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NP241 Rebuild

39K views 37 replies 21 participants last post by  mbryson 
#1 ·
Anyone have experience rebuilding one of these suckers?

My 97 GMC is making a grinding noise in 4x4 when coasting. The guess is the bearing that the gear rides on is hosed, and needs to be replaced.

I've been searching and searching the net for a rebuild write-up but I have yet to find one.

Anyone? :D
 
#28 ·
Attention NP241 experts, help needed

I searched and found this old thread. I need some help with a NP241D with a JB Conv. Super Short SYE, and mated to a 700R4 with a JB conversions adapter.

PROBLEM: The mode fork does not fully engage the front wheel drive sprocket with the shifter in 4lo or 4 hi. As the slider gear partially engages the front drive sprocket, it will "pop" if the front wheels are in a bind as the meshing side of the gears jump from notch to notch.

It appears that either the mainshaft is too far back relative the shifting forks, or the shifting forks are too far forwards.

After the problem was discovered 2 weeks ago, we replaced the plastic slip-on sleeves for the shift forks and the slider gear itself as it had worn the beveled gear edges. We replaced those and reassembled the case. After only a few yards in 4 lo... same problem. This time the plastic sleeves were fine, but the range fork was slightly contacting the slider gear.

ONE INTERESTING FACT: The adapter and the new SS main shaft were both JB conversions, BUT when originally bolted up the input shaft was 1/8" too long and a 1/8" spacer was added between the Adapter and TC. That makes us wonder if there is some discrepancy in the mainshaft which displaces the main drive gear too far back???

Yes, we will call JB Conv. on Monday, but are hoping to run Hot Springs next weekend so we were hoping for help on PBB.

Any ideas/input would be most appreciated. Thank You
 
#30 ·
I searched and found this old thread. I need some help with a NP241D with a JB Conv. Super Short SYE, and mated to a 700R4 with a JB conversions adapter.

PROBLEM: The mode fork does not fully engage the front wheel drive sprocket with the shifter in 4lo or 4 hi. As the slider gear partially engages the front drive sprocket, it will "pop" if the front wheels are in a bind as the meshing side of the gears jump from notch to notch.

It appears that either the mainshaft is too far back relative the shifting forks, or the shifting forks are too far forwards.

After the problem was discovered 2 weeks ago, we replaced the plastic slip-on sleeves for the shift forks and the slider gear itself as it had worn the beveled gear edges. We replaced those and reassembled the case. After only a few yards in 4 lo... same problem. This time the plastic sleeves were fine, but the range fork was slightly contacting the slider gear.

ONE INTERESTING FACT: The adapter and the new SS main shaft were both JB conversions, BUT when originally bolted up the input shaft was 1/8" too long and a 1/8" spacer was added between the Adapter and TC. That makes us wonder if there is some discrepancy in the mainshaft which displaces the main drive gear too far back???

Yes, we will call JB Conv. on Monday, but are hoping to run Hot Springs next weekend so we were hoping for help on PBB.

Any ideas/input would be most appreciated. Thank You
Pretty sure you can put the slider on backwards and it will barely engage the drive gear for the chain.
 
#31 ·
so I dug up this thread also... my chain has a lot of slack, i can feel it just by rotating the front prop shaft side to side. it also wobble up and down. I'm thinking bearings, seals, and a chain, and see what that does for it. I've checked JB conversions and drivetrain.com, summit, and jeg's. where in the hell can i get a kit that has the chain, fork pads, seals, and bearings to rebuild this thing?
 
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