Does a lift determine motor mount type?

[joshwellborn]

I just got a somewhat maintenance neglected 99 2.5L that I have virtually no history on and I’ve been trying to get her healthy.
It has a pretty good vibration. I’ve replaced the timing chain/gears/tensioner/damper/crank seal.
Exhaust seems good.
The vibration is still pretty intense. I’m looking at motor mounts next. The Jeep does have a lift—not sure how to measure how big a lift it is.
How does a lift determine what mounts I choose and is there anything different that must be done when installing mounts to a lifted Jeep?

 

[hosejockey61]

Start with your driveshafts before anything else. Remove the rear driveshaft, put it in 4 wheel drive and then take it for a drive at the speed you got vibrations. If they are gone, then you most likely have a pinion angle issue that is causing your vibrations. This is due to people installing a lift and then not correcting the driveshaft angle. If you have a small lift, then a spacer or even some washers between the belly pan and frame can put the angle back to stock. If you have a large lift, then a double cardan shaft and slip yoke eliminator will be needed to correct the angle. That is a can of worms without a plan as you will have to get some other components to make that work such as adjustable control arms.

As far as determining your lift size, measure from the lower spring perch to the upper. Stock is 8" in the rear and 12" up front. Any measurement over those is your effective lift.

 

[AndyG]

Pull the front shaft and drive it

See if red oxide powder is coming from the U joints

Check the Transmission mount

Drive shafts can lose weights and require balancing.

Check the rear pinion angle- may need an SYE or lower it if you don’t want to go deeper in.

Lifts don’t determine motor mounts , but motor mount lifts are used to keep the rear driveline angle from being as steep after a lift.

 

[Jerry Bransford]

Where do you feel the vibrations from, through the steering wheel or up through the seat? Through the steering wheel means a front tire is out of balance. Through your seat means it's a drivetrain vibration most likely from your suspension lift height.

As above, measure the height of your springs to determine how much suspension lift is installed, do this with the tires on the ground. Stock springs are 12" long up front, 8" long in the rear. So if your front springs are 15" tall and your rear springs are 11" tall you have a 3" suspension lift.

If you end up replacing your motor mounts do NOT go with mounts that have polyurethane bushings or you'll have even more vibrations. Stay with rubber bushings and if you can find Mopar mounts go with them. Some cheap motor mounts will say their bushings are rubber but cheap rubber is often as stiff as polyurethane is. Don't use polyurethane bushings anywhere in your Jeep's suspension, steering, or body mounts.

 

[joshwellborn]

This is all great info!
Thanks everyone. I will definitely work my way through all of these diagnostics in the coming weeks.

As for the source of the vibration. Seems to be coming from the engine bay. It is most pronounced when I accelerate, even when in neutral. The motor mounts look like crap, so I’ll definitely order those today!
I thought it was the timing belt guides. When I opened the timing front cover, I found a trashed tensioner and NO damper here’s the pics:

There was also a fastener that had come out and was just sitting in the caked up grease in front of an empty hole where it should have been.
Here is the pic:

Merry Christmas! Thanks in advance for any help or feedback. Even though it’s Christmas, I got Jeep on the brain.
P.S. front springs are 14.5 inches.

 

[hosejockey61]

If you're feeling the vibes through the motor then I would bet your tranny mount is trash.

 

[joshwellborn]

I’ll add the kit to my cart—engine and transmission motor mounts.

 

[joshwellborn]

If you're feeling the vibes through the motor then I would bet your tranny mount is trash.

I should also note that the engine Gets very loud when I accelerate.