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Atlas: 3.8 or 4.3?

3.8 or 4.3?

  • 3.8

    Votes: 11 21.2%
  • 4.3

    Votes: 41 78.8%

  • Total voters
    52

Jeepin Jason

NAXJA Member #1100
Location
Lewisville, TX
Probably won't happen until later in the year, still gotta save up some more $$$. Going to be running this with 36" IROKs and 4.56 gears. basically stock 4.0/AW4 combo. Of the two XJ'ers I wheel with that have Atlas t'cases, one has a 4.3, the other has a 3.8. They both like their respective ratios. Both have similar setups as I do as far as 4.0/AW4, both with 4.56's I think, and 35's.

The terrain we normally wheel often has loose rock, and it's sometimes wet, which is why I was considering the higher 3.8 to help with wheel spin when needed, but there's a part of me that thinks if I'm really going to pony up for an Atlas, go with the lower ratio, I can always just put the trans into 2nd or even 3rd for higher range. Unless my math is off (it is friday afterall), 2nd gear with the 4.3 would be just slightly higher than the stock t'case and 1st gear.

Thoughts?
 
If your going to spend the money at all, might as well get the best case they have.

If you wheel on difficult wet rock get some snow chains.

I'm serious.

Snow chains do wonders on slippery rocks.
 
I think the 5.0 and 6.0 would be a little too low for my uses. ;) But yeah, that is kinda what I was thinking on the 3.8 vs 4.3. Just didn't know if anyone was using the 3.8 or not, and how they liked it.
 
http://www.grimmjeeper.com/gears.html

Jason, take a look at this site. It really helped me decide on which STaK transfer case gear ratio set to go with. Let's you see what ratio's your gonna have available in all gears and you can compare two different setups. I would go with the 4.3 ratio. I went with the STaK with the 5.44 low position and it works great in the rocks of AZ, keep in mind though with the STaK, I also have the 3.05 ratio too. I run 35" MTR's and 4.88 gears in the diffs. I was impressed with how much more control I have with the 5.44 range.
 
Jason, really you can't go wrong with either setup. The common wisdom has always been to get the 3.8 with an auto and the 4.3 with a stick, but there are other variables.

My observations FWIW. I have a 4.0 to 1 Tera in my yellow XJ with 5.13 gears, and I've never wished it was lower. In that rig, if I had the choice between a 4.3 or a 3.8 I'd go with the 3.8. I do like the control that the lower ratio gives in rock gardens, but otherwise I'm always in 2nd gear. My driving style has also changed, I drive much faster on the trail now (and most of my wheeling is rocks) so the slow, comfortable crawl allowed by the lowest gear ratios isn't an issue for me any more. When in tight, technical spots where you're carefully picking your way, it doesn't matter at all since the torque converter is doing the work and a slight difference in overall gear ratio isn't even noticed. You'd notice the difference between 2.71 and 3.8, but not the difference between 3.8 and 4.3.

In the buggy, the drivetrain came the way it is, which is an Atlas 3.8 and 4.56 gears. I wondered if it would be low enough, but with the automatic so far I've never wished it was lower, and this is strictly rock crawling.

Comparing my 4.0 and 5.13, that's 20.52 and the 4.3 and 4.56 would be 19.61, so I think you'd be happy with the 4.3. However, if you don't do much technical crawling and your speed on the trail usually isn't a slow crawl, you could easily be happier with the 3.8.

So, flip a coin? :)
 
If you go deeper than the 3.8 with an auto, aren't you going to have issues with keeping hte Jeep stopped if your brakes are stock?
 
Gaius said:
If you go deeper than the 3.8 with an auto, aren't you going to have issues with keeping hte Jeep stopped if your brakes are stock?

I've seen guys with CJ's have trouble stopping with 4 to 1's, but I've never seen anyone with an XJ have a problem. Maybe the AW4 has a higher stall speed torque converter or something, but I've never known it to be an issue.

Also, I don't know of anyone who would run low t-case gears with stock brakes, usually you've already upgraded at least the rear axle by then.
 
With a 2 speed and 4.56 gears I would opt for the 4.3. Toss it in 1:1 for the fire roads with the front disengaged till you need it. OR
Save a few more pennies and go for a 4 speed altas. The lowest they go is 3.8 but when you need it you get an awesome 10.1:1 for the really technical stuff.
I run 5:38 gears with 38's and the 4 speed atlas. The gear selection is fantastic. I can have just the rear engaged and run the fire roads in 3rd, drop to 1st/2nd for the moderate stuff and have 155:1 when I need to crawl the big stuff.

4 speed all the way...

As for the point about braking, in 3.8 the jeep stops fine, in 10.1:1 with the front disengaged it also stops fine. with the front engaged it does tend to drive right through the brakes.
 
DaffyXJ said:
Save a few more pennies and go for a 4 speed altas. The lowest they go is 3.8 but when you need it you get an awesome 10.1:1 for the really technical stuff.

4 speed atlas has a 2.72, 4.3 and then the crazy 10 something.

Or they have the one that has real close ratios. Like 2.07, 2.72, and 5something.
 
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