rworks Posted January 26, 2009 Share Posted January 26, 2009 Went to the shop today to put her up on a lift so I could check for a rattle noise (transmission mount looks to be the culprit) and noticed something that I never picked up on before. Turning the rear driveshaft by hand only the left wheel moves forward. Turn the shaft the other way and only the right wheel moves backwards. Both wheels never turned together. So in 2WD the truck is really only 1WD?????? :huh???: BTW, the rear end is a stock Dana 35. OK, so I go to the front driveshaft and turn it. Both front wheels turn together. NP242J transfer case. Correct me if I'm wrong, but shouldn't a stock 242 let the front shaft turn freely without the wheels turning too? Unless the CAD "mod" has been done, but I haven't done that. I must be having a stupid day or something. This is my 2nd 4WD truck and I just never noticed these things. :dunce: Link to comment Share on other sites More sharing options...
mvusse Posted January 26, 2009 Share Posted January 26, 2009 That's how an open differential behaves. If someone would hold the wheel still while you turn the drive shaft, the other one would spin. To have both wheels turning takes a limited slip, locker or spool. Link to comment Share on other sites More sharing options...
Pete M Posted January 26, 2009 Share Posted January 26, 2009 Yup. An open diff send the power to whichever tire has the least resistance. The t-case has nothing to do with whether or not the front shaft is connected to the front tires. That's the CAD's job (if it is there). Link to comment Share on other sites More sharing options...
maddzz1 Posted January 26, 2009 Share Posted January 26, 2009 You also said a "stock 242", MJs didnt come with a 242. So if your truck has a 242 that is a sign that someone has changed some stuff. Link to comment Share on other sites More sharing options...
rworks Posted January 26, 2009 Author Share Posted January 26, 2009 You also said a "stock 242", MJs didnt come with a 242. So if your truck has a 242 that is a sign that someone has changed some stuff. IIRC, the MJ came with a choice of Selec-Trac or Command-Trac 4WD, which was the NP231 or NP242. Am I mistaken? http://jp.automotive.com/75422/154-0610 ... index.html And yes, my MJ isn't stock. AW4 came from a '94 XJ, front and rear axles from a '91 XJ, and the engine from a '01 Grand Cherokee. Link to comment Share on other sites More sharing options...
james750 Posted January 26, 2009 Share Posted January 26, 2009 Yes, Mjs were offered with a 242. No, Mj's with the 242 didn't have the CAD (its a good thing) Yes, open diffs are supposed to act that way (rear in your case) Yes, If both tires turn together (front in your case) you have LSD or a locker Link to comment Share on other sites More sharing options...
Pete M Posted January 26, 2009 Share Posted January 26, 2009 I don't really want to get into this debate again (since no new material has come forward), I can only offer that the dealership brochures make no mention of a select-trac option except for 1986 (and that was the 228/229 t-case). If it was special-order item through a dealership, that's a whole 'nuther ball game and I'm not privy to that documentation. Link to comment Share on other sites More sharing options...
BLHTAZ Posted January 26, 2009 Share Posted January 26, 2009 If it has a 242, it should not have a CAD. If it has a CAD & a 242...it has been changed as the 242 does not support the CAD front axle. If you have a CAD and a 242, that would explain why both front tires turn with the shaft as someone has locked the CAD or replaced the right side axle shaft with a one piece :thumbsup: Link to comment Share on other sites More sharing options...
jeepcoma Posted January 26, 2009 Share Posted January 26, 2009 One question though, you said the front wheels turn together. Did you mean that they both spin the same direction, or just that when one spins the other does too? If they are spinning in opposite directions, you have an open front diff as well. Link to comment Share on other sites More sharing options...
Eagle Posted January 26, 2009 Share Posted January 26, 2009 I don't really want to get into this debate again (since no new material has come forward), I can only offer that the dealership brochures make no mention of a select-trac option except for 1986 (and that was the 228/229 t-case). If it was special-order item through a dealership, that's a whole 'nuther ball game and I'm not privy to that documentation. ^^^ That's also my understanding. "Selec-Trac" does not necessarily mean a 242 transfer case. The 242 was not used in 1986 ... which was the only year Selec-Trac was offered in the MJ. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted January 26, 2009 Share Posted January 26, 2009 I don't really want to get into this debate again (since no new material has come forward), I can only offer that the dealership brochures make no mention of a select-trac option except for 1986 (and that was the 228/229 t-case). If it was special-order item through a dealership, that's a whole 'nuther ball game and I'm not privy to that documentation. ^^^ That's also my understanding. "Selec-Trac" does not necessarily mean a 242 transfer case. The 242 was not used in 1986 ... which was the only year Selec-Trac was offered in the MJ. agreed. your truck is bastardized enough that It may well have one. but it's not stock. Link to comment Share on other sites More sharing options...
rworks Posted January 26, 2009 Author Share Posted January 26, 2009 One question though, you said the front wheels turn together. Did you mean that they both spin the same direction, or just that when one spins the other does too? If they are spinning in opposite directions, you have an open front diff as well. Yes, both fronts go the same direction. I did some further looking last night and the front has no vacuum disconnect (nor any boxes or attachments outside the gear housing). So I guess I have a "newer" Dana 30 front end w/o vacuum disconnect. Link to comment Share on other sites More sharing options...
BLHTAZ Posted January 26, 2009 Share Posted January 26, 2009 I did some further looking last night and the front has no vacuum disconnect (nor any boxes or attachments outside the gear housing). So I guess I have a "newer" Dana 30 front end w/o vacuum disconnect.Correct...and the fact that they both turn in the same direction says that there is some type of traction device (locker / limited slip) in there. Link to comment Share on other sites More sharing options...
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