looking for info for 1st gen AWD to 4x4 swap

[markinnh]

Hello I have been building /modifying my 89 Astro RS for a long time. Well its 98% done and I decided to buy a 98 AWD with a bad transmission for 400 cash recently and after going through it I then decided to use the frame to build it up to put under my 89 with the 350 and 700R4. so I need to know stuff like which transfer to use without any electrical hook ups and I would like to have neutral but do not really need it. Thanks guys/Gals for your input. I would also like to know if anyone has lockdocs email address since he has not been here in a while and he has done some 1st gen stuff like this. Thank you, Mark

[Herbie]

For transfer case, you have a number of choices for manual 4x4. You can swap in an NP231 which is naturally manual-shift, or you can convert an NP233 to manual shift (see the link in my sig, LiftedAWDAstro did this on his unit, then sold it to me.) (No neutral on the NP233)

Neither of the NP23x is massively robust, but they get the job done. If you're going to make really big power with your 350, you may want to look at NP242, etc. from a GM fullsize truck. I'm not sure about the clocking on those, though - you may have to notch the transmission crossmember, or play lego-part-swapping if it is clocked in such a way that the front driveshaft fouls on the crossmember.

One of the advantages of the NP233 was that there were a number of GM offerings with a bolt-in friendly clocking orientation.

[markinnh]

I would like to go with a 231HD or C version but I have no idea which drive shafts I will need or do I need to change any thing to make it work. I know they put the 231 in the S-10 but that's about all I know. My 350 puts out about 330 ho at the flywheel but I do not plan on racing or beating this van to death. I decided to go 4x4 because I own 10.5 acres in New Hampshire with a river running through it and it would be tons of fun to drive all over my land and carry tools over to an Island I own within the 10.5 acres. Basically over the years of building this van my ideas and reasons changed as time went on. I was originally wanting to car show the van but gave up on the idea since car shows here in California are way different then shows back in New England. I did however clean, prime, paint then undercoat the complete frame from the 98 AWD I am using under my 89 RS.

[Captn. Crunch]

The 231 is a good choice. Utilitarian its make up. You can order parts Like wider chain and six planet vs. three planet bits to beef it up to HD standards. When I put the cast iron front diff under mine it still had the S-10 prop shaft flange on to. I swapped it out with the Astro style with no issues so you do have some freedom with mixing and matching there. Let me know and I’ll help you open up trails!

[markinnh]

what year and what did it come from on the 231 you used? I went to pnp today and only found 95 up S-10's so when I climbed under a few they had a driveshaft on the front that was I believe in a sleeve type whereas my 98 has a bolt in type front shaft. is this something that can be changed?

[markinnh]

Well from my searching I found this site: http://old.drivetrain.com/parts_catalog ... #S10BLAZER
Form it I believe I will need to buy at least the front drive shaft from a 99 to 2004 AWD Astro to use the NP231C transfer case on my build.

[markinnh]

OK so Thanks to Capt.crunch I finally found the info I was looking for: To do the swap I need the front frame from an AWD Astro/Safari which I got from a 98 I bought for 400 cash. I will need a NP231C and the rear drive shaft from the 98 but I will also need to get a front drive shaft from a 99 to 2004 AWD Astro/Safari. I will post updates as I go along as well as pictures. So far I removed the engine, transmission and transfer then power washed the frame and front diff. Then I primed with epoxy primer, painted and undercoated the whole frame. I also cut off the antilock brake bracket since I will not be using it as it will go under my 89 Astro RS shorty. Thanks for reading.Mark

[Astrophysics]

Hi Everyone,

Yes, I put the no231c in my 2003 AWD Astro.
It is great with the manual shifter.

I got nice floor shifter from the guy in Oregon that does 231 shifters for Jeeps, etc.

JB Fab Salem Oregon
Jon B.

Jonb@jbfab.net

503 749-3099
503 932-6978

The floor shifter is very good. It has nice heavy duty push/pull cable.

Just make template and cut slot in floor with jig saw. My 2003 Astro has the automatic tranny . I needed to add a jumper wire to the ECM to tell it it was in Low range. Then also just install a small micro switch on the shifter linkage that detects when you shift into low range. Otherwise on this electronically controlled tranny , only 1 st and 2nd gear will work when in LR.

AP

[Captn. Crunch]

And poof! Just like that, the ASV 4x4 club expands by one!!

[MountainManJoe]

I needed to add a jumper wire to the ECM to tell it it was in Low range.

That's rather interesting. I had no idea that the Astro had provisions for low range pre-installed. Do you have more info about that?

[Astrophysics]

Hi,

Well, to be clear, the AWD Astro came from factory with single speed transfer case, T-case.
There is no Low Range in OEM single speed T case.
A 4 wheel drive 2 speed T case is of course what you need to install in AWD Astro to make it truly off road cable.

A typical low range is 2.78:1. Reduction ratio where High Range is 1:1.

Low range lets you crawl along up hill or down hill at 3 mph when transmission is shift to stay in 1st gear.

Since low range gives so much extra torque, you can safely go up hill at low speed. And with the extra torque and compression braking, low range lets you go down hill slowly without using brakes so much.

4L60E is the newer so called electric controlled GM automatic transmission that I have in my 2003 Astro. For Astro with this tranny, you m]need the jumper to the ECM and micro switch on the T case linkage .

AP

[Herbie]

I needed to add a jumper wire to the ECM to tell it it was in Low range.

That's rather interesting. I had no idea that the Astro had provisions for low range pre-installed. Do you have more info about that?

Like many GM parts, the ECU in the Astro is often shared to other vehicles. In this case, many of the late-model ECUs were shared with S-10 blazer, etc. Those have an extra wire in the harness that is grounded when 4LO is engaged - this tells the ECU to expect a different range of values between the transmission sensors and the speed sensor (post transfer case). If this signal is *not* received, then the ECU senses what it thinks is an error between the driveshaft speed and transmission speed, since the driveshaft is now turning more slowly. Under this error condition, the ECU tells the TCU to limit things to 1st and 2nd gear.

If you add a wire to the harness and a pin to the connector to the ECU, the programming to understand 4LO is present, so it skips the error condition. Most people just add a microswitch to the shift mechanism (or even a manual switch on the dash) to short the pin to ground in 4LO.

EDIT: There's a bit more info and some photos and a schematic on my Blog from when I swapped in the NP233:
https://herbiesworld.blogspot.com/2017/ ... -with.html

[MountainManJoe]

EDIT: There's a bit more info and some photos and a schematic on my Blog from when I swapped in the NP233:
https://herbiesworld.blogspot.com/2017/ ... -with.html

Thanks. That's perfect. My Express AWD has a 4L60E as well so this could come in handy in the future.

[Herbie]

EDIT: There's a bit more info and some photos and a schematic on my Blog from when I swapped in the NP233:
https://herbiesworld.blogspot.com/2017/ ... -with.html

Thanks. That's perfect. My Express AWD has a 4L60E as well so this could come in handy in the future.

At least one person over on Expedition Portal has done a 4x4 swap on an AWD express, so this should be doable. (With a Silverado NP242, IIRC) Definitely pull the computer pinouts for your year van and comparable units before you start inserting pins, but know that this is not entirely uncharted territory.

[MountainManJoe]

The 242 looks pretty slick. Full time constant mesh center diff AWD , or locked 4WD, or 4WD low range, and neutral. My documentations says the 242 was used in Jeeps (2500 kg weight rating) and H1 Hummers (4700 kg rated)