Topic: Tera 4:1 or SM420

[FourbangerYJ]

So go all out with a 4sp Atlas ...  .   Well, it would be pretty awsome!  I'll have to save up for a bit longer...

It's well worth the wait and the extra coin. 

[BarneyJeep]

what kind of problems with the stak?

my personal favorite is a "black box" + bronco d20

[sharpxmen]

what kind of problems with the stak?

my personal favorite is a "black box" + bronco d20

what's a black box?

[FourbangerYJ]

what kind of problems with the stak?

my personal favorite is a "black box" + bronco d20

It locked up on him when he was on the FWY and it snapped the output on his tranny. The replacement one is having problems staying gear. It keeps popping out.

http://www.northwestfab.com/blackbox.html

The black box is a nice unit. But it lacks a 4:1 option for gears. It's only avail in 2:72 plus it's about 3/4 of an inch longer than the Klune. I do like the Bronco D20. I have had great luck with it! It's a small case but it's fairly strong.
IMO if you run a doubler you should have a fair size split between gear ratio's. The 2:72 and 2:46 is not a wide enough split. I thought about putting in a set of 3:15 gears since the 2.46 are not very good with the small motors we run.

[sharpxmen]

I do like the Bronco D20. I have had great luck with it! It's a small case but it's fairly strong.

when i was researching and contemplating which t-case to go with it came down to D300 or D20 Bronco (not as easy to find at least at the wreckers i've been to) - anyway, found a D300 and a Bronco with a D20 on it at the same wrecker, i went with D300 even though from what i read the D20 didn't need to be flipped but what was said in a couple of articles was that the D20 had straight cut gears as opposed to the D300 which are helical and that makes it noisy - do you find it noisy at all? i have a hard time imagining how that can cover the noise from the tires and in my case the soft top - i went with the 300 just 'cause i new the case better and i already had rebuild instructions (and the writeups on upgrading the transmission to AX15/NV3550 that i read had a 300 mated to it but from what you say it makes it a nice setup since is already a driver drop). You should post a little writeup on how you did it so it maybe helps the guys deciding which case to buy - i for one would have given it more thought as getting my shifters right took forever.

[sharpxmen]

http://www.northwestfab.com/blackbox.html

yeah, that's nice and clean.
Couple of things though, they went with only one gear ratio option (2.72:1) so that doesn't really give you a 4 speed setup. And I think is somewhat the same as mad rooster's or dd machine np231 crawler box kit in the end, not sure if these are still available, but if you find one + a 4:1 kit for np231 (i think you can get these) would make it a better setup imho for probably the same money (in case you have a 231 at hand) - with more work however. In my case would bring the driveshaft to about 13'' distance between yokes though, not sure how steep that would make the angle even with the use of CV joint might be a bit messy to setup - any of running short d/s in the rear?

[FourbangerYJ]

when i was researching and contemplating which t-case to go with it came down to D300 or D20 Bronco (not as easy to find at least at the wreckers i've been to) - anyway, found a D300 and a Bronco with a D20 on it at the same wrecker, i went with D300 even though from what i read the D20 didn't need to be flipped but what was said in a couple of articles was that the D20 had straight cut gears as opposed to the D300 which are helical and that makes it noisy - do you find it noisy at all? i have a hard time imagining how that can cover the noise from the tires and in my case the soft top - i went with the 300 just 'cause i new the case better and i already had rebuild instructions (and the writeups on upgrading the transmission to AX15/NV3550 that i read had a 300 mated to it but from what you say it makes it a nice setup since is already a driver drop). You should post a little writeup on how you did it so it maybe helps the guys deciding which case to buy - i for one would have given it more thought as getting my shifters right took forever.

I don't find the D20 noisy at all. On the street or trail. In Lo you can hear it but it's not loud. The Klune on the other hand is noisy. The planetaries are loud, just like with the Tera 4:1 231 gears. When the RPM's get around 2K it starts to scream. Anytime you get alot of gear reduction you will get noise. It's normal. The biggest weak link for the D20 is the rear output shaft. It's a 10 spline. There is a couple of upgrades for it. I have not had any problems with mine and have a spare with tailcone incase it breaks.
I did not do the install. I had Four X Doctor in Burbank do it. They also move the drivetrain forward 4 inches. I could of left it in the stock position but since there is room to do it I had it done. I know they took about a day to get the twin stick set up working right.  In my build up thread there is some PICS.

[FourbangerYJ]

yeah, that's nice and clean.
Couple of things though, they went with only one gear ratio option (2.72:1) so that doesn't really give you a 4 speed setup. And I think is somewhat the same as mad rooster's or dd machine np231 crawler box kit in the end, not sure if these are still available, but if you find one + a 4:1 kit for np231 (i think you can get these) would make it a better setup imho for probably the same money (in case you have a 231 at hand) - with more work however. In my case would bring the driveshaft to about 13'' distance between yokes though, not sure how steep that would make the angle even with the use of CV joint might be a bit messy to setup - any of running short d/s in the rear?

The DD and MR seem to be hit or miss for inventory. They are kinda long I forget the measurement. I would think a XJ/MJ would be A better fit.
The 231 does have a 4:1 avail thru Tera.
IMO leave the stock 2:72 gears in the 231 and add a Klune 4:1. In my club we have seen alot of failures of the Tera 4:1 gear sets. Not sure if its just bad luck or what but there have been about 4-5 people that have had the gears eat themselves due to the welds that hold the planetaries inplace.
Infact my buddy who runs a Klune in front of his 231 took out the Tera stuff and put back the stock stuff when he added the Klune. He has been running this set up for about 5-6 years. It's held up great.

[Jeepn95yj]

You will need to cut a new hole in the floor under the dash and then you can cut and extend the shifter so it comes back to the stock location.

That would work with my YJ, but I've already swapped out the 4.0 for a 5.0 and automatic.  On my 4-cyl TJ I'd like to keep the stock center console and have the shifter pop up through the stock boot location.

[Bounty Hunter]

The DD and MR seem to be hit or miss for inventory. They are kinda long I forget the measurement. I would think a XJ/MJ would be A better fit.

A 231/300 is about the same length as a stock 231, correct?

[FourbangerYJ]

A 231/300 is about the same length as a stock 231, correct?

According to Duffy it's + or - 1/4 inch of a stock 231 with slip yoke. I would imagine that the MR is the same since Duffy copied the design.

[neale_rs]

Here is an analysis of the Atlas 4sp with 3.8/2.72 ratios that will surprise you:

The lines show the gear ratios you get with 4.56 axle gears and a stock AX5.  Line 1 shows the ratios with the Atlas in LO LO (10.34:1), line 2 shows the ratios with the Atlas in 3.8:1, and line 3 shows that ratios with the Atlas in 2.72:1 (like a stock 231).  Line 4 shows the ratios with the Atlas in HI HI (1:1).  Line 5 shows the ratios you get with a 5:1 Atlas and line 6 shows the ratios you get with a 4:1 LO.

The surprising thing is that even though it seems you will get a lot of forward gearing options  (4 Atlas speeds X 4 Tranny speeds = 16) you really only get 11 that are truly distinct (differ by more than 2, e.g. 47:1 and 49:1 are considered the same here).  This is being pretty lenient because the ranges overlap quite a bit.  To sum it up, it looks like an Atlas 4sp actually only gets you 3 gear ratios lower than the stock setup (68:1, 110:1, and 185:1).  The well known ratios like 80:1 and 100:1 are also missing.  All in all, it is kind of disappointing although the 3 lower gears may be worth the $ in any case.  The 5:1 gets you the 90:1 and some ratios very close to the stock 231 ratios.  The 5:1 looks pretty good for the $ difference as long as you don't need even lower gearing than 90:1, and with 4.88 axle gears it would give 96:1 which is pretty close to the 100:1 that is often recommended for serious rock crawling.

[FourbangerYJ]

Good points. But I look at it this way. With the 5.0 you get lines 4 and 5. With the 4speed you get lines 1,2,3,and 4. It costs more but you get more. You bring up a good question as to wheather you need the 185:1 or the 110:1. It all depends on what kind of wheeling you do. I know I have never beenable to stall the motor when I was at 188:1. Even on dry pavement in 2LOLO with the brakes on so hard the front tires where skidding. I have stalled on the trail in 2nd gear 4LOLO which was around 115:1.
There is some overlap between the gear choices. But it comes in handy so you don't need to take one box out or put one in to get the ratio you want. To be honest I use the 4:1 the most. When I need more I kick in the 2:46. That combo comes in real handy for alot of things. Once I had it I can't imagine being without.
Personally I think the 4speed would be better with a set of 4.3 and 2.7 gears. I don't know why they don't have that option.

Just a FYI I saw a write up in JP where they put in a 4speed, I think it was a TJ anyway they used the stock front D-shaft (fit just fine without mods) and the rear shaft was in the 17 inch range. The rear one needed to be adjusted.

As far as the $$ the Klune is still a cheaper option. Even if you take off your SYE and get a SS-SYE.
Or just the Tera 4:1 still have some deep gears with that choice.

[neale_rs]

That's true, you have to factor in the convenience and strength too.  Thanks.

Here is a chart for your setup:  5.38 gears, 4:1 Klune and 2.46 TC. I hope I got those three ratios right.

[FourbangerYJ]

That's true, you have to factor in the convenience and strength too.  Thanks.

Here is a chart for your setup:  5.38 gears, 4:1 Klune and 2.46 TC. I hope I got those three ratios right.

Ya, you got them right! 
Help me with this.

1. Both boxes in low
2. Just the 4:1
3. Just the 2.46
4. Both in 1:1
5. ?
6. ?