TRX-4 Sport gearing

[troutshark]

So I sold my Bronco to a buddy and decided to get the new Sport as I didn't care for the 2 speed and locking diffs but thought the truck had a lot of potential. Got my Sport in yesterday along with a giant pile off hopup parts. Woohoo! I didn't even drive it, I tore it apart and rebuilt it the rccrawler way. Hop up everything! Metal axle housings, all the brass stuff, OD and UD gears, HH servo, HW1080 esc, Predator compound Hyraxes, LCG battery tray, 80mm shocks for the lower stance, steelies, and a Bronco body with lights etc... It took me all night but I got it done.

Then I drove it.... Much anger and sadness....

So I guess Traxxas thought it needed it to be fast. Feels like it's stuck in 2nd gear. It'll pop a wheelie. Sigh, I have other trucks for that stuff.

Anyways, RTFM so I broke out the manuals. I'm not happy if I have to read a manual. Just saying

Comparing the gearing compatibility charts of the regular TRX-4 to the new Sport I see that it isn't too big of a deal. They used the low gear from the 2 speed trans but switched to the 39t spur with a 17t pinion. That's 39t/17t x 15.8 low gear for a Final gear ratio of 36.25.

The regular 2 speed TRX-4 uses a 45t spur with a 11t pinion. That's 45/11 x 6.32 high gear for a 25.85 Final gear ratio in 2nd. The low gear ratio is 45/11 x 15.8 for a Final gear ratio of 64.64. I like my crawlers geared 60 plus, so that's what I was wanting.

It's an easy enough fix. So if you are expecting a slow crawling experience from your new Sport like 1st gear in the original TRX-4 you will need a 45t spur TRA8053 and a 12t pinion TRA6747. If I would have known, I would have ordered them with my truck in the first place. Hopefully, I'll keep somebody else who likes their trucks all crawlerly and slow from cussing their new Sport like me.

What struck me as really odd though, if you compare the two charts, the 2 speed chart for low gear lists the gear ratio of 36.25 that the Sport uses as "Not recommended for the stock motor". Since that's exactly what the Sport chart recommends as ideal or whatever, I thought I'd test that out to see if it's fine like Traxxas says.

So for SCIENCE! I stuck the stock esc back in the truck and pretended my all brassed out heavy metal truck was light again. I ran it around like a basher on 3s for about 15 minutes in 95+ degrees of beautiful sunshine before it shut down. Motor temps were over 160F and the ESC was 150F. Yeah, it's not a fair test as it's really heavy but that's not a healthy gear ratio IMO. At least for the stock motor. I'd definitely recommend changing the gears or using a lower turn motor to keep temps down. The electronics survived my little test but I doubt they would for long.

If you plan on running a higher kv brushless combo in the Sport as folks are prone to do, it might be trouble without changing gear ratios. A low kv Puller Pro or maybe a Revolver might work. I'm sure Mr. Holmes will have some motor recommendations for us soon.

It's a really nice little crawler but i think they screwed up on that pinion and spur combo. Oh well, my box full of Traxxas stock parts had a little bit of space left in it.

[mikemcE]

Always remember Traxxas is the fastest name in RC !


Hang up and Drive

[Jtlittle]

Traxxas knows theres thosands of bashers for every comp crawler. The build for the masses. Gotta gear it down period. IMHO

[troutshark]

I've been poking fun of their fastest name in RC thing for years. It was funny before people actually bought into it. Back in the 90s they were anything but. Every other brand on the market it seemed was an actual race truck but usually in kit form ie. no electronics. Losi, Associated, Yokomo, Schmacher, Kyosho and many others actually raced and were fast. Traxxas marketing has obviously paid off over the years.

I'm used to having to change most everything on a new vehicle to get it to perform as I like but this one actually surprised me I guess as they took the correct gears out and put in something completely inappropriate for it's current configuration. In the end, it will perform like I want it to. I was probably more aggravated that I missed something when making my performance parts order. Being hours away from a hobby shop makes accurate part research important for sure. Plus qualifying for free shipping. Normally my builds are more linear over time as I add parts as I need them. This time I thought I'd be like one of the cool kids that do the sweet build threads and have everything ready beforehand. Bilinvic, new2rocks and many others always make it look so easy. lol It's not easy for sure. I'm happy though as my truck is super stable and now feels competitive with the other trucks in my fleet. Well, except the wheelie popping thing...

In true Traxxas style I should do a speed run video! I bet the OD/UD locked diffs would be awesome for that.

[tim the toolman]

Well crap I'm glad I decided to read this post! Just got myself a sport, haven't ran it yet. Figured I'd power it up and run it once, then sell the stock electronics to a buddy of mine that is kind of needy lol. I have a roc 412 and an rx4 I plan to stick in it. I'll still want the lower gearing with that setup I assume? Or maybe something in between?

[troutshark]

Originally Posted by tim the toolman

Well crap I'm glad I decided to read this post! Just got myself a sport, haven't ran it yet. Figured I'd power it up and run it once, then sell the stock electronics to a buddy of mine that is kind of needy lol. I have a roc 412 and an rx4 I plan to stick in it. I'll still want the lower gearing with that setup I assume? Or maybe something in between?

Depends on the kv of the roc 412 and how you like your truck geared. I run mine as a crawler only and I like them really slow. The manual has a gear chart showing what spur/pinion combo will fit and the ratios. The gears are cheap enough to try different combos pretty easily.

Also, it looks like other people with Sports are having good performance running aprox. 1800kv brushless motors with the stock gear ratio. That's probably a pretty good all around setup for most folks. If your's is a lot higher kv you may need to switch to the 45t spur and try a lower pinion, then work your way up as needed to suit your driving style.

[tim the toolman]

Good info, thanks. I've switched out the receiver & servo but not the esc & motor yet. It works surprisingly well on crawl mode, gearing seems about right for the 550 Titan motor at any rate👍

[troutshark]

I think the 21t titan motor is approximately the same speed as a 2200kv brushless so that should give you a good baseline to work with. It was too fast for my application but I'm weird like that.

[tim the toolman]

First full on test for me yesterday, 5 hours of crawling on comp style lines��. Stock esc & motor worked great with no issues until I was almost thru battery #2 (2200 3s). Esc thermal safemode once shortly before lipo cutoff. Battery #3 did this 4 times, but to be fair it was an older battery, hot weather and extreme comp style crawlin lol. If I continue to run stock motor & esc I'll go a tooth smaller on the pinion and or esc fan. I should note this was on a sport, all stock other than stronger servo with a Bec and brass portal outers, so fairly lightweight too��. Very happy with this car though, outcrawls my totally unstick scx10 right now as is��

[rattmobbins]

Has anyone re-geared their Sport that might have some pointers?

I added the lift kit and Pro-line Super Swamper XL 2.2 tires to my Sport but haven't really driven it since I did that. Wanting to dial in the gearing just right before I start beating on it.

Any tips would be appreciated!

[travis c.]

Larger spur gear, smaller pinion gear, problem solved.

[pyroM!KE]

Holmes hobby trailmaster 550 45t...20 bucks
9t pinion...6 bucks

Problem solved....

[DukeMinnix]

I've got the assembly kit on the way. I have a 3100kv roc412 laying around waiting for a home, along with a mamba. I've been reading all over anywhere I can find about gearing on these little trucks. I've not owned a trx4 of any variety yet. I have several 12-13t pinions I keep around for running these tekin motors on various axials I own. So two part question

1 Are the trx4 32p like axials?

2 For a crawler, lower speeds and steady control wanted, will I need a lower tooth pinion than this?

Moving on, I may be overthinking this. I also have a HW1080 laying around I can get a cheap HH 550 and run. Save myself the time and guessing and get a HH trailmaster 45t 550? If so, what pinion? I'm not sure the assembly kit comes with one period, I haven't received it yet. Question 1 still applies to pinion/spur pitch.

[svt923]

Originally Posted by DukeMinnix

I've got the assembly kit on the way. I have a 3100kv roc412 laying around waiting for a home, along with a mamba. I've been reading all over anywhere I can find about gearing on these little trucks. I've not owned a trx4 of any variety yet. I have several 12-13t pinions I keep around for running these tekin motors on various axials I own. So two part question

1 Are the trx4 32p like axials?

2 For a crawler, lower speeds and steady control wanted, will I need a lower tooth pinion than this?

Moving on, I may be overthinking this. I also have a HW1080 laying around I can get a cheap HH 550 and run. Save myself the time and guessing and get a HH trailmaster 45t 550? If so, what pinion? I'm not sure the assembly kit comes with one period, I haven't received it yet. Question 1 still applies to pinion/spur pitch.

The TRX4 is 32P.

12-13T pinions will be a fine starting point but you will need the 45T spur from the 2 speed versions since the smallest pinion that fits with the Sport's spur is 15T.

The Tekin motor would be my choice by far. A 45T 550 motor is close to a 55T 540 and is going to be unbearably slow, consider the 21T or 27T Trailmasters for a brushed motor if you prefer that direction.

[kincer]

I have a 1080 and 21t and 27t 550 Trailmaster motors, I'm gonna try the 27t first in the sport then go to 21t if need be.

[DukeMinnix]

Originally Posted by svt923

The TRX4 is 32P.

12-13T pinions will be a fine starting point but you will need the 45T spur from the 2 speed versions since the smallest pinion that fits with the Sport's spur is 15T.

The Tekin motor would be my choice by far. A 45T 550 motor is close to a 55T 540 and is going to be unbearably slow, consider the 21T or 27T Trailmasters for a brushed motor if you prefer that direction.

Originally Posted by kincer

I have a 1080 and 21t and 27t 550 Trailmaster motors, I'm gonna try the 27t first in the sport then go to 21t if need be.

My logic with the 45t was that was the recommendation for those with sports wanting to keep their stock pinion/spur combo, having to order or run a pinion I already have at home opens me up. Sounds to me like o should order up a 45t 32p spur and try the 13t pinions I have and take it from there with the roc

[SlagMan]

Originally Posted by kincer

I have a 1080 and 21t and 27t 550 Trailmaster motors, I'm gonna try the 27t first in the sport then go to 21t if need be.

I’ll be very interested in your opinion. Because this is the combo I’m currently considering as well for my kit. I have some 35t and 55t motors but think they’ll be too slow. I plan on taking it swimming and don’t want to stress about ruining a brushless system.


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[svt923]

Originally Posted by DukeMinnix

My logic with the 45t was that was the recommendation for those with sports wanting to keep their stock pinion/spur combo, having to order or run a pinion I already have at home opens me up. Sounds to me like o should order up a 45t 32p spur and try the 13t pinions I have and take it from there with the roc

While the top end speed be about the same, a 21T 550 with 60:1 gearing will make more torque, run cooler, and do literally everything else better than a 45T 550 on stock sport gearing of 35:1. For how easy and cheap it is to gear down incredibly low on the TRX4 (getting to 79:1 can be done for about $7 worth of pinion and spur), there is no reason to not run the higher KV/lower turn motors.

[DukeMinnix]

Originally Posted by svt923

While the top end speed be about the same, a 21T 550 with 60:1 gearing will make more torque, run cooler, and do literally everything else better than a 45T 550 on stock sport gearing of 35:1. For how easy and cheap it is to gear down incredibly low on the TRX4 (getting to 79:1 can be done for about $7 worth of pinion and spur), there is no reason to not run the higher KV/lower turn motors.

especially since I already own the Tekin and it needs a home. Point taken.

[SlagMan]

Originally Posted by svt923

While the top end speed be about the same, a 21T 550 with 60:1 gearing will make more torque, run cooler, and do literally everything else better than a 45T 550 on stock sport gearing of 35:1. For how easy and cheap it is to gear down incredibly low on the TRX4 (getting to 79:1 can be done for about $7 worth of pinion and spur), there is no reason to not run the higher KV/lower turn motors.

Where would be a good place to start reaching the ratios you mentioned?


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