Custom "FJ40" build Advice

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Joined
Mar 24, 2002
Messages
634
Location
Peachland BC Canada
Website
www.rmlca.ab.ca
One thing I have noticed wheeling with guys with 4:1 single cases is that reverse is just so low. Going forward you can start in 2nd and bomb around in 3rd and 4th, but when you need to back up, its like being in double low. I think a 4 speed atlas, or couple cases with 2x2:1 or even a 2:1 and a 3:1 is ideal. Maybe you don't need this for rock crawling, but I thought I would share my experiences.
 
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Joined
Sep 16, 2015
Messages
51
Location
Northern California
One thing I have noticed wheeling with guys with 4:1 single cases is that reverse is just so low. Going forward you can start in 2nd and bomb around in 3rd and 4th, but when you need to back up, its like being in double low. I think a 4 speed atlas, or couple cases with 2x2;1 or even a 2:1 and a 3:1 is ideal. Maybe you don't need this for rack crawling, but I thought I would share my experiences.
Great insight! This ratio discussion has been super helpful.
 
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Joined
Sep 16, 2015
Messages
51
Location
Northern California
You want to build and go rock crawling ? have you been off roading before or rock crawling in your own vehicle ? if so tell us !
If not why not just go off roading and crawling to see if you like it.
Yes, @alberta mac. I’ve been rock crawling for 10 years plus+ and absolutely love technical rock crawling trails. I’m building this specifically to rock crawl, but needs to be streetable. Not ready to tow the LC everywhere;)
 
Joined
Dec 23, 2005
Messages
795
Location
Denver, Colorado
Yes, @alberta mac. I’ve been rock crawling for 10 years plus+ and absolutely love technical rock crawling trails. I’m building this specifically to rock crawl, but needs to be streetable. Not ready to tow the LC everywhere;)
Being street-able and versatile are reasons for installing the Atlas 4 in my Cruiser. I do not tow my Cruiser. I have 2.11, 2.72 or 5.74:1 options for low. Know that AA advertised my 2.11:1 configuration as 2.0:1 but they marked the case with the former figures and I checked these figures for accuracy.

I have not tested this configuration yet as I am finishing the rest of the build. In the future I may opt for a smaller number reduction for the rear case to try and achieve a 4:1 overall. I was also looking at the Black Box/Orion configuration when I was considering FJ80 axles. I believe that @EWheeler posted about that configuration either here or in another post recently. I am looking forward to having options for various driving applications (street, light offroad, crawling, etc.).
 
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Joined
Oct 10, 2007
Messages
52
Which is why I originally wanted 4-speed Atlas @GLTHFJ60 but if going with a 2 speed, sounds like you would recommend the 4:3:1. Do we think the 5.0:1 would be too extreme? I appreciate technical rock crawling at slow and controlled speeds the most.
My 5:1 atlas is perf but that's my $0.02 and honestly just finishing her up but the crawl speed is perfect/controlled/and can barely stop her at idea with the Willwood racing brakes and the diesel torque
 

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