This is only semi GRM other than the fact that it involves a vehicle. Definitely GR, but not M. As Meatloaf says....
Is there a good resource for finding good swap info on transfer cases? I tried over at Pirate4x4 (that forum is really awful) and got one response saying "The only answer is NP241." Seems like NP241 is the Miata of Pirate4x4.
Long story short; looking to possibly swap a 4x4 transfer case into my AWD Express. At this point I'm just gathering data. It's not that the factory AWD isn't capable, it's actually very good and dirt simple, it's just that the BW4473 transfer case is known for some failures. I figure when it does die, I'd like to have another case to throw in it.
I know the BW4470 was used in the trucks and is likely the same. Rumor has it that the NP246 is a direct swap, but that is super complex electrical viscous clutchy-type stuff. That's evidently the one with four buttons that does the 2hi, full-time 4wd (which I assume is basically AWD), 4hi, 4lo. Seems like a lot of complex things that would work brilliantly... until it didn't. I would need lots of wiring and TCM stuff as well. Part of me wants a stick and a cable, the other part of me wouldn't mind a simple electronic unit
So, I'm looking for a big database I guess... somewhere I can find the specs of each case based on their application so I can be ready.
I start here
https://www.novak-adapt.com/knowledge/transfer-cases/
(sorry, trying to do links on my phone sucks)
I have been there many times. They only list about 5 transfer cases, and only the ones for which they make adapters.
This is a stretch , but might point you in the right direction.....
Ujoint Offroad | 4x4 Vans!
What are your goals? If this is anything remotely close to daily driver status just pop in another replacement when it dies - they are $400-600 from car-part.com. Otherwise NP241 truly is the answer.
https://www.randysworldwide.com/np261-transfer-case/
261 is manual shift... should fit.. stronger..
This case is really just a stronger NP241, so NP241?
The goal is:
- 70% dry street (where 2wd or AWD would work)
- 15% snowy streets (where AWD would shine)
- 15% overlanding, off road, recovery, muddy farm fields (where 4wd and 4lo would shine)
In truth, the AWD on these Express vans has proven pretty capable in some pretty smeary situations, but the lack of 4lo and the lack of being able to directly link front/rear limits my offroading.
I'm really tempted to do one of the AWD/4WD cases like the 246 and 243c, the ones that some GMCs and Jeeps got. It's basically a 4wd unit with variable clutches on the front output. You can select "full time 4wd" and it sets the clutches to limited slip making it AWD, or 4hi which locks the clutches together. I would prefer it be manual shift in that case just because two complete electronic systems inside a transfer case is A) likely a pain to install and have it work, and B) a recipe for something not working while I'm out in the wilderness.
One of the problems is that I get conflicting information. One site says the 243c is full time/part time, another site says just part time. Another site says depends on application.
TL;DR....
First choice (asking a lot) - a manually shifted case with 2wd/awd/4hi/4lo that bolts in place
Second choice - an electronic version of the first choice, although I may need different electronics
Third choice - a manual or electronic traditional 2wd/4hi/4lo.
Last choice - anything that doesn't bolt in place without big modifications. For instance, I'm told the NP241 requires a custom front driveshaft in this application.
Also, potentially willing to split the case to add parts that make it a bolt-in... for instance, if what I need to make it fit is a GM front half, a Jeep back half, and the GM front output yoke, I can do that. I'd prefer not to, but it is a possibility.
What I lack is the knowledge of how they're different. I can tell you all about how a TH350 is a direct bolt-in for a THM200 or a 200-4r if you get the right shift linkage, or how a Buick 455 drops into a 82 Monte Carlo with the right mounts, but when it comes to transfer cases I'm clueless. One would assume that an NP from a similar year truck should be the same configuration, but it's also not unlike GM to just take whatever transfer case is on sale and re-engineer driveshafts for the application.
My research is telling me that I probably want an NP242 or 243 or 244. The 242 appears to be Jeep only (wrong input flange) and the 243c is one that I can't find conclusive information about whether or not it is FT or PT. Nor do I have any idea if it will even fit or come close. I don't even think a 244 exists.
Have you looked at expedition portal? You might get lucky there.
Edit: just found this big ol' thread from a person doing an AWD to 4x4 conversation on their Express van: ExPo Van Thread. I haven't read any of it, so I make no claim of helpfulness 
In reply to thatsnowinnebago (Forum Supporter) :
That's the original thread where I got the NP241 info. Great info, but he had to modify exhaust, crossmember, and have a custom front shaft built.
I actually became a member there for that thread and because of buying the van. So far, that's the only 4wd conversion thread I've found (aside from something like a Quigley)
In reply to Curtis73 (Forum Supporter) :
Aw dang, it did seem too good to be true for that thread to answer all your questions.
Pirate4x4 is dead, has been for about a year now. Vertical Scope killed it. We're all over at irate4x4.com now.
The majority of our efforts of letting the remaining Pirate visitors know where everyone has gone, has been met with censorship and often banning. Vertical Scope has such a sandy vag over it that if you try to post the text irate4x4 over there, it's automagically changed to Pirate4x4.
I suspect it wouldn't be too hard to fit a Jeep 242 to a GM, it should be about the same bolt pattern, it's easy enough to swap a Jeep D300 to a 700R4/4L60 with an input shaft swap, D300 fits in place of a 231J, and I stuck a 242J in place of the 231J on my XJ, bolted right in place. Wil a 241C input fit in a 242J?
Also Berkley Vertical Scope!
Somehow having to shift into 4WD feels better.
When I researched this for the Astro vans, I spent a lot of time with google, sending me to forums... but the different forums and t-case numbers have all blended together, and the Astro / s10 stuff is slightly weaker than the full size.
I did get the chance to buy a s-10 blazer 4x4, for parts, but then found out it has the fancy computer/clutches/AWD/4WD case.... and am never going to build that van. We could prolly work a deal on it, if it’s strong enough for the full size.
bigdaddylee82 said:
Pirate4x4 is dead, has been for about a year now. Vertical Scope killed it. We're all over at irate4x4.com now.
The majority of our efforts of letting the remaining Pirate visitors know where everyone has gone, has been met with censorship and often banning. Vertical Scope has such a sandy vag over it that if you try to post the text irate4x4 over there, it's automagically changed to Pirate4x4.
I suspect it wouldn't be too hard to fit a Jeep 242 to a GM, it should be about the same bolt pattern, it's easy enough to swap a Jeep D300 to a 700R4/4L60 with an input shaft swap, D300 fits in place of a 231J, and I stuck a 242J in place of the 231J on my XJ, bolted right in place. Wil a 241C input fit in a 242J?
Also Berkley Vertical Scope!
I'll give irate4x4 a shot. Thanks for letting me know.
Hotrodders.com is headed in a similar direction. Same format.
The Jeep/Dodge 242 won't really work on a GM trans. At least, there is a healthy aftermarket for adapters, so I think if it were easier then it wouldn't support the adapter market. I also discovered the "code" for NP cases; first number is number of speeds, second one is a basic strength, third one describes the type and shifting method. That still doesn't help me much seeing as how (for instance) a 241 came in about 30 different applications, some passenger drop, some driver's, some 23T, 27T, 32T, different input lengths, yoke styles, shaft styles.... and that's just within one marque. It stands to reason that going from a BW to an NP is going to be tricky enough. My only hope is that GM engineered the yokes to match the application, and not made the driveshafts to match the Tcases. Since the AWD express was made in exactly one configuration (all 5.3L/4L60E/BW4473) I don't have the easy part of mix'n'match driveshafts. I gots what I gots.
There is light at the end of the tunnel... at least for making a 242 physically work. Hummer H1 and H2 both used the 242 for several years. The H1 of course is out because it used the 4L80E with 32 spline output. Buuutttt.... the H2 used a 4L65E. My hope is that I could either buy a Hummer T-case (big money because only used a few years on a luxo truck) or find some way of stuffing the appropriate GM parts onto a Jeep 242.
.... and then still have no idea if it's a bolt-in for the driveshafts.
bigdaddylee82 said:
http://astrosafarivans.com/bb2/viewtopic.php?f=58&t=7844
Oh my gosh... this puts me light years ahead.
No Time
SuperDork
2/10/21 6:54 p.m.
bigdaddylee82 said:
http://astrosafarivans.com/bb2/viewtopic.php?f=58&t=7844
I'm not sure how similar the expres and Astro drivetrains are, but this may be useful.
There's a few more that may be useful if you end up going with electric shift:
Astro NP233 info
Another Astro NP233 using blazer harness and module
On edit: One with a manual shift converted NP233
At this point, if I can get a manually-shifted AWD/2WD/4HI/4LO Tcase that bolts up, it might be worth it to me to do custom driveshafts (I'm going to totally regret saying that later)
FWIW, my favorites are the 242 and 249. I was under the impression that the Hummer 242HD is a direct swap for the 241C in my GMT400. The 249 is manually shifted and yes, it has a viscous coupling, which IMO is a beautiful thing if you use it as intended. If you're strictly buying used, I guess I'd avoid it, but a rebuilt unit with a new viscous coupling should be fine. Supposedly, they gained their bad reputation from the off-road crowd who can't keep all 4 on the ground. The resulting radically different side to side wheel speeds kills the VC. For your use case, it should be fine and last 150K or better if starting with a fresh coupling.
I wonder what T-case Quigley uses.
759NRNG (Forum Partidario) said:
This is a stretch , but might point you in the right direction.....
Ujoint Offroad | 4x4 Vans!
used to work down the street from this guy, see his stuff around town all the time. he does cool things
Also the atlas 2 or 4 is always my rec but those are big money
Curtis73 (Forum Supporter) said:
The goal
- 15% overlanding, off road, recovery, muddy farm fields (where 4wd and 4lo would shine)
I'm really tempted to do one of the AWD/4WD cases like the 246 and 243c, the ones that some GMCs and Jeeps got. It's basically a 4wd unit with variable clutches on the front output. You can select "full time 4wd" and it sets the clutches to limited slip making it AWD, or 4hi which locks the clutches together. I would prefer it be manual shift in that case
First choice (asking a lot) - a manually shifted case with 2wd/awd/4hi/4lo that bolts in place
Third choice - a manual or electronic traditional 2wd/4hi/4lo
Last choice - anything that doesn't bolt in place without big modifications. For instance, I'm told the NP241 requires a custom front driveshaft in this application.
The Jeep box used in xj's in the 80s and 90s is the only AWD/ 4wd unit that actually engages the front drive with a gear. All the gm ones use a clutch pack, which requires electronics and speed sensors. None of them are manual, and they are not at all accepting if tire stagger in AWD.
I think. Definitely could be wrong, but I don't think I am.
I very much doubt you will be able to junkyard a front shaft, but building a front shaft is easy.
I installed the Jeep "Quadratrac" case in my Commanche years ago, in place of the original part time box. Other than having to seal the case to the manual trans because if a shorter input stub that didn't reach the seal, it was painless.
Uncle David (Forum Supporter) said:
FWIW, my favorites are the 242 and 249. I was under the impression that the Hummer 242HD is a direct swap for the 241C in my GMT400. The 249 is manually shifted and yes, it has a viscous coupling, which IMO is a beautiful thing if you use it as intended. If you're strictly buying used, I guess I'd avoid it, but a rebuilt unit with a new viscous coupling should be fine. Supposedly, they gained their bad reputation from the off-road crowd who can't keep all 4 on the ground. The resulting radically different side to side wheel speeds kills the VC. For your use case, it should be fine and last 150K or better if starting with a fresh coupling.
I wonder what T-case Quigley uses.
I'm in agreement... at least from an operational side. Assuming they are a good, reliable TC, I like those two as well.
The plus side with the 242 is I get 2wd as an option, but the AWD is an open diff, not viscous. With the 249 I don't get 2wd, but I do get the viscous AWD. The only real benefit I can see to the 242 might be reliability and the extra half MPG in 2wd, but without having a means of disengaging the front axles, I doubt I'll be saving much fuel.
The real thing I dislike about the 249 is that I don't get 4hi. I just get AWD/N/4lo
I suppose a 242 is what I want. I can't imagine the open AWD being that much different from VC AWD. I haven't found any BW cases that have all the AWD/4wd choices unless I'm missing one. Seems like they're all either/or.
