Time to decide...3.8 or 4.3

[rockjeep44]

Ok guys, I've got the dough and I've got all the other parts of my drivetrain finalized as far as what I'm using, input/output spline counts, etc so I'm ready to order my Atlas and Klune setup. I'm deadset on the Klune 2.7 box because it's the beefiest and offers a range right there with my old NP208 which was 2.62. So, that leaves the question of Atlas II 3.8 or 4.3. I've already ruled out the 5.0 (too low) and the 3.0 (too much like the klune). I made an excel spreadsheet and I've been staring at crawl ratios all morning. Here's the numbers...bear with me now

Underdrive high, tc high:
1st: 30.51
2nd: 15.23
3rd: 8.16
4th: 4.56

Underdrive low, tc high:
1st: 83.28
2nd: 41.58
3rd: 22.28
4th: 12.45

I listed the above first because those ratios stay the same regardless of t/c. Now, here's the differences

Underdrive high, 3.8 tc low:
1st: 115.92
2nd: 57.88
3rd: 31.02
4th: 17.33

Underdrive low, 3.8 tc low:
1st: 316.47
2nd: 158
3rd: 84.68
4th: 47.31

Underdrive high, 4.3 tc low
1st: 131.18
2nd: 65.49
3rd: 35.1
4th: 19.61

Underdrive low, 4.3 tc low
1st: 358.11
2nd: 178.79
3rd: 95.82
4th: 53.53

Now, I'm not the type to just make a decision based on nothing. I really studied these and thought the gear ratios over. I know some of you will look at the 4.3 numbers and say well Great Googley MoogleyGreat Googley MoogleyGreat Googley Moogley are you gonna do with the 358.11 crawl. Well, what I want is options. The more I look at the options the more I lean towards the 4.3. Correct me if I'm wrong but it looks like there are more identical/close to identical gears with the 3.8. By going with the 4.3 I have a more widely spread range of gearsets to choose from. I can hit anything from wide open tire spinning to the most controlled crawl imagined. Anyhow, sometimes when you stare at numbers long enough they all look the same so I figured I'd get some advice/help/opinions as well. For those of you with excel here is a nice spreadsheet so you can look at the numbers side by side.
http://www.joycarpets.com/rrr/gearchart.xls
Thanks
-Andrew

edit: on the excel file notice there are 4 worksheets, click the tabs at the bottom to switch between the different setups. each worksheet fits on one page for printing and side by side viewing [img]smile.gif[/img] Also, one thing to note here are the ratios I'll have available.
1:1, 2.7:1, 3.8:1, 10.26:1 OR
1:1, 2.7:1, 4.3:1, 11.61:1

[ July 31, 2003, 08:08 AM: Message edited by: rockjeep44 ]

[orangecherokee]

aren't you supposed to be working? you know the place where you get paid to do stuff besides stare at gear ratios. remember little Dobosh, you work for Joy, not Poison Spider.

my opinion, go with the 4.3

[FSJeeper]

AT that level of gearing, I would say it does not matter. Both options give you all the gear spread you could ever use. If it were me, I would pick the cheaper one.

[LRRH]

I'll agree with FSJeeper. You've got plently of crawl....do doubt about that. Try and save a few bucks if it's even applicable.

[rockjeep44]

I think you guys are missing the point. I'm already spending close to 4 grand on these two range boxes alone. A couple hundred bux is pocket change at this point. I want to put together the best drivetrain possible. If I wanted cheap I'd double 15 Dana 20s [img]tongue.gif[/img]
FSJeeper, you get my last e-mail? When ya comin back to the states?

[FSJeeper]

I am back now, plan on crating up and shipping the NP435 this weekend. I'll email pics before I ship it.

[Bob Barry]

The 3.8 will already give you ridiculously-unusuable ratios in low-low. The 4.3 will be even more unuseable.

You don't necessarily want a wider spread of gears.

What engine are you going to be running? Unless you're running a 4-cyl, I'd have to say that even with the 3.8 box, most of your driving would be with the Klune in direct and the tranny in 1st or 2nd gear. Check me if I'm wrong, but wheel-speed is an important factor in the climbs you seem to do. With a 300:1, 200:1 or even a 150:1 ratio, you're going to be lacking wheel-speed. Then, when you go out to Moab, you can drop the Klune into low and climb away at 1mph@3000rpm.

[rockjeep44]

Originally posted by FSJeeper:
I am back now, plan on crating up and shipping the NP435 this weekend. I'll email pics before I ship it.

SAWHEEEEEETTTTT, perfect timing cuz I'm getting ready to order my shiot. I've got to get the drivetrain bolted up before I can get started on the chassis. I'll get your stuff together this weekend and ship it out Monday UPS if thats cool with you.

Originally posted by Bob Barry:
The 3.8 will already give you ridiculously-unusuable ratios in low-low. The 4.3 will be even more unuseable.

You don't necessarily want a wider spread of gears.

What engine are you going to be running? Unless you're running a 4-cyl, I'd have to say that even with the 3.8 box, most of your driving would be with the Klune in direct and the tranny in 1st or 2nd gear. Check me if I'm wrong, but wheel-speed is an important factor in the climbs you seem to do. With a 300:1, 200:1 or even a 150:1 ratio, you're going to be lacking wheel-speed. Then, when you go out to Moab, you can drop the Klune into low and climb away at 1mph@3000rpm.

I'm running my 360. Bob, you're right about needing wheelspeed around these parts. But, I'm building this crawler to do something my Jeep couldn't...double duty. My Jeep was completely uncrawable. It was either on or off. My goal here is to be able to spin the meats like no other or crawl at a snails pace and everything in between. That being said, if you look closely there are several duplicate/close to duplicate ratios with the 3.8 setup while there is a wider range with the 4.3. Once you go over 300:1 whats the difference really.

[nxcj]

I'd go 4.3....

Let's face it, if you're going to be hammering up some mud hill, you'll likely be in the high side of the t-case anyway. Since they're equal, it doesn't matter which case you get, for that type of wheeling.

For crawling, you have enough deep ratio either way you go...but the 4.3 will let you win the "who can walk next to their driverless, moving rig the longest" contest!!!!!!!

[jeepxjga]

i think you should ditch the buggy idea and get a samurai lol

[JeepKahn]

Hey, just think, you could even snap rockwells with that kind of reduction, or shear all your lugs off your hubs, or turn leafs or links into pretzels, rip the beads off your tires if you run bead locks, etc ad nauseum... But it definietly sounds cool...

[Sambo]

andrew i say go with the 4.3 that way you have have good ratios in all 4 gears from the
tranny...personally i think 53 to 1 in fourth isnt bad at all

[FSJeeper]

This is really not about gearing, it is about BLING!

Hey Rockjeep44, I still have more gears than you will have! [img]tongue.gif[/img] [img]tongue.gif[/img] [img]tongue.gif[/img] [img]tongue.gif[/img]

[rockjeep44]

ROFL...you know what they say about the guys with the most gears. When it all comes down to it total blingage is really whats on the line here [img]smile.gif[/img] AND, I have a fetish for billet aluminum. Can you say camp mirror?!?

Speaking of gearing, Pascal, you worked out all 32 of your ratios? Whats your final crawl? That bling mobile is gonna be sweet.

[kyrel]

is there a str. difference between the 3.8 and the 4.3 case????

I know with the low range gets for other cases they are not as strong(so have I read)

So I would go with the stronger of the 2

[gsmikie]

and then go with a twin pitch converter and 2 speed portal axels add a gear vender to the rear ..............

[80258WT]

don't do klune v man, i know a guy who just ditched one (32 spline off a chevy drivetrain-if interested) because it was too low. He only had a 700r4/klune 4 (maybe 2.7 i don't remember)/atlas 4.3/ 5.38 axle gears. He did some test runs in the driveway and couldn't even get the brakes to stop it. With gears that low 150:1 and lower i would recommend to at least have a clutch to stop it because brakes don't do ****e with that much torque amplification. I've wheeled just about every good trail at moab (proving grounds, upper helldorado...) and some good ones in colorado with a about a 90:1 and it was perfect in my opinion But there are some crazy yota guys out there that have 200:1-600:1 ratios and i guess they have some use for them. If you really got your mind set on these kind of options i would go 4.3 or 5.0 just for braggin rights.

[FSJeeper]

Originally posted by rockjeep44:
ROFL...you know what they say about the guys with the most gears. When it all comes down to it total blingage is really whats on the line here [img]smile.gif[/img] AND, I have a fetish for billet aluminum. Can you say camp mirror?!?

Speaking of gearing, Pascal, you worked out all 32 of your ratios? Whats your final crawl? That bling mobile is gonna be sweet.

I have over 550 ft lbs at 1900 rpms. Did not need ultra low gearing at all. I have a 120 to 1 low low range, but can also cruise at 70 mph and 2000 rpms with the gear splitter OD.

Did I need the doubler, no. Even Stephen at ORD told me I did not need the doubler at all due to all the low end torque I have and warned of snapping front Dana 60 axle shafts and U joints. So I bought the doubler anyway and upgraded to Moser 35 spline alloy shafts all the way out and bought beefed up steering joints. Now I have to worry about the lockouts so will be going to drive plates intead.

So why did I buy the doubler when I did not need it, it seemed rude not too! lol

You will never use all that gearing ever, but I like the way you think!

Bling Bling Bling

[Stuka]

I say go 4.3 since cash isnt an issue. Only thing I wonder is how much weaker the gears are for the 4.3? As the lower the gearing, the smaller one of the gears is going to be, and possibly the teeth. Although i dont think they are easy to break. Just curious. As I dont know enough about em.

And like FSJeeper said, i hope you have some very beefy axles [img]smile.gif[/img] With a V8 and that kinda gearing if you so much as let your foot slip while in low low you would spit parts all over the place.

[rockjeep44]

Originally posted by 80258WT:
don't do klune v man, i know a guy who just ditched one (32 spline off a chevy drivetrain-if interested) because it was too low. He only had a 700r4/klune 4 (maybe 2.7 i don't remember)/atlas 4.3/ 5.38 axle gears. He did some test runs in the driveway and couldn't even get the brakes to stop it. With gears that low 150:1 and lower i would recommend to at least have a clutch to stop it because brakes don't do ****e with that much torque amplification. I've wheeled just about every good trail at moab (proving grounds, upper helldorado...) and some good ones in colorado with a about a 90:1 and it was perfect in my opinion But there are some crazy yota guys out there that have 200:1-600:1 ratios and i guess they have some use for them. If you really got your mind set on these kind of options i would go 4.3 or 5.0 just for braggin rights.

Bzzzzzt, thanks for playing . But, in all seriousness, all whether or not he was using the 2.7 or 4.0 is a moot point. It was dumb@ss to gear that low with an auto. The reason he can't stop is cuz the torque converter is locked up like 100% of the time with that kind of ratio. I'm using an NP435 4 speed which makes the crawl ratio even that much more usable. Just slip the clutch and go. Also, everyone is looking at my final drive ratio and gawking. My point was look at all the OPTIONS I'll have. Like you said you're junk at 90:1 was about perfect, well I'll have that ratio as well as 15 others to choose from . Beat that shiot (except for pascal). Granted most of my driving at Tellico is high RPM high wheelspeed balls out but I can honestly say that I will use my low+low option at least once every trip (i'm thinking of the obstacle now) and thats just at Tellico. Basically my buggy will be setup to do any terrain any time any place. Mud, rocks, waterfalls, anything you throw at it.

Stuka, the 4.3 and 3.8 are comparable in strength or so I've heard. Either way I'm not worried about it [img]smile.gif[/img] Hehe, and you know I got some beefy axles (35 spline 60s all the way). But, when you're crawling that slow it can actually reduce breakage because of the added control you have on the gnarly obstacles. Plus I'm going 1410 front and rear with 32 spline outputs on the Atlas, 32 spline input and the Klune will be sporting a 32 spline output and 31 spline input. Got beef?

Originally posted by FSJeeper:
You will never use all that gearing ever, but I like the way you think!

Bling Bling Bling

Foooorrrrrrr shiiizzzzzeeeeeee...Pascal you know whats up Great minds think alike