2001 2wd 3.0L 5 spd manual 131xxx miles

[read this] About 1200 miles ago I changed my rear main seal, clutch, and oil pan gasket (in my driveway, an adventure). To do this I had to drain the transmission fluid and naturally replaced the old fluid with new fluid. When buying the necessary parts I trusted autozone to be able to look up the correct tranny fluid for my truck. They had the truck taking Mercon V ATF. I did the whole repair, and fully reassembled the truck. When I started the truck for the first time everything seemed ok except for one thing, the truck (not the motor to be clear) was running a bit loud, but not so loud that it really worried me, I just assumed I was imagining it. I've been driving around since with no issues except a slight increase in noise coming from the transmission.

[definitly read this!] The nature of the noise however is what is perplexing. The truck makes the most noise in 5th gear, no noise in 4th gear, some noise in 3rd gear and really no noise in any other gear. When the clutch is pushed in the noise goes away (but i replaced the throw out bearing so I don't think its that). What is most striking is that when the stick is in the neutral and I push the shifter to the right side of the transmission (towards 5th but still in neutral) the noise gets louder AND when i push the shifter towards the drivers side of the vehicle (towards first and second) the noise goes away.

I had hypothesized that I might have underfilled the tranmission with fluid, however this is very unlikely. Then, Eureka! I double checked my owners manual and found that it recomended Mercon ATF! After some further searching though I found ambiguity online about what type of fluid this transmission takes, and furthermore found that the two types of fluid are largely the same.

What is the differnce between Mercon ATF and Mercon V?

How likely is it that this issue is a result of replacing Mercon ATF with Mercon V ATF?

PLEASE HELP
and thank you for reading this mess

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2001 6cyl 3.0 2wd Manual Trans.