You cannot put the cap on backwards, since the two halves of the seat mate across the parting line of the journal.
HOWEVER, you CAN possibly bend the dust shield on the bottom of the bellhousing, and that might make a light scraping sound that could sound like a hiss.
1992 XJ -- stock (RIP)
2000 XJ -- lots of basic mods. Sold to fellow forum member. I miss it.
2014 JK -- the project is just starting!
For Sale to Good Home---2000 XJ Factory Service Manual (Printed Version) PM for details.