Topic: Atlas Dilemma

[neale_rs]

On a few trails around here, the 2.71 or lower is good for some sections but then it gets easy for a while and you end up shifting higher and higher all the way to 4h or 5th, then decide it's better not to rev it too much, so you shift to high range just before you need low range again.  I think this is a fairly common scenario for an expedition vehicle.  It gets to be a pain with 2.71:1, can only imagine how it could get with 5:1.    I used to think gearing overlap was a waste (almost decided on a 5:1, actually ordered a 4.3:1 but was lucky the order got botched so had a chance to get the 4 speed) but it really makes the Jeep more pleasant to drive when the trail difficulty is changing along the way. Doubler is the way to go, you will be happier in the long run. 

The way I see it:  5:1, cheaper, very good but could have some regrets;   4 speed, more expense up front, but most versatility and no regrets.

[VA_YJ]

I went with the 5:1 on my TJ for the reasons others have mentioned.  Also, I am trying to keep my rear drive shaft as long as I can - 2 speed Atlas and 4" rear stretch.  If you go with the 4 speed, you might think about running some longer springs (e.g., XJ leafs) in the rear to regain some of the lost driveshaft length.

[FourbangerYJ]

On a few trails around here, the 2.71 or lower is good for some sections but then it gets easy for a while and you end up shifting higher and higher all the way to 4h or 5th, then decide it's better not to rev it too much, so you shift to high range just before you need low range again.  I think this is a fairly common scenario for an expedition vehicle.  It gets to be a pain with 2.71:1, can only imagine how it could get with 5:1.    I used to think gearing overlap was a waste (almost decided on a 5:1, actually ordered a 4.3:1 but was lucky the order got botched so had a chance to get the 4 speed) but it really makes the Jeep more pleasant to drive when the trail difficulty is changing along the way. Doubler is the way to go, you will be happier in the long run. 

The way I see it:  5:1, cheaper, very good but could have some regrets;   4 speed, more expense up front, but most versatility and no regrets.

Agreed!
I would think that on most expo type trails your just in 2wd. But if you need to do some mild wheeling then a 5:1 would be to low. I guess it would depend on the situation but I found that 4:1 on pretty easy stuff is to low.
I know I am way biased but I would agree with having more choices is better.

[Jeffy]

On a few trails around here, the 2.71 or lower is good for some sections but then it gets easy for a while and you end up shifting higher and higher all the way to 4h or 5th, then decide it's better not to rev it too much, so you shift to high range just before you need low range again.  I think this is a fairly common scenario for an expedition vehicle.  It gets to be a pain with 2.71:1, can only imagine how it could get with 5:1.    I used to think gearing overlap was a waste (almost decided on a 5:1, actually ordered a 4.3:1 but was lucky the order got botched so had a chance to get the 4 speed) but it really makes the Jeep more pleasant to drive when the trail difficulty is changing along the way. Doubler is the way to go, you will be happier in the long run. 

The way I see it:  5:1, cheaper, very good but could have some regrets;   4 speed, more expense up front, but most versatility and no regrets.

Here's the actual gear spread charted out

With a 231 and 2.72:1 you get 3 gears that overlap between HI and LO with 2 gears that almost match.  3rd gear LO is exactly the same as 1St HI.  5th gear LO is basically the same as 2nd gear HI.  Other then not having as low a gear as the 5:1, the other ratios seem to fall right below with only a .4-5 deviation.  This is what Art was saying earlier.

Orange = HI
Navy = LO
* Ratios calculated with 4.56:1 gears

2.72 - 48.57, 28.79, 17.92, 17.92, 12.36, 10.62, 10.50, 6.61, 4.56, 3.88

4.0 - 71.68, 42.50, 26.45, 18.24, 17.92, 15.50, 10.62, 6.61, 4.56, 3.88

4.3 - 77.06, 45.69, 28.43, 19.61, 17.92, 16.67, 10.62, 6.61, 4.56, 3.88

5.0 - 89.60, 53.12, 33.06, 22.80, 19.38, 17.92, 10.62, 6.61, 4.56, 3.88

[neale_rs]

Those numbers look familiar!  Many hours were spent looking at them when trying to decide what to do.

[aw12345]

With a 6 speed those numbers look even better since the step from 1st to second and second to third and third to 4 are smaller. Anyway 10 usable gears is pretty good even though 12 is better. I love my setup and do use pretty much every gear available. For some one thing works better than another, but in Jeffy's case and what he would like to do with it, a 2 speed Atlas with a 5:1 ratio ought to serve him very well.

[sharpxmen]

5:1 looks the best of the bunch with 4.3 as a close second i think. Any reports on the 5:1 gears (as far as reliability)?

[Jeffy]

5:1 looks the best of the bunch with 4.3 as a close second i think. Any reports on the 5:1 gears (as far as reliability)?

I've never hear of any issues with any of the Atlas transfer case except for the 6.0:1 which they stopped making.  The only ones I've heard of breaking an Atlas were comp buggies which spurred the comp editions.

I'd love a 6-speed but I don't think I'll be able to do it unless someone comes up with a kit.  The AX-5 does well though.  I just rev it up when necessary.  If I keep the 2.5L, which is still running strong, I probably won't bother with a transmission swap unless something happens.

[sharpxmen]

maybe AA will come up with a kit, the one i made is similar to this one
http://www.advanceadapters.com/products/716133--jeep-th400-to-chevy-small-block/


at $292 it's quite cheap, if they had an NSG one would have probably just buy it rather than making it.
there's also a matter of mounting the crank sensor which is a fairly extensive mod on it's own not to mention the cost of the transmission (and would have to be the one out of the 4.0L - Art pointed out that the 2.4L one has a different bellhousing).

I couldn't get them made for that price even welded from flat bar like mine (laser cut would jump the price quite a bit and same for waterjet), if there's enough takers i can look into it but would be more than the similar AA one.

imo from a total cost perspective would be prohibitive.

EDIT: this is mine





and this is what i had to do to get the crank sensor relocated (probably the trickiest part)

[Jeffy]

I don't think anyone's going to offer a NSG370 6-speed conversion kit, even though it would be a better option then the NV3550.  I just don't see people jumping off the New Venture ship.

I wish AA would have made a slim tail housing with a hall effect sensor like the JB Conversion SYE.  Seems they could get a really short tail while still having a place for people to put a VSS.  They have a GM VSS option but it looks about as big as the geared housing.

[sharpxmen]

i thought they have an upgraded spline output for Atlas with super short output housing, or am i mixing that with Novak (i know they have one but somehow i remember seeing it at AA as well, can't remember for sure though).

[Jeffy]

i thought they have an upgraded spline output for Atlas with super short output housing, or am i mixing that with Novak (i know they have one but somehow i remember seeing it at AA as well, can't remember for sure though).

They do but it has no provisions for any VSS.

[sharpxmen]

They do but it has no provisions for any VSS.

the Novak does and that's probably why i thought AA does too.

[Jeffy]

the Novak does and that's probably why i thought AA does too.

You only gain 2" from the Short Tail shaft to the VSS Tail shaft.  I guess they run it long so it can be used as a support point and be able to run a disc and caliper on there.

[sharpxmen]

2'' is massive if you put that in perspective with an 18 or 20'' driveshaft, but without a doubler is really not necessary (i would love a super short output but the Novak with VSS is like $6 or 700).