MBX4 XR Works Problem
 

I bought my MBX4 Works, pre assembled , I have not run it yet, but I hear a strange noise comming out the diferencial, and I notice that If you move the car with your hands forward 2 or 3 turns of the wheel is easy to move, but after that it gets hard to move it forward, after the wheels turn again , the car gets again easy to move forward!!!! which is my problem?

Sometimes the spur gear is not 100% true mounted on the center diff. It may need to be centered a little bit, and if it's not too bad of a drag, I wouldn't let it worry you. Check that first, second make sure the brakes are not grabing. If all else fails then remove the front and rear and check the individual ring and pinion gear mesh by holding onto one wheel and turn the other.

But
 

But I dont think the problem is in the spur gear, I think the problem is in the conical gear, due to a strange situation If I tie the screws strongly, the diferecial gear begings to sound, and one turn soft, and other turn hard!!! Why ? i dont know!!!

Are you talking about the differential itself that you are tightening? If so, the differentials, believe it or not are adjustable. The more you tighten the four screws the less it will allow power to transfer from one side to the other by making the gears mesh tighter. If you are talking about the ring and pinion gears that drive the differential, then if the drag isn't really really bad, I wouldn't let it bother you, it will be fine like that. If it is really bad then I would inspect the diff. case to see if it is bent or something.

Is It?
 

I saw in the page one of the MBX4 RR Manual that we have to put a washer 13.5X15.9X0.2 in the left side of the gear box, but my car doesn´t have that washer, I dont know if this is the problem!!!!! Let´s see do you say that the diferencial is ajustable? you mean the four screws of the conical gear? cause I untight a little bit the screws of the left side of the rear gear box, and it feels more soft , and the noise has almost desapered!! What do you think?

You know, yesterday I removed the front gear box and sonds almost the same, but it feels softer to turn the wheels!!!!

CLORO
 

Take the diff out and rebuild to instruction specs,than put in buggy and just make the 4 screws snug to a littte loose,not tight.As far as i can tell the 4 screws just hold the housing together ,no adjustments that i can tell from these 4 screws.My diffs also make funny noises and hard to turn when you tighten those 4 screws .i've had no problems out of my diffs in over a year and some like this""make sure the bearing on {co272 the gear}and the bearing on {co256 the end of diff housing} are clean and freely moving .It would not hurt to tear apart one section of your buggy and look over those parts to get a good idea of hows things work since you did not put together when you can,just my 2 cents worth""hope this helps...p.s. co258 is gear for front diff and co 272 is for rear diff.i hope that did not confuse you.....Has the manual and stuff i sent to you helped in identfying stuff??:cool:

YES
 

yes !!!!!!!!!! I have seen the Kiosho MP7.5 and it sounds very likely!!!!!! I think all<is correct!!!!!!1


thank you very very much

I think I know what the problem is and I know how to fix it. You'll need to remove the body and set that aside. Once the body is off, simply pull the Mugen out of the way and slide a 7.5 in there. LOL

All kidding aside, it sounds like the diff isn't properly shimed in the diff case/housing with the pinion. You should be able to tighten down the screws and the conical gear and pinion should have proper clearance. If you have to loosen the screws that hold the diff in the housing then the mesh is to tight and you'll need to re-shim the diff in the case/housing. Hope this helps...