Replacing the Mounts

Have you ever thought about the condition your engine mounts?

Did you ever wonder what an engine mount really does, besides hold the engine in place? Okay, I didn’t really think about it much either. Why should I?

Setting: I was crawling along the rocks on the Fordyce Trail.  Toward the end of the day, coming back up the hill over all the large loose rocks, I started to hear this rat-ta-tat-tat sound coming from under the hood as the CJ twisted over the rocks. Upon closer inspection, I noticed the fan blades were hitting the radiator shroud. "How odd?" I thought. Then it would go away.

I knew deep down that this was just the excuse I needed to go buy a new floor jack for the garage! When I brought the new jack home, I slid it under the engine and lifted it up to see what would happen... sure enough, there was a lot of daylight between the rubber blocks on the old engine mounts!

11-99 exist motor mount.jpg (30706 bytes)

After a little research, I discovered there were two basic types of material for these mounts. The stock variety is rubber and is by far the least expensive (about $13 each mount).  The next grade up is the polyurethane medium, mounted to a zinc coated plate. These run about $70 for a set, or $35 each if you’re comparing. Finally, if you really want to spend some cash, there are these "bombproof" mounts made by M.O.R.E. that will tap your wallet for about $200. Tempting as that was, I elected to go for the better-than-stock option, yet still be able to eat.

Through the Dirt grapevine, it was recommended to me that I also invest in a new transmission mount while I was at it. Sounded reasonable, I thought, so another $25 was invested into the "matching" polyurethane transmission mount. Did anyone mention those transmission stabilizer bushings, too? Better get those as well (with the new stud), add another $10 to the bill... whew!

About a week later...


Once everything arrived and time was willing, I took on the task of first changing the engine mounts. Without thinking too far ahead, I slid the jack under the oil pan and started lifting. Once an acceptable amount of daylight was reached I began the disassembly. Two bolts attach each mount to the engine block, one more attaches the mount to frame platform – pretty simple. Getting to some of those bolts however, took some maneuvering.  Also, don't forget the transmission mount!   This mounts to the bottom of the skid plate (see story below).  Be sure to loosen them a little before raising the motor.

Two things worth note: the mount on the driver’s side is right next to the stock exhaust pipe. By "right next to" I mean that I was unable to get a socket wrench on that bolt. Also, let the engine cool first! The other side of this mount has the grounding strap on it. This is a wide flat braided metal strap that connects the grounding circuit between the block and the frame (since the mounts are rubber, right?). Anyway, make sure you clean all the hardware while you have it off and securely fasten everything back together firmly to make that circuit connection.

Broken motor mounts on floor.jpg (43729 bytes)

Now I mentioned before that when I slid the jack under the engine, I did so without thinking. Here’s where that missing thought caught up with me. After I removed the blocks (which were in several pieces and VERY compressed) I determined that I needed even more room to fit these fresh new taller mounts in this gap. Back to the jack... Again, I tried fitting the mounts in, but I STILL needed more room, back to the jack... SNAP!!!

Broken shroud.jpg (41168 bytes)

That was the sound of the fan blade (which is attached to the engine, oddly enough) making its way though the top of the radiator shroud (since it is attached to the body)! So, the most helpful tip I can provide here for this project is that you first detach the radiator shroud from the back of the radiator/body!!!  The radiator is mounted to the grill with four bolts - which also holds the shroud.   Remove the four bolts from the shroud, and temporarily place them back through the radiator into the grill (letting the shroud hang-out there while you work on the project) before lifting the engine.  When you're finished installing the mounts, replace the shroud back onto the radiator.  If you stop here, don't forget about the transmission mount (re-tighten) either!

(See sub-project: "Fixin’ the Shroud" here!)

Once your fan makes it way through the shroud – assuming you also missed this – and the engine is high enough, the center bolt will fit through the mounting perch on the frame. The rest is all nuts and bolts! Make sure everything is tight, and re-attached.

New motor mount - driver's side                                 New motor mount - passenger side

Another tip: If you hoist the engine up using a typical floor jack (see photo below), keep in mind that as those types of jacks lift they will also "pull" the engine back toward the handle end of the jack!  This will cause the engine to be pulled slightly to one side.  With the first set of mounts I installed (on my Jeep) I didn't have any problems - the jack was placed under the engine from the passenger side.  However, on the second set of mounts I installed (on my friend's CJ7) I inserted the jack from the driver's side.  After the two new mounts were attached to the engine, we couldn't figure out why one of the mounts wouldn't align with the frame mount.   We tried twisting and pushing the engine, with little success.  Then it came to me, I switched the jack back over to the passenger side... bingo!  Both mounts fit perfectly into the frame platforms.  The subtle pulling of the jack from the other side made all the difference!

Fuzzy Foto of my Floorjack

TRANSMISSION MOUNT (and stabilizer)

In comparison, it is a little easier to access the transmission mount. The transmission mount actually sits atop that wide cross-member of the frame (also known as the skid plate). There should be two studs extending through the skid plate and two nuts securing the transmission mount to the bottom of the skid plate (and there should be a third stud and nut combo on the driver’s side for the stabilizer). The skid plate is held on by three 9/16ths bolts on each side of the frame.

FIRST, after removing the two (or three) nuts holding the mount (and stabilizer) to the skid plate, place a jack beneath the transmission and carefully lift and support the transmission. If you lift too much, go back and review the "Fixin’ the Shroud" section one more time – only this time, apply the same skills to the bottom side of the same shroud!

Once the two transmission mount nuts are removed from the stud (and stabilizer nut), remove the six bolts holding the skid plate and drop the plate.

WARNING! I used this opportunity to remove the dents from my skid plate. In doing so, I was able to torque the plate enough – ever so subtly – that the mounting holes would not line up with the bolt holes in the frame. Be careful not to twist the plate too much while it is off the frame.

With the plate removed, my stock (also rubber) transmission mount fell off the bottom of the transmission in two pieces! The remaining portion of the mount was detached by removing the two bolts holding it up to the bottom of the transmission body. The new mount was replaced and everything bolted back together (with some minor adjustments) without incident.

Old and New transmission mounts side by side!

The stabilizer stud holds the two bushings (disks) with the mounting bracket sandwiched between them. The other end of the stud attaches to the bottom of the skid plate.

After all the new mounts were installed, I immediately noticed I could "feel" the drivetrain’s actions more firmly through the vehicle. Also, ever so subtly, I noticed the stick shifter felt a bit taller once I replaced the transmission mount. Now I should be able to crawl over those rocks and not hear the fan hitting the shroud! I wonder what else I will be able to hear, now that I’ve solved that problem?