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NP 249 Viscous Clutch - Do's and donts


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jaz1314
10-24-2007, 09:08 PM
OK I am dealing with my failed VC now. In my prior post I mentioned the difference between a recharged and new. Go with new because the recharged units do nothing to take care of the internal seals that have hardened from heat/age.

Now.... Ive tossed up trying to pull the VC inthe vehicle, after looking closer and thinking I would need to cut a small hole in my floor to get the top two TORX screws that hold the cover to the bearing retaining snap ring, I opted to pay a local trans shop to R&R the transfer case for me ( $200.00 ) since I no longer have a garage. So they called me today, had it out. I brought it home and toyed with the idea of just pulling the rear housing and replacing the VC, in essence, a short cut since there were no leaks or bearing noises while driving. Well, having spent 15 years rebuilding trannys myself professionally, I couldnt do it. So I opened the whole unit and let me tell you...I AM GLAD I DID!!!! :iceslolan Heres why.....

I found, lying in the bottom under my pickup screen for the transfer case pump, GOBS of black RTV from a previous reseal! Somebody had resealed the unit before and went crazy with RTV and when it squeezed out into the tcase the RTV was not cured and the fluid washed it away from the inside edges CLOGGING the pickup screen for the pump. COMPLETELY. So, my theory is that this is what casued the VC to fail, lack of good lube and overheating.

A little more work but worth not having to do it all over again and then find out what I should have found out in the begining.

Nver time to do it right but always time to do it over? :banghead:

Take heed. :smokin:

94 JGC ZJ 177K

reekor
10-25-2007, 10:37 PM
For me a failed VC is just another reason to scrap the 249 and replace it with a 242.

OK I am dealing with my failed VC now. In my prior post I mentioned the difference between a recharged and new. Go with new because the recharged units do nothing to take care of the internal seals that have hardened from heat/age.

Now.... Ive tossed up trying to pull the VC inthe vehicle, after looking closer and thinking I would need to cut a small hole in my floor to get the top two TORX screws that hold the cover to the bearing retaining snap ring, I opted to pay a local trans shop to R&R the transfer case for me ( $200.00 ) since I no longer have a garage. So they called me today, had it out. I brought it home and toyed with the idea of just pulling the rear housing and replacing the VC, in essence, a short cut since there were no leaks or bearing noises while driving. Well, having spent 15 years rebuilding trannys myself professionally, I couldnt do it. So I opened the whole unit and let me tell you...I AM GLAD I DID!!!! :iceslolan Heres why.....

I found, lying in the bottom under my pickup screen for the transfer case pump, GOBS of black RTV from a previous reseal! Somebody had resealed the unit before and went crazy with RTV and when it squeezed out into the tcase the RTV was not cured and the fluid washed it away from the inside edges CLOGGING the pickup screen for the pump. COMPLETELY. So, my theory is that this is what casued the VC to fail, lack of good lube and overheating.

A little more work but worth not having to do it all over again and then find out what I should have found out in the begining.

Nver time to do it right but always time to do it over? :banghead:

Take heed. :smokin:

94 JGC ZJ 177K

Illimit
10-25-2007, 11:35 PM
Thanks for that excellent Info!

Illimit, Inc.
Pure Consciousness
http://www.Illimit.com

jaz1314
10-26-2007, 07:27 AM
For me a failed VC is just another reason to scrap the 249 and replace it with a 242.

Replacing it with the 242 would have cost me over 1000. Repairing it with a new VC and seal kit cost me 560.00. Since I do not drive this truck off road and need the 4X only for snow here in the winter, repairing the 249 came out to be the better choice considering the $ I am investing into the truck elswhere.

When working properly, the 249 is a good unit, but like anything else, when she is bad, she is bad, and she likes to be taken care of, ya know what I mean? :evillol:

With proper maintenance, proper tire pressure balance and wear, with regular fluid changes at a cost of about 8 bucks for the synthetic ATF, I think I can squeeze another 177K out of this unit before it grunts to a halt again. I do believe that if the prior reseal hadnt clogged the sump screen with RTV, that I would not even be having this conversation. Just my :2cents: worth

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