How to: Change a 4th Gen F-Body Transmission Mount (V6)
Why Do This?:
If you’ve noticed any abnormal shaking, vibration, thumping, or even grinding coming from your console area (especially suddenly) whether you have a manual or automatic there’s a good chance it is being caused by a bad transmission mount – replacing an old mount is much cheaper than replacing a transmission where the gears have been eaten off from excessive vibration or improper angle between engine/transmission/driveshaft.
Which mount is best?:
Ideally, you want to use one suited to how you drive. OEM replacement mounts are obviously a direct-fit and perfect for daily drivers, but won’t last as long as a performance polyurethane mount that’s highly stress and more chemical resistant, especially if you take your car to the track. On the other hand, a poly mount will transfer more vibration to the body of your car and in V6 applications may require a spacer to make it the proper height and some drilling to get the stud to line up with the hole in the cross-member. And while many say it is possible to use a stock V8 mount with spacers in a V6 car, I had no luck with this: to me, it was well worth the extra $25 to buy the V6 mount and be done with it as opposed to messing up my transmission trying to save a few bucks. The great thing about the V6 mount is that it’s hydraulic, so vibrations are transferred and dispersed into oil inside the mount and virtually eliminated before they ever reach the chassis, which is why I chose stock vs. the poly upgrade.
Will this guide work for me?:
Yes and no. This guide was written using a 1995 V6 Firebird as the example. The process for a V8 or a poly mount is essentially the same, but things like the L-Bracket are only relevant to V6 F-Bodies from 93-02 – and of course, the mounts themselves look different. This guide isn’t all-inclusive, but if you can’t figure out the rest from the information given here, you probably shouldn’t be doing this yourself.
- About 20-30 minutes
- New Transmission Mount (V6 mount shown–$40, V8 mount ~$15, V6/V8 “Universal” Polyurethane ~$30-$50)
- 13mm wrench and shallow socket
- 15mm wrench or deep socket
- Flathead screwdriver or needle-nose pliers
- Ramps (or equivalent)
- Hydraulic jack
- 2×4 or other block of wood
- Optional: Loctite Thread Locker, flashlight
Step One: Prep the Vehicle
Get your vehicle onto flat ground – preferably in a garage, but the driveway or yard will work in a pinch as long as it’s solid. Wedge the ramps under the front wheels and drive up them – I purchased some 12,000LB. GVW Rhino Ramps as they have a low angle of entry and don’t require any “stepping stones” for F-bodies. If you don’t have ramps I recommend these, especially if all your vehicles have low a ride-height, but if you don’t like the $50 price tag you can always stagger some 2×8′s on top of one another and drive onto them (enough so you and your jack will fit under the car). Once the car is on the ramps, put it in park, chock the back wheels, and pull the E-brake.
Step Two: Inspection
Crawl under the car and inspect the currently installed transmission mount. If it’s cracked, twisted, spongy, or otherwise falling apart, consider yourself lucky for catching it before it did any damage. My mount had never been changed and was 15.5 years old. The green circles are why I decided to change it (besides age!) – the lower one is a crack (see Fig. 6), and the upper is a leak (V6 mounts are oil-filled).
Step Three: Removal of old mount
First, use a 13mm wrench to break loose the bolts from the mount to the transmission (Fig. 1: locations shown in RED, Fig. 2: PS circled in RED). You can likely reach both from the driver side (I did), but the passenger side one is much easier to see from the PS – of course, you may be contending with some heat from the catalytic converter even if you’ve just been on a short drive, so let it cool if that’s the case.
After the nut is removed, this is where the jack and block of wood come in. Position your jack beneath the transmission pan with the block of wood on top. You’ll want to start jacking until the wood just touches the pan – then adjust the block so it disperses the weight across the entire pan but still clears the cross-member – I used a 4×4 post about 18″ long, but a 2×4 will also work fine (Fig. 4). Once it’s all in position, slowly start jacking – keep your safety in mind! You’ll want to jack it up enough that you can get a 13mm wrench on those bolt heads with ease: the bolts are pretty long, kind of difficult to get to, and space is limited so it might take a while… a socket will speed up the process, but you may not be able to get it out once the bolts start coming out. Once these bolts are out, the mount is free. You’ll need to jack up the transmission until the stud on the bottom of the mount just clears the cross-member. Lift up and tilt the top of the mount toward the rear of the car to free it.
Step Four: Prepping the new mount
Once you have the old mount out, on a V6 you’ll notice it has an L-shaped bracket that your new mount doesn’t have (Fig. 5b: YELLOW). This bracket is what prevents your mount from twisting too far and breaking, so you’ll need to remove it from your old mount and put it on the new one. Mine had a retaining washer on it: I used a pair of needle-nose pliers to break it off – alternatively, you could pry it off with a flathead screwdriver. Yours may or may not have this washer, but you also don’t need to replace it as it’s just for convenience during the assembly process (with this washer installed, you don’t have to hold onto the bracket when installing the mount). Once you have the bracket on the new mount, crawl back under the car.
Step Five: Installing the new mount.
The process here is basically the reverse of removal. I had to give my transmission a couple extra jacks because my new mount was about 1/8″-1/4″ taller than my old worn out mount (Fig. 1 vs. Fig. 7). Slide the new mount in until the stud falls through the cross-member. If you want to, you can put a couple drops of Loctite on the bolt and stud threads, but I just torqued them good and tight. I started by securing the mount to the transmission – give the bolts a few turns by hand, then a few more with a wrench to get them started good, and then switch to your 13mm socket to finish them up: the socket makes this part go MUCH quicker. Check that the bracket is properly hooked on the rubber nub on the driver side of the mount (V6′s), and that the lower stud is aligned properly with the cross-member, then slowly let your jack drop down until it’s no longer supporting the transmission. Pick up the 15mm nut and put it on the stud. Torque all the bolts/nuts firmly (I couldn’t find a torque spec for these–I went until I couldn’t push/pull any more so I’m sure they won’t be coming out). Admire your work briefly, get out from under the car, put up the tools, wash the grease off your hands and go for a test drive!
Author’s Note: I wrote this guide for three reasons: 1) because I’ve noticed a LOT of threads about transmission mount related issues recently 2) Because I was replacing mine anyway and 3) because it’s something that’s easy to do, but that a newbie might want a few pointers for before tackling it on their own. And yes, I know the under-body is dirty. I promise I’ll clean it.