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dual tc's


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ive never seen one on a jeep but a friend of mine has a chevy K5 blazer with a dual transfercase setup. he hooked it up to a tree one time, put it in low and low and drive, let it idle and got out and it was chirpping the tires. pretty neat to watch.




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I tried one for a short time




I never even built shifters for it,

just got to the mock-up/build stage, and decided I didn't like all the driveline slack, and the weight of the D300 hanging that far beyond the trans mount, off a hunk of thin cast aluminum

(the chopped down 231).

I could've built a 2nd trans mount,

but Advance Adapter had a great deal on Atlas's a couple years ago, and I jumped on that instead.




compared to the box-4-rocks:




bling factor:






Tho the D300 is much more compact:



but you have to cut more of the floors to fit a doubler + 300 than you do to fit the Atlas.

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$499 + your chopped up NP231.




NP231 Planetary crawlbox (box4rocks)$499




This is a simple kit that takes a np231 Transfer case and makes a low cost crawl box out of it, It uses the front half of a NP231 case that you provide and in about a hour or so of work you can have a crawl box that will lower your gearing by 2.73 to 1 ...

Just take a 231 case with the right input spline count to fit your trans output

(21 or 23 spline for the jeep guys) and (27 spline for the GM guys) and pull it apart , lay the big plate on the front casting and mark it about 1/2 inch "PAST" the left edge of the plate and cut it there, then file or grind the block off plate that comes in the kit to fit where you cut it off. Next tig weld the block off plate to the front casting, And thats it!


Its just that simple to make a crawl box ( doubler ) out of a np-231


All of the parts are made in house on CNC equipment

The plates are made from 6061-T6 alum and we make all are shafts out of 4340 cromo steel then through harden them.


What sets us above the other kits?


We offer clocking every 6 degrees meaning 60 clocking positions

(they offer 3 positions)


We are the leader in sales and support with more than 500 kits sold to date.

( they`re at about 25 ) We have shipped more in a single day than they have "EVER" shipped


We offer mid shafts in 21,23,27,31 and 32 spline

(They offer 23 spline only )


We offer two oil drains and a fill hole. so even if you flip the crawl box you can still fill and drain it

( they offer "NO" way to fill or drain the box)


We offer a "full" kit

we ship you the block off plate and the shifter rod you will need.

(They don`t only not provide them they want you to gap the 8" where the block off plate goes with out any bolts to seal it) just asking for a leak and a burned up gearbox


Here at D.D.Machine we do all the work in house on our equipment, We have been splining shafts longer than

the other guy has been alive. the other guy jobs his parts out to other shops. so what that means to you is simple ( We have a huge investment in our equipment and our products ) we`re not some part time side hobby.

We are there to support you before and a long after the sale.



There $499 and a set $15 shipping in the US


We keep a good stock on the shelf and ship orders 2 or 3 times a week.








we do paypal ( 4x4machine@gmail.com

or visa / mastercard direct

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