I am upgrading from a four lug to 5 lug rearend, should I change the oil in the rearend, or should it still be good, it is a 65 rearend. If I change it, how and what type do I change it with? Thanks in advance, Keith

 

Never hurts to change fluids as preventative maintenance. Could have moisture from condensation or metal from normal wear. Use 90W gear oil and fill until it starts to seep out the fill hole. Don't have a service manual in front of me to tell you the exact capacity. kennyg

 

The chunk usually requires about 2 quarts. I just did my '67 8" rear end!

 

Yeah, I just had mine redone as well.