NP241 Replace?/Rebuild?/Upgrades?

[Enginebuilder]

So, my 1995 GMC K2500 needs its x-fer case rebuilt. 202,000 miles on it, and it likes to pop out of 2hi when I let off the accelerator, and does NOT like going into 4hi, and forget about 4lo.

First, I was wondering if a lower-mileage NP241 from a more recent year truck or SUV would work? Mine is behind a 4L60E, so it has the 27 spline input shaft, right?

If swapping in a lower mileage unit isn't really an option, where would you recommend getting a complete rebuild kit?

Are there any upgrades that can/should be done to the NP241 when rebuilding them?

ETA: my truck has the floor-mounted 4x4 shifter, which I am lead to believe indicates that it is equipped with the NP241.

[Enginebuilder]

So, my 1995 GMC K2500 needs its x-fer case rebuilt. 202,000 miles on it, and it likes to pop out of 2hi when I let off the accelerator, and does NOT like going into 4hi, and forget about 4lo.

First, I was wondering if a lower-mileage NP241 from a more recent year truck or SUV would work? Mine is behind a 4L60E, so it has the 27 spline input shaft, right?

If swapping in a lower mileage unit isn't really an option, where would you recommend getting a complete rebuild kit?

Are there any upgrades that can/should be done to the NP241 when rebuilding them?

[andrewmp6]

I would have yours rebuilt so you know it will fit and everything in it is new.As far as upgrades besides slip yoke eliminator aka sye there is none for it.And that slip yoke eliminator is only needed with a big lift and if you go off road a lot.

[Tx Firefighter]

I'm sure the little pads on your shift forks are worn out causing the gear issues.

In my opinion, I'd rebuild it before replacing it. I just did mine last week. It had 227k miles on it. I got the rebuild kit locally at a transmission shop. The industry part number is BK241. Cost to do the whole job was about 150 bucks for the kit, sealer, paint, everything. Its a real fun job and not hard at all. It you buy a used one, you're just buying someone else's problems. Might as well fix yours instead. That way you know its good.





There's a guy on youtube that did two videos on rebuilding an NP243. It's the same as the 241 except for the electric shift deal. Watch his videos. It covers pretty much everything. I think his name is BroncoJeff or something like that.

[Enginebuilder]

I appreciate the advice to rebuild the unit that is in the truck already, as it would certainly eliminate any chances of getting one that is in worse shape, or worse, doesn't fit.

That said, the 'rebuild' kit doesn't replace *any* hard parts. Not even the fluid pump. It can best be described as a bearings and seals kit. I am not convinced that hard part replacement wouldn't be called for in my transfercase, as it is A: the original, B: was used as a plow truck for 70,000 miles, and C: the popping out of gear has been getting progressively worse, to the point where there is now a howling noise emanating from the TC area when the truck is running in neutral.

If I had to replace just one of the actual hard parts in this transfer case, such as the chain, it could easily justify the expense of buying a low mileage replacement, and then using the 'rebuild' kit on it, instead. (There are a number of NP241c's listed locally for anywhere from $150 to $500, with less than 80,000 miles on them.)

Engine: completely rebuilt
Transmission: completely rebuilt

The transfer case is next, followed by the front and rear axles.

The part number you referenced, BK241, shows as not being suitable for my truck; instead, BK241A is the recommended part. The difference between the two kits (both are for the NP241-c) is the size of the input bearing, with the latter being a 16mm bearing, and the former being a 24mm bearing. Any way to be sure of the bearing size prior to disassembly? I'd hate to get the transfer case apart, only to find that the bearing I needed wasn't included in the kit...

Another reason I'd like to get a second transfer case and rebuilt it, is that this truck is my only transportation, and being able to rebuild the second transfer case and swap it in would result in minimal down time.

[Tx Firefighter]

All good points you're making. I admit my experience with transfer cases is much more limited than my experience in other areas.

That said, the jumping out of gear deal is typical of worn pads on the shift forks.



Since yours has so much 4wd usage as a plow truck, it would stand to reason that your chain would be suspect. That's much harder use than the average truck gets.

I think the reason you only get bearings and seals in the rebuild kit is that basically that's all that wears on these units (excepting the chain). The oil pump is typically reused upon rebuild. The kit comes with the new oil pump seal and o ring for the pickup tube. Once you remove the bearings, seals, chain, and wear pads on the shift forks, there's not much else to fail.

As far as the bearing deal and 241bk vs 241bk-a, the guys at my trans shop told me the early units like mine with the wide bearing were not common at all and the narrow bearing was used in the majority of 241s.

The deal about your truck being your only wheels is deal deal breaker though. I agree that it would be a bit sketchy to dig into your transfer case knowing that you're afoot until you get it back together. You seem like a very hands on guy with your history of rebuilding stuff. I know I very much enjoyed the transfer case rebuild project. Maybe you could find a good used core and rebuild it at your leisure then just swap it in place. In the end, you'd be happy knowing you had a fresh case under there that you rebuilt personally.

[Enginebuilder]

Originally Posted by Tx Firefighter

Maybe you could find a good used core and rebuild it at your leisure then just swap it in place. In the end, you'd be happy knowing you had a fresh case under there that you rebuilt personally.

This is definately the way I am leaning right now, but the question stands:

Anyone got a list of interchange years/models of truck/SUV that would have the appropriate transfer case? Any subtle changes I should be aware of throughout the years? The bearing size- anyone know what years apply to which size?

[Tx Firefighter]

If you're interested, click on my 4wd build thread in my signature, go to page 4, post number 89. That's where I started documenting my transfer case rebuild. Lots of pictures there.

[Bigdav160]

I'm with Kevin. That is an easy unit to work on. Sockets and snap ring pliers are that are needed. The pump is not a pressure pump and made of plastic.

Watch for the broken snap ring on your output shaft.

[Tx Firefighter]

Output shaft snap ring....

I mentioned my concern on that to the trans shop guys since I'd read its a common 241 fail point. They sold me a heavy duty problem solver snap ring for that application. It was like 2-3 bucks.



Supposed to not be fail prone like the stocker.

[Enginebuilder]

That's a darn sight cheaper than the "transfer case saver" that sells for $40.

$2-3 vs $40? SOLD. Could you get a part number for me?

I'll be working in the Arctic for the next few weeks, but when I get back I'll locate and tackle the 241 rebuild.

[Enginebuilder]

Found a very nice exploded view of the NP-241C:
http://www.manualtransmissionpart.co...np241-2012.pdf

[Mr. 250r]

I swear rsgear.com used to have a piece on i think upgraded case halves or something but i can't find it anymore anything to make the 241 stronger is fine in my book i like the 241 compared to my 205 i will eventually get a sye kit but i want a 1410 to match my yoke that's the only problem i have found so far.

[ETsC10]

Don't know an answer but here's a bump for you Eric and to the forum!

[truckdude239]

np241 is normall a pretty beef tcase i'd think a stock rebuild will work

[andrewmp6]

The np241 is stronger then most give it,I have seen some of the late k5 blazers with one live up to big tires and drove hard off road.The jeep rubicon uses a np241 but its built a little different then the gm one.