E-maxx 3905 driveline
 

I've recently been testing a fairly new 3905 on a 6S setup in preparation
for the MMM to arrive and am having problems with the centre rear driveshaft.

Firstly, I don't have reverse so there is no jamming it from back to forward etc. And so far I haven't even jumped the thing.
But both times I have driven it offroad (gravel then sand) the plastic centre splined driveshaft lasted less than 3min. It just twists out the holes where the universal joint is at the back. I repaired it like new by grinding down and making new holes but it did the same thing again.
Also the drive yoke became sloppy on the pinion output shaft which had to be spaced with a washer so the R&P wouldn't strip.

Anyway, what I did notice both times was that the metal UJ was too hot to touch! I'm wondering if the failures are due to the friction of the UJ heating and softening the surrounding plastics.

I want this thing not to break, I will not abuse it, just want it to handle the power. Its only geared for around 35Mph so isnt more extreme than a typical 4S setup I imagine.

Sooo.. will switching to those metal centre CVD's cure this problem? Have people found them to be the only driveline upgrade required for BL power, or will the 4 wheel driveshafts need doing as well??

Any advise will be appreciated, thanks. :smile:

I've been running mine on 5s and 6s with a MMM v1 and 10xl for a little over 2 months and haven't had anyproblems with the shafts at all. The only problem I had is the trans case spliting open.
Here is a pic:
http://img.photobucket.com/albums/v1...g?t=1217986838
http://img.photobucket.com/albums/v1...g?t=1217986835

Hmm. CVDs might be an improvement, or you might just shear off the little pins. I think some beefy dogbones might be an improvement, but in all honesty I havent heard of anyine having many issues like this..

Thanks for your replies, wow I would not be happy if the gearbox split in two:oh:

I just pulled the broken shaft out again and noticed that the bearing for the
pinion shaft has been destroyed also. That would explain why I needed to shim the drive yoke
the first time it broke. Maybe that caused the heat build up that distorted the plastics?
Hmm, not sure why the UJ would get so hot though. Unless a little rock jammed in there or something,
causing sideways force and friction...

Oh well, The Traxxas CVDs 5151R have been added to the MMM backorder :wink:
At least they're all metal.

http://i109.photobucket.com/albums/n...R/emaxx001.jpg

I have destroyed the pinion bearings before. The possible wobble that bad bearings could cause may have also damaged the UV joint. I can imagine that some dry graphite lube might be good around the pins in the UV joints. I have seen the plastic stretch around the pin holes after heavy use. I will say that I have had better success with stock sliders than any cvds that I have tried.

My 3905 has been holding up to 6s for three months now. All stock except for the radio.

Hmm, please tell me you havent tried the Traxxas one, 5151R.

I sold the missus on this truck being strong enough from the box not to
need constant parts replacements. If the stock plastics are holding up for you guys I would definately get some more, but can't find them here in Aus and tower is out of stock ATM.
I guess I can blame the bearings now, they're both destroyed (inner one looks like a hassle to get to). So the question becomes how do I stop that happening again? Well actually I guess I don't know what really started all this off first...
Dang it, I wanted to leave this truck stock for no hassle runnings but one of
the Titans was weak out of the box making for a sluggish drive.

The pin in the traxxas cvds can shear quite easily as many have found.

There are some cheaper fixes though, such as the rcbest cvds on ebay (just choose the 3905 version), or some custom dogbones and cups from mike would be bullet proof ( I have some, holding up fine). You can occasional get bad beaings from the get-go, I would suggest hassling traxxas customer support for some new ones.

Ahh man, why does this stuff never show up in web searches!

Thanks for the info.:smile:
Its now gone from a $5 plastic part to $30 cvds to a $60 set.
Live and learn, its never going to be simple.:yes:

Nope, nor cheap usually either... :mdr:

Bugger, I just stuck my finger in my new Robobugs fan and broke it while testing. (great fans BTW)
I think I should take a break from this stuff until the MMM arrives,
I keep making things worse and its doing my head in. :eyes: