Auto Crawler Question

[cebby]

I'm planning on running dual cases with an automatic trans.  I have 5.29's and will be running 35's eventually.  Is a dual ultimate (4.7's in the rear case) overkill or can I get by with the stock gearset (2.28) in both cases?   

[BigMike]

You can get by with just a reg. Dual case. I am not sure what your first gear is, but you should be somewhere close to 90:1, and I've heard that anything above 70:1 with an Automatic is excellent.

With an Ultimate, you'll be around 180:1-something and I think that will be so low that you may have problems stopping the vehicle. You will have to use alot of brakes just to bring it to a stop and I think that will be annoying eventually..

Anyone with an Auto want to fill in some advice ?

[freds40]

I have heard the same about 65:1+ is good for an auto setup. I'm going to be running a TH 350 into a dual ultimate w/ 5.89 gears and I'm at 159:1. To solve the stopping issue, you just need to throw the trans into neutral when you need to stop.

[cebby]

Depending on the trans I may use, I'm pretty sure my first gear ratio is 2.531.  There is a slight possibility that it could be 2.804, but it isn't likely. 

Using the Marlin calculator, with stock gearing in both cases, my crawl ratio is 69.60:1.  If I go to 4.7's in the rear case, the crawl ratio goes to 143.47:1.

This is with using an a341 trans.  I need to find the ratio on the a340f and see what that would yield.

[cebby]

OK, it appears that the a340f has a first gear ratio of 2.804.  I will have my pick of which trans to use (2.531 or 2.804 first gear).

For the a340f:

With 2.28's in both cases, the crawl ratio is 77.1:1

with 4.7'S in the rear case, the crawl ratio is 158.95:1

So, the question is - is 69.6:1 good enough?  How about 77.1:1?  Or are these too close to making it not worthwhile and I should go 4.7's in the rear case?

[cebby]

BTT

[BigMike]

I would say that those numbers are too close to notice any useable difference.

As for the Ultimate setup, if you are unsure, then just go with a reg. dual setup for now, and later if you desire to be slower, then drop in a gear set-

[cebby]

As for the Ultimate setup, if you are unsure, then just go with a reg. dual setup for now, and later if you desire to be slower, then drop in a gear set-

Seems to be a good amount cheaper to do the gears with the adapters in the V6 dual kit vs. the V6 dual ultimate kit.  $1054 vs $1323.  Only $269 for the 4.7 gearset.

What about going to 4.0's in the rear case with the auto?  This would bring the crawl ratio to 122:1 for the 2.53 first gear trans.  Is there clearancing of the case required if using the 4.0 gears?

[cebby]

BTT - Also, did the V6 adapter leak get solved?  (internal leak from trans to t-case that is - ATF mixing with gear oil)

[cebby]

BTT - Also, did the V6 adapter leak get solved?  (internal leak from trans to t-case that is - ATF mixing with gear oil)

Anyone?

[pjohnson]

I've been running dual cases with 2.28 in front and 4.7 in the rear behind an A340F for about 5 years now. I've been through the Rubicon many times as well as Clawhammer, Deer Valley and many others. Here's the article I wrote back then:
http://www.4x4wire.com/toyota/tech/autocrawler/

I have found that I use the 4.7 gears most of the time when I'm in rocks. When it's light wheeling in dirt/mud I use the 2.28 gears. When I need to control braking down a steep descent, I use both gearsets. Here's a table showing my crawl ratios.

The spacing gets screwy when it posts, but you can figure it out if you look at it long enough 
A340F w/gear driven dual cases                     
Xfer #1   Xfer #2   Total   R/P   1st   2nd   3rd   4th
2.28   4.7   Reduction   4.88   2.8   1.53   1   0.71
H   H   1   X 4.88   13.66   7.47   4.88   3.46
L   H   2.28   X 4.88   31.15   17.02   11.13   7.9
H   L   4.7   X 4.88   64.22   35.09   22.94   16.28
L   L   10.72   X 4.88   146.42   80.01   52.29   37.13

Phil