Just for an FYI in case anyone is concerned
I contacted Moss Bros Dodge in Riverside and San Bernardino California
http://www.mossbrosautogroup.com/ou/riverside-dodge/
I spoke to Mark in their service Department and he is
100% insistent that if my truck is a 2004 SRT-10 it takes 75/140 synthetic gear grease.
I asked several times and
each time he was insistent on 75/140 and would not consider any other option I mentioned (75/90 or 90 wt) -
I asked what rear end was in the truck, he didn't know without looking, I asked if that would determine the weight of the fluid and once again he said
"If it is an SRT-10 it takes 75/140" PERIOD END of CONVERSATION.
Guess I will be staying with 75-140
I mentioned the shop manual for the 04 doesn't specify and he still didn't budge