Based on some of the previous threads I read, I changed the rear differential fluid in my truck today to Royal Purple.

My truck is a 2005 GMC SLT SWB CC Dmax/Allison 4x4, w/ 1050 miles on it.

I read previously where it takes just less than 4 quarts of fluid to fill it, but I was able to put a full 4 quarts in it, without it running out. When I stuck my pinky in the fill hole, I could touch the fluid easily.

I was wondering if I should fill it until it runs out of the hole, or leave it as is.

Any advice would be greatly appreciated.

Based on the discussion in this thread, I think you're fine. Mine took four quarts and I could just feel it as your describing. Thats the way I left it.

http://dieselplace.com/forum/showthread.php?t=37358&highlight=rear+differential

Check replies 14-17

Thanks for the reply.

Did you do your front diff and if you did, How much did it take?

A little under two quarts.

Dave

Right around 4 quarts is the magic number so you're ok. Around 2.5 for the front if you're curious as well. Transfer case takes ATF and is around 2 quarts.

are yall taking the rear inspection cover off when yall change the oil?

are yall taking the rear inspection cover off when yall change the oil?

I would. you can inspect everything and make sure you got all the fluid/shavings out

I didn't this time, but plan on installing a Mag-Hytec cover at around 30k, will be inspecting at that time.

Thanks for the info on the front end and the Trans Case. I will be doing those changes shortly.

Right around 4 quarts is the magic number so you're ok. Around 2.5 for the front if you're curious as well. Transfer case takes ATF and is around 2 quarts.
I assume the Tcase is done similarly to the axles... drain on the bottom and filler about halfway up, need to pump the juice in?

I looked at mine today, saw two of what COULD be drain bolts... one facing the rear and one pointing down.

Also, since it's spec'd for Dex-III ATF... no problems with a synth like M1 or Amsoil?