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Thread: 3906 bl

  1. #1
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    3906 bl

    Here's some pics and video of my 3906 E Maxx.
    Bought it when they first came out over 10 years ago. My friend talked me into going with a BL system and it is a HOOT!!!
    8.4 lbs. AUW with two 5000mah 2s lipos.
    These threads were a great help and I want to Thank all who have contributed.
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    http://youtu.be/2rysfIcnHuI
    http://youtu.be/YuOT3LRQBGQ
    Last edited by LD; 05-13-2011 at 11:16 PM.

  2. #2
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    Had a problem with the pics to load...hope this works
    http://
    http://
    http://

  3. #3
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    LD,

    Thanks for posting. I am in the process of doing the same as well. Might I try to pick your brain on this? Note that I DO NOT want to increase the width of my Emaxx. So I am just interested in fixing the drivetrain. I don't want longer suspension arms and I don't want to change the knuckles or turnbuckles. From ArmyofDarkness' "E-MAXX 3906 UPGRADE GUIDE", I found that I need the following:

    Traxxas Steel Idler Gear #3996X
    Traxxas Input Shaft #3993
    Traxxas Center CVDs for Emaxx 3906 #4951R (Is this the correct length or is this for the new Emaxx's?)

    What did you use for the other 4 drive shafts?
    Did you change the slipper? I would consider going with the Kershaw slipper spring $9 and the center dogbone kit $35

    Thanks in advance

  4. #4
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    An RRP slipper clutch assembly will help too, since you get zero life out of the stock slipper when you loosen it to help take some of the SHOCK out of the drivetrain.
    11 Traxxas trucks, and counting!!

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    M3Armand, we think alike .

    The drive shafts are stock length. Part# TRA4951X. So far they've held up very well and I like that their easy to get and replace.

    My tranny was still in good shape when I opened it up to see what I had to work with.
    I used my stock Input Shaft #3993. If yours is in good shape you won't need it.

    Mines a single speed so I removed the steel 1st gear from the shaft. I made a plastic collar from my old plastic E Maxx drive shafts to hold the shaft in place. Worked great with less rotational mass.
    Instead of removing the roll pin from 2nd gear and replacing it with drill blank, ect., I found some small piano wire that had a tight fit inside of the roll pins hole and glued it in. So far that's worked and it was easy to do.

    Are you going to make it a single speed tranny?

    on the steel idler. I lubed it with Lithium Grease.
    on the TRA4951R. It is correct. If you want to use the center dust boots you'll have to remove some chassis plastic or they'll rub. I used a Dremel and it took awhile to get it right.

    I'm running a stock slipper. Put in a new Kimbrough 70T spur gear and new friction pegs. I run it all the way tight and it's held up. Kimbrough uses good plastic on their spurs and they hold up to heat better.

    I did an inspection on the tranny after about 4 hours of solid run time and everything looked good.

    Rootbeer, I was looking at RRP's slippers. Wish they didn't have two different sizes. Be nice to run a 66T or 72T spur with the same unit.

    LD

  6. #6
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    wow...awesome man...im gonna go play around in your backyard. cool having a track in there. liking the truck
    Hows that nitro taste on your electric?

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    Thanks ToXiC,
    We just brought in more dirt and changed up the inside design and of course made Bigger Berms .
    It's been raining here and that's put a dent on track preparation. I'll get another video once the tracks complete.
    Come on by if your in Chino Hills and we'll do some body rubb'n .

    LD

  8. #8
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    LD, thanks for your reply. I still plan on keeping the 2 speed. This is one of the great things I liked about this model. But I'll be sure to be gentle with each shift!

    I think you forgot to answer my question on what you did for the 4 drive shafts. What did you use for those? Did you use the stock ones? I would think that the stock ones would pretzel pretty easily since they already do so with the stock brushed setup.

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    I'm using stock TRA4951X. They are beefier than the original shafts that came on the truck.
    So far their holding up and I haven't noticed any twisting with 25+ runs on the backyard track. Track time and bashing are two different things so your mileage may vary.

    I'd recommend to strengthen both gear pins on the input shaft.
    Two steel idler gears for 1st & 2nd and the tranny should be good.

    Another one I did was upgraded to the four screw diff housing TRA4980X.

    Are you going to shim and o-ring seal the diffs?

    LD

  10. #10
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    Quote Originally Posted by LD View Post
    I'm using stock TRA4951X. They are beefier than the original shafts that came on the truck.
    So far their holding up and I haven't noticed any twisting with 25+ runs on the backyard track. Track time and bashing are two different things so your mileage may vary.

    I'd recommend to strengthen both gear pins on the input shaft.
    Two steel idler gears for 1st & 2nd and the tranny should be good.

    Another one I did was upgraded to the four screw diff housing TRA4980X.

    Are you going to shim and o-ring seal the diffs?

    LD
    Is the TRA4951X for the "wide EMaxx"? My 3906 wasn't even the "wide EMaxx". It's the original original. Thus, I just don't want these to be too long.

    I wasn't planning to shim/o-ring seal the diffs... I'm thinking that I would leave well enough alone until it breaks... then I'd replace it. So far, my truck is doing well with the Castle Creations Mamba Monster 2200kv motor. I'm running 18/66. I will do a speed run tomorrow with the GPS duct taped to the truck...

  11. #11
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    4685 Traxxas Slipper Friction Pegs (12 - I put as much as I can to the stock 66T spur, it looks good so far) $4.29
    3993X Traxxas Input Shaft Drive Gear Low E-Maxx $13.49
    3985 Traxxas Output Gear 31T E-Maxx (extra 2nd speed gear, just in case it breaks) $2.89
    3996X Traxxas Idler Gear 20T/Idler Gear Shaft E-Maxx $5.29
    4951R Traxxas Drive Shaft Center E-Maxx Front/Rear $34.99
    4951X Traxxas Half Shafts Long T-Maxx (2) $7.69 + $7.69
    5626 Traxxas Mamba Monster ESC Mounting Plate $2.89
    Castle Creations 1/8 Mamba Monster/Neu-Castle 2200kV (comes with 18T pinion) $281.97

    TOTAL TO CONVERT = $361.19 assuming you already have the batteries

    One might add another $9.30 for a 22T pinion for more speed. But I don't know if this will fit yet! Can anyone confirm???
    Last edited by M3Armand; 05-25-2011 at 10:57 PM.

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    Quote Originally Posted by M3Armand View Post
    Is the TRA4951X for the "wide EMaxx"? My 3906 wasn't even the "wide EMaxx". It's the original original. Thus, I just don't want these to be too long.
    They'll fit. I have the original "narrow EMaxx ".
    I managed to break two 4951X shafts. Both times while trying to save a jump with throttle and landing on one tire.
    So I ordered a set of MIP CVD's for the rear. Also found a great deal on a RRP slipper and a 70T gear. That will be a big improvement over stock.

    I have an idea to improve the strength of the 4951X shafts. I'm going to add a piece of 3mm carbon fiber rod to the smaller half shaft air breather hole. It should help with the twisting force that broke mine.

    Quote Originally Posted by M3Armand View Post
    I wasn't planning to shim/o-ring seal the diffs... I'm thinking that I would leave well enough alone until it breaks... then I'd replace it. So far, my truck is doing well with the Castle Creations Mamba Monster 2200kv motor. I'm running 18/66. I will do a speed run tomorrow with the GPS duct taped to the truck...
    My front diff needed new spider gears before the BL motor went in so I decided to shim and o-ring seal both diffs. I used a 3M silicone paste for the diff oil. Big improvement over the stock diffs.
    That's A LOT of power with the MM 2200kv.
    Did you get to do a speed run?

    LD

  13. #13
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    Quote Originally Posted by M3Armand View Post
    4685 Traxxas Slipper Friction Pegs (12 - I put as much as I can to the stock 66T spur, it looks good so far) $4.29
    3993X Traxxas Input Shaft Drive Gear Low E-Maxx $13.49
    3985 Traxxas Output Gear 31T E-Maxx (extra 2nd speed gear, just in case it breaks) $2.89
    3996X Traxxas Idler Gear 20T/Idler Gear Shaft E-Maxx $5.29
    4951R Traxxas Drive Shaft Center E-Maxx Front/Rear $34.99
    4951X Traxxas Half Shafts Long T-Maxx (2) $7.69 + $7.69
    5626 Traxxas Mamba Monster ESC Mounting Plate $2.89
    Castle Creations 1/8 Mamba Monster/Neu-Castle 2200kV (comes with 18T pinion) $281.97

    TOTAL TO CONVERT = $361.19 assuming you already have the batteries

    One might add another $9.30 for a 22T pinion for more speed. But I don't know if this will fit yet! Can anyone confirm???
    I'd back the spur gear a little back from full tight and 12 pegs are the way to go.

    I wouldn't recommend the 3993X. If your original 3993 is in good shape just hard pin both 1st and 2nd gear.

    I'd go with two 3996X idler gears for 1st and 2nd.

    My total to convert was a bit cheaper because of the motor/ESC combo. It's been worth every penny .

    LD

  14. #14
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    Sent the defective ******* ********* 150 amp ESC back to China and have a new servo on it's way .
    The old Cirrus servo was under powered and slow. Also ordered the bellcrank upgrade TRA4945. Can't wait to try it.

    Question; Does the bellcrank post have to be cut to install the TRA4945 bellcrank?

    LD

  15. #15
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    Yep- check this:

    http://i115.photobucket.com/albums/n...axxguide19.jpg

    You'll see the little diagram of the 3906 chassis under the 3905 diagram with a note for what/where to cut
    Keeping the Mods busy is my specialty...

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    Thanks AoD ,
    Excellent website you've provided. Made my build a whole lot easier. Kudos!!!

    I found these TRA4954R and ordered a set of four. Nice upgrade from the plastic and cheaper than aluminum. Could step up to 17mm but I just don't like the rim choices. So far I like the Traxxas 3972X. Great price @ $7.45 for a pair.

    I'm looking to get some tires. Has anyone tried the HPI DirtBonz? Wondering how they compare to the Pro-line Bow-Tie.
    Also is there something special the old .15 T-Maxx tranny is used for. I've seen a few on EBay and can't believe the prices.

    LD

  17. #17
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    Quote Originally Posted by Rootbeer View Post
    An RRP slipper clutch assembly will help too, since you get zero life out of the stock slipper when you loosen it to help take some of the SHOCK out of the drivetrain.
    got the p/n for that slipper clutch assy.... im going thru the same even with new friction pegs installed-all 12!
    Last edited by seventwo99; 06-27-2011 at 01:24 PM.

  18. #18
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    Quote Originally Posted by seventwo99 View Post
    got the p/n for that slipper clutch assy.... im going thru the same even with new friction pegs installed!
    I used as much frictions pegs as I could install and I don't seem to have any issues. But most of my BL usage has been for "top speed" runs and not doing any large jumps which would exercise the friction pegs. I will know more after this coming 4th of July holiday where I will be using the truck more. I will report my findings. I will also report the GPS recorded top speed.

  19. #19
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    Quote Originally Posted by seventwo99 View Post
    got the p/n for that slipper clutch assy.... im going thru the same even with new friction pegs installed-all 12!
    The Useful links page is your friend...

    http://www.robinsonracing.com/catalog/catalog.html#

    Click the link for just 'E-maxx' and then it'll have all the parts and optional spurs etc. There are other options, such as modding the tranny slightly to accept the new emaxx slipper design:

    http://www.rc-monster.com/forum/show...0&postcount=51
    Keeping the Mods busy is my specialty...

  20. #20
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    Nice mod for the Traxxas slipper.
    Be better if the gap was less than 7mm. Puts more stress on the motor bearings having the pinion out that far to meet the spur.
    Also don't think my motor shaft is long enough to make it work.

    The RRP slipper went on with only minor sanding of the shaft. I used a emery nail board and took a little at a time till the bearing fit. Works great!
    I also read a review were they couldn't get the RRP spur to run straight and true. I didn't have that problem with mine. RRP has eliminated the washer that was included in the kit. The washer may have been the problem.

    Try doing a search for the RRP slipper and part#, there's some good deals out there.

    Got the tires and rims ordered. Should be here tomorrow .


    LD

  21. #21
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    Yeah, that shaft does stick out a little much- a few shims to move the whole thing back a couple mm should do the trick,- less work compared to doing the single-speed gorillamaxx conversion + modding that shortened input shaft to accept the new slipper parts though; cross drilling the input shaft ain't much fun.
    Keeping the Mods busy is my specialty...

  22. #22
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    Quote Originally Posted by ArmyofDarkness View Post
    The Useful links page is your friend...

    http://www.robinsonracing.com/catalog/catalog.html#

    Click the link for just 'E-maxx' and then it'll have all the parts and optional spurs etc. There are other options, such as modding the tranny slightly to accept the new emaxx slipper design:

    http://www.rc-monster.com/forum/show...0&postcount=51
    so is the RR spur combo better? what more will i get out of it over stock?
    i dont want to have the front end flip over because of too much torqe (i know adjust the slipper), just a good dig and take off.
    mine just seems to wheele when the throttle is hit, and when i loosen it ever so slight, it just seems to roll out with no real bite, cant seem to get that sweet spot on the slipper? there a way to find it?

    if i go to the 775 mod eventually, will a RR 72t spur be a better option, since ill have to run a larger pinion to mesh the gears because of the can hitting the tranny when on the moded twin plate mount.

    steel or plastic?

  23. #23
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    It's much better, IMO.
    Large dual slipper pads along with a vented slipper plate give way more friction area and dissipates heat better. Almost a drop-in install. Also nice to be able to change a spur gear without messing with the slipper adjustment.
    I got mine for a few cents over $20.00 delivered and it's the way to "get that sweet spot".
    I went with the plastic spur. Light and durable.

    I've seen that mod done on the Gorilla Max tranny but not the 3906, AoD.
    Doesn't look like there's any room to shim. The pic that has the 7mm distance has the plate ground down pretty good and it's tight to the tranny. Be nice to flip the whole slipper assembly around on the shaft but that's not possible.

    Like to see what speed your getting M3Armand.
    Mines a variable speed with the Proline Bow-Ties. I had it upside down with the lipos plugged in and decided to hit full throttle. WOW!!! Those suckers grew to over double their size. It was scary!!!

    Got my new tires and rims and weighed them against the Prolines. Saved about 20 grams per wheel . Love it when it's lighter.
    The steel 14mm hexes weigh 5.7 grams each and the plastic hexes only weigh .9 grams . Those metal hexes are heavy but should be worth their weight.

    LD

  24. #24
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    Quote Originally Posted by M3Armand View Post
    ...One might add another $9.30 for a 22T pinion for more speed. But I don't know if this will fit yet! Can anyone confirm???
    Ok, I can confirm that a 22 tooth with a 66 spur fits. Looks like I can put a larger pinion in there still..

    Quote Originally Posted by M3Armand View Post
    I used as much frictions pegs as I could install and I don't seem to have any issues. But most of my BL usage has been for "top speed" runs and not doing any large jumps which would exercise the friction pegs. I will know more after this coming 4th of July holiday where I will be using the truck more. I will report my findings. I will also report the GPS recorded top speed.
    So I put the 22 tooth pinion and duct taped my GPS to the body (bad mistake as I crashed and scuffed it up quite a bit). So the top speed in 2nd gear was 40.1 mph and 26 mph in 1st gear. This is with a 66 tooth spur. The tires are the original "paddle" tires as shown in the pics below.

    I can still go faster with non-paddle tires and you have to take into account the extra weight of the GPS and the original Titan motor. That Titan motor does NOT have a pinion gear attached to it. It's just along for the ride. I just didn't want to upset the left/right balance of the truck as much so I left it on.



    Last edited by M3Armand; 07-09-2011 at 06:48 PM.

  25. #25
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    Very clean truck, M3Armand!
    Those are some nice ThunderPowers. Is the case actually carbon fiber?
    Gets up and goes @ 40mph! and a eyeblink to get there I bet.

    Here's a neat little part that I've ordered (TRA4956) and it should fit. Ties in both bulkheads and turnbuckles. Much stronger and it's a bolt-on .

    Anyone know if MIP CVD's have any warranty? I managed to break one .

    LD

  26. #26
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    Quote Originally Posted by LD View Post
    ...Those are some nice ThunderPowers. Is the case actually carbon fiber?

    Here's a neat little part that I've ordered (TRA4956) and it should fit. Ties in both bulkheads and turnbuckles. Much stronger and it's a bolt-on .
    No, it's just plastic. Looks great, though.

    Where exactly does that TRA4956 fit?

  27. #27
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    My friend just got a couple Blue lipos from Hobbypartz and they came with that same CF look. Very nice!

    The tie bar screws to the rear bulkhead. It goes between the two turnbuckles rodends and "ties" the turnbuckles to each other and also ties the bulkheads. I installed it today and it works and fits perfect.

    I figured out what caused my MIP CVD to fail. I'll post some pics.

    LD

    I've read that the newer E Maxx diffs will bolt into the 3906. Is this correct?

    Thanks,
    LD
    Last edited by cooleocool; 08-15-2011 at 09:17 PM. Reason: merge

  28. #28
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    Yes, the diffs, bulks, towers, front & rear skid, bumpers & a-arms will be a direct fit between any maxx-based trucks.
    Keeping the Mods busy is my specialty...

  29. #29
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    Thanks AoD.
    Do you know if the newer diff is any wider from output gear shaft to output gear shaft than the 3906 diff?
    I had a little binding problem and I'm limited for space.


    This is what my new MIP CVD's look like after a few runs......OUCH!!! I figured out what caused it.


    Traxxas Big Bore aluminum shock compared to stock black shock. Not much difference in the extended length and no binding at the CVD's with either shock.


    When both shocks are fully compressed the shorter aluminum shock body allows more upper wheel travel. When the truck had full shock compression the MIP's would have severe bind. I didn't have a clue till it was too late. Had the upper pivot ball set with no treads showing and the lower pivot ball set with a few threads out for camber and thought all was good.
    I had to back out both pivot balls a few mm to stop the binding. Seems to work and I haven't seen any wear marks on the replacement CVD's.


    LD

  30. #30
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    The diffs should be exactly the same width like that, the only changes internally are an extra brace for the spider gears and a different sized bearing on one side of the diffcup essentially.

    It is kinda funny how the Bigbore shock is smaller than the standard one though...
    Keeping the Mods busy is my specialty...

  31. #31
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    Forgot to mention that the Traxxas steel 14mm hexes even made the problem worse. With the plastic hexes there was no slope in the shafts when pushing/pulling the tire in and out. The steel hexes had more than a mm slope when I installed them. That made the shafts slide in to the drive cups farther and really chewed things up fast.

    I added two teflon washers to each axle shaft and their tight now.
    Running the MIP's front and back and no problem so far.

    LD

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    Just got a pair of backup 3905 E Maxx diffs for my 3906. The width from spider to spider is fine but the pinion gear and case are shorter. The old collar is offset and the new diffs collars aren't. Small change that won't affect stock plastic shafts but CVD's is another story. Should still work with my Traxxas center CVD's but I won't know till I blow up my stocker diffs.

    LD

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    Here's some video of the new track layout. What a Blast!!!


  34. #34
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    Blew a rear 3906 diff and it was time for the 3905 diff upgrade. To my suprize it bolted right in. I had read that it wouldn't work because the center CVD's shafts are too short and I've seen pictures to verify it.
    I noticed that my tranny's output shaft was longer at the rear. Because of the way I locked/spaced the tranny into 2nd gear the output shaft was a perfect rear length. But now what to do for the shorter front shaft? This part should solve the problem TRA 5153R. Their a reported 1.5mm longer than the standard Traxxas CVD's drive cups.
    I'll report back when I blow the front 3906 diff and replace it with the other new 3905 diff with the deeper drive cups, but it should work .

  35. #35
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    so no one uses the 3993x? or is it worth buying or is the 3996x worth buying ?
    Last edited by civiccrush; 12-27-2011 at 09:08 PM.

  36. #36
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    The 3993x is'nt needed. It has lightweight aluminum gears but with BL power your better off with steel. Your stock 3993 shaft (steel gears) will work fine. The trick is to pin the gears on the shaft. The stock roll pin can't hold up to much power before it shears so it has to be strengthened.

    The 3996X is a must have item. Yours may have this mod already since it came with a BL system.
    Last edited by LD; 12-27-2011 at 09:38 PM.

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