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Thread: 2wd vs 4x4

  1. #1
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    2wd vs 4x4

    I think the real thing is 2wd? So why this ultra detailed one is 4x4?
    Just wondering, not complaining.

  2. #2
    RC Racer Killroy's Avatar
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    The real one is a 4x4.

  3. #3
    RC Champion fourdub's Avatar
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    A lot of people like to the run the slash 4x4 with out the front diff and driveshafts. this gives it a 2wd with most of the weight infront of the rear axle.

    i hope this truck is perfect the way it is. i am sure you can remove the parts and make it rear wheel drive only.

    A little while back i made a solid rear axle rustler (Slash wide and length with slash body.) i was gonna use a 4x4 stampede/slash front end. decided to just use the rustler. it worked great.

    seems traxxas took note haha. (not the first one to do it)

    its 95% zipties....



    i thought about making this one 4x4....

    in the unlimited class, anything goes. like long distance. all sorts of different types of 2wd and 4x4's. Stadium Racer's (trophy truck 2wd circuit racing trucks are very different than the UDR)

    hope that makes sense.
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  4. #4
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    Quote Originally Posted by Killroy View Post
    The real one is a 4x4.
    Did some more reading, and it looks we are both right.

    Justin Lofton’s truck (orange/white) is 2wd.
    Justin Matney’s truck (red/black) is 4x4.

    But if I understood correctly, all trophy trucks are 2wd, except Justin Matney’s.
    Please correct, if I’m wrong!

  5. #5
    RC Champion fourdub's Avatar
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    not incorrect but pressing too hard.

    generally speaking there are more 2wd tt's than 4x4's. but even wiki says theres no restriction on drivelines for entering trophy truck events.

    History[edit]
    After the class introduction in 1994, with no proven formula the initial Trophy Truck designs were very varied, usually with no two Trophy Trucks the same. Over a development process of ten years, eventually engineering firms like Geiser Brothers,[4] Jimco,[5] Racer Engineering[6]& ID Designs[7] became known after their trucks were winning races immediately. Arguably, these manufacturers became successful due to being able to fund the necessary time and R&D costs needed to create a competitive Trophy Truck platform.
    Truck design[edit]


    Steve Olliges Team Ford Trophy Truck
    Trophy Trucks are generally two-wheel drive, although a four-wheel drive class is in operation.



    first video on YouTube for 4x4 trophy truck lol
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  7. #7
    RC Qualifier MAC FAB's Avatar
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    The reason you aren't seeing a lot of 4wd Trophy trucks stems basically from 2 things. First, they are down on front wheel travel compared to a 2wd truck, CVs being the problem there. Like a 1:1 U4 front end. Its like running them in your Slash, you have angle restrictions. Roughly 28 degrees max so they will live in full sized stuff, class 1 buggies included, limiting wheel travel because of axle length and angle, compared to 32 degrees max on your Slash with MIPs. Doesn't cause problems on your Slash, not enough wheel travel. They currently don't run U-joints because of axle bind (class 1 included), rips the mounting tabs off the suspension mounts (just the opposite with your Slash, plastic axles, more angle with no bind). Second, is they are having some issues with the front drivetrain surviving. Heavy trucks with 800 hp beats the crap out of stuff. Mason Motorsports built a new truck for Andy McMillin, 4x4, complete with A/C in your Parker pumper helmet fresh air. Race-dezert.com did a feature on it. Simply incredible. Story goes that TT guys like them, especially in the silt beds or sections where others are stuck. U4 and UTVs blaze around with the 4wd. Once the bugs are worked out, 2wd will be a thing of the past for the most competetive trucks on the podium. All that said, it would be interesting to pull the front axles out of the UDR to see what it does in 2wd as it wouldn't effect poower transfer with the difs per the design as I understand it, but the front geometry would be off for that application, more caster required.

  8. #8
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    Thanks for very enlighting writing This is a new world to me, and couldní t find any good info anywhere about the cars and technical specs. Those were exactly the reasons I tought that could be why trophy cars are 2wd. Well, if those were 2wd, I even didnít know that for sure...
    Iíll keep my UDR stock. As I said, I wasnít complaining, just wondering why

  9. #9
    RC Turnbuckle Jr. Greatscott's Avatar
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    For years and years they were 2WD because of engineering problems with 4WD systems not being able to take they kind of punishment. In recent years they have solved a lot of those issues, thanks to programs like Solid Works, and now they are just different classes.
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  10. #10
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    Class 1 Unlimited 4WD Trophy Trucks are getting more and more common. They hardest part, and probably the main or only reason, was designing CV's to work with their drastic suspension travel. Being at such a great angle most CV's couldn't handle much over 30 degrees. Transfer cases, front IFS Axles, Control Arms, Spindles, and Hubs were easy to manufacture to handle the abuse, once a strong CV was engineered. A few companies, such as RCV, have designed them to work at an angle of 45 degrees or more. I seen four 4wd Trophy Trucks in the last Baja 1000, and two in the Mint 400 here in Vegas, and expect to see more year after year. Cost is drastically more with 4wd, each front CV axle can cost upwards of $3000, Transfer Cases upwards of $5-6000, Front IFS Axle, upwards of $3000, and so on. $25-30 grand, or more, just to add 4wd. But, being sponsored, as probably every Trophy Truck is, then your set.

    I have messed around in my buddies custom AWD sandrail, which has ridiculous amount of suspension travel. He had RCV Custom make CV axles for it, and they have been holding up for the past 8 months now with 1550 Hp.


    The UDR, was completely designed after Lofton's 4WD Trophy Truck. I prefer 4wd, especially in a fast desert RC Truck. I have driven a few 2wd HPI Baja's with larger engines, and once you start hitting whoops and other obstacles at 40+ mph, it can really throw the truck around causing you to loose control much easier.
    Last edited by BadAssRC; 02-10-2018 at 04:41 AM.
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  11. #11
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    Does it seem weird to anyone else to have a center diff in it, especially while ruining a spool in the rear? That just bugs me.

    I wish traxxas would have made it 2wd/4wd selectable from the transmitter. It wouldn't be hard for them to do, they could even sell it as an upgrade.
    I need R/Cers anonymous.

  12. #12
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    Spool in the rear is different thing than locked center diff. Plus, locked center diff with a spool in rear would make that car really hard to turn.

    In a city car maybe, you save some gas by switching to 2wd when 4wd is not needed.

    UDR is not a crawler (nor city offroader), so I don’t see why there should be hi/lo or 2/4wd select?

  13. #13
    RC Racer Sneetches's Avatar
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    Quote Originally Posted by RobWilJas View Post
    Does it seem weird to anyone else to have a center diff in it, especially while ruining a spool in the rear? That just bugs me.

    I wish traxxas would have made it 2wd/4wd selectable from the transmitter. It wouldn't be hard for them to do, they could even sell it as an upgrade.
    It actually makes perfect sense for the handling and the spool. Coming from a Yeti XL which is similar in size to the UDR and also solid axle, it had 2 handling quirks to get over. The first was "torque twist" where the truck will always pick a front wheel up on one side due to the forces acting upon it from the solid rear axle, the only solution then was to add very stiff sway bars to counteract it. Once you add the sway bars though, you still have the problem of wheelies under high traction, which there is no solution for aside from customizing the transmission to add a center diff.

    With the center diff you get better cornering and solve the torque twist/wheelie problem. Just look at the promo video of the Yeti XL vs the UDR promo video, the UDR might as well look like a fully independent suspension truck.

  14. #14
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    Traxxas compensated for Torque Twist by using a Gear Reduction (Planetary Reduction) in the rear axle to keep driveshaft speed down, and max torque at the axles and not the driveshaft.

    I would assume the Cush Drive is installed to keep maintenance down by eliminating a slipper, and, Like Sneetches Mentioned, to keep all 4 wheels planted during hard acceleration by transferring power to the front when needed for maximum traction and grip. The Cush drive also helps keep you from breaking parts by transferring the power equally to all wheels.
    Last edited by BadAssRC; 02-12-2018 at 11:23 PM.
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  15. #15
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    Quote Originally Posted by BadAssRC View Post
    ....(Planetary Reduction) in the rear axle to keep driveshaft speed down, and max torque at the axles and not the driveshaft.
    I guess you ment to say; ”driveshaft speed UP...”

  16. #16
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    Quote Originally Posted by BadAssRC View Post
    The UDR, was completely designed after Lofton's 4WD Trophy Truck.
    In 2017 Lofton’s truck was still 2wd in mint 400. How was the other races, when did they change the driveline to 4wd?

  17. #17
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    I think based off his future truck.
    The Rigid Body is based off of Justin Matneys 4wd Trophy Truck as well. I do not know if he is currently racing it or is still just a Prototype

    Edit: The Lofton Truck that this is based off of, the White and Orange, is a Prototype 4wd truck and not currently race ready. It will use his current White and Orange body, expected race ready day will be towards the end of the year hopefully for the Baja 1000.

    So maybe it was based off Justin Matney's truck with intention of Lofton's Prototype 4wd Truck being race worth in the near future. Traxxas did state that both these trucks (Traxxas UDR) are based off of their corresponding 1:1 Scale trucks as close to 100% as possible to resemble the real thing.
    Last edited by BadAssRC; 02-13-2018 at 03:28 AM.
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  18. #18
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    Quote Originally Posted by BPee View Post
    I guess you ment to say; ”driveshaft speed UP...”
    Ya I had it backwards.
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  19. #19
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    Speak about 4 wheel drive, the history of it in desert racing. Starts at 14:45

    https://youtu.be/F0Cx5A-Oh3M

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