If you still have worn out OEM motor mounts...change 'em!
I am guessing a lot of you have already found the benefits of changing your beat up motor mounts out, but I just thought I would share my experience for those of you who may not have touched them yet.
My Cherokee had 145k, and as far as I know original motor mounts. I discovered a crack in my exhaust manifold, and was told bad motor mounts can cause that. So, I decided to grab a pair of Brown Dog poly motor mounts.
I didn't really notice anything wrong my my existing mounts, but thought if I was going to repair my exhaust manifold it would be crazy to leave old motor mounts on there.
Brown Dog poly mounts cost somewhere around $85 after a cherokee forum discount. Brown Dog seems like a phenomenal company, by the way, as when I had a question the owner of the company answered the tech line within 2 rings and set me straight. He also suggested I pick up a transmission mount if I was going to go the trouble of changing motor mounts, as it helps limit vibrations. I got an Anchor mount for $26 at Advanced Auto, though they are way cheaper at places online.
Anyways, installing the mounts was pretty straight forward but it took some time to get everything lined up right with my jack and the through pin. I won't get too much into the instal, as there is lots of good write ups already. But, it sounds like most people take 2-3 hours for all 3 mounts (2 motor and 1 transmission). I took closer to 5 hours for all 3 but I'm a bit of a novice.
A couple bits of advice, on the passenger side just take off the bracket that holds the motor mount to the block. I also took out the battery but everything else stayed in place. On the drivers side I took out the old motor mount but left the bracket. I then struggled to get the through pin through both sides of the motor mount, but after loosening the bracket to the engine block I was able to finagle it into place.
Well, after I finished, I had lots of good and unexpected results. The throttle response is so much better, a clunk I had when coming to a stop and going over pot holes is gone, and it feels sportier when taking corners and on acceleration. Another result, though I think it must be coincidence as I am not sure how motor mounts can do this, is that my XJ is starting quicker on the first crank (almost instant compared to 1-2 seconds before). I have no idea how that may have happened, but I'll take it!
So, really long post just to say that if you haven't replaced your motor mounts and transmission mount, go for it! I am very happy with my result.