Here is a collection of pertinant posts and information to help with anyone doing a swap from AWD to a manual shift 2 speed transfer case. This information was originally posted in the http://www.astrosafari.com
As originally posted by sandfly:
Everyone talks of replacing the awd with a 4 hi-lo t-case with elec shift. What about a manuaul shift T-case with a shift between the front buckets????
Reply by Rockwerx:
Manual shift would be great! You may be able to put the control linkage in a few places so that it is easy to engage.
Go for it! Do you have a T-case yet? I have an NP243 which is the electronic shift model. I think that an NP208 and an NP241 will work. They are manual shift models.
Reply by atljwpepper:
I'm new to the forum myself, but perhaps I can help you out.
I've been running a NP231 out of an S-10 blazer for over 3 years now. It was a simple bolt-on to the 700R4 trans. The only difficulty is with the shifter, adapter between the transfer case & the trans, and the drive shafts.
The transfer case is a lot lower in its relationship to the floor of the astro than the S10's transmission tunnel and T-case. This requires raising the shifter bracket, and extending the shifter rod. Pretty simple, but it requires a little welding.
Problem two, if you don't get the transmission/T-case adapter that comes with the NP231, you must drill and tap the holes in the original astro T-case adapter. The astro's adapter actually has provisions for the three holes necessary. Pretty simple, but it's a lot less of a hassle to use the S10 one.
The NP231 that I have actually requires a larger rear slip joint than what the astro has. I simply replaced the astro's with the S10's on the rear drive shaft. Don't forget to have the rear shaft rebalanced and you might as well put in new U-joints.
For the front shaft, I used the S10 version with conventional U-joints. I only had to have the front shaft lengthened and rebalanced.
I am also running a front assembly out of an S10 with 4:10 gears. This allows me to disconnect the front drive shaft when I don't need it. I also used a cable adapter to engage/disengage the 3rd member. The front assembly boths in with no modifications to the subframe or the axle shafts.
Needless to say, the rearend must also be regeared to match the front. I find that 4:10 gears work great with my needs. I really enjoy the increased towing ability. It puts the engine in a better part of the power band on hills.
I converted my astro to 4x4 for a couple reasons.
1) My T-case and front drive shaft were broke when I bought the van.
2) There are thousands of NP231 S10s on the road, so parts are readily available and inexpensive.
3) The astro is my support vehicle for my Rock climber.
4) The conversion was done for under $800 US dollars using recycled parts.
I've driven my van into many areas that require 4-wheel drive with great results. In reality, the Astro is no Rock Climber, but the look on bystanders when they see an Astro covered with mud, slinging debre 8 feet into the air while coming over a hill is priceless.
I'm sorry for the long post, but I've always wanted to pass a lot of this information on to others that have considered the swap. This conversion has never let me down and its very unique. I am so confident of this conversion that I shipped my van to South Korea where I am serving in the US Air Force and have been driving it hard for the past two years.
2013 Toyota Tundra DC 4x4
2008 Dodge Nitro 4x4
2005 Nissan Sentra 1.8S Special EditionMileage spreadsheet
1986 Safari 2.5L 4 speed manual - scrapped
1995 Astro 2WD conversion 4.11 posi, shift kit, DHC rock rails - sold to Skippy
1998 Astro 4x4 D44, D60, NP231, full hydraulic system with 9k# Milemarker winch and snow plow - sold to Lockdoc
2003 Astro AWD all stock - traded for a 3/4 ton truck
2005 AWD, 4.10's - sold to skippy