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How To: Changing Your 4x4's Transmission Mount Bushing

Once you've pulled the old transmission mount, it's a good idea to compare the new and old bushings side by side, making sure the new one is actually the one that is designed for your application. You can't always trust the part number on the box, or the clerk at the store to give you the right part. Don't forget to inspect the new part as well. Making sure, to the best of your ability, that you are not installing a bad, used, or defective part.  Photo Credit: Eric McGrew

It would seem that it’s gotten to the point in my off-roading career that I’ve developed tone deafness. This can happen easily. See, your mind starts to associate certain uncommon sounds with needed maintenance/repairs for your 4x4/Off-Road vehicle, and refuses to acknowledge that they exist.

Ok, so I’m joking a bit. But just a bit mind you. Fact is, sometimes, we can become accustomed to subtle sounds that build up over time. That is, until finally, only others hear the sounds. These “others” are most likely going to be your friends. These, “friends” point out the maintenance need that you have, and then all of the sudden, you finally hear it…the horrible sound of needed maintenance.

In all honesty, many times the sounds are less noticeable due to your being inside the vehicle, where as if you had heard the vehicle run, turn off, crank, or the like from outside, you would have noticed it instantly.

After years of use and abuse it's common for transmission mount bushing to wear out. Factors such as extreme temperature changes, repeated contact with sand/oil/grease/gas/diesel, being exposed to salt water, resisting constant torque fatigue, and absorbing constant vibrations, are all factors that wear out transmission mount bushings. Since most of, if not all of, the aforementioned conditions are common in off-roading and 4x4 use, it's very common for bushings to wear out and need replacement. The frequency in which they need to be replaced depends greatly on the frequency of use and many other 4x4 specific factors. Photo Credit: Eric McGrew

This actually happened to me the other day. My friend told me that my transmission bushing was bad. I was like, no way… He told me "yeah, it’s going bad". It just so happens that my wife came home the next day while I was outside. Sure enough, I heard the dreaded clunk of a bad transmission bushing. Well…I guess “dreaded” is a bit strong for the emotion felt. Still, it’s never nice to have to add to the ongoing maintenance list. So, any problem is technically “dreaded”. One good thing about transmission bushings replacement is that it’s fairly easy to do.

This is the Isuzu Trooper/Holden Jackaroo that is the subject of a 4x4 manual transmission mount bushing replacement. As the photo indicates, there is little hesitation to subject this 4x4 to harsh conditions. Using it for Off-Roading and it having a 2.8l intercooled turbo diesel (4jb1-t) swapped in are just a couple of reasons that this 4x4 is in need of a manual transmission mount bushing. Photo Credit: Eric McGrew

Let’s go over what it takes to change this important bushing assembly on a typical 4x4. It should be noted though, that each 4x4 manufacturer is a bit different. So, 4x4 transmission bushing and mounting systems may change 4x4 to 4x4. For our purposes of illustrating, we will be changing the transmission bushing on a 1992 Isuzu Trooper/Holden Jackaroo. However, most 4x4 transmission mount bushings are similarly oriented and can be replaced using the concepts found in this article.

First Things First
Before you do anything, you’ll want to make sure that your 4x4 vehicle is parked safely for doing maintenance work. You will be working under the vehicle, so working on flat ground it your best option. Performing this repair on a cement pad, or in a garage, is even better.

Here are few things to check out before you crawl under the 4x4:
-       Make sure the emergency brake is applied
-       Make sure that there is space for you to move comfortably (relatively speaking) under 4x4
-       Make sure you have sufficient light under the 4x4. This will help you see what your doing.
-       Make sure you have all the tools that you need before getting started.
-       Make sure that the family, or your spouse knows that you will be working on this particular vehicle.
-       Make sure that the transmission and transmission mount cross member are clean before starting any work
-       Make sure to pay close attention to all jacks and tools, how they are placed, what they are holding up, and what potential hazards could be involved before continuing.

When working under your 4x4/Off-road Vehicle, it can be a bit dark at times. So, to help out with the dark conditions, a good option is to open the hood. This usually allows sunlight/ambient light to flood in. Even when working with "Work/Shop Lights", having the hood open can help eliminate the harsh shadows cast on the under carriage when bright lights are employed from the underside of the 4x4.  Photo Credit: Eric McGrew

Setting Up And Required Tools
After making sure that everyone knows you’ll be doing work under the vehicle (This is so they don’t try and drive off with you under it), and that the other preparations have been taken care of, now you can get all your tools out and get to work.

You will only need a few basic tools to do this job. Having a few power tools will help make the job even faster. Here’s a short list of what you’ll need:
-       Jack to lift/support your transmission. Just make sure that it has enough reach to actually pick the tail of the transmission up a couple/few inches.
-       A wooden board Strap piece of 1”x4” or 2”x4”
-       Socket set and Ratchet: You will probably only need two or three different socket sizes for this project. Having the whole kit is best though. Incase someone has changed out or adapted a different bolt/nut in the past.
-       Breaker bar/Impact gun
-       Wrenches
-       Transmission Bushing

Some of the tools in this photo may not be needed for you to accomplish your personal 4x4 transmission Mount Bushing replacement. However, having basic tools like a good floor/bottle jack, breaker bar, wrenches, ratchet/sockets, a scrape piece of board, and the replacement transmission mount bushing are all important components to have handy. Using power/pneumatic tools aren't required. However, they can make this job much faster.  Photo Credit: Eric McGrew

Reviewing the new transmission bushing is a good idea. You’ll want to make sure that it includes the needed nuts for installation. If, for some reason, these nuts are missing, you will need to purchase them before you start the replacement process.

Changing The 4x4 Transmission Mount Bushing
There are a various ways to remove your transmission cross member. My preferred method only requires one jack, and there is no need to reposition the jack until the very end of the process. Here’s how it works. 

 Make sure and remove all transmission and transfer case "protectors"/"bash guards".

Each model of 4x4 will have more or less under body protection. Most models will have some form of protection for the transmission and transfer case. When removing these protectors, be cautious as dirt and debris, as well as rocks, can be trapped behind the protection pieces and may fall out in your face.   Photo Credit: Eric McGrew

Using your ratchet (or your impact gun and socket), undo the two nuts that attach the transmission mount bushing of your 4x4 to the cross member.

It's really important to remove the nuts that attach the transmission mounting bracket to the transmission support cross member. Doing this before placing the jack under the transmission assembly gives you more space to work with until it's completely necessary.  Photo Credit: Eric McGrew

Place the jack toward the rear of the transmission. Using good judgment, place the jack on a portion of the transmission/transfer case that will withstand the pressure of the jack pushing up on the casing. Now jack up the transmission and transfer case until relieves pressure off of the transmission cross member.

Make sure that your jack will be stable when it is supporting the rear of the transmission. As shown in this photo, if the ground is uneven or soft, using some scrap boards and possibly ever items like bricks will help your jack be stable and keep it from sinking into the dirt. The same is applicable if you are doing this job on gravel. Don't forget to make sure that your jack will have enough stroke to, not only, reach the transmission assembly, but also lift the transmission assembly a few inches above the 4x4's transmission mount cross member (support). To make sure that the weight of the transmission sitting on the jack, and board, wouldn't damage anything, I chose to place the jack (w/ the board), behind the transmission mount cross member, right on the transmission/transfer case mounting flange is.   Photo Credit: Eric McGrew

Supporting the transmission support cross member, remove the bolts that attach it to the chassis rails on each side of the 4x4. 

Transmission mount cross member bolts are exposed to extreme conditions. Because of this, they may be extremely rusted or deformed. Under such conditions, you may find that a breaker bar or impact gun is needed. Photo Credit: Eric McGrew

After removing the transmission support cross member, using a wrench (or ratchet and socket) remove the transmission mount bushing nuts that fix the bushing to the transmission casing/housing.

This photo still has the Transmission Mount Cross Member installed. However, the bolt that you see in the just to the lower left of the transmission fill plug is one of the two bolts that attach the transmission mount bushing to the transmission outer casing. The other mounting bolt is located on the opposite side,  just to the right of the transmission fill plug, on the bottom of the transmission casing.  Photo Credit: Eric McGrew

Once the old transmission mount bushing has been removed, attach the new transmission mount bushing to the transmission casing/housing.

When installing the new Transmission mount bushing, you just have to reverse the removal process. Photo Credit: Eric McGrew

Now lower the transmission assembly so that it's a bit lower than the 4x4 chassis rails.

Lowering the Transmission assembly below the chassis rails will make re-installation of the transmission mount cross member even easier.  Photo Credit: Eric McGrew

Loosely attach the transmission mount bushing to the transmission mount bushing.

When re-installing the transmission chassis cross member. I’ve found it helpful to lower the transmission and transfer case to a position that brings the bushing slight below the chassis rails. Then loosely fasten the cross member to the transmission mount bushing. Making sure not to tighten it. This way you will be able to move the transmission mount cross member to enough to line up the holes in the chassis with the holes in the cross member. Photo Credit: Eric McGrew

Raise the combined assembly until the transmission cross member lightly touches the chassis rails. Line up the bolt holes in the transmission mount cross member, with the corresponding holes in the chassis, then install and tighten the bolts appropriately.

It's always a good idea to go back and re-check all the bolts on the cross member and transmission mount bushing to make sure that everything is tightly buttoned down. Photo Credit: Eric McGrew

Now tighten up the nuts on the lower portion of the transmission mount bushing. Making sure to fix it firmly to the transmission mount cross member.

Always remember to tighten all of the transmission mount bushing stud nuts. Tightening the firmly is a good idea, but be careful not to strip the stud or over tighten it, causing it to shear off. Photo Credit: Eric McGrew

Re-install the transmission and transfer case protection plates, reaffirm that all the bolts are installed correctly and tightened appropriately, remove the jack, store your tools, and go have some fun in your 4x4.

If after having replaced the transmission mount bushing, you still hear excessive movement in your drive train under load or during start up and turn off, then you will want to inspect the 4x4 motor mount bushings as well. Having someone stand outside of the vehicle during circumstances that produce the undesirable sounds, is a good way to determine where the sound is actually coming from too.

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