I have an 04 fx4 and my axle code is b6. I did some searching and found out that it's a 3.73 ratio but when I get on eBay or other parts stores all the ring and pinion kits say they only fit 04 herritage and 05-10. Is there something different about this rear end in 04? I've looked at Yukon and motive on eBay and all of them leave out the 04 new style. How many teeth should there be? Also what else do I need for redoing the ring and pinion? I want to buy everything so the shop can just put it in.
Have you asked your mnechanic? If he knows enough about gears to install them correctly He should know what parts you would need. Might be a good starting point.
Also, I assume you are trying to save $ by buying the parts yourself (I don't blame you) but if he buys them then its on him if he gets it wrong.
04 "Heritage" was the continuation of the 97-03 run. There is also a 04 new body style which is the 04-08 run. So the question is, do you have a 04 Heritage (basically a left over 03) or do you have the newer body style?