First off, what's the correct torque spec for the bolts that hold motor mount bracket to the engine? The ones that screw into the side of the motor? I have seen 27 lbs inch but my FSM says 45 lbs inch?

Anyway, I did this last weekend. All the hardware ready to go. Dorman bolts, Mopar transmission mount ($72 at dealer), and Pioneer motor mounts (around $10 from RA) made in India.



I had replaced the motor mounts and the transmission mount a few years ago with one of the cheap brands, and the motor mounts were now sagging, and the transmission mount didn't quite fit.

But first I wanted to do the bolts that connect the motor mount brackets into the side of the engine, the ones that can break off after time. I started replacing one at a time. 5 out of 6 came out easy enough, none broke.

The original bolts (the one on the left of the picture below) looks to be grade 8. Some other threads say grade 5, but these say otherwise.


I replaced them with 3/8 16 1.25 long grade 8 bolts from Dorman (btw Advanced Auto has a great collection of Dorman bolts, neatly organized). I added grade 8 washer and split lock washer, and some antiseize.




Driver's side. I measured each hole with a paper clip to make sure I had enough distance for the new, 1.25 inch long bolts. All the holes had more than enough clearance.


Some of the bolts came out easy because they had what looked to be motor oil on the threads. I figure the head gasket lets some oil slip out?


This is the passenger side, with one of the new bolts on with washer and lock washer. Notice the torx 45 head bolt on the left side of the picture, I could not get that one off, as I didn't have the right tools to turn it with enough force. What kind of sick joke did Chrysler engineers have in mind here? Did they run out of hex head bolts at the factory?


Is the washer and lock washer going to compromise the bolt in the long run by changing the flex point of the head?

After that was done, I went after the motor mounts.

FSM instructions for changing the motor mounts say to raise the vehicle. I did that last time, and it just made it more difficult, because, I think, it shifts the weight of the engine back. This time, I just supported the engine with the floor jack and a block of wood on the oil pan. Then I released the 4 nuts holding the transmission mount to the crossmember. Then I did the passenger side first and then the driver's side.

Do yourself a favor and move the AC compressor out of the way on the passenger side, and remove the air intake box on the driver's side. This will make the job much easier because it will give you room to swing the wrenches and move much faster. You can do it with those things in the way, but it is much harder.


The old mounts had collapsed.


Once I got the motor mounts on with the big thru bolt mounted, I decided to not put on the bolt and nuts that attach the mounts to the body brackets until after doing the tranny mount, to allow for the up and down movement of the transmission with the floor jack.

I placed the floor jack and block of wood under the transfer case to support the transmission while I removed the crossmember (just press the jack on the transfer case very lightly, it doesn't need much force, just enough pressure to support it). I was afraid I would break a stud or a bolt removing the crossmember, but luckily I didn't. The old mount didn't look too bad, but I swapped it out anyway. On the old non-Mopar mount, I remember struggling to align and mount the crossmember back on. But with this Mopar mount it went on easy. As you can see below, the mount compresses some when installed.



I decided to install new bolts, the big ones that hold the mount to the tranny. 12M 1.75, 50mm. Washer and lock washer.


Like other members have noted, the Mopar mount makes the transmission ride higher. I also gained some more clearance between my fan clutch and radiator, close to an inch I would guess. And the ride is quieter now, especially going over bumps. I used to get a rattling noise when I went over bumps, but not now.

 

Good write up, but I am going to throw in a slight caution here...imo dont use cheap *** Rock Auto Mount Kits (like I did)

The rubber is very soft...I had to throw away the trans mount as soon as another one could be ordered... wont even fit the motor mounts, but order ones with decent rubber...the factory ones do last a fairly long time

 

I agree. And I was going to buy the Mopar motor mounts from the dealer, but my steering components bit the dust in early June and ate up most of my fix it budget. I have to say though, that the Pioneer motor mounts are heavier, the rubber feels stronger, and the metal frame is tighter to the rubber than the cheaper options. And they are made in India, which I think I saw in another thread is better quality. So far they are holding up.

 

Inch pounds of torque on the bolts to the block?????

 

Yes. My FSM says 45 but other threads say 27. Thanks, Cruiser.

 

FSM says 45 FT*lbs on the bracket to block bolts. That 27 might be the bracket to the cushion bolts, which the FSM says should be 30 ft*lbs.

 

Per Quadratec:
Bracket bolts / nuts = 30 ft. lbs.
Through bolt nut = 48 ft. lbs.

https://www.quadratec.com/c/howto/ho...ep-cherokee-xj

 

I would reuse the bolts and add a washer.

 

Thanks, guys, I guess 45 FT lbs it is.

 

Looks good, the only thing i would put caution to is using the lock washers. The factory did not install washers there for a reason. If everything is torqued to spec there is no need for them. Now with them installed and they break, which they do you are going to have loose engine mount brackets in turn is going to be busted mount holes in your block, worst case scenario. Another suggestion is go with hd motor mounts, a bit more money but way worth it. Specially if you dont want to change them every other year. The hd mounts will last years and when tou need new ones just change the bushings. Just swaped mine out after 10 years of hard *** wheeling. Even the poly mounts go to hella after a few years but at least i know im good to go for another 10 or so

 

Make sure those bolts into the block are NOT one bit longer than the originals.

Actually, using the original bolts with a flat washer is best.

From Jon Kelley aka 5-90 @ www.kelleyswip.com

This is a known issue.

1) Unless you're going to get silly with the skinny pedal, 2xSAE8 screws on one side won't be a huge problem. You'd be better off with three, but if you don't get silly you'll be okeh.

2) The Brown Dog engine mounts use two or three additional holes on each side, and spread the mount/clamping force over more of the block. This is invariably a good idea, and I'll probably be doing it as I refit my 88.

3) The primary reason that the screws snap is because, sometimes, the screw holes in the block aren't drilled & tapped deeply enough. This causes the screw to bottom out in the hole, so you end up torquing against the bottom of the hole instead of stretching the screw (as you're supposed to do. Not your fault - you aren't doing anything wrong.) The screw is not stretched properly, and the head is not butted up against the bracket, so there's some room to move there. Vibration then causes wear cycles on the screw, which generally leads to rupture.

The easy/cheap fix? When you replace the screws (3/8"-16x1.25", as I recall,) put two flat washers under the head before you screw it into the hole.

The check? Take a feeler gage (.003" to .005") and try to slide it under the head of the screw. You'll be able to get under the corners (look at the hex head, and you'll see that the surfaces curve toward each other slightly) if it's a standard hex head - if it's a flanged hex head, you should not be able to get under the head anywhere. If you can slip the gage under the head, you have a problem. If you can touch the shank of the screw, you have a big problem!