QUick question: I have a Blazer 1999 and today get a huge oil leakage trought the crankshaft oil seal. I need to just replace the seal or the entire timing chain cover? (haynes recommend says the latter)

Also: rear and font seals fails at the same time?. It is necessary to change both seals?

 

the front seal is pressed into the timing cover. you can just pop that one out and replace it. the back is a way bigger job if its not leaking leave it alone. you will need to remove your transmission and flexplate to get at it.

out of all the stuff ive done on chevys ive never had one go bad in the vehicle. when rebuilding engines i have changed them with the timing cover off which makes it really easy. so i dont know how much of a pain its going to be to pop it off with the crank coming out of it. try searching on youtube and see if someone has a how-to vid on it