Plastic part failure again..

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C

cunabit08

Member
Messages
17
Location
San Antonio
Today I went through my 3rd rear diff cover with a break at the exact same point as the others.

The cover comes apart at the pinion and I heard from the guys at Largescale that someone here has a way to reinforce that weak link and I sure would appreciate a few pics of the fix, since I broke this cover on flat ground under WOT.

It appears that the motor has too much torque for the plastic diff without a support, unlike the front diff.

Any help would be appreciated before I end up buying stock in MCD...

Is there a stronger diff cover out there?
 
marderbeet said:
try talking to mono at www.mcdrc.com , good luck., by the way what kind of motor were you running?
Click to expand...

I will contact them with pics from both disasters..

I sent some to LargeScaleRC where I bought it and was told they would forward to manufacturer, but have no idea if that ever happened..

I am running a hot little 29CC Zenoah/CY that is truly faster than any Zenoah I've ever seen or tuned anywhere!!

I love it but it does appear to have an appetite for destruction..
 
I sent them pics in the forums and none of them have ever heard of this..

Here is a couple of pics so you know what I'm talking about..
 

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Various surfaces...

It's broken on hard unimproved loose surfaces and on flat hard packed dirt..

I can't actually tell when it's going to fail before hand, it just blows apart when I least expect it..

It's such a clean break that I can't even see signs before it breaks..

Totally confused and frustrated..

I heard that someone on this board had devised a bracket much like the front diff support with success..

The front diff is setup/designed much better then the rear... This last time it bent the pinion screws..
 
I think I am spot on with the power to weight ratio and all the extra stress because nothing else makes sense..

I've run this truck around a lot of RC guys and all of them say the same thing.. That truck is insanely quick out of the hole for a large scale and it's constantly building power no matter the surface..

This engine is like one of those diamonds in the rough.. It's either more powerful than it's supposed to be or more CC than what it actually has!!

I think I'll hunt down a fabricator after I get the new cases and have them build one out of aluminum or at least build some structural support around the pinion.

Like I said before, the front is rock solid as far as I can tell because of the added support at the pinion..

If anyone happens to run across a mod/upgrade for this, please hit me up so I get this resolved...
 
Here is a response I got from the manufacturer.. It appears this isn't an isolated issue!!


Hello,


Thanks for the information
The monster truch hase very big tyres and if you land with the throtle
on
The weak point (diff case) is breaking we are working on midificfation
and
will be much stronger the part will be available end of april
the new monsters with the strong diff plastic caseses will be replaced

There is a way for midification wich is a also solution but try to not
land
with throtle on
I will shott picture of and will send you mail tommorrow

Regards - Sinan
MCD Racing Ltd
 
Don't know exactly, but possibly enough to break the diff case!?!

I'm looking for a solution to the breakage. I think the car should be able to handle this motor and pipe.

Greetz Koen
 
I've got a mcd monster truck also and my rear diff housing has come apart twice now. The second time it did it I actually broke in half 2 of the planetary gears. Since i've fixed it this last go around I've had no real issuses, I'm just cautious of when I'm on and off the throttle. The guys out at Largescale RC have been real good to me in helping me to get it fixed. Even after all those problems I still would not get rid of that truck. Its been that best 1/5 scale i've bought yet (even if they are alittle pricey). I'm trying to get some money together to get a MCD RR or a Baja 1000.
 
pete379 said:
I've got a mcd monster truck also and my rear diff housing has come apart twice now. The second time it did it I actually broke in half 2 of the planetary gears. Since i've fixed it this last go around I've had no real issuses, I'm just cautious of when I'm on and off the throttle. The guys out at Largescale RC have been real good to me in helping me to get it fixed. Even after all those problems I still would not get rid of that truck. Its been that best 1/5 scale i've bought yet (even if they are alittle pricey). I'm trying to get some money together to get a MCD RR or a Baja 1000.
Click to expand...

Hey pete don't buy another one convert your MT.

I just converted my Baja to a MT.

I have not yet broken any diff cases on any of mine, but I have the spares when I do.
 
Maybe the shaft is not start. If it is bent it will vibrate, and the case will face uneven forces coming in the wrong directions. Just a thought.
 
Last edited:
As of yet, I still have no additional data on the upgraded diff from MCD.

They said it would be out by the end of April 08 and I can't find anything on the market from them or anyone else.

Someone mentioned a bent shaft?

Look at the response I posted directly from MCD, it should clarify and eliminate any guess work..
 
Clubin said:
Hey pete don't buy another one convert your MT.

I just converted my Baja to a MT.

I have not yet broken any diff cases on any of mine, but I have the spares when I do.
Click to expand...

Clubin, I'm sorry man I don't understand when you said don't buy another one, could you please explain?
 
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