knocking underneath

i have a 1990 cherokee 4x4 and sometimes when i drive i feel a knocking under the car, i know its not the exhaust hitting something. i just hope its not something too serious.

Could you please be more specific about when it occurs? How do you know it's not the exhaust?

well it seems to occur more often when i turn left and when i go over bumps. im not 100% certain its not the exhaust but i just replaced the exhaust which was making a simalar sound. and it hasnt been doing it too long, i replaced the exhaust a while ago.

If it does it more when you turn left and go over bumps a couple of things come to mind. It could possibly be either the front right shock where the bolt goes through the wheel well and the rubber spacers on it have deteriorated (mine were almost completely gone) causing the shock to bounce around making a very distinct knocking sound going over bumps and around corners as the suspension moves. The other thing is it might be the front wheel bearings (haven't gotten to in depth on the drivetrain of a 4wd so not sure if they are present like on 2wd) but if they are bad then it would cause noise while driving and if it's left turns then it might be the right wheel bearing.

mine does that and its the exhaust pipe hitting the tranny crossmember

i know its not that because i fixed that exact problem not too long ago. but its obviously nothing serious cause it hasnt done it for a few days. but thatnk all you guys for your input. ill just have to check all the exhaust.

I replaced very many transmission rear mounts for this condition. They tend to sag and allow the exhaust to hit the crossmember,skidguards, and/or frame members.

You can have someone load it up in forward and reverse and see the excess movement. Front mounts can affect exhaust noises downline sometimes too.