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Old 05-18-2020, 10:05 AM   #1
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Default TRX-4 Sport Upgrade Path

Hi All,

I wanted to get some thoughts on my planned upgrade path for my TRX-4 Sport. I'm still new to the hobby, and there are a lot of people here who've much more experience. I'll state right away that I wish I purchased a more powerful servo immediately. I made the mistake of trying some cheap servos that both broke within 1 week.

Upgrade ideas in planned order of acquisition below. I'd love some feedback/recommendations on choices!
  1. Servo - Savox 1210sg, 3 Brothers G12, or any strong and durable servo $80 or less - running @ 7.4v via Hobbywing 1080 ESC
  2. New motor? HH Crawlmaster Expert or something in the $50 range
  3. New body (TRX-4 Bronco or Proline FJ40)
  4. Any other recommendations?

The truck is around 8.5lbs now RTR, which is I think around where I'd like to keep it. I have the new motor listed there because I've lost wheel speed with steel wheels and other added weight, and I want to get wheel speed back. I actually really liked the balance of the stock Titan motor on 3S when the truck was stock (and light), so I am looking to find that balance again with a slightly more powerful motor. I'd like to keep low-speed control as much as possible, obviously. I'm mostly crawling, but like to "pop" off of low ledges when needed/wanted and get some good pre-obstacle wheelspin when needed/wanted.

Upgrades already installed or pending install:
  1. Hobbywing Quickrun 1080 ESC
  2. FlySky GT3B radio system
  3. GMade SR02 steel wheels
  4. Brass front bumper & servo mount
  5. Brass front portal covers (these are currently installed in the rear because the stock servo won't turn the wheels with all the weight in the front)
  6. Metal diff covers

Last edited by slothRC; 05-18-2020 at 04:11 PM.
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Old 05-18-2020, 10:14 AM   #2
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Default Re: TRX-4 Sport Upgrade Path

Sounds like a good path.

If you are planning on running stock radio system, the RX is only rated to 6VDC. While some have reported running > 6VDC through their traxxas RX with success, most of us have fried them when we tried it.
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Old 05-18-2020, 12:06 PM   #3
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Default Re: TRX-4 Sport Upgrade Path

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Originally Posted by Greatscott View Post
Sounds like a good path.

If you are planning on running stock radio system, the RX is only rated to 6VDC. While some have reported running > 6VDC through their traxxas RX with success, most of us have fried them when we tried it.
Whoops, sorry, I forgot to list the FlySky GT3B radio system. I just edited the original post to correct.
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Old 05-18-2020, 12:44 PM   #4
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Default Re: TRX-4 Sport Upgrade Path

HH Trailmaster Sport 21T, HW 1080, and the Savox 1210SG are solid choices. I have the same set up.

I was running it at 7.4V BEC, but I added the two-speed conversion kit and its stock servo can only run at 6V and I haven't replaced it with a third party micro servo yet. I'll be waiting for it to burn out. But I haven't found it to hurt the 1210SG's performance much.
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Old 05-19-2020, 04:37 AM   #5
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Default Re: TRX-4 Sport Upgrade Path

Did you watch the YouTube trx4 series between Harley designs and scale builders guild?

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Old 05-19-2020, 05:03 AM   #6
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Default Re: TRX-4 Sport Upgrade Path

Holmes hobbies Brushless motors are best if you want a wide throttle range in a crawler. For brushed options I would buy a 2 speed trx4 trans from ebay. That 21t titan is as fast as I would recommend in brushed. Holmes 21t trailmaster is about the same, but it lasts longer because it has bearings not bushings. 4s is also an option.

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Old 05-19-2020, 06:11 AM   #7
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Default Re: TRX-4 Sport Upgrade Path

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Originally Posted by Voodoobrew View Post
Holmes hobbies Brushless motors are best if you want a wide throttle range in a crawler. For brushed options I would buy a 2 speed trx4 trans from ebay. That 21t titan is as fast as I would recommend in brushed. Holmes 21t trailmaster is about the same, but it lasts longer because it has bearings not bushings. 4s is also an option.

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This is helpful, thank you. Iíve been quite interested in the 2 gear transmission but have yet to read about how they actually work. Iím interested to read about how it maintains torque in ďlow gearĒ. Also interested in how much added weight with the 2 gear setup; do you happen to have a ballpark idea?

I like the idea of both brushless and 4s, but theyíre out of my price range considering the peripherally required components to run those. Iíve already exceeded my ďcapĒ, and Iíve yet to purchase a very sorely needed $80-$100 servo (again, I wish this was the #1 upgrade I made)

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Did you watch the YouTube trx4 series between Harley designs and scale builders guild?
I have not, but Iím assuming you recommend?
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Old 05-19-2020, 11:31 AM   #8
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Default Re: TRX-4 Sport Upgrade Path

basically the weight of a tiny servo and 2 gears.
Gearing works like this, the motor produces power, Power=torque*speed so if your first gear is half as fast as 2nd gear it produces twice as much torque, since the power remains constant.

If you haven't purchased a radio, then I would cross that off the list and get a castle mamba x and a brushless puller pro instead. Nothing wrong with traxxas remotes. Extra buttons for lights...I have them, never use them, a button on the car is just as good IMO. Oh nm you already bought an ESC and the remote. :(
Well you can run a brushed motor nn 4s for extra speed, but not with the HW1080.
And 2200kv or a 21t 550 3slot or 10t 550 5slot are the only brushed motors I would recommend.
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Old 05-20-2020, 09:39 AM   #9
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Default Re: TRX-4 Sport Upgrade Path

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Originally Posted by Voodoobrew View Post
basically the weight of a tiny servo and 2 gears.
Gearing works like this, the motor produces power, Power=torque*speed so if your first gear is half as fast as 2nd gear it produces twice as much torque, since the power remains constant.

If you haven't purchased a radio, then I would cross that off the list and get a castle mamba x and a brushless puller pro instead. Nothing wrong with traxxas remotes. Extra buttons for lights...I have them, never use them, a button on the car is just as good IMO. Oh nm you already bought an ESC and the remote. :(
Well you can run a brushed motor nn 4s for extra speed, but not with the HW1080.
And 2200kv or a 21t 550 3slot or 10t 550 5slot are the only brushed motors I would recommend.
Thanks again. This is all very helpful. This is my first real crawler, and I'm sure I will have multiple rigs as time goes on, so all this good info is going into the "for next time" knowledge bank.
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Old 05-20-2020, 06:27 PM   #10
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Default Re: TRX-4 Sport Upgrade Path

Much faster then a 21t on 3s things get pretty unstable. Then you spend almost as much time going to put it back on its wheels as you do driving it.

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Old 05-20-2020, 08:35 PM   #11
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Default Re: TRX-4 Sport Upgrade Path

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Originally Posted by Voodoobrew View Post
Much faster then a 21t on 3s things get pretty unstable. Then you spend almost as much time going to put it back on its wheels as you do driving it.

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That makes sense. I think down the road I’d be happy to have 1 (or more) strict crawlers, and then a “rock racer” or 4x4 short course truck to satisfy my desire for something faster. The Traxxas Slash 4wd seems like a lot of fun. I’m a mountain biker, so every once in a while when I’m in the woods with my crawler I get the desire to “hit that section with speed”, and I’m coming to terms with the fact that there’s a different RC for that!

Last edited by slothRC; 05-20-2020 at 08:40 PM.
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Old 05-22-2020, 10:45 PM   #12
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Default Re: TRX-4 Sport Upgrade Path

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That makes sense. I think down the road Iíd be happy to have 1 (or more) strict crawlers, and then a ďrock racerĒ or 4x4 short course truck to satisfy my desire for something faster. The Traxxas Slash 4wd seems like a lot of fun. Iím a mountain biker, so every once in a while when Iím in the woods with my crawler I get the desire to ďhit that section with speedĒ, and Iím coming to terms with the fact that thereís a different RC for that!
I'm also a Mountain Biker with a Slash 4X4 and a TRX4 Sport. It is really nice to have a truck that goes fast and busts the triple. That's why I don't mind not having the 2 speed TRX4. The Sport is a Crawler. I'm actually researching new ESC options and was just about to pull trigger on a 1080 but now I am thinking maybe a Mamba to make up for what the 1 speed lacks. Hmmm... Down the rabbit hole...
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Old 05-23-2020, 09:35 AM   #13
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Default Re: TRX-4 Sport Upgrade Path

Hey guys. I'm waiting for my sport kit to come in and am doing tons of research while i wait. Stumbled on this thread and its exactly what I've been debating. Is the 2 speed worth it or not? Can i just buy a couple gears and a servo and install them while im building the kit to have 2 speed right away or do i need a whole different transmission? Do you need to be able to unlock the diffs if you go 2 speed or is it fine to run it locked?
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Old 05-23-2020, 06:49 PM   #14
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Originally Posted by ActonRC View Post
I'm also a Mountain Biker with a Slash 4X4 and a TRX4 Sport. It is really nice to have a truck that goes fast and busts the triple. That's why I don't mind not having the 2 speed TRX4. The Sport is a Crawler. I'm actually researching new ESC options and was just about to pull trigger on a 1080 but now I am thinking maybe a Mamba to make up for what the 1 speed lacks. Hmmm... Down the rabbit hole...
Nice! I figured there had to be more like me. I think I'll hold out on the motor swap and the two-speed setup for the time being. Maybe if I decide to get a Slash 4x4 down the road, at that point I'll replace the TRX-4 Sport motor with something that spins slower for a bit more control. I ran the truck all day today, thought about it, and definitely don't need anything that spins faster than this stock motor on this truck.

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Originally Posted by mr_alister View Post
Hey guys. I'm waiting for my sport kit to come in and am doing tons of research while i wait. Stumbled on this thread and its exactly what I've been debating. Is the 2 speed worth it or not? Can i just buy a couple gears and a servo and install them while im building the kit to have 2 speed right away or do i need a whole different transmission? Do you need to be able to unlock the diffs if you go 2 speed or is it fine to run it locked?
I'm still very new to this so I am very far from an authority, but I'd say maybe try it single speed first? I have a ton of fun with mine with the single gear. If you're decent with your hands you should be able to quickly learn to feather the throttle for a good, slow crawl.

About the locked diffs question... My understanding is that the Sport without the 2-speed is always in "high gear" (someone please correct me if I'm wrong). And, the Sport's differentials are always locked. I kind of don't see the point in wanting to run the differentials unlocked in a crawler. In the month that I've had my Sport, running it every day since I bought it, I never wished my differentials were unlocked.
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Old 05-23-2020, 06:58 PM   #15
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Default Re: TRX-4 Sport Upgrade Path

you want unlocked diffs if you plan on going much faster as your truck will spin one tire and be less flippy when turning quickly.

Ms Allister, as far as I know the TRX4 a speed and 2 speed transmissions are different and you need to swap the whole assembly. You don't worry about the locked diffs, it's just a bit more unstable at higher speeds on hard surfaces.
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Old 05-23-2020, 07:44 PM   #16
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Default Re: TRX-4 Sport Upgrade Path

Okay thanks guys!
Haha, reading this post is amusing to me since i already own a slash 4x4 I'm looking to try a different area of rc that's more family friendly and as my kids are getting older we're doing a lot more hikes so naturally a crawler caught my eye. I have had quite a few rc's and they've all been fast offroad vehicles. Super excited to try crawling/trailing!
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Old 05-24-2020, 07:43 AM   #17
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Default Re: TRX-4 Sport Upgrade Path

i had rc buggies back in the day, and always found them too fast/uncontrollable and unless i was at a trck, not much fun in the yard. i picked up a TRX4 and have been loving it. so has my 5 year old, so of course he needed his own!
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Old 06-02-2020, 11:58 PM   #18
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Default Re: TRX-4 Sport Upgrade Path

TRX4 Sport & Rustler 4WD VXL make a nice combo IMO, I enjoy driving both a lot. I considered the 2spd gearbox but it's just something to break/cost $, the Sport goes a decent clip stock and still crawls OK. I was not interested in (un)locking diffs since its primary purpose is gnarly terrain. If I were to do another TRX I'd do a Sport (kit this time) again. Just my 2c in case anyone is on the fence.
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Old 06-03-2020, 09:23 AM   #19
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Default Re: TRX-4 Sport Upgrade Path

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TRX4 Sport & Rustler 4WD VXL make a nice combo IMO, I enjoy driving both a lot. I considered the 2spd gearbox but it's just something to break/cost $, the Sport goes a decent clip stock and still crawls OK. I was not interested in (un)locking diffs since its primary purpose is gnarly terrain. If I were to do another TRX I'd do a Sport (kit this time) again. Just my 2c in case anyone is on the fence.

Thatís pretty spot on to me. Iíve done a lot of thinking while running the truck lately and honestly, I think I want a slower motor with more torque and control. The speed my Sport has is fun, and the idea of a 2-speed transmission with remote lockers definitely seems very fun, but Iíd rather have this be a dedicated full crawler. If I want something fast for the trails, Iíll build a different RC. 4WD ďMonsterĒ Slash seems up my alley for that sort of thing.

Iím actually trying to do research and looking for some recommendations on a good quality, brushed motor in the $60 or less range for my Sport. As said, I want something slower and stronger with good control.


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Old 06-03-2020, 09:30 AM   #20
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Default Re: TRX-4 Sport Upgrade Path

The Holmes hobbies crawlmaster series are in that price range and I've only heard good things about them.
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