Good morning, I hope I have found the correct sub-forum. I have a 2002 F250 with ZF-6 M/T and Manual Transfer Case (NP-271). The ESOF is a (NP-273). The original owners manual called for genuine Motorcraft MERCON in both the Transmission and the Transfer Case. The same ZF-6 was also found in the GM trucks of that same period (2000-2005'ish) and called for DEXRON-III (I think). Over the next 20 years, Ford superseded the MERCON by MERCON-V (which had atleast one revised formula preceding the change). Now Ford calls for MERCON-LV in the same vintage ZF-6. Over this same period, The Transfer Case MERCON ATF was superseded/replaced by Motorcraft Transfer Case Fluid (XL-12). XL-12 was discontinued in early-2019. (I found this to work quite well in the TC). What fluids would you recommend for this ZF-6 M/T and what fluid would you recommend for the Transfer Case (NP-271 & NP-273)? I am requesting this information for hot summer climates of 100*F. Due diligence has found so many various recommendations but without a reason why. I have tried the M1 synthetic ATF (Multi-Vehicle) in the M/T but I find it results in "notchy shifts" . I am considering going back to basics such as the CASTROL Transmax DEX/MERC. I understand this would require more frequent change intervals but it appears to have a good reputation for a low price. Is there a reason that the MERCON "LV" would be better? It just seems that these "one size fits all" modern fluids designed for modern applications might not be the best suited for my older truck. I also have a concern about the yellow metals in the synchros on this ZF-6. Thank you for all your insights.