Overdrive/Underdrive?

[Naughty Dawg]

I didn't want to high jack the thread about improving turning radius, but one of the platters suggested overdriving the front axle and under driving the rear axle. What is meant by this? It sounds like using different gear sets in each axle?

[CBR74]

Correct. Overdrive 36/14 front, underdrive 43/13 rear.

[johnnyh66]

Great investment/mod!
Overdrive for front: Axial HEAVY DUTY BEVEL GEAR SET 36T/14T
Underdrive for rear: Axial HEAVY DUTY BEVEL GEAR SET 43T/13T

[TacoCrawler]

IMO one would do one or the other...
but not both.

I don't think it would be beneficial
to OD the front and UD the rear axle.
That span is too far apart IMO

possibly leave the stock/orig. 38 up front and use the UD 43 out back...
or drop the front to 36 and leave the rear at it's original 38.

[Naughty Dawg]

Interesting. I'm a newb to RC and didn't know you could do that. I would have thought chaos would ensue by having different gear sets between the axles, lol. Thanks for the info.

[509hooligan]

I ran just the 36/14 front and stock rears and it turned and climbed like a different truck! I would agree with taco doing both wouldn't be nedded...

BuIlT nOt BaUgHT!

[JesterSpec]

I've ran both, and personally I didn't like it. It bound up the drivetrain something fierce, and when driving in reverse the front pushed the rear end everywhere.

[TrimbleTractor]

This is my next mod after the xr10 steering is done. Glad to know you really only need to change one gear set!

[Fergy]

In my G6 I am only running UD in rear with stock front. In my comp rig with AR60 axles I run both for max turning and traction, I'm not looking for scale driving with that rig. I need it to climb rock faces.

Like said only one or other really needed for trail/scale rigs IMO.

[WHITE-TRASH]

2 of my rigs have both over and under drive gears. One is my crawler the other is my TTC rig and the large gearing spread is very beneficial on both rigs in all situations.

I will be doing overdrives in the front of fofftarded II and leaving the rear stock since it's a high speed rig. Same with my exo although it'll be underdriven rear and stock fronts. A bit of pull on a high speed rig is fantastic but the spread of having both OD and UD gears in a go fast is too much so the rear just gets drug over everything bouncing all the way.

Taking advice about carpentry from someone who's never swung a hammer doesn't make much sense to me.

[Meatwad]

My c2 rig is geared od/ud and occasionally run in comps, you'll want all the steering you can get (and then more) in a 10 gater comp.

It also is powered by a Holmes sensored outrunner on 3s. If one is worried about drivetrain binding, time to do all the strength upgrades.

[mark32]

I have run the over and under drive. over drive front stock rear. stock front and under rear. if u run a lot of rock and comp courses than the over/under is a great set up but for trail running u only need to do one or the other. i did notice while testing and tuning in lots of different terrains such as sand and mud the od/ud did seem to help the front stay a float if u have a good weight balance but like everybody says on here it is just my opinion. you should really see what works best for u. after all it is ur rig and driving style that really makes the deference.

[tznutts]

I recently ordered both to get my limo to turn 13.5 wheelbase class 2 . I do comp it but trail run it also. I'm gonna put in the rear first and see how it works and go from there..

Devious PowerSports ,Tyler

[SwampDawg]

Imo...i wouldnt have two ratios.
Keep both axles the same!

Just divide the crown by the pinion for the ratio or
To get the FDR.....

Spur/pinion
Topshaft gear/driven shaft gear (trans)
Crown/pinion

Take all the denominators and multiply the three.

[Naughty Dawg]

Originally Posted by SwampDawg

Imo...i wouldnt have two ratios.
Keep both axles the same!

Just divide the crown by the pinion for the ratio or
To get the FDR.....

Spur/pinion
Topshaft gear/driven shaft gear (trans)
Crown/pinion

Take all the denominators and multiply the three.

Huh?

Anyway, guys, I think I'm gonna start with OD in the front and see how that goes. I guess I should have mentioned that this isn't a competition rig, just a SCX10 Rubi with a few mods. Thanks for all the good info.

[autonomous]

Might be a self explanatory question but i have never ran od/ud and i am quite interested in the concept. Question is, would running OD in both front and rear of the truck have the same or similar effect as increasing pinion teeth and decreasing spur teeth? That is, would it make the truck have a higher top speed/slower acceleration?

[SwampDawg]

Play with pinion for speed.
Diffs are for fine tuning especially when
Using larger tires

[WHITE-TRASH]

Overdriving both axles would raise the top speed. It's pretty common in foff builds since most paddles are short so higher gearing is important.

[jdmguy760]

in the same boat thinking of ODing the front

[tech712]

The od front or ud rear both work great for a scale rig. Having the front turn fractionally faster than the rear helps a lot with turning and climbing. I've noticed this most with off camber obstacles going downhill where with stock gearing my front end would push out and my line would widen out off course ( which was a ledge on our proving grounds.) After under driving the rear the front would tend to pull the truck through this same corner keeping it tight to the inside avoiding a nasty spill over the edge.