2001 Blazer Zr2

[SkunkedGorillaz]

Well decided to bash up a build thread. While my thread might not be as fancy as some of the skilled builder on this forum (some amazing work some of you all do), I'm more of a back yard mechanic. While for the past 20 years I've been able to keep my Jeep on the road, doing 90% of the work myself. Engine, T-Case, transmission, clutch Jobs etc. I'm definitely not a fabricator doing custom work.


I kinda aquired this Blazer in this forum.
It was Already SAS'ed. And as she sits.
Factory 4.3L with NV3500 (5speed)
-Ford Dana 44 Front with manual hubs
-Ford 9 inch rear with posi axles geared with 4.88
-James Duff Longarm kit with coils upfront. Some said the front coil kit came from a Ford application and was modified for this Blazer...
-Rear leaf springs






Here's where I'm a little confused was sold to me as a custom built transfer case supposedly Transfer Case is a NP241/231



I'm not really sure what the custom transfer case entails... last week I was out trying to pull my sister husband's truck who was stuck at the farm. Ended up cracking the rear tail section of the Transfer case completely off.

Now I'm trying to find a simple replacement for this unit. But there are no tags on the transfer case I pulled. But doing some reading I'm thinking it's possibly an NP231 (?) But I'm not very versed with patched together rigs.. if it was a jeep I'd look for a simple replacement and be on my way.

Transmission--》Transfer Case is 5bolt and 27 spline on the Transmission output.



The Rear output on the Transfer case is 5bolt and 32 spline.



Front is a fixed yoke and it's cable shift.


So how do I figure out what I have with out a tag and go about finding a replacement for this unit?

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[SkunkedGorillaz]

So I'm pretty sure I've figured it out...

Case is an NP231C with the 6 planetary Gear swapped from an np241.

This is all kinda forgin to me... the P/O sold it as custom NP241/231 Transfer Case. I was assuming it was a 241 case but after spending a few hours online I'm pretty sure it a simple NP231c Case out of an S10.

There aren't too many s10 231c cases listed on market places/buy and sell places near me.... so being the cheap guy I'm hitting YouTube videos and forums trying to figure out if I'm able to bash 1 Case together from 2.

I've got a bunch of NP231J cases from jeeps. Believe 2 with 21 imput spline count (YJ & TJ) and one with 23 (XJ)
Not sure about their output spline count.

From my research the imput shafts are easy swapped. But the problem maybe be the Speedo gear. Still have alot of internet digging to do to see if it's even feasible.

Gunna spend the weekend researching this idea, and come Monday I'll call some local wreckers and see what they have kicking around. Guess if sll else fails I'll find a transmission shop amd buy a remanufactured one which I'm trying to avoid and save money. But I need this rig back on the road.

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[Scott Cee AKA 2drx4]

I think that might have a 241 output shaft in it too then. Or maybe that's what GM used in their 231? I believe the Jeep ones are 27 spline rear output, so you won't want to use one.

Sucks that it's the weird 5 bolt pattern crap GM used in the Blazer, they're just not that available and incompatible with everything else.

How is the 4.3L for power with those tires and gears?

[SkunkedGorillaz]

I think that might have a 241 output shaft in it too then. Or maybe that's what GM used in their 231? I believe the Jeep ones are 27 spline rear output, so you won't want to use one.

Sucks that it's the weird 5 bolt pattern crap GM used in the Blazer, they're just not that available and incompatible with everything else.

How is the 4.3L for power with those tires and gears?

You might very well be right about the rear output shaft being 241.

I'm pretty sure the P/O swapped in the 6 planetary gears from a NP241 and may very well have swapped in the output shaft as well.

Hope to start pulling the case apart this evening. Of the internals are in good shape i was thinking I could use the back haft of the 231J case to replace my cracked 221C case. They should be the same. And the Speedo gear comes off the tail housing so I really just been the back half of case provided the internals survived the crack.

The 4.3 with the 5spped NV3500 and the 4.88s with the 35s are amazing. I was worried she wouldn't be very good. But she pulls great on the highway, and we have alot if hills around here. Lots if power to pull hills. And has power through aol gears 1-5. She's great for daily driving. Way better than my previous jeep TJ whom never had a 5th gear unless i had wind pushing me from behind

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[Snowracer]

cool rig, didnt know these came with the 5speed

[HillBilt]

This rig is pretty rad! welcome to the site

[SkunkedGorillaz]

cool rig, didnt know these came with the 5speed

I guess it's a kind of rare option on these zr2's.

Glad it does have stick. I prefer it over auto.

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[SkunkedGorillaz]

This rig is pretty rad! welcome to the site

Thanks for the Welcome!

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[SkunkedGorillaz]

So luckly things were not as bad worh the transfer case as I thought.

I was fortunate enough to have the NP231J out of a jeep project from years ago. Raped and pillaged it for it rear housing, Clutch fork and shift fork and pads. Grabbed seals and bearings and I'm back in the game.
Donated Rear Case from an NP231


Clutch forks both had the same part number and casting number amd pads were good so swapped then into the 231/241 case.



Shift forks were swapped as well same casting #s



While taking this Transfer Case apart I finally understand the NP231/241. Has the 6 Planitary Gear set & Wide Chain @ 1 1/4" sitting next to the jeep Chain @ 1"




Tomorrow I'll finish assembly and seal it up, and weather looks to be nice Saturday so will get her back in the truck.

Unfortunately I'll only have front wheel drive while my double cordon joint on the rear shaft gets rebuilt at a shop. Probably won't have it back till the new year.

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[Scoobienorth]

Glad you got it figured out.

[SkunkedGorillaz]

Glad you got it figured out.

Ya you and me both. I was over thinking the whole custom NP231/241. Then not having the actual tag on the transfer case was a little confused trying to nail down what it actually was...

I've never rebuilt a transfer case, and was a little worried at 1st. But after reading through the Np231 transfer case Service manual and watching a really detailed YouTube 2 part video. I jumped into it and really wasn't that complicated..

I'll be servicing (Rebuilding) my own transfer cases from now on. Was a great learning experience.



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[SkunkedGorillaz]

Well dam, I'm at a little loss for words....

The refurbished transfer case seemed to be working fine on the bench, appeared to be shifting into 2wd, 4hi, n and 4 low. So it was assembled sealed and today installed it back Into the truck. Was kinda hoping to boot around town in 4wd with only the front drive shaft installed, as the rear driveshaft is being rebuilt.

Well-get everything bolted up, shift it into 4wd and try and go nada. I shift between 2wd, 4hi, n, 4low amd back and forth and nada.

Only thing I can possibly think of is it needs to be moving/rolling to shift into 4wd......? Anyone have any ideas as to why I can't get 4wd engaged or what the issue could be?

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[Scoobienorth]

Is the rear output spinning at all in any range?

[SkunkedGorillaz]

Is the rear output spinning at all in any range?

I'll have to confirm this tomorrow.

I never checked rear output spinning from the bench as I used the rear output while engaging shifter bracket. Which seemed to work on the bench.

Unfortunately I don't really have anyone to help me confirm if the rear output is in fact spinning while in gear. Guess I'll have to do some sketch shit and put it onto gear while running and climb out and observe.

I went through this case for over a week, and thought everything was quality.., I'm gunna be so let down if I have to rip into it again.


Edit** guess I can just use my phone to record rear shaft instead of risking a runaway vehicle...

[Scott Cee AKA 2drx4]

There's not much you can do wrong in them. I once managed to put the shift fork/collar in cocked (I have no idea how to this day) and it jammed up. Otherwise if you shift it, it should shift.

That said, I did break the welds from the fork to the rail on a 241. It just stayed in 2wd after that as moving the shifter just caused the rail to slide inside the fork and not move the collar. But it took a good tug on the shifter to do it.