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  1. #1
    RC Racer
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    Another UDR to be Unleashed Soon

    Hello again Traxxas forums. I've been away in scale crawlers for a few years after building several Traxxas models up (Slashes, a Summit and a Telluride).

    Loving scale RC trucks led me to interest in the UDR when it came out, and for this Christmas I'm finally getting one. It's the blue Traxxas body with the light kit pre-installed.

    While I wait for December 25th to arrive, I'm planning out batteries (4S) and scale modifications. I already have four 2S batteries, but being 4000mah, I suspect I won't have the run times I'd like to see. I'm thinking two 4S batteries above 5000mah each will give me enough fun if I leave the house with two full batteries.

    I plan to drive the UDR as scale as possible. Meaning, if full size trophy trucks aren't getting 35 vertical feet of air, then I won't be doing 5 foot jumps (7th scale truck - 357=5). I probably won't be jumping this truck any higher than 1.5 feet, as I've never seen a trophy truck hit more than 10-12 vertical feet. Even landing those jumps to flat probably have their race teams cringing. Jumping to flat I will likely keep below 1 foot. My #1 goal is always to get across the finish line in one piece. If I get there quickly, then good.

    So I plan to start with painting the wheels, painting the scale items and adding little scale touches here and there. I suspect my driving style won't result in many breakages to stock parts but time will tell. Things that do break will be upgraded.

    I don't have anything against bashing, it's just not how I like to drive my RC cars. Now, your RC cars you can drive however you have fun with them, and I think that's rad. My UDR will probably spend more time being tinkered with on the bench than putting rubber to the earth. But for now, she rests in her box under my Christmas tree, patiently awaiting her days in the sun (San Diego, CA).

  2. #2
    RC Enthusiast
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    Jan 2019
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    I ordered my UDR today! I can't wait to get it in. Got my tracking # from Traxxas today. I'm assuming it will be on the road tomorrow. I went ahead and ordered it with 400 brushless servo and the steel wheel hexes.

  3. #3
    RC Qualifier
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    When I read the title of this thread I thought you meant Traxxas were about to release a new UDR model!! lol
    https://www.youtube.com/iftibashir

  4. #4
    RC Qualifier USMC1984's Avatar
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    Quote Originally Posted by IftiBashir View Post
    When I read the title of this thread I thought you meant Traxxas were about to release a new UDR model!! lol
    Same here.


    Congrats OP, let us know when you get it!

  5. #5
    RC Qualifier JatoTheRipper's Avatar
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    Congrats on the purchase! The UDR is an awesome truck for sure.

  6. #6
    RC Racer
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    Dang, sorry for the misleading title. I suppose I can call it my first attempt at clickbait.

    It sounds like you nailed some of the most recommended upgrades already Mariposa. Nicely done.

    And I will eventually get some photos going. The only thing to see now is a box under a tree, which you guys probably have enough of at your houses already.

    I'll do a build thread for it, even though it's already built... My 11 year old son is amping to drive it. I've made him study the real driving conditions and performance limits of trophy trucks prior to him getting behind the wheel of the UDR. He is fairly experienced too, having his own Losi 22 buggy, and he's been driving for a few years.

  7. #7
    RC Enthusiast
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    Quote Originally Posted by Fallen View Post
    Dang, sorry for the misleading title. I suppose I can call it my first attempt at clickbait.

    It sounds like you nailed some of the most recommended upgrades already Mariposa. Nicely done.

    And I will eventually get some photos going. The only thing to see now is a box under a tree, which you guys probably have enough of at your houses already.

    I'll do a build thread for it, even though it's already built... My 11 year old son is amping to drive it. I've made him study the real driving conditions and performance limits of trophy trucks prior to him getting behind the wheel of the UDR. He is fairly experienced too, having his own Losi 22 buggy, and he's been driving for a few years.
    May 11 year old daughter has been running a Bandit for about 2 years now so this year she'll have a TRX-4 Sport under the tree. Her favorite color is red and she loves the size and drivability of my Defender.

  8. #8
    RC Racer
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    Mar 2015
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    Well your daughter is a lucky girl. My son thinks UTVs are the coolest things ever, so I bought him a used Axial Yeti Jr. I'm hoping it will pique an interest in crawling, as all he's really been into so far is go-fast stuff.

  9. #9
    RC Racer
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    Mar 2015
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    So my UDR has indeed been unleashed. While it looks great sitting still, I think it looks best in motion. And the particular motion that looks best to me is hanging the rear end out on loose surfaces. This truck does not like high traction surfaces, but that isn't what I bought it for.

    I've only run it on 4S so far, and I don't want to try 6S. Full throttle on 4S is enough to frighten me and I only keep it there for a few seconds.

    I added 1/4" of preload to the front shocks and 1/2" to the rear. Stock ride height (zero preload) seems alright for on-road driving but too low for any real off road driving. It also looks more like a real trophy truck with some added ride height over stock.

    *

    I added a chassis skirt to help keep the rear axle clean. I've read that dirt entering the rear axle is a problem and while this won't entirely solve it, it'll help keep the axle cleaner. It's tool box mat with a 3/32 steel rod zip tied at the bottom for weight. Think it's a lame idea? Check Rob McMillin's 2019 4X4 trophy truck. That's what gave me the idea.

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    I painted several of the scale items, but still have the oil cans and jack to paint, so they're removed.

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    My shocks leak quite a bit and will need refilling eventually. My front diff also has fluid showing around the passenger side drive cup. I've run 5 or 6 packs through it so far, and wish I wasn't seeing fluid leakage like this already. However, if I took a real trophy truck through the desert 5 or 6 times I'd probably have more work to do than just fluid re-filling.

    I can't wait for Pro-Line (or anyone else) to start releasing bodies for this thing. That'll be fun. And while stock Traxxas bodies have never been my flavor in the past, I actually like this truck body. I go back and forth between body off and body on. I cut the space for the bumper light bars to be wider as that space being very tight makes the body a real pain to put on.

    No broken parts yet. My 11 year old son gave it it's worst crash yet, a 2 foot high jump landing straight to the front bumper. All the rest of my jump landings have been soaked up by that glorious suspension. As previously stated, I don't jump this thing very high. My UDR's time spent on its roof has been from turning too fast with too much traction.

    Short term review: drive it like a real trophy truck and the UDR will reward you with fun and durability. It's worth what it costs in my opinion, and I'm glad Traxxas did such a good job on this model. I really enjoy it both sitting still, and in motion. But moreso in motion.

  10. #10
    RC Racer
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    I got around to painting my wheels. I prefer for my wheels to stand out from the tires, and the beadlock rings to stand out from the wheels. So I like the way black wheels look, but I didn't like how the wheels disappeared into the tires, especially at a distance.

    *

    I painted them with Tamiya PS-49, Baby Blue Anodized Aluminium. The wheels actually look like aluminum wheels, which is pretty rad. The downside is that this is it's paint for lexan, so I don't expect that it will adhere super well to the plastic wheels. But for now, it looks good.

    I could have boiled the wheels to remove the tires, but I just masked them off instead. Either way was time consuming. If you use a regular masking tape, it takes a lot of little pieces to make the circle look round. But in the same way that a 30 sided polygon feels like a round wheel when you get it going fast enough, the small pieces of tape make up the circle for good enough masking.

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    Eventally I want to paint the trailing side of the axle housing, either silver or gloss black so that it looks like its metal. But that will be a project for another weekend. This weekend's project is in the books.

    *

  11. #11
    RC Racer
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    Good news about these darn leaky shocks on this UDR. After 5 or 6 runs I decided to take the shocks off, clean them and refill them. There was a lot of dirt and oil residue at the spring perches and where the shafts enter the shock bodies.

    So I removed all 8 shocks and cleaned them off. Then I went to refill them and found that only one of them needed any oil. And that one only needed 3 or 4 drops. The other 7 shocks still had about 1/4 of oil above the piston at full compression.

    One of the shocks' oil was dirty. The other 7 shocks' oil was crystal clear.

    So I know these things are leaky, because I can see the oil on the shocks, but apparently they can leak and still have plenty of oil in them. It looks like they can run about 12-15 battery packs before they'd need actual filling.

    My driver's side front diff cup is still an oily mess, which will be what I address next. I might just run grease in the front diff instead of oil, if I can't get it to stop leaking.

    Speaking of what to put in the front diff, anyone done an Ultra 4 build off of the UDR yet? It seems prime for it.

  12. #12
    RC Racer
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    Well my hobby shop tricked me. I went in to get a battery which I did. Lectron 4S, 5200 MAH, 25C (I think). It fits the tray perfectly.

    But they started stocking UDR upgrades, so of course I had to look! The GPM AL axle housing was just too expensive for me, and I'm not sure I want that much extra weight on this truck. I really don't like a bunch of aluminum on a car, unless the car needs the weight.

    But I did buy my first, and possibly only AL upgrade for the UDR, the Hot Racing sway bar kits for front and rear. The only thing I didn't like about the stock sway bars was the bars themselves being pretty much non-performing due to being so flexible. But these kits came with new linkage too, and I do like the way they look.

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    I also painted my cage panels, which was really easy. 1/2 inch masking tape on the edge of each panel where it bolted up next to the edge of another panel, and voila!

    *

    Eventually I'll start working on my front diff...but this weekend was devoted to running at a fun track, and some bling.

  13. #13
    RC Racer
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    I took my rear axle apart after hearing so much talk about dirt getting in there...yep. It was a real mess, after about 10 battery packs. I think Traxxas did a GREAT job with the UDR. So much so, that even with this axle issue, I would still buy another one. But it is a problem, and one I hope Traxxas will address in the future, with a properly sealed axle because the stock axle housing, isn't. This is a real knock on what is supposed to be a "desert" truck.

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    To balance this out, Traxxas does deserve some props for designing a drivetrain that can accept this much debris, and keep on trucking with no problems. These steel gears are thick, and the axle shafts are beefy. The ring gear would probably pulverize small pebbles, and can stand up to some abuse. That being said, only very fine dust was able to enter, the size of which I don't see doing any real damage to these gears...unless it's left in there for a while.

    But having to spend two hours on maintenance every 10 batteries is still lame, when a simple seal could prevent that. Come on Traxxas, or even aftermarket... someone give me a plastic axle housing that is properly sealed please. I plan on adding my own sealant to the housing, and not driving the UDR until I've done so. An AL housing isn't what I want to put on the truck, but if it solves the seal problem, that might tip the scales for me.

  14. #14
    RC Racer
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    Finally took my front differential apart to find what I think caused the leak.

    The blue seal pictured below that goes between the ring gear and the diff housing was slightly deformed around one of the screw holes. All of the fluid had leaked out after approximately 10 battery packs.

    *

    Either that screw was severely overtightened, or the screw was inserted at an angle. Either way, it deformed the seal, but it didn't tear the seal. There was a nick in it, but since the nick didn't go clear through, I layed it flat and reused the seal. We'll see if it leaks again.

    I put 100k weight oil in it, as I only run on loose surfaces. I also sort of like the possibility of turning this into an Ultra 4 build. The 100k oil feels pretty loose though. I might eventually silly-putty my front diff, especially if it leaks again.

    The builder error makes sense, considering I haven't seen people posting about leaky front differentials. Mine must have just been a build mistake, and not a design flaw seen in the entire line.

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