What made me think about the new CK-4 standard vs. CJ-4 was what happened in the change from DEX-3 to DEX-6 in my Allison 1000 transmission. DEX-6 weakened some seals and caused leakage in transmissions built before 2006. I went with the TES-295 standard in the trans.
I was wondering about a possible effect on my 2003 Duramax because they also said DEX-6 was backward with DEX-3. I can't afford a new engine, much less major repairs to it.
Thanks
TiredTrucker and BrocLuno for your responses.
There was an oil cooler line re-call on GMC/Chev DHs with Allison transmissions.
Was Dex-6 ever recommended for Allison?
TES 389 and 295 are the proper fluids according to Allison depending on the vintage.
GM did their own thing with Dex-3H.
Your 2003 Dmax would have been CI-4.
CK-4 passes CI-4, CI-4+, CJ-4 and all previous C for compression ignition classifications.
From a formulation standpoint - there may be some big differences in the chemistry choices - especially between the high phos and low phos options (diesel only vs universal oil). There may also be some significant changes in the detergents used looking forward.
CK-4 platforms have been worked on and developed for a long time, and I'm sure that the oil companies have been running fleet trials on their planned formulas. I don't think you would have any issues with the upgrade.