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Need help rebuilding NP241J Rock Trac Transfercase

XJalltheway85

NAXJA Forum User
Location
Colorado
I recently purchased a Rock Trac 4.1 transfercase from a 2005 TJ with hopes of rebuilding it and swapping it into my 2001 XJ. When I met the guy selling it I found out the case was already taken apart, and I could see some damaged parts, like wear from a severely loose chain on the rear case half and a damaged speedo tone ring chewed up from a missing dowel pin. But I was overwhelmed with excitement and bought the box of damaged parts anyway. When I got home and fully disassembled the case I found even more damage. The planets in the 4.1 set had a lot of side to side rock and you could see the pins holding them in the carrier were badly worn. So as you can see I have many problems, I'm not sure if I even got all the parts! Can anyone help me that's been inside one of theses cases before? Just general pics of how to stack the gears and details of where the thrust washers and stuff go, I'm pretty sure I didn't get all the little things in my box of parts. I'm also considering replacing the pins that hold the planets in the planetary carrier since the gears themselves all look ok. Now don't freak out, I've already been told by many people that I'm crazy for even thinking about it and that it can't be done. I'm not looking for more of that, just wondering if anyone here has done it before, as I'm certain it can be done. Any help would be welcome.
 
You are going to need more than a few pictures. You should have a $ 7.95 genuine Jeep Service Manual for the donor vehicle from www.pacificcoastmanuals.com/jeep_service_manuals.html. Complete drawings of the parts, and their relationship to each other, and the disassembly/service/assembly procedures you might need are in there.
 
Great! That's exactly what I needed, thanks Tim_MN. After reading through the NV241 section I see that it mentions not disassembling the oil pump for alignment purposes. Mine was disassembled when I bought the case, anyone ever messed with the oil pump without replacing the rear case half like the fsm states?
 
I have never messed with a 241 but the Service Manual should describe and show what you need to do even starting with a pile of parts.
 
Ok, the service manual says not to remove the oil pump housing from the rear case half due to alignment with the inner race of the rear output bearing. My oil pump housing was already removed when I bought the case and I see that several websites sell the oil pump housing and gears. My question is should I just part this case out or is it possible to realign the oil pump housing?
 
Is the old oil pump housing in question? If you think it is still good reassemble that one or buy a new one and put it in. My opinion is that you shouldnt scrap your idea and part it out just because of one issue...
 
Thanks for the encouragement POSJ. Has anyone successfully rebuilt an oil pump on their NP241J rock trac transfer case despite what the service manual says? That's what I really want to know.
 
So I just talked to JB conversions and they told me that they have never heard of an oil pump alignment issue, and that they disassemble and clean their oil pumps before resale. I'm not sure why the service manual talks about this issue, but I'm not going to worry about it. Back to my original problem, has anyone ever successfully rebuilt a planetary gear carrier?
 
So I just talked to JB conversions and they told me that they have never heard of an oil pump alignment issue, and that they disassemble and clean their oil pumps before resale. I'm not sure why the service manual talks about this issue, but I'm not going to worry about it. Back to my original problem, has anyone ever successfully rebuilt a planetary gear carrier?

Typically this is a part people purchase complete. Though it may be rebuildable, not sure where you would get the individual parts. JB or AA could better direct you there.

Here is a nice cutaway of the assembly.

rock-trac-cutaway.jpg
 
Thanks for the help everyone! So I stumbled across this picture while researching about the NP241J rock trac. The picture shows the rock trac 4.1 planetary carrier next to a 241 2.7 carrier for size comparison. In the picture it appears that the pins the planets ride on in both carriers are the same size. I didn't measure or anything, just going off this picture I would say they probably used the same pins and needle bearings at the factory for both carriers. I recently talked a transmission shop near Denver that said they might rebuild my planetary carrier, but they want to look at it first. The planet gears look ok, they just have bad side to side rock in them. I'll let you guys know what I decide to do after I visit this tranny shop.

1c_NP241ORvsNP231_Planetary_1.jpg
 
So I took the planetary from my 4:1 rock trac case and a six pinion planetary from a 241C to a transmission shop near Denver and they were able to rebuild my 4:1 planetary using parts from the 241C planetary. They told me that the pins were the same diameter but different lengths, so it was kinda a pain for them, but they got it done. The planet gears now have no side to side rock and spin great. While the planetary gear was at the shop I discovered a large crack coming from the front output yoke on the front half of my case. Apparently this is caused by a design flaw in the case where the front output bearing snap ring window was cast causing theses cases to crack when abused. So I think I'm going to turn this case into the front half of a doubler setup.
 
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