Beware of High Mileage 241 Transfer Cases

[damork]

Just and FYI from an experience I had over the weekend. I was 600 miles into a 1000 mile trip and my transfer case went into neutral (about 8:30 PM one recent evening on I-94 Eastbound into Bismarck ND after crossing the Missouri). I couldn't get it to move unless I shifted it to 4L, but it wasn't smooth. After finding a tranny shop the next day, I found that the wimpy shift forks were worn out.

These forks are aluminum and from the shop's experience they tend to do what happened to me in high milers, especially if they see a lot of highway miles, and many do. I was even running synthetic ATF in that case.

Anyway, a gasket kit, new forks, some bearings, seals and a new chain and $800 and I was underway again.

If you have 120-150k miles on one of these, you might consider a pre-failure repair, I know the fix would have been less than half of what an on the road repair cost.

[ 09-23-2003, 08:31 PM: Message edited by: damork ]

[cruzer]

You have to change the fluid often w/a NP241 or NP231. Your shift forks wore out, but here's the kicker, there were little plastic pads the go over the shift forks. The pads ride between the shift collar and the fork. The T/C has a pump in it to get fluid to the top, and it pumps a lot.The T/C doesn't hold a lot of fluid either. I mention this because, knowing there is plastic riding on steel & a pump, drives home the point that changing the fluid is very important. Sorry for your loss.

I've seen 231's have the same failure at 75,000 miles.

[StephenA]

Anyone know what xfer case is in my 92 K2500? It clanks after shifting abruptly... Sound familiar to anyone? Could it be the xfer case going?
Thanks, Stephen

[CareyWeber]

If its the newer 88 - 98 (2000 in the heavy duty trucks) K1500 - K2500 it has a NP 241.

The K3500's have a Borg Warner transfer case.

Carey

[StephenA]

Ok, so NP (New Process) 241.... Great. How often should the fluid be changed? I'm running Amsoil, and when I first checked it it was low. Then 10k later, it was low again, with no apparent leaks. Someone said that these cases can "use" oil, but dogged if I know how... Still have that clank after shifting abruptly. May not be the T-case, though. On an earlier thread, someone said it may be the snout missing a ring just prior to the shaft. Haven't had the guts to look yet, but don't want to ruin the T-case! Just need a little guidance.

[StephenA]

P.S. - Anyone know if the 5 speed tranny in my 92 is the coveted NV4500 or NV4500HD? Did that year have the lower 6 something granny or the 5?
Thanks, Stephen

[cruzer]

StephenA, There is not really a NV4500HD.They 're
all pretty tough. New Process's 1st models of the NV4500 had a lower 1st gear, and reverse was not synchronzed. They changed it a couple of yrs later. According to Novak Industries 93-94 had a 6.34 1st gear and 95- has 5.61 1st gear w/synchro reverse. I think GM put the 6.5td in trucks later in 92, so you probably has the 1st design of the NV4500.

[StephenA]

Thanks Cruzer. The 6.34 granny or first is nice, especially with the NP241 in 4 low. The non synchro reverse is kind of a bummer, since I won't be able to suddenly go from 2nd or 3rd into reverse at 40 mph, but I rarely do that... (just kidding!). Say, the Amsoil in my tranny is pretty black- is this normal?
Anyone ever notice their NP241 "using" oil but not leaking? Also I read where the 241's can be picky about requiring none other that the dealer synthetic oil. Is this true? I run Amsoil presently.
Still trying to figure out the clunk after abrupt shift...
Thanks a bunch. Stephen

[lafrance]

Stephen A my transfer case also used oil with no external leakage.Found the front input shaft seal was dumping oil into the intermediate housing at the back of the transmission .Replace seal should fix.

[StephenA]

lafrance- that's got to be it! I think you've nailed it. A few questions: Does the case have to be r&red & opened to replace the seal? Does the leakage damage the transmission in any way? Lastly, could a loose or worn chain in the 241 cuase enough slop to explain the clunk I get on abruptly shifting? oh yeah, & are 241's easy to rebuild at home?
Thanks
Stephen

[cruzer]

Don't know about clunk. You say "shifting abruptly" do you mean foward to reverse or L1 to
L2 and so on. If fwd to rev.there is normally a little play in chain. Also check U-joints & driveline componets. The T/C is not that difficult to work on. Mostly put together w/a
bunch of snap rings.

[StephenA]

Hey cruzer, I get the clunk upon shifting from 1st thru 5th (not sure about reverse) unless I engage the clutch softly and gently accellerate. Almost like a broken motor ot tranny mount, but they are all fine, as are the u-joints, etc.
I found an upgrade for the output shaft snap ring & started a new thread ... Have you tired this product? Is it any good?
Stephen

[cruzer]

I've only had to work on NP241/231's out necessity. They put 231's in J**P Wranglers. I usaully have to replace the shifting forks. It's
a J**p thing and I don't understand. I prefer gear driven T/C's.

[Inspector]

StephenA:

Try greasing the slip coupling on the drive shaft. My 93 would do what you are talking about when it needed to have the drive shaft greased. It is also a manual with the NV4500 and a Gear vendor behind the T/C. Check the yoke going into the T/C on the end of the drive shaft to be sure that it isn't dry. It has to slip.
Denny

[StephenA]

Thanks Inspector! Good call- I'll try it. Say, what's a gear vendor?
Stephen

[Inspector]

A Gear Vendor is a two speed gear box for split shifting. When towing heavy using a two speed you can shift in between the normal gear ratio of the OEM trans thereby maintaining engine rpm and power.
Denny

[StephenA]

Hey Denny- that's what I hoped you'd say! I saw another one on the website that sells the t Case save snap ring upgrade. When I get my drive train all up to speed, I want to look into one of those. How much was yours & are you happy with your choice?
Thanks, Stephen