10-12lb Rig & Over-Unders on pavement?
 

Hey fella's..

I got a quick question/concern about over/under gearing in my 10-12lb 2.2 truck.

Im running a tuber chassis, wraith axles with axial hard ring & pinions.. 36/14(over) in the front axle and 43/13(under) in the rear.
Im a little concerned about the excess stress & wear on drivetrain components while getting traction on sticky ground or pavement. I could see how the over/under setup wouldnt really matter while in the dirt/mud/sand or in loose traction situations.

Am I over-thinking this? Is 10-12lbs not that heavy?

any comments?

Thanks.

I can see a lot of tire scrub in the front happening, but as long as it is able to break traction on either the front or rear, it shouldn't hurt anything further in, in the drivetrain.

IMO that's a bit of a spread, and no, you're not overthinking it.
If my math is correct, one full turn of the front tires comes from roughly 2.5 turns of the front driveshaft. One full turn of the rear tires would be from 3.3 turns of the rear driveshaft.

Which tire's traction gets broken will depend entirely on weight distribution. The more weight you can get on the front, the more likley it'll drag the rear tires. The more weight you can get over the rear, the more likely the fronts will spin.

The results I would expect to see would be stretching of the wheelbase- pulling the suspension taut and lowering the chassis (very likely, but IMO no real pennance to pay, maybe increased wear at the mounting points), putting the driveshafts under constant stress (I'd guess the output/final gear in the trans would be strong enough, but expect a lot of wear in your u-joints. Loc-Tite the screws in those yokes if you haven't already), and significantly increased tire wear (on the upside, you'd get a lot of experience trying out different tire makes/models if you switched it up every time they wore out).

For something primarily on-road, I'd say the over/under wasn't the wisest way to go, but off-road you should be fine. Might wanna stay away from velodromes and the decks of aircraft carriers, though.

it's fine going forward on pavement... reverse, not so good "thumbsup"

What is the intention of running this gearing for high speed pavement driving?

My rig was 11 lbs. I had over/under gearing on it also.

You'll need to make sure that your set screws on your Driveshafts are locktighted or the newer through screw. I'm just running set screws, and they like to come loose. I'm sure its because of the constant binding.

On high traction areas you'll see tire slippage. Its not that much of an issue.

Its not intended for high speed pavement use.. I was just concerned about damaging drivetrain components IF I were to drive it in high traction areas OR If i should just carry it over those areas to the next dirt spot.

Thanks for the help guys! I think I'm going to stick with the over/over setup I currently have.

I would think you'd be fine driving it.