Chevy & GMC Vans

AWESOME!!!! Total cost would be nice to know for me as well. Drivetrain.com has a replacement modified 231 with AWD and low range as a replacement for the 136 in the 99+ vans for about $1k.

Having all the steps listed here is great. I will make this a sticky so we can keep it for reference for the next guy!

LiftedAWDAstro wrote:AWESOME!!!! Total cost would be nice to know for me as well. Drivetrain.com has a replacement modified 231 with AWD and low range as a replacement for the 136 in the 99+ vans for about $1k.

Thanks Lifted

I remember reading that thread. Knowing what I now know about the internal workings of many of the NP TC's (and that's just enough to be dangerous ) I'm thinking the 231 AWD may be a misnomer, though I would be gladly proven wrong.

Also keep in mind that the 242 conversion may be considerably less for a post '99 van; you probably could use the input shaft/gear and VSS from the 136 as well as the OEM trans adapter (with clocking ring or a 242 from a Hummer). Don't know if maybe the rear driveshaft might work too.

timelessbeing wrote:Congrats!
4-Low is high on the list of wants for my Astro. I'm still trying to figure out how to implement AWD+4Low with minimal fabrication.
Unfortunately, your conversion sounds complicated. :( What was the total cost?

Thanks Timeless

Really the most fabrication and complicated part was the shifter and linkage which will have to be done for any manual shift (and that doesn't have to be as complicated as I made it). Other complications were self-inflicted to save a buck. For instance, if you went with one of the complete adapter kits, you wouldn't have to mess with the VSS or the ECM as it is supplied in the adapter housing.

In reality, if you went with the Advanced Adapter kit, you would only have to change out the TC input (easy), fab/modify a shifter and probably fab a crossmember mount. Then have driveshafts built.

Here's the breakdown. Because I live remotely I purchased many items from ebay. I'll leave out shipping costs so people can get an idea of what it might cost from a junkyard and local parts store:

NP 242 $120
NP 231 $100 (for input gear and VSS)
Novak Adapter, o-ring and gasket $300
NP 241 front output shaft and flange $50 **forgot this**
new TC seals $30
Trailblazer driveshaft $22
conversion u-joint and installation $40
shifter $10
misc. hardware and steel ~$20

$692

Shipping was probably another ~$200

Did I leave anything out?

I hope to recoup some of the costs by selling leftover parts; anybody need a used u-joint?

Less money than i'd have guessed, good to know!

I have that same center console! :-)

Yeah $650 is very doable. It's stuff like "make a crossmember" that scares me, and I'd prefer a button to a shifting stick.
But I would consider having someone else do it for under $1k.

Hey! You copied my centre console.

timelessbeing wrote:Hey! You copied my centre console.

I especially like the custom restraint strap!

Just drove the van home (300 miles), the drivetrain was smooth, no vibrations. If it ever snows here this winter I'll see how the AWD works. In the meantime, maybe a photo trip to the desert to see how lowrange does.

I am very curious as to the snow handling. That was the only thing I missed when switching to a 231 transfer case. Loved the low range and 2wd Hi but missed the AWD a lot!

Yeah, some video of you wheelin' would be awesome.

Ok, we finally got some snow! First impressions of the 242

Highway driving, mixed snow, ice, slush and pavement; no noticeable difference from the BW (no pulling as reported with other tc's). Steepish, paved county road with 6-8" (just dragging the under carriage), no problem in AWD. Steeper dirt road (1st gear) with 4-6", felt the AWD loose traction a little. I think this type of awd probably works best when forward momentum is maintained. Though I did try to break traction from a stand still, it was more difficult in awd then 2wd. So even with the open differential system, it still seems to provide more traction than 2wd under power.

The only weird thing about the 242 is that it doesn't have a "positive" shift mechanism. That is to say that even though there is a shifter detent, the actual shift (at least thru the hi ranges) is spring activated internally. Since you have to go through 4hi PT to get to 4hi FT (AWD), you never really know which gear your in until it/if it binds on the pavement. I'm not sure that's going to be an issue though. I think it has more of a tendency to "hang up" in 4hi PT if you are shifting on a firm surface.

Still preliminary, but quite happy so far.

Excellent report! Glad its working the way we want. I am looking forward to getting to work on my conversion soon.

A couple things my buddy Darrel and I were talking about were:

1. the reason we get the pulling in 4WD with any t-case with a 4high lock, such as a 231/241/233, is because of the gear ratios in the diffs. On most true 4x4 vehicles such as Jeeps and trucks, the front diff actually has a slightly taller gear ratio. For example, the rear might be a 4.11 ratio where the front is a 4.09. This essentially makes the front axle pull slightly faster than the rear and keeps them going straight. On our AWD vans, the front and rear diffs are the exact ratio, meaning the same number of ring and pinion teeth.

2. the 242 in AWD mode will actually send power to 1 wheel if that wheel basically has no traction whatsoever. Darrel tested this on his wife's 98 Grand Cherokee by jacking up the left front tire and putting the Jeep in drive. That front tire spun with no problem and the jeep never moved! Light application of the brakes would give enough resistance and it would move again. Basically if that happens, lock it into 4x4 and go!

LiftedAWDAstro wrote:Excellent report! Glad its working the way we want. I am looking forward to getting to work on my conversion soon.

1. the reason we get the pulling in 4WD with any t-case with a 4high lock, such as a 231/241/233, is because of the gear ratios in the diffs. On most true 4x4 vehicles such as Jeeps and trucks, the front diff actually has a slightly taller gear ratio. For example, the rear might be a 4.11 ratio where the front is a 4.09. This essentially makes the front axle pull slightly faster than the rear and keeps them going straight. On our AWD vans, the front and rear diffs are the exact ratio, meaning the same number of ring and pinion teeth.

That makes sense, and would explain why some (all?) AWD cases send more power to the frontend.

BTW, when I first put the tc in and took it for a test drive w/o the front driveshaft, I put it in 4hi FT and the van didn't move; for a second my heart sank... lol

Got to use low range on some dirt roads and deep snow; the tap into the ecu works great with the transmission shifting through all gears in low range.

Excellent, thanks!