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  1. #1
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    3.3 axles don't fit 3906 with RPM A-arms!

    OK, so after ripping my stock 3906 axles in two with my lipos, I decided to upgrade them with the same ones used on the brushless/t-maxx/revo drive shafts.

    I've read that I will need new axle carriers/steering knuckles and tie rods as well so I ordered all of it last week and it arrived today.

    After installing them I noticed two major issues that are really bumming me out:
    1. The axles are so fat/thick that they rub against my Proline Powestroke shocks
    2. Also the axles rub against the underside of my upper rear RPM A-arms. (it rubs near the diffs where the pins of the exposed ball joint are)

    Anyone else have any issues like this?

    Now I am considering selling the prolines and using the stock shocks and even dremeling down the rub spots on the RPM arms...

    Suggestions?

  2. #2
    RC Enthusiast
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    How about just getting metal CVD's? I would keep the shocks, not mess with the arms and eliminate breaking more stock shafts by going steel.
    I recommend RD Logics over MIP as they have a longer drive cup and won't bend in the middle and pop out of the drive cup. I bent 2 MIP shafts that I had for 2 years and switched to RD Logics. I only have 2-700 Kershaw motors and 2-6 cell ProMatch 4600 in my 3906.

  3. #3
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    Well, Ironically I have a set of metal cvd's that I got in a trade and was using them. I didn't think much of them b/c all 4 were bent slightly. I assumed that must be common with the metals ones...not sure of the brand, but they look like the ones on ebay...black on the end, rubber boot and silver shaft. Maybe that's what I should do, but I just didnt want to deal with bent shafts again.

  4. #4
    RC Champion
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    Dremel it I can't believe you are thinking of giving so easily. Dremeling would take 20min. The new RPM arms fit my PowerStrokes nicely with out mods and you don't have to dremel anything including for the shafts, but now I use CVDs.
    15" WB HCR Mutant-Maxx Castle UE FLM 3906

  5. #5
    RC Enthusiast
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    before you do anything double check t make sure you have the upper arms installed on the correct side. the rpm arms have a small depression on one side to make room for the drive shaft. if the depression is installed facing up then they are on the wrong side. that should help with your drive shaft issue
    Rustler VXL w/Upgrades

    E-maxx w/Upgrades

  6. #6
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    I appreciate the help everyone. I checked for an indentation on the RPM arms...no luck. Maybe they are an older version.

    Here are some photos to help explain the situation:

    THese photos show how the Proline shocks rub both the axle at the bottom and the RPM arms at the top




    THese photos show how the axle pins rub (heavily) against the underside of the RPM arms.




  7. #7
    RC Champion
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    It looks like you've got a great truck, I see the garc bulks, can we see the rest of it?
    15" WB HCR Mutant-Maxx Castle UE FLM 3906

  8. #8
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    Yeah, I'll try to get some photos up soon. I think I may switch the axles to these:Should solve all my problems...




    Anyone know if they are any good?

  9. #9
    RC Qualifier
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    Don't spend your money right now!!!!
    Dremel it!!!
    I've done this with mine.
    If you run them like this, you'll loose some e-clip ( 2.5mm)

    Last edited by EMaxx_Quebec; 06-06-2010 at 06:45 AM.
    3906 CC 1717 / MMM GA 7075 UE Khead LST2 DIFF

  10. #10
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    I thought about it, but then I still have the problem with the proline shocks rubbing hard against the axles.

    So my choices are:

    • Buy new metal CVD's, keep the proline shocks and avoid dremeling my rpm arms
    OR
    • Dremel the arms, sell the proline shocks and buy some stock shocks.


    I think I am going to go with the first option. The questions is, which metal cvd's?
    • I have 6 bent RD logics...so I don't want anymore of those.
    • I think MIP's are too expensive, plus you have to buy rubbers boots extra.

    • I like the look of the Tsais Racing ones pictured above...$45
    • Or, maybe the Traxxas ones for $55...They look pretty good.

  11. #11
    RC Turnbuckle Jr.
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    I got here late, sorry. But I ran the exact same setup. I Dremelled the arms and used washers to set the shock out away from the shafts....{I used to have a pic around here somewhere}

    {found it!}

    This is a pic of the groove that the spring base wore into the shafts.


    Last edited by mkrusedc; 06-06-2010 at 09:27 PM.
    E-Maxx Neu1515 1y/MGM 5s

  12. #12
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    I just bought the traxxas CVDs and will install them in the next day or two. I'll report back if I think they'll also solve your problem. It appears this shouldn't be a 3906 specific problem since the bulk heads are the same unless arm length comes into play.

  13. #13
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    Traxxas website says their cvd's are only for the newer e-maxx (not the 3906)...I assume that's only b/c of the different axle carriers/steering knuckles. (I have the newer ones, so it should work)

    I just called Traxxas. They told me the metal CVD's will not fit the 3906 E-Maxx b/c of the Diffs! I thought they were esentially the same size/fit, only built tougher....

    Anyone know more about this?
    Last edited by cooleocool; 06-07-2010 at 09:32 AM. Reason: merge

  14. #14
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    Thanks! I just posted pics...here is the link:

    http://monster.traxxas.com/showthrea...=1#post4505852

    PS- the Traxxas CVD's fit the 3906 just fine... all you need is the newer steering knuckles and tie rods.

  15. #15
    RC Racer
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    lets us know how the traxxas driveline work out for ya
    Last edited by rcslsafut; 06-20-2010 at 08:05 PM.

  16. #16
    RC Competitor
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    When you put the traxxas cvd's on do you just hug the rubber boot up against the bulks or do you leave a little space. I have a set I'm just waiting for new bulks to take it all apart. I just didnt know if the boots rubbing against the bulks would cause them to distort.

  17. #17
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    Quote Originally Posted by Smoothies
    When you put the traxxas cvd's on do you just hug the rubber boot up against the bulks or do you leave a little space. I have a set I'm just waiting for new bulks to take it all apart. I just didnt know if the boots rubbing against the bulks would cause them to distort.

    Mine don't touch...there is a small space, which I think is the way it is supposed to be

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