231/D300 doubler. discussion

[raf2379]

Anyone here done a 231/d300 doubler? I've been doing some research and reading some tech articles. it seams like a cheaper solution than an Atlas-II. it doesent look all that hard to do, but it still costs money.

the Atlas-II 2 speed with the following low ranges cost about $2300 and I'm sure the 4 speed is much much more.
4.3:1
2.0:1
3.8:1
5.0:1

now for the 231/D300 doubler you can chieve the folowing gear ratios.
1:1
2.62:1
2.72:1
7.13:1

and if you upgrade the D300 to a 4:1 gears you can have these ratios
1:1
2.72:1
4:1 &
10.88:1

but there is more,  you can use a twin stick shift for the D300 and you have the option for shifting into

front low only - rear neutral
front high only - rear neutral with a minor modification
rear low only
rear high only
4x4 low
4x4 high

i think the versatility of this makes it a great upgrade, you can use the front as a dig for the hard core guys and if something happens with your rear you can drive home in Front high with out removing the drive shaft.  Also i`m sure the strength is higher as well than the  a 231 or the 4:1 rubbi case.  teraflex low kit for the 231 runs you about $1300 and the 2wd low kit is another $250. I think you might be able to build the doubler for around $1500 just a guess

anyone have any input or experience with this setup it seams to be quite popular and I think it could be significantly cheaper than the Atlas-II with more features. time to find a D300

also forgot to mention that the D300 would have to be flipped to make it a drivers side drop.

[tubby]

I'm impressed with how your brain works Rafal. I tossed  around the 231/300 doubler idea  in my head a few times in the past. A millwright friend of mine has done a similar swap into his fullsize Blazer a few years ago. Are you contemplating the "Box 4 Rocks" kit from D.D Machine? Madrooster Offroad used to make a kit a long time ago, but I think they folded production on these adapters a while back.
 I think the kit comes with all the needed parts to make it work. I think you have to get the output shaft of the 231 cut and resplined to go into the Dana 300 ?

You also need new driveshafts made and now would be a good time to replace the 1310's to something bigger. Twin sticks  would also need to be made. Novak makes a slick cable linkage with brackets to make it work.I don't remember if you have to "modify/cut" the tranny tunnel of your XJ . I think the Box 4 Rocks adapter allows you to almost flat clock it. A crossmember/mount would have to be made.

You can also get Lomax or Tera 4:1 gears that you can toss into the D-300 for more mind-boggling reduction.

Me? I think I'm sorta okay with my stock t-case gearing for now( or until I figure a way to snag Kevin's out of his Rubi. Ever hear a wrench fall on pavement at 4AM?) I'm leaning towards something that requires less work(like an Atlas) for myself, but I hope you pull the trigger on this doubler idea of yours. The option of different ratios  for different terrain/obstacles is interesting.

Good luck my friend.

[raf2379]

I was definitely contemplating the D.D.Machine kit which runs $500 and you get everything you need, the adapter plate, clocking plate, bolts, block off plate and the mid shaft, so no need to cut and spline the np231 output shaft. it really is a full kit. I already have an NP231 sitting in my garage, I just need a D300 which might be possible to find for cheep. I know there was one for sale here a while back for $50. wish I would have thought of doing the doubler back then.

If you want i can be the look out when your dropping wrenches at 4am 

[tubby]

Yup. Gear multiplication is sexy.

You have to get a hold of "Duffy" at D.D Machine by phone. He doesn't like emails or PM's much...or questions for that matter. I'm not sure what D-300 is a better candidate for the swap. I believe the overall length of the doubler is a hair shorter than a stock NP231?

I'm still on the fence about going lower in my t-case right now. The Tera Low kit from Sam's Offroad has some "blem specials" for under $1000 US for the 231 but the instructions state that you shouldn't spin it in 4-low past 3000 RPM. Not my first choice. JB conversions has the Rocktrac 4:1 for $1650(and our dollar is good) and it's a near bolt in for XJ's(gotta do the GM VSS though), but the big kahuna has to be the ATLAS. I spoke to a rep on the phone and they said the 3.8 is more conducive to our area and style of wheeling.  I'll see how bored I get with my stock 231 and wait till next year...maybe.

[tubby]

If you want i can be the look out when your dropping wrenches at 4am 

Thanks for the offer Raf, but I don't think your wife would be okay with this.

-" Hun? Where are you going  at this time?"

-"Just stepping out to help a guy steal a transfer case from SpecialK's Rubi "  " I'll be back in a bit. You want me to pick anything up from the store?"

[specialk]

Let me know when you are coming by and I'll leave the jack out for you...

I'm going to have buy a big, hungry dog...

[Bnine]

Couple things to consider with 300s.

The outputs on 300's are realy weak and should be upgraded.

By the time you do a flip kit, upgraded outputs, twin sticks, and low gears in a 300 you are getting into atlas territory. But, a 300 is still shorter then an atlas, and almost 40lbs lighter with virtually the same strength.

Another option to look at is the aftermarket 300 aluminum case from stak 4x4. It can go on either side. Flipped 300's can be a pain at times. The shifters alone are famous for causing headaches because of the routing issues.

I've always like the idea of a built 300. Just never got around to doin one.

I run a 2.0 atlas thats mated to a 2.72 Klune underdrive, which is essentially a fancy 231 crawl box. I wouldnt have it any other way. I love the options I have with gearing.

Also, I would shy away from getting into the combined 10:1 stuff. Its to low, and will up just being used as a gimic.

[tubby]

Yuppers. Billy is right.

1. Advance adapters makes a 32 spline output shaft kit  for the D-300

2. Stak makes a beefy,billet "Replace-a-case" for the D-300 for the driver's drop

3. Do you run an automatic tranny Raf? Stopping in super-low is going to be very tough

All these add-ons are adding up.This is starting to make an Atlas sound better to me, but I'm lazy like that.

I still want you to do this doubler Raf !

[raf2379]

hmm yeah i'm running the AW4 right now. i guess 10:1 would probably want to crawl away on idle, but there is also a cool mod for the aw4, the electronic manual shift, which allows you to shift the tranny into any gear with a button and lock, unlock the torque converter, but thats another topic to discuss.

your right it is adding up quite fast huh? JBconversions makes 32 spline front and rear outputs as well.

[Zombie]

hmm yeah i'm running the AW4 right now. i guess 10:1 would probably want to crawl away on idle, but there is also a cool mod for the aw4, the electronic manual shift, which allows you to shift the tranny into any gear with a button and lock, unlock the torque converter, but thats another topic to discuss.

your right it is adding up quite fast huh? JBconversions makes 32 spline front and rear outputs as well.

I saw something like this where you can wire up some switches and have it stay in whatever gear you want, I think it was likely on the naxja website somewhere.
a little different, but a nifty idea if I play off road more.

[cLAY]

I saw something like this where you can wire up some switches and have it stay in whatever gear you want, I think it was likely on the naxja website somewhere.
a little different, but a nifty idea if I play off road more.

I had this on my old XJ. I consider it a must have if wheeling an AW4 to be able to get it to stay in 1st or 2nd gear. Never noticed much of a benefit to manually locking in the torque converter though.

[i_go_commando]

i have a 203/ 208 setup that i made with the help of a machine shop in bc.

custom shafts are expensive

the adpaters are the cheep part

oh, and that jeep still doesnt run so ive never tried it but on a bench

[raf2379]

well its happening, the billet doubler 231/300 is on its way

this with Brink's d300 i bought will be sweet combo. in the near future will throw in 4:1 LOW gears and stakk replace a case.

[Bnine]

Manual or auto Raf?

I think you will find running a doubler you will have no need to for a 4:1 ratio. It renders the combined ratio virtually useless for anything other then slow racing.

But a 2.0 and a 2.62 combined, or used individually are all practical ratios.

[raf2379]

it will behind behind the 4L60 auto, I guess the 4:1 will be a bit too much for reduction and probably never used.