a handful of packs... I've had it happen a few times to me. Couldn't believe it.. but it does happen. If this is the case, an aluminum gear would do nothing to help the problem.

Make sure that you are applying enough silicone diff grease to the balls and plates.. make sure if it is the older style diff, that the rings with the "D" shaped hole are seated correctly.

This is not a normal happening. The diff should be able to handle that motor without a problem.

You might need to seek some local help. Maybe your LHS or track.. have someone take a look at the problem and help you with reassembling and adjusting it.

Jerome :cool:

[obzelite]

the xxxt-cr runs an extra washer thats supposed to stop that, losa3039, they fit between the washer your destroying and the outdrive.
but it does sound like you might have it too tight.