2008 Tacoma OR rear differential fluid change

So I changed the fluid on my 4x2 Prerunner with some Amsoil Severe Gear 75W90. Looking at the full and drain plugs, it looks like it's been serviced in the past. The truck has aprroximately 67,000. When I drained the oil, it was pretty thick. Kinda looked similar to moly lube in color - dark gray. Also seemed to have the normal metallic color in it. I suspect the person who services it poured some limited-slip additive.

Since owning it, I noticed that the truck decelerates fairly quick when you get off the gas. No gear noises or anything like that. So far I have driven a little over 75 miles and the truck seems to drive a little smoother and deceleration is not as quick. I'm hoping whatever was in there didn't cause any accelerated wear.

Anyone have similar experiences?

 

I dont think that the limited slip additive has anything to do with it. More than likely someone put a heavier weight gear oil in in.

 

You think the heavier gear oil will have negative effect down the line?