Do most of you guys just add an extra amount of oil to your manual trannys or do you add synthetic oil to it? My mechanic said everyone is changing to the new synthetic oil in their manual trannys.

 

I run Amsoil Synthetic in mine. No problems as of yet.

 

I run an extra qt of oil in mine, its synthetic but I think thats what the 5600's came with. I use 6 qt's of royal purple.

 

Your 6 speed can use only synthetic.

 

Very true. Standard oil doesnt hold up in the NV5600's. The guy I bought my truck from decided he would change the original fluid out of the trans for me before I bought it. 10k miles later I had to get a new one. The shop said if it weren't for my driving habits it would not have lasted that long.

 

That's all we use in Heavy Truck trannies is synthetic...