Topic: Which one first?

[FourbangerYJ]

I don't think anyone's going to say not to get the 4spd.

Agreed. Just make sure the driveshaft angles are good, and you will be fine.

[neale_rs]

Thanks.  Now back to saving up!

[jagular7]

I'd look into a doubler setup that uses the front reduction of the Jeep tcase (planetary gear setup in an aluminum case). There are several different types out there now. Black box, DD Machine, Klune are some names I know.

However, couple of things.....
- with your 5-sp, your trans output is 21-spline so you will be getting a specialized setup due to that configuration.
- using stock 231 tcase does not provide disconnect for front output only (no twin stick setup).

Other options:
- Toyota tcases have developed into doublers and can be right or left out front output. They have a strong aftermarket following. Tacoma cases on left hand drop. Aftermarket has also developed quick disconnects for tcase outputs to remove the drive to the axles and they have developed twin sticks for the Toy cases as well.
- Install doubler setup w/ flipping D300 or using a Ford D20 case. Aftermarket has upgrades for the D300 and D20 for outputs and ratios. There is a left hand drop D300 case available out there as well.

Vast available options depending on cost and assembly. To add, to gain rear ds length, you have the option to move forward the driveline forward.

[neale_rs]

You bring up some good points.    I would definitely move the engine forward with the doubler setups like Black Box, DD Machine, Klune V since they will make the drivetrain a bit longer.  With the Atlas 4sp, the length of the rear driveshaft ends up right at the point that made me unsure which way to go.  And the 21 splines have also made me think about this a lot.  I guess in the end it is just another thing to enjoy trying out.

Actually here locally, the combo of the chopped up NP231 with a flipped D300 has become very popular lately.  It gives about 7:1 but the two ratios are pretty close to each other so it is equivalent to a 3 sp TC, although the D300 can be changed to 4:1 to make it like a Klune V, NP231 setup.


Thanks for all the replies.

[Jeffy]

You bring up some good points.    I would definitely move the engine forward with the doubler setups like Black Box, DD Machine, Klune V since they will make the drivetrain a bit longer.  With the Atlas 4sp, the length of the rear driveshaft ends up right at the point that made me unsure which way to go.  And the 21 splines have also made me think about this a lot.  I guess in the end it is just another thing to enjoy trying out.

Actually here locally, the combo of the chopped up NP231 with a flipped D300 has become very popular lately.  It gives about 7:1 but the two ratios are pretty close to each other so it is equivalent to a 3 sp TC, although the D300 can be changed to 4:1 to make it like a Klune V, NP231 setup.


Thanks for all the replies.

You would then want to do a Tera 4:1 in the 231.  This would allow you to use your existing front half to cut up and not give you so many duplicate gears.

You can get lower gears for the D300 as well as the D18 but like the 231, they don't come cheap and you'd already be buying a Klune V as well.  Also, you would want to upgrade the chain and sprocket set on the 231.  Upgrade the output shaft on the D300 as well.  Oh and then you could do a 231 2Lo fork swap as well.  Lots of money and time fabricating stuff though.

[sharpxmen]

You would then want to do a Tera 4:1 in the 231.  This would allow you to use your existing front half to cut up and not give you so many duplicate gears.

You can get lower gears for the D300 as well as the D18 but like the 231, they don't come cheap and you'd already be buying a Klune V as well.  Also, you would want to upgrade the chain and sprocket set on the 231.  Upgrade the output shaft on the D300 as well.  Oh and then you could do a 231 2Lo fork swap as well.  Lots of money and time fabricating stuff though.

might as well just go with the Atlas in that case

[neale_rs]

Among the NP231-based doubler setups probably the most reliable combination would be a 2.72 NP231 with 6 gear planetary (from a 241) feeding into a D300 converted to 4:1 and with an upgraded output.  This would keep the 4:1 "mega torque" away from the TC input.  One local jeeper is running this on a stretched TJ.  I haven't heard that he's had any problems so far with the doubler setup itself although it has helped him break a couple of axle shafts!

[FourbangerYJ]

I have had zero issues with my 21 spline input. If you plan on a tranny swap down the road it would be a issue.
I try and talk everyone out of the Tera 231 4:1 kits. I have seen waaay to many fail. In my club alone there has been at least 4 I am sure it's more like 6 but it's been a while. They all put in Atlas's and have never looked back.
The AA 4 speed is the shortest thing on the market for a dual type set up.

[neale_rs]

A few months later and it turns I ordered an Atlas 4.3 2 speed.  The wait on the 4 speed was quoted at 5 months and I wanted to get this in before the end of the Summer and the about $1000 price difference also came into play at the time due to some home expenses.  One advantage of the Atlas is that it does not have a rev limit like the Tera 4:1 so it can be used in any tranny gear.  With 4.56 diff gears and the AX5, this will give me 77:1 in first, 46:1 in second (fairly close to my current 49:1 in first), and 28.4:1 in third (very close to my current 28.9:1 in second).   The 77:1 will be nice in the rocks and the 28:1 "secret weapon" will still be available for climbing wet ledges and steep wet hills when anything lower is just too slow.  Low range in 5th (17:1) will still overlap with high range in first (18:1) which may help not having to shift between high and low range on trails with hard obstacles separated by easy stretches.  It's a far cry from the 4 speed in terms of gearing options but I think it will work out well enough for the use I'll be giving it.  If I feel the need for a 4 speed, I can always sell this one which works well here in Mexico where used items sell for just a bit under the price of new.