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1990 K-3500 4x4 Thermal Actuator Replacement

Discussion in 'Chevy Trucks' started by TLS, Feb 12, 2003.

  1. TLS

    TLS PlowSite.com Addict
    Messages: 1,425

    My 4x4 floor shifter engagement light sometimes comes on while driving for awhile in 2x4 all by itself. Dealer says its probably the 4x4 Thermal actuator. I've heard that they are prone to go bad, but never had problems with the 4x4 engaging or disengaging. This is a $108 part, and I want to make sure that this IS in fact the problem.

    Question is,..... Does removal of the actuator release gear lube? I see where my Helm's manual states to coat T/A threads with GM P/N 1052942 or equivalent, and tighten to 16 ft. lbs.. It doesn't say to get a drain pan ready, and have gear lube ready to top it back off, but why then would it NEED a thread sealant?

    Anybody done one of these that knows for sure?
  2. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    Tom,on my K25LD's no fluid came out when i replaced them.After I replaced one,I did the othero ne,just because it was so much faster.I got mine for 84 bucks from the GM dealer in december.Your K3500 has a larger diff housing,but as long as the actuator is above the center of the diff,it should leak fluid unless you have it overfilled. You also need to tap into ne wire back under the tcase,at least I did. Its kind of a PITA to get to,but once its done,you'll wish you'd done it sooner.No more waitong 8 seconds for the axle to engage.It will go in instantly now 1 second usually.