Is it easier to install the rear main seal with the rear cover off or on?

I already have the rear cover off the engine, and tried to install the rear cover with the seal already pressed in the cover. It was a b*tch

I gave up before I tore up the seal. Probably, I should take the seal out of the cover, install the cover, then install the seal. Is this right?

Thanks

 

There is a special tool needed to ensure the seal goes on right or you'll have a leak most likely.
Dealers have that tool or any reputed LS1 shop.
Take the cover and seal and have them do it for a minimal fee.
IMO this is safer than messing it up and having to tear it down after that.
At least that is what I do.

 

The i.d. of the seal is a little smaller than the o.d. of the crank. It will stretch, but because the lip is facing the wrong way, it tries to fold over when you install it.

I took the plastic protector ring that came with the new seal, and wrapped several layers of masking tape around it, until I could use it as an expander for the seal.

Pushed the ring in from the other side so it wouldn't fold the seal. Left enough hanging out that the ring would contact the crank first, then just let the crank slide the ring out while I pushed the seal on.