Running different gear ratios, front and rear

[4WDwannabe]

Hey guys, just making a list and checking it twice, of SCX parts that is. I saw an SCX build for comps in a magazine and they used 38/13 HD gears in the front and 43/13 HD gears in the rear axles. The aim was to keep the front end planted when making climbs.
2 questions. First, I'm going to trail run and rock climb this rig. Does this mismatched ratio theory make sense?
And second, running mostly on rocks and dirt, is this very hard on the rest of the drivetrain? I know in a 1:1 it would be but I'm keeping this rig as light as possible.

Oh, one more. I was going to instal the Axial AX10 Scorpion universal joint set
AX10 Scorpion Universal Set (2pcs). Are these only for the front axle? If so what do I put in the rear axle.
Oh I lied, what's a good servo for this rig?
Thanks dudes, you rock!

Oh and I'm switching to lipo (finally). Would you run 2s or 3s? Tekin FXR esc so it should run 3s if need be.

[dstrbd1]

First off please don't buy the axial universal axles. They are extremely weak. The stock dogbones alot stronger and with some grinding you can achieve the same steering. With a bit of effort you can retro fit the XR10 front shafts, chubs and knuckles. If you search you can find some good info on that.

CHUDS SPORTY

[C*H*U*D]

I run overdrive in the front of my SCX with no problems. It helps with turning and climbing...great mod. I'd avoid overdrive and underdrive though...pick one or the other since it does have an effect on trail running.

I'd also stick with dogbones over those universals. I've never run the Axial universals...mostly because of all the broken pins I see on other trucks. You can also give the RC4WD universals a try. I just ordered a set last night...I want to try them out before next years comps start.

3S all the way

[johnnyh66]

I run OD in front and stock ratio in the back. It does help with climbing, tracking straight at speed and it really improves turning radius.

I had been running MIP CVD's in my scaler for about 8 months with no problems.
I needed to change my knuckles and had a bearing stuck on them so I switched to Axial CVD's... the Axial ones snapped in the middle of their first comp! (My fault I think, I had my steering EPA's to high... I think).

So back to MIP for me.
It took an hour of searching every corner of the web but I found a couple of more sets... they may have been the last in the known universe... but they are worth the search effort.

[4WDwannabe]

Ok just to be clear, you guys are running the optional 43/13 HD gears in the front and the stock 38/13 HD in the rear. So 43 and 38 are a good combo? In RCcar action they did it the other way around, 43/13 rear and 38/13 front. Might have been a typo? The only other gear set Axial has is 36/14 and I'm staying away from that.

Thanks for the heads up on those Axial universals. Saved me $30, might just run the stockers till something breaks. And search for MIP while I wait!

RCC.com comes thru again, thanks for promt answers guys! Anybody else have an opinion please chime in.

[josh6575]

they were right you don't want to under drive the front. use the bigger gear with more teeth in the rear. I will make it slower than the front.

[dstrbd1]

43/13 = 3.31 Underdrive for rear
38/13 = 2.92 Stock
36/14 = 2.57 Overdrive for front

[Jus]

I like a little wheel speed with my Honcho so I have overdrive gears in the front. Helps a lot with climbing and adds a tiny bit of speed overall.

My other scx is slower and works better at barely moving speeds so I underdrive the rear... Still helps climbing as it's essentially made the front wheels turn faster.

Either way it's helpful, depends on if you want faster or slower.

[dstrbd1]

Keep in mind also that the under drive in the rear will help fight torque twist. On the other hand the overdrive front tends to exaggerate it just a bit at times. It does this because when you decrease the gear ratio numerically you increase the amount of torque that you have to apply to the front driveshaft for it to turn the front axle which in turn helps increase torque twist. Hope this makes sense.

-Trent

[steele42]

This all helped me a ton. Thanks guys! Thank you search function.

[heinie_21]

why are you up at 2am?

[TheOgre]

Why are you up at 2:06?

[steele42]

Originally Posted by heinie_21

why are you up at 2am?

Learning about underdrive gears . It's always a good time to be on RCC and working on my rig

[DV8ion]

Redbull....it gives you wings. LoL I'm gonna order the rear underdrive setup.

Sent from my BlackBerry 9700 using Tapatalk

[natskiboy]

Just got linked to this thread. From my understanding. I should be OK with 36/14 front and 38/13 rear?

[johnnyh66]

Yup, you want the front rotating faster than the back.
Anyone of these combos:
36 (od) in the front and 38 (stock) in the rear
38 (stock) in the front and 43 (ud) in the rear
36 (od) in the front and 43 (ud) in the rear


From Axials website

• Use the gears in different combinations front and rear to reduce torque twist in the rear and overdrive the front axle to help pull you through climbs easier
• The heavy duty gear set offers improved gear mesh reducing slop in the drive train.
• Spiral cut gears offer increased gear tooth contact and run quieter.
• New gear ratios offer a low gear and high gear range
• The lower gear range set reduces torque twist (43/13)
• The higher gear range offers higher top speed (36/14)
• Hardened steel for increased strength and additional weight in the axle
• One set per axle required
• Laser etched markings

[avanord]

I run overdrive in the front and stock in the rear. It has made a huge difference. I highly recommend it.

[jvella]

I have od and ud on my comp rig and i love it.The only problem i find is when reversing.1 rear wheel will lift up from the ground. I also use axial cv and never broken 1 except for the pins and even that issue is solved when i bought Gunnar pins

[4WDwannabe]

Hey thanks Johnnyh66. Your explanation of under/over drive gearing made it very clear:
"Yup, you want the front rotating faster than the back.
Anyone of these combos:
36 (od) in the front and 38 (stock) in the rear
38 (stock) in the front and 43 (ud) in the rear
36 (od) in the front and 43 (ud) in the rear"

Your explaination is almost as good as your Buxom Melons Bug. I've been following it for a while and think it looks better without the roofrack personally. I must have a thing for bugs cause my Stampede and Losi MRC are both green bugs.