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Discussion Starter · #1 ·
I'm in need of a tcase upgrade, my 231 in 4lo just isn't low enough!! I have a D300 that I was planning on using.

My setup is: 92 XJ with 4.0L, Auto, 4.88s, 37in Creepy Crawlers. I'm currently running 35s, but am getting the 37s next weekend. So I'm not sure how 4lo will be with the current setup and 37s.

I'm looking at my options as:

231/300 doubler with stock gears in both.
300 with a 4:1 kit.
Other?

I'm worried that the 7.23:1 (or what ever it is) in Lo-Lo will be too low? Will I still be able to really spin the tires if I need too? I would run in the normal 2.73:1 4lo (stock setup) for most of trail riding, and then go lo-lo for the rocks and stuff where I'm currently 2 footing it on the brakes!

Those of you running a 231/300 doubler, how much floor/seat reconstruction did you have to do? How will my D44/9in combo like the 37s and Lo-Lo? I'm running alloy shafts all the way around, but it will still probably be a lot of stress? Will they hold up?
 

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first, I'd go with the doubler system for pice, and gearing options.

second, the 37" creepy crawlers seem to hook up real well, but with alloy shafts you should be ok.

third, did you upgrade your brake system at all? If you can't hold the thing still in 4 low as it is, doubling that down is going to make it unbearable.
 

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Discussion Starter · #3 ·
Ya I keep leaning toward the doubler setup!

I'm running Chevy 1/2ton brakes all the way around. Stops wells, it will hold it in 4lo even with alittle gas. Plus I'm used to shifting into N when I need to REALLY stop and hold it where its at if I need too.
 

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Budget?

What kind of budget are you on? One of the new Atlas 4 speeds would be perfect if you can shell out about $2800 for it (from porc). It is shorter, lighter (still 125lb but I believe the doubler is around 180 or more), and overall stronger. Just as versitile and lets not forget how sexy they look.
Wide range option has: 2.72:1, 3.8:1, and 10.34:1. Almost identical to the doubler ratios.

Of course, with an automatic having the advantage of the torque converter, it may not be necessary to go that low. If you just go with a 4:1 (either use just the D300 or get the kit for the 231), it may be all the low you need, depending on your wheeling style. I have heard that when an automatic has a reduction that huge, it can be uncomfortably difficult to stop the vehicle when idling in gear. A brake upgrade may be in order.

As far as spinning, with the doubler, you are getting 10.88:1 reduction. This will only be good for non-momentum-based crawling - the tires will spin, but unbelievably slowly. Top speed would be 10MPH or less in overdrive.

Anyway, if you still want to double it up, do it for a budget build. But if you can swing the cash, do an Atlas - you'll be happier.
My 2 cents.:D
 

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Discussion Starter · #5 ·
Budget is LOW! I'd run a Stak, but they aren't cheap either!

I'm stilling looking to see what I would like to do.
 

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Oops

Whoops - just read your other post about the brakes. Unnecessary to mention. My bad.

If you already have the D300, it is a full $2800 cheaper to NOT go Atlas...but I think it would still be more reliable in the end. From what I have read, it takes some big upgrades on the other two trannies to get them to the "practically unbreakable" status, whereas the Atlas comes that way. Also, the length and weight can be problematic. But if you like to fab and improvise, it is probably worth a shot anyway. If you change your mind later, you would just be out a rear driveshaft and a couple extra holes/moldings in the floor.

Good luck!
 

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I have the 231/300 doubler and I am going to go lower gears in the axles because my ratio still isnt low enough. So with 37s and those gears I think you will be fine.

You can always put it into 2nd gear if you need a little more wheel spin.:flipoff2:
 

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93 XJ, 4.0L, AW4 Auto, 38's, and 4.10 gearing in the axles...

I've got the 231/300 combo, both with stock gearing, and wouldn't trade it.

To make it useful though there are a couple things that need to go with it.
-Twin stick the 300 (might as well since you have to make somethin work)
-Upgrade the rear output (it will break eventually)
-Upgrade to 1ton MC and disc brakes (you've got the discs but the MC?)
-Put a line lock on the rear axle
-Cut a giant hole in the floor :)

Those are my recomendations. I wouldn't want it any lower than low-low (stock gearing), but it is very useful in the sticky crawling... Not a chance at wheel speed in low low but it is wonderful where the rocks are sticky...

-Box4Rocks:$399
-Cheap 300 flip:$169
-Rear 32spline: $390

Just under a grand (likely just above with nickle and dime shit) without the cases....
2K cheaper than an Atlas...
 

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My setup is: 92 XJ with 4.0L, Auto, 4.88s, 37in Creepy Crawlers.

I'm worried that the 7.23:1 (or what ever it is) in Lo-Lo will be too low? Will I still be able to really spin the tires if I need too? I would run in the normal 2.73:1 4lo (stock setup) for most of trail riding?
I woudent wory about the 7.23.. With the auto you wouldent really need the 4:1 in teh d300 but it would be fun.. I think youll be in 4:1 most of the time.

I desire lower then 4:1 but not enough to buy a lowmax 205 or something...

do it.
 

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Sorry to butt in on your post, but im considering doing a 231/300 doubler.
currently running 4.88 and 231 with tera low and 36's but its not low enought for the downhills. With the box 4 rocks, would i keep the 4.1 in the 231 or is that part of the case that you loose?
 
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