doubler and d30?

I recently installed a ford 8.8 and a HPd30 both with 4.10's and Aussies. I was looking at doing the Box4rocks doubler kit with a dana 300, twin sticked (not gonna use front digs). I have read that the added torque will be much harder on the axles, dshafts, ujoints, etc. Im on 33's. Will it be significant enough to make me start blowing sh*t apart?

Yes, more torque is harder on stuff, however with the added gearing, i would bet you will be doing a lot less "bumping" to get over obstacles that you don't have enough gear currently to negotiate.

firstly I can't imagine why you need a doubler on 33's.

but yes, you will blow up axle shafts and possibly rings and pinions.

Sure, you won't be "bumping things" but if you get a tire wedged or something all that torque multiplication will expose the D30 u-joints and the ring and pinion as the weak links.

If the OP is wheeling an AX-15, it would be useful to have more gear to avoid having to slip the clutch so much. To build torque the vehicle has to maintain traction, so a slow and easy acent would put less strain on the running gear. However if you drive like a tard and hammer it over everything, then yes the doubler will help remove ring gear teeth faster.

Transmission and terrain play into the equation. 33's AX-15 and 4.10's are less than optimal in the rocks. Or at least from my experience

souske said:

If the OP is wheeling an AX-15, it would be useful to have more gear to avoid having to slip the clutch so much. To build torque the vehicle has to maintain traction, so a slow and easy acent would put less strain on the running gear. However if you drive like a tard and hammer it over everything, then yes the doubler will help remove ring gear teeth faster.

Transmission and terrain play into the equation. 33's AX-15 and 4.10's are less than optimal in the rocks. Or at least from my experience

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I wheeled 34's and 3.73's in the rocks for a long time.
with a clutch that was in the truck when I bought it 5 years ago with an unknown amount of miles on it.

I've never burned out a clutch.

that said, I do enjoy the 4.56's that are in the axles now.

With my doubler setup I blew up every part in my front 60 except the ring & pinion, including 35-spline cro-moly stuff. Multiple times.

YMMV.

87manche said:

I wheeled 34's and 3.73's in the rocks for a long time.
with a clutch that was in the truck when I bought it 5 years ago with an unknown amount of miles on it.

I've never burned out a clutch.

that said, I do enjoy the 4.56's that are in the axles now.

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I have 35s, 4:1 231, and an automatic and I want lower gears. I cant imagine wheeling a manual with that tall a gear in the rocks.




Friend of mine has a 4.0, AX15, and 231/300. D30 in the front and D44 in the rear on 35s. He has had pretty good luck with the set up, however he has alloy shafts all around. I think he has popped two alloys, and a couple stock shafts, but he does pretty hard trails with it.


Its not a D60 by any means, and it does break on occasion, but for what it is, the D30 does pretty good. Just be sure to carry a lot of spares.

I have an NP435 (6.69:1 first) D20 (2.46:1 low) and 5.38s on 40s.

I want lower gears.

Do the doubler and be aware of the D30. On 33s, I would just carry spare stock shafts with x760s and full circle clips.

Google broken Dana 30 some of the pictures are cool. I seen one where the owner sheared a Spartain locked case right in two. I am currently building one for myself and started researching a few months back. I have found they are pretty tuff for what they are. (small) but like said before, stick a tire and with a doubler and I think it's all over for that little guy. The only reson I am building a 30 is because I've gotten super deals on all the parts so far. That and I'm not very hard on mine just trail driving and some small rocks.

Dave

I forgot to mention that yes, i do run an ax15. right now im actually on 31's but the plan is 33's in the near future. Even on 31's the 4.10s arent great in the rocks when i have to pull up to a ledge, or drop off of one it makes it hard to negotiate. Im not the type of driver that hammers on it to make it, or that will wedge a tire against something and use my steering to move me. I would like the low crawl ratio to make it a little easier on suspension parts by not bouncing off of stuff all the time. It is also my DD so the low gearing for the trails, while keeping my highway rpms down would be nice. I have 760's with tacked caps and stock shafts.

I'm actually parting out my XJ with a built D30/D44 and AX15/231 doubler/early Bronco D20 with twin sticks. 116:1 with the 4.56's. I beat the ever loving crap out of this thing, and we've only ever broken 1 front long side u-joint and twisted the inner shaft...winch line buried the right front beadlock/tire sidewall into a rock face, and we twisted it apart (in other words, driver error).

The nice low crawl is actually easier on parts, as well as having way more controllable traction. Love it! Parting it out because I used up the body, and we want the cash to finance the Samurai build.

PM me if you're at all interested in the doubler setup (I'm selling the whole package with shafts and shifters).

Starboard M said:

I have 35s, 4:1 231, and an automatic and I want lower gears. I cant imagine wheeling a manual with that tall a gear in the rocks.

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it takes some finesse.
and sometimes you stall it

like 4 times in a row.

other times you put your foot on the floor and abuse the clutch.

4.56's are mo better for sure.

How is your fuel cell treating you these days?

Just a couple runs on my 4.3 Atlas but so far it's been awesome. 4.3, 4.88s, auto. A doubler would be half again as low though.

I know a guy running 36s on a dana 30 with a similar setup.
He has broken less parts since going with the lower tcase than when he was with stock tcase with 33s

You can only apply as much torque as you can react. Just think how much torque is on your drive shaft when your tires are off the ground? Zero.

So your axle torque is really only a factor of traction and tire Diameter.
So more weight= more traction wider tires=more traction
Taller tires = longer lever arm from ground to the axle which creates torque.

Basically a 2.72 T-case and stock gears is enough torque to snap an axle.
2.72*3.55*(say 3:1 first gear) about 30:1 100ft-lbs of torque= 3000ft-lbs of torque available at the axles. enough to snap most axles gearing it down at all just makes it worse.
Why don't we just snap axles all the time because tires slip or the jeep moves forward.
You need to bind the tires up (more traction) to be able to react more torque, enough to snap an axle.

So basically if your not snapping axles right now a doubler will not create anymore traction or increase your tire size. All it will do is if the tires bind up you will not have to hit the gas as hard to snap the axles.

Now the doubler will make everything up stream work 2.72 times easier. so reduced heat and strain on the engine and trans. Traction and tire size is what creates more traction down stream.

Basically lower axle gears are the best so the yoke up see less force all the way up but it is not much it is only about 0.05 per gear ratio split not like 2.72 you see from a T-case.

Good luck,
I think the ability to wheel slow and position your tires correctly makes a huge difference. Once I got my 231 crawl box in I was able to control my jeep a lot better.

Good Luck
~Justin

Phil said:

How is your fuel cell treating you these days?

Just a couple runs on my 4.3 Atlas but so far it's been awesome. 4.3, 4.88s, auto. A doubler would be half again as low though.

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it's great!

we're headed out there in 2013. I owe you drinks.

Go for it, you don't not add a double just because of your dana 30, Jeeps are progressive, if the dana 30 becomes a problem you will simply move past it.
I have a extremely polished dana 30 on 35's and have been consistenly working it harder and harder with no issues. I say go for it. You can break an axle without the doubler, its like anything else just use the skinny pedal with common sense.

87manche said:

it's great!

we're headed out there in 2013. I owe you drinks.

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If we don't have a very small baby by then we may be there. Although, when I repeated that back, it didn't sound quite the same.