rear axel gear down

[Willy Smellson]

I am currently reseaching under gearing the rear end so it isn't allways trying to out climb the front end. I think this is a good way to over protect the drive train nad increase climbing ans turning performance. The number one thing you see on wraiths is the back thier always diggn and bouncing and over driving the front end right on over in steep approaches. Am I getting warm? Does anyone happen to have a reccommendation on ratios? I was going to replace my diff gears with HD gears and gear the rear end down.

from what I gathered the Wraith has a stock ratio of 36-13 stock in both Diffs. correct?
The other two HD bevel gear choices are 36-14 and 43 13. I just don't know enough about ratios to make the right decision.
So,what do I put in the front and what do I put in the rear?

I will be running a super shafty 5mm output transmission with the 56 spur and a 11 14 or 16t 32p pinion, I will start with 14. I am also running a tekin FXR pro BRUSHED 35t motor and 3s lipo safe FXR pro ESC and either 2 or 3s lipos. This rig will be a crawler/trail runner so I don't need any speed demon stuff. just need descent wheel speed want to have more control on rocks and trails with steap climbs and tons of obsticles. Running external bec and hitech 7995. so there is plenty of power wheel speed and tourque. just need the right gearing to turn tight and go slow in descents. I may go to a dig in addition i do have enough channels in my rx. Will I need it with the gear down?

[crawler nut]

The Wraith has 38/13 stock. You could go 38/13 front and 43/13 in the rear. I'd also start out with a spur/pinion combo closer o 5 to 1.

[Kitty]

in my comp crawler i have OD/UD,so the front will spin more faster than the back.

36/14 in the front and 43/13 in the back.in my wraith-o-ax10 i have the stock gears,for bashing a rock racer.if u are making allot climbing/crawling it is good to do this on your rig

[crawler nut]

Originally Posted by Kitty

in my comp crawler i have OD/UD,so the front will spin more faster than the back.

36/14 in the front and 43/13 in the back.in my wraith-o-ax10 i have the stock gears,for bashing a rock racer.if u are making allot climbing/crawling it is good to do this on your rig

I don't think I'd go with that much of a spread in a Wraith. That's 2.77 in the front and 3.31 in the rear. 38/13 43/13 wound be 2.92 front and 3.31 rear. That should get him the little bit faster speed in the front that he wants.

[xgerstandtx]

I used the overdrive in the front on my current wraith build. It has worked well for me by reducing the torque twist a bit and decreasing my turning radius. Small increments is what i would recommend. Change out the rear gear ratio than if you want more change the front. Take your time and it will be just fine.

[Meatwad]

I use od/ud in everything axial that I own. The numbers may look scary but the function far outweighs that.

[k9popo]

I'm nervous about the Pro4 granading the rear end but its worth it if it holds...

[Kitty]

Originally Posted by crawler nut

I don't think I'd go with that much of a spread in a Wraith. That's 2.77 in the front and 3.31 in the rear. 38/13 43/13 wound be 2.92 front and 3.31 rear. That should get him the little bit faster speed in the front that he wants.

he said that's he's using wraith for climbing,and maybe for crawling,that's why i think tht's a good setup,but hey,everybody is free to choose what he wants

[Willy Smellson]

Thanks for all the good advise. do any of you think I should go to a aluminum bearing retainer in the diff at first? I will eventually put aluminum axels on this build as well. Will either of these minimise the risk of grenading the rear end If I choose to go to the 36 14 in the front?

Also I am building an scx10 with the same goals in mind... A trail rig crawler. I may do G6 with it but not until down the road and I'm willing to have another set up for that.
I will be running a super shafty 5mm output transmission with the 56 spur and a 11 14 or 16t 32p pinion, I will start with 14. I am also running a tekin FXR pro BRUSHED 35t motor and 3s lipo safe FXR pro ESC and either 2 or 3s lipos. This rig will be a crawler/trail runner so I don't need any speed demon stuff. just need descent wheel speed want to have more control on rocks and trails with steap climbs and tons of obsticles. Running external bec and hitech 7995. so there is plenty of power wheel speed and tourque. just need the right gearing to turn tight and go slow in descents. I may go to a dig in addition i do have enough channels in my rx. Will I need it with the gear down?

Also, I want to know the same info for this rig. What axial HD bevel gear set do I run in the scx10 with the above set up, to OD?UD my SCX10 trail rig.

[TOEDORG]

Why are you worried your going to blow your rear end apart, if you run underdrive it should be easier because the front end will be rotating faster and will take some load off of the rear and the numerically higher gear ratio will be easier on the ring and pinion. Although your axle shafts and locker will be under more stress, mainly if most of your weight is on that axle for instance a wheelie.
Right now on my wraith im running od in the front and standard rear, it wasnt a huge difference but it helped turning alot. My only hesitation with running od/ud is some weird binding on high traction surfaces but it seems that quite a few people are really liking that combo.

[Clk1982]

I run over drives in the front and under drives in the rear and i am running a 4000kv pro4 geared 56/11 and have not ran into any issues

[Rjohn929]

Run overdrive in the front and underdrive or stock ratio in the rear. Works for just about everybody who has ever built an axial anything to help minimize torque twist and help turn.

43/13 = underdrive
36/14 = overdrive
38/13 = stock

I personally run overdrive front and stock ratio rear in my wraith. I have VP chubs, knuckles and lock outs along with aluminum bearing retainers and HR lockers for now. My fancy expensive clamping lockers were nothing but trouble and kept getting loose no matter what I did.

[indiana mudcat]

The only time the OD gears should ever be used is in a OD/UD setup.

Wraith/SCX doesn't matter, UD the rear first, then OD the front if you want a bigger spread.



When broken down and looked at each axle individually, OD gears actually increase torque twist. It's only the effect of gearing differences that help. In fact sometimes with OD/stock TT can be worse than stock/stock IMO. UD gears decrease TT by ratio alone plus the effects of the gear spread.

I've ran OD/stock and stock/UD in the same truck about an hour apart on the same rocks with no other changes and stock/UD was the better setup by far.

Really wish Axial had just made two underdrives instead. A UD about 3.73-1 in the rear with stock front would be better than the current OD/UD setup and offer other choices all with more TT reduction also.

The setup that really confuses me is the OD/OD guys. All they are doing is increasing TT for a gain in speed that could have been had with a simple pinion and or spur change. I can see running UD/UD as that is the best equal gearing setup and best stress relief on the driveshafts and tranny. UD/UD is a much better setup than OD/OD at the same price. It's not like you can't get the speed with the pinion/spur, it's a lot harder to gear down than up.

[Rjohn929]

ODing the front is an improvement over stock. Maybe if you put them both front and rear you will increase TT but not just the front.

If my Wraith was a crawler I would absolutely put the UD's in the rear but since it's a racer/basher/TTC I'm going to leave the wheel speed where its at. Again, all positive atributes with the OD front over the stock.

Best thing to do is buy a couple of sets, make up some diffs and run them on the same lines in different configurations to see how performance changes.

[Willy Smellson]

Thanks eveyone!

[indiana mudcat]

Originally Posted by Rjohn929

ODing the front is an improvement over stock. Maybe if you put them both front and rear you will increase TT but not just the front.

If my Wraith was a crawler I would absolutely put the UD's in the rear but since it's a racer/basher/TTC I'm going to leave the wheel speed where its at. Again, all positive atributes with the OD front over the stock.

Best thing to do is buy a couple of sets, make up some diffs and run them on the same lines in different configurations to see how performance changes.

Your not looking at the front and rear individually. Lets try to explain this again. TT is caused by the axles resisting the turning force of the driveshafts. Higher gear ratios will always increase twist as the strain goes up. Gearing down in the diffs will always decrease twist as it lets the shafts spin the gears easier.

So while the gearing difference is what makes OD/stock better is some spots, stock/UD will have those same effects plus the effects of lower diff gearing.

That "speed" excuse again. Why don't people understand that higher diff gearing makes you gear down at the pinion/spur and the trucks end up the exact same speed. The one with lower diff gears just performs better with less drivetrian stress.

[Rjohn929]

I assure you I know about pinion and spur ratios. I have little to no TT and have everything set up to the point here I don't feel it could be better for what I do. UD in the rear made no difference on the TT for me on my setup so I took them out and put them in my crawler. The OD front DID make a difference. Just my personal opinion and what has worked for me so I thought I would share it. I don't need an explanation. Thanks though.

[hagnyosaroyo]

so wich one is better?
OD/stock, stock/UD, or OD/UD?
I need more explanation of each setup

[Tonysmini]

I run HD gears all round on my axial trucks, but it was experimentation on them to really get it all sorted

Gearing front/rear
Wraith basher -stock/uD general trailer and basher (VP hubs and CV's)
SCX based recovery truck - UD/UD used as a puller and scaler, high clearance knuckles and CV's
Dingo - Stock/UD high clearance knuckles and CV's trailing and general basher
SCX axle'd Wraith cage-OD/UD beater rig, again high clearance knuckles and CV's this set up tends to drag the rear and squat on high grip runs, but this one gets flogged relentlessly and doesn't seem to break.

I would UD the rear first, and I found the 'stock' HD spiral geared diff gears smoother than the supplied ones. Try the first before OD'ing the front.

[LucasAutomotive]

Originally Posted by hagnyosaroyo

so wich one is better?
OD/stock, stock/UD, or OD/UD?
I need more explanation of each setup

The only reason you change your diff gearing is to reduce torque twist or to reduce wheel hop/skip while turning like Indiana said. When you turn your rear wheels travel a shorter distance than your front wheels. So if your gear ratios match your rear wheels will be pushing your front wheels. Putting UD gears in the rear reduced torque twist in the rear and also improves tight turning.

Stock/Stock= ok
Stock/UD= reduces torque twist and better turning
OD/UD= good for slower crawling and off road driving (gear train could bind up due to the difference of wheel speed front and rear)
OD/Stock= does the same as stock/UD but increases torque twist.... so stock/UD is better.
OD/OD= just silly
UD/UD= reduces torque twist in the front and rear but you loose the turing benefits gained by running different ratios in your axles.
If you're looking to go faster or sower just change your pinion/spur combo. It's cheap, easy and effective.