This project is a long time a come'n. I've planned and cancelled an Atlas at least 5 times before. This time, I'm just going to get it over with. My NP231 has held up fantastic over the years and is still in perfect shape. It's got a 4:1, MIT SYE and a 2Lo. Pretty well equiped, but lacks "front only" drive. Also, the Atlas is an all steel case and is gear driven. That is a heck of a lot stronger than the 231 and with the way I've been driving, I think I need the strength before I break something. I found a buyer for the 231 so that will help offset the cost.
I did some math... With the current setup (AX-15, 4:1, 4.88) I'm at 75:1 gear reduction. With my tires that's 1.68 feet per second at 750 RPM. With the 5.0 I'll be at 93:1 gear reduction and 1.35 feet per second. Sounds great to me. :)
06/01/04 - Ordered the Atlas
I ordered the Atlas from 4 West today. It's due to arrive in 3 to 5 weeks. :( I've got a trip planned to Dinkey Creek in about 3 weeks, so it looks like it's not going to get installed before then.
07/09/04 - Atlas II arrived
Well they pushed the 5 weeks to the very last day. Actually, the case came in yesterday, but the shift kit was shipped seperate. It arrived today so I went and paid the bill and picked it up. I'm delivering the 231 to the new owner tomorrow, so I went right to work getting it removed and cleaned up. There was plenty of daylight left, so I went to work on the install. Got most of the work done, but there's still some work left for Sunday and Monday.
07/11/04 - Further progress
I got some more work done on the install. All that is left now is front driveshaft modifications. I modified the rear shaft myself since all it needed was a little more length.
07/12/04 - Front drive shaft mods
I'm having the front shaft redone at the driveline shop mainly because it needs a CV joint where a standard u-joint currently is at. In the past I've had a 2 piece front driveshaft with a carrier bearing. A short piece, about 14" long went from the t-case to the carrier bearing mounted on the front of the skid plate. The Atlas output is further forward and higher than the 231 output, so I don't have to have the carrier bearing anymore. The shaft should be ready tomorrow or the next day.
07/15/04 - Complete, except for real world testing
I picked up my front drive shaft today. No more carrier bearing. When I tried to install it, the body interferred with the CV when it rotated. I hammered up the body just a little to get the shaft installed. On the first test drive down the street, the CV rubbed the body under hard acceleration. I went back in the garage and made more clearance. No more rubbing. I went to a dirt lot to try out the front wheel drive with the cutting brakes and it seems pretty good. There's a few guys going up to Big Bear this weekend and I plan to go. That will be some better field testing. I'm expecting the CV to still hit the body every once in a while, but we'll see.