Shakes, rattles and rolls

I've got a 2000 Wrangler Sahara which has been rebuilt, and had 20K miles on it. It has a new (used) frame under it. When I first bought it, from a private sale, I drove it for 3 months before having to have the engine rebuilt. It had a bent pushrod, wrecked lifter and one of the lobes on the camshaft was gone. OK, I choked that one down.

A couple months later the left side motor mount broke from the block. Had to have a new mount fabricated to use some other available threaded holes in the block. Seems very solid now.

2 days after getting it back, the front end started to shimmy at 50-55mph. I was headed to work and it shook so violently that it snapped a motor mount bolt at the frame.

The engine (4.0L) runs great, but I don't feel safe in the thing. Everything seems tight underneath. Could something in the suspension be so worn that it would cause it to shake like that? Seems fishy to me that this started as soon as I got it back from the shop after getting the motor mount rebuilt.

Any ideas?

dr

if the new mount is a solid mount, bolting the engine directly to the front end frame, it would cause this. the I6 is a solid engine but they do run unevenly and will cause harmonic vibration. if you bolted it directly to the frame this vibration will shake the front end, and could be severe enough to shear off that bolt you were talking about.

Thanks for the reply. The new mount is solid, but it mounts to a rubber bushing, which inturn mounts to the frame. It's the same set-up as the right side. Not sure what the old left side mount looked like.

dr

ok well then i dont think thats your problem. i guess take it somewhere and have the front end alighment checked, and looked over to see if something you may have missed is loose. or take it back to where they did the work on the new mount, and tell and show them what happend.

I'd also check all the front end parts, we had an old car that shimmied over 45, (ok I was a kid in the 70's, but still) and it turned out to be worn front end parts.

also, check the alignment of the drivetrain. If the wrong holes were used at any point (since the frame is different) there could be a slight misalignment problem that could break stuff.