Topic: Atlas 2 vs 4

[Jeffy]

Just thinking about which one I should go with.  I do that a lot when my driveshaft/yoke makes the ball bearing in a coffee can noise at 65mph.     Now if I was to keep the 2.5L then it would make sense to go with the Atlas 4 with the 11.70:1 gears.  I've been thinking about the long term future and there might be an engine swap in the distant future.  Been thinking about an LS3...    Another question, should I get a VSS?  With a VSS, I could shave off a bit more from the driveshaft length.  Would need a calibrator but there are a bunch of those.  I like the one that was on the forum a few months back.

Actually, other then the transfer case noise, it drives pretty good now.  A lot nicer then when it was running 35's for long distances.  4:58's are almost enough to cruise with.  About 2500RPM @ 60mph.  Would rather have 32-3500 rpm @ 65-70mph in 5th.  5:13's sound nice...  I'm getting 17+ MPG with all the city driving I'm doing though.

[chrisfranklin]

In my case, I'd probably keep my 4banger jp and buy a second jeep somebody already spent a fortune on installing a V8, auto, axles, and so forth -- talking the kind of rich guy's Jeep that has the goodies but never sees a trail and is getting sold at a loss. 

[sharpxmen]

if you spend the money go with Atlas 4, and yes to super short output, couple of inches make a big difference when we're talkine 18'' d/s length.

[neale_rs]

After having and wheeling the Atlas 4 for a while I would say that for a rocks only jeep a 2 speed with 5:1 would be great and a 4.3:1 would do just fine too and you would end up with a longer rear DS but shorter front DS.  If you plan to do sand and and mud and not so tough trails as well as rocks then the 4 speed would be the way to go to keep the 2.72:1.  With the standard output the rear DS will end up about 2 inches shorter than with the 231 and SYE but it has worked well for me.   Also, I´m not sure if the Atlas VSS uses a shorter tail housing, I think it is the same as the standard output.  When I ordered mine, they did have a short output option but it had no speedo provision.

[stan98tj]

Why not gear to proper cruising gears or road gears, unless you like what you have now, and drop in a Rubicon t-case. Will that work in a YJ?

[sharpxmen]

Why not gear to proper cruising gears or road gears, unless you like what you have now, and drop in a Rubicon t-case. Will that work in a YJ?

you need an nv3550 in front of it (or an NSG370)

[aw12345]

After having and wheeling the Atlas 4 for a while I would say that for a rocks only jeep a 2 speed with 5:1 would be great and a 4.3:1 would do just fine too and you would end up with a longer rear DS but shorter front DS.  If you plan to do sand and and mud and not so tough trails as well as rocks then the 4 speed would be the way to go to keep the 2.72:1.  With the standard output the rear DS will end up about 2 inches shorter than with the 231 and SYE but it has worked well for me.   Also, I´m not sure if the Atlas VSS uses a shorter tail housing, I think it is the same as the standard output.  When I ordered mine, they did have a short output option but it had no speedo provision.

Having done a bunch of wheelin with a 5:1 2 speed Atlas, here is what I have found ratio wise it turns the trans into a 10 speed. Top gear in low range is just below 1 st gear high range which in my book is just what you are looking for. No need to have gears overlap.  1st low will give a good crawl ratio, my 4 banger does sand hills ok, provided I can take a run at it. 5th gear low range tached out it climbs them suckers with ease

[neale_rs]

Having a manual transmission saves a lot of trouble because you can select the gear.  The automatic Jeeps have more problems with the low geared TCs, often being too low or too high for sand hills and such...and then not being able to stop with the stock brakes when in low range.  But it's also worth considering when you might need to use reverse, not as many gear choices in that direction (although I have to admit wheel speed in reverse has never been a must have since I've owned my YJ, but then again there is not much mud nor sand dunes around here).

[aw12345]

For sand you want big wide tires, those Pitbulls work like a charm for it

[Jeffy]

Why not gear to proper cruising gears or road gears, unless you like what you have now, and drop in a Rubicon t-case. Will that work in a YJ?

Regearing back to stock would put me around 5.13:1 which I plan on doing.  Just not right now.  I think the theoretical top speed is still over 100MPH.  I want to bring that down to maybe 80mph which would be rev limited and not theoretical.

The transfer case/yoke has maybe a year or two in it.  I don't want to fix it which is why I'm going with an Atlas.  I just need to decide which one.  Like I said earlier, I might not need the doubler if I eventually do a V8 swap.  I don't do anything as hardcore as what Art does.  The only trails I have in mine are stuff like the Rubicon and maybe Sierra Trek at Meadow Lake though.  Other then that maybe Moab but who knows if I'll be able to make it out that way.  Nothing too tough really.  No sand and no mud.

If I do an engine swap Id imagine I'd have enough torque to make up for the lack of lower gears at least.  Not sure on the transmission but the 6L80 looks pretty good.  Still a ways out though.  The transfer case is somewhat of a priority right now.

[neale_rs]

A friend of mine ran a 4.0 TJ with 2.72:1 TC, 4.88 gears and 35" tires. That TJ crawled very nicely, so super low TC gears are not quite as important with an automatic and more engine torque.  With a V8 and an automatic transmission, an Atlas 3.0:1 would probably work very well, with 3.8:1 getting to be about as low as you would want to go.  Or get the 4sp with 2.72:1 and 3.8:1 or maybe just 2.72:1 and 2.0:1.

[Jeffy]

A friend of mine ran a 4.0 TJ with 2.72:1 TC, 4.88 gears and 35" tires. That TJ crawled very nicely, so super low TC gears are not quite as important with an automatic and more engine torque.  With a V8 and an automatic transmission, an Atlas 3.0:1 would probably work very well, with 3.8:1 getting to be about as low as you would want to go.  Or get the 4sp with 2.72:1 and 3.8:1 or maybe just 2.72:1 and 2.0:1.

The problem with an engine swap is getting it all to fit.  That extra 3.75" could mean the difference of fitting.  Though that's not really my immediate concern.  (At low rpm the TC will slip and give almost 2:1 advantage, IIRC.)

In any case, I'm wondering if I'll ever use the 11.70:1.  It's nice having 2.72:1 but it's too high for the Rubicon with a manual.  Although, I'm turning the Jeep into an expedition vehicle more then a rockcrawler now.  I'm making it a bit more street worthy while retaining better then stock offroad-ability.  I don't want gear overlap though. Going with a 2sp would also save me $800-1000.

[neale_rs]

On my latest trail rides, I've spent almost the whole day in 4.3:1 in 1st (77:1) and 2nd (46:1) gears and just one or two obstacles in 11.7:1 in 2nd gear (124:1).

11.7:1 in 1st (209:1) is so low that I've only used it to try it out, not for any actual need so far.

As for gear overlap, in high range first gear you will be at 18:1 and in 4.3:1 in 4th you will be at 19.6:1.  With the 5:1 you would be at 22.8:1 in 4th and your crawl ratio would be 90:1.  So 5:1 actually looks pretty good, you would save quite a bit compared to the 4sp and have a much longer rear DS.

[Jeffy]

On my latest trail rides, I've spent almost the whole day in 4.3:1 in 1st (77:1) and 2nd (46:1) gears and just one or two obstacles in 11.7:1 in 2nd gear (124:1).

11.7:1 in 1st (209:1) is so low that I've only used it to try it out, not for any actual need so far.

As for gear overlap, in high range first gear you will be at 18:1 and in 4.3:1 in 4th you will be at 19.6:1.  With the 5:1 you would be at 22.8:1 in 4th and your crawl ratio would be 90:1.  So 5:1 actually looks pretty good, you would save quite a bit compared to the 4sp and have a much longer rear DS.

Yeah, that's what I'm thinking as well.  With 5.13's that would give me 100:1 and with a NV4500 it would be 144:1.

I was looking at the VSS and it says something about it being a GM 40 PPS.  Anyone know what the Jeep is?

[sharpxmen]

Yeah, that's what I'm thinking as well.  With 5.13's that would give me 100:1 and with a NV4500 it would be 144:1.

I was looking at the VSS and it says something about it being a GM 40 PPS.  Anyone know what the Jeep is?

you mean ppm?

i think the Jeep is at 8000 pulses per mile output from VSS.