I've been dealing with this issue for about a year on my nitro evader. If there isn't 100% traction (like on the street or wet dirt/mud), the car spins out under ANY type of throttle. I can get it going walking speed, and then slowwwly ease into the throttle, and the back end just slides out. I've tightened the diff down all the way, but still cannot for the life of me keep the stupid car straight. I know tires can play into this, but this is more than just that; it's like i'm driving on ice.. literally. I also own an rc10gt and do not have this problem at all.. in fact to put it in perspective, the traction of my rc10gt with road tires in dirt is better than the evader with proper dirt tires in the dirt!

So here's my idea. I rebuilt the tranny awhile back on the Evader, however I packed the ball diff/diff case with differential grease. I didn't just put a little, I really packed it in there. Is that the proper thing to do in these type of ball diff; could that be the reason I can't get that diff to lock up? (assuming the lack of lock is the cause of my straight line traction issues).

Do you bearings spin smooth? Does the normally spin out to one side all the time? When the tires are off the ground, and you give it gas, do the wheels shake immensly? If so, you might want to consider a tire balancer. got the Dubro prop/wheel balancer and lead tape to balance the tires and my buggy is alot smoother and more consistent now. What motor are you running in the Evader? Put AE black grease in the thrust and AE diff grease in the actual gears. If your not running an extremely fast motor, loosen the diff screw about 1/2 a turn and see what happens. You want to get it kinda loose, but if the diff barks, TIGHTEN it to the place you had it before as it flat spots the diff balls. Is the diff smooth? Packing it is fine, as long as you wipe the excess grease that comes out from the outdrive.

Yeah the diff is as smooth as can be. When I did the rebuild I replaced the plastic internal gears with aluminum and carbine diff balls. It has been about a year and no grittiness at all in its operation.

Concerning the tires, I honestly cannot say that they're balanced. I'll check that out tomorrow.

The motor is the stock DTX .18.

ball diff? sounds like you have it too tight, especialy if youi say its been a year and its not in need of a rebuild... loosten the diff a bit so it can have a little diff action and I bet your probem goes away....

Well it hasn't worn out due to the hardened gears and carbide diff balls. I'm afraid if I loosen the diff it will increase the problem. Remember, I can't increase throttle in a straight line without it losing traction in the back-end. I can only guess that that's because one of the two wheels is starting to pick-up speed over the other. I'll try to loosen it but I really think it's not tight enough; I would even prefer locking the thing.

Loosen the dif just a bit.....what's happening is you have the rear basically locked....if one wheel looses traction with the locked diff, it basically spins out the other tire....

Hmm, never thought of it that way. I've always been thinking that a non-locked diff was beneficial only for keeping traction in corners, but your logic works as well. I'll give that a try this week!

yup, like in a 1:1 vehicle, driving in the snow with a locked diff is really scary, because it fishtails all over the place. since the wheels are locked together, any time one loses traction they both do and you start to spin out. But with an open diff, when one loses traction and starts to spin, the other is still gripping the road, and so long as you let off the gas to let the spinning tire regain traction, or it hits a higher traction spot, you will keep going straight....