RCCrawler Forums

Big Daddy · 12-08-2011, 07:28 AM

I'm thinking of changing gear ratios in one axle. If you were going to do one axle only which one is better bang for the buck? Is only doing one axle worth it, i.e. is the gain noticable?
Would either one affect the run time dramatically? If the front is overdriven, is the wheel speed different enough that the pinion gear needs changes to regain the low speed?

I will be adding high clearance knuckles, aluminum C-hubs, and CVDs to the front axle, and a set of beef tubes if I can find some.

jeepster73 · 12-08-2011, 07:31 AM

Overdrive for sure.

Bananaclip · 12-08-2011, 07:36 AM

I have ran the over drive with much sucess. I am trying the hd front underdrive rear in my wraith. We will see

ClassicGMJunkie · 12-08-2011, 07:36 AM

overdriving the front will help with better steering from it not pushing so bad, but the underdrive has more of a speed changing ratio compared to OD.

I recommend both in a sportsman rig, you have to get used to it but you won't want to go back! scalers, well, hell I dont even change the r&p but I might later on down the road.

jeepster73 · 12-08-2011, 07:43 AM

I also noticed that with the OD that my turning radius increased(tighter).

AX10wannabe · 12-08-2011, 02:56 PM

if you can afford it do both, overdrive front underdrive rear... but if i can only afford one at a time i say overdrive the front.

i was crawling with a guy 3 weekends ago that had a heavily modded/blinged out ax10 with OD/UD gears and it was ridiculous how tight the turning radius was. by overdriving the front if your on flat ground and there is 1 small rock by its self and you rest 1 rear tire behind the rock (like your going to drive over it) and give the throttle a few blips the front end will spin around like you have a dig.

your front tires will spin faster than the rear and will with crawling.

Big Daddy · 12-08-2011, 03:01 PM

The reason I don't want to do both is I'm not sure what it would drive like on a trail in between obstacles. Maybe I'll do the front for now and see how I like it and then later underdrive the rear. We do a lot of scaling on hiking trails so there is some driving on pretty easy terrain and I don't want to be dragging the rear tires along the whole time.

AX10wannabe · 12-08-2011, 04:41 PM

Quote:

Originally Posted by Big Daddy

The reason I don't want to do both is I'm not sure what it would drive like on a trail in between obstacles. Maybe I'll do the front for now and see how I like it and then later underdrive the rear. We do a lot of scaling on hiking trails so there is some driving on pretty easy terrain and I don't want to be dragging the rear tires along the whole time.

ya that makes sense.. when you have both gears all tires will still spin like normal. where it shines is, if your on a sidehill and driving across it and there is some pointy rocks for the tires to grab onto and the truck is sliding sideways the front tires is spin faster and the rear tires will slow down and will grip a little better then if they were spinning.

so overdrive the front and try it out, even on flat ground and you ease into the throttle the front will start turning and then the rears. if you want a tight turn blip the throttle and spin the front tires in the direction you want to go.

im supposed to be crawling this weekend at a friends house (and hopefully picking up my ax10 that i ordered) and if the guy with the modded/blingy ax10 is there i'll get some video of his run because OD/UD makes a big difference!!

waggaclint · 12-08-2011, 05:14 PM

Ive been kooking at doing both on my rig but ive found it very hard to get the Axial 36/14T Overdrive gears (AX30401) anywhere everybody is out of stock..

So im going to keep the normal ratio 38/13 gears in the front and ive purchased the Axial 43T/13 underdrive gears (AX30402) for the rear axle. This gives both an overdrive effect (for more steering) as well as puts more overall gear reduction in the axles (reducing chassis torque twist).

NFA Fabrication · 12-08-2011, 05:36 PM

Quote:

Originally Posted by waggaclint

So im going to keep the normal ratio 38/13 gears in the front and ive purchased the Axial 43T/13 underdrive gears (AX30402) for the rear axle. This gives both an overdrive effect (for more steering) as well as puts more overall gear reduction in the axles (reducing chassis torque twist).

I was getting ready to reply to say just this. I think the benefits of this idea are often overlooked/misunderstood.

Big Daddy · 12-08-2011, 07:10 PM

Yeah I was looking around and couldn't find the overdrive gear anywhere. I wonder if Axial discontinued that too

I may do the underdrive or just leave it alone for awhile... it's not broke yet...

mudn_1 · 12-08-2011, 08:58 PM

my scaler is overdriven in the front and underdriven in the rear and it works great.... It climbs well, and turns better as well.....

Meatwad · 12-08-2011, 10:38 PM

Od front/stock rear= least numerical gearing difference
Stock front/ud rear= middle of the road
Od front/ud rear= most numerical difference

Right now I'm running stock front/ud rear in some ar60's. I'm liking the turning radius, tt isn't horrible.

9700trevor · 12-09-2011, 01:09 AM

I have recently changed the rear R/P to the under drive and love it. I already had the over drives in the front I recommend doing both is will help with step climb and descents as the rear tires are going to not want to dig in as much on climbs and with descents it will drag a little more making your rig more stable, also turning radius becomes even tighter

NFA Fabrication · 12-09-2011, 01:35 AM

Quote:

Originally Posted by Meatwad

Od front/stock rear= least numerical gearing difference
Stock front/ud rear= middle of the road
Od front/ud rear= most numerical difference

Right now I'm running stock front/ud rear in some ar60's. I'm liking the turning radius, tt isn't horrible.

I figured this out a while ago so I would have a visual to compare, thought it was applicable to this thread

36/14 Overdrive = 2.57
38/13 Normal = 2.92
43/13 Underdrive = 3.31

Overdrive To Stock Difference= .35
Underdrive To Stock Difference= .39
Overdrive To Underdrive Difference= .74

wally101 · 12-09-2011, 09:29 AM

I recently installed Underdrive in the rear of my Tundy and love it! So much so I bought a set for my Bronco. Climbs way way better. Didn't notice turning radius being better, but that was never a problem. I am running a 35T hand wound on 3S. If I was only using 2S I may have gone with just Overdrive in front. I heard there can be binding issues using both over/under but don't know for sure...

12-08-2011, 07:28 AM	#1
Big Daddy RCC Addict Join Date: Jun 2011 Location: Gilbert, AZ Posts: 1,634	Over or underdrive? I'm thinking of changing gear ratios in one axle. If you were going to do one axle only which one is better bang for the buck? Is only doing one axle worth it, i.e. is the gain noticable? Would either one affect the run time dramatically? If the front is overdriven, is the wheel speed different enough that the pinion gear needs changes to regain the low speed? I will be adding high clearance knuckles, aluminum C-hubs, and CVDs to the front axle, and a set of beef tubes if I can find some.

12-08-2011, 07:43 AM	#5
jeepster73 Rock Crawler Join Date: Mar 2006 Location: Up North Posts: 617	I also noticed that with the OD that my turning radius increased(tighter). Last edited by jeepster73; 12-08-2011 at 07:46 AM.

12-08-2011, 07:31 AM	#2
jeepster73 Rock Crawler Join Date: Mar 2006 Location: Up North Posts: 617	Overdrive for sure.

12-08-2011, 07:36 AM	#3
Bananaclip I wanna be Dave Join Date: Dec 2006 Location: Where the sheep run scared. Posts: 3,008	I have ran the over drive with much sucess. I am trying the hd front underdrive rear in my wraith. We will see

12-08-2011, 07:36 AM	#4
ClassicGMJunkie Quarry Creeper Join Date: Jun 2010 Location: Wheeling Posts: 454	overdriving the front will help with better steering from it not pushing so bad, but the underdrive has more of a speed changing ratio compared to OD. I recommend both in a sportsman rig, you have to get used to it but you won't want to go back! scalers, well, hell I dont even change the r&p but I might later on down the road.

12-08-2011, 02:56 PM	#6
AX10wannabe RCC Addict Join Date: Jun 2009 Location: Salmon Arm BC Posts: 1,777	if you can afford it do both, overdrive front underdrive rear... but if i can only afford one at a time i say overdrive the front. i was crawling with a guy 3 weekends ago that had a heavily modded/blinged out ax10 with OD/UD gears and it was ridiculous how tight the turning radius was. by overdriving the front if your on flat ground and there is 1 small rock by its self and you rest 1 rear tire behind the rock (like your going to drive over it) and give the throttle a few blips the front end will spin around like you have a dig. your front tires will spin faster than the rear and will with crawling.

12-08-2011, 03:01 PM	#7
Big Daddy RCC Addict Join Date: Jun 2011 Location: Gilbert, AZ Posts: 1,634	The reason I don't want to do both is I'm not sure what it would drive like on a trail in between obstacles. Maybe I'll do the front for now and see how I like it and then later underdrive the rear. We do a lot of scaling on hiking trails so there is some driving on pretty easy terrain and I don't want to be dragging the rear tires along the whole time.

12-08-2011, 05:14 PM	#9
waggaclint Quarry Creeper Join Date: Sep 2010 Location: Perth Australia Posts: 322	Ive been kooking at doing both on my rig but ive found it very hard to get the Axial 36/14T Overdrive gears (AX30401) anywhere everybody is out of stock.. So im going to keep the normal ratio 38/13 gears in the front and ive purchased the Axial 43T/13 underdrive gears (AX30402) for the rear axle. This gives both an overdrive effect (for more steering) as well as puts more overall gear reduction in the axles (reducing chassis torque twist).

12-08-2011, 07:10 PM	#11
Big Daddy RCC Addict Join Date: Jun 2011 Location: Gilbert, AZ Posts: 1,634	Yeah I was looking around and couldn't find the overdrive gear anywhere. I wonder if Axial discontinued that too I may do the underdrive or just leave it alone for awhile... it's not broke yet...

12-08-2011, 08:58 PM	#12
mudn_1 Quarry Creeper Join Date: Sep 2010 Location: too close to LRC.... Jealous???? Posts: 479	my scaler is overdriven in the front and underdriven in the rear and it works great.... It climbs well, and turns better as well.....

12-08-2011, 10:38 PM	#13
Meatwad I wanna be Dave Join Date: Jul 2009 Location: Rancho Relaxo. California. USA. Earth. Posts: 3,292	Od front/stock rear= least numerical gearing difference Stock front/ud rear= middle of the road Od front/ud rear= most numerical difference Right now I'm running stock front/ud rear in some ar60's. I'm liking the turning radius, tt isn't horrible.

12-09-2011, 01:09 AM	#14
9700trevor Quarry Creeper Join Date: Jan 2011 Location: armstrong Posts: 260	I have recently changed the rear R/P to the under drive and love it. I already had the over drives in the front I recommend doing both is will help with step climb and descents as the rear tires are going to not want to dig in as much on climbs and with descents it will drag a little more making your rig more stable, also turning radius becomes even tighter

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12-09-2011, 09:29 AM	#16
wally101 Quarry Creeper Join Date: Dec 2008 Location: La Costa, CA Posts: 375	I recently installed Underdrive in the rear of my Tundy and love it! So much so I bought a set for my Bronco. Climbs way way better. Didn't notice turning radius being better, but that was never a problem. I am running a 35T hand wound on 3S. If I was only using 2S I may have gone with just Overdrive in front. I heard there can be binding issues using both over/under but don't know for sure...

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Thread: Over or underdrive?