Poly Transmission Mount - Tips and Impressions
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Joined: Sep 2004
Posts: 6,814
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From: Hou. TX.
Poly Transmission Mount - Tips and Impressions (I posted this in the manual tranny section and thought it might be useful over here as well in case anyone was interested)
I was looking all over the forums for some good info on the poly mounts but only found bits and pieces, so I decided to create this post in the hopes that it will help some people.
First of all, I have a 99TA M6 and recently needed to replace the tranny mount. I decided to get a poly one, but was worried of the noise problems I've heard other people post about. I still have the rubber TA (torque arm) and rubber engine mounts. I'm going to be changing those soon and will report back if I feel it necessary.
Our cars use a standard GM tranny mount, nothing fancy or exotic. Your local parts store will try and tell you they don't stock the ones for our cars, but just ignore them and get the standard GM universal mount. I picked up an Energy Suspension unit from my local speed shop, part number 3.1108R for red and 3.1108G for black.
The basic installation is described here at the Install University.
I will fill you in on the specifics concerning the poly mounts. I can't speak specifically to the Prothane mounts as I haven't seen those. The Energy Suspension mounts will come with a metal bar called the preload spacer, 2 bolts and various washers. After looking at everything under the car I decided that the preload spacer bar is not needed, I also removed the 2 bumps that the spacer would have compressed. I just used a bench grinder to remove the raised bumps. It was quick and easy to do. All that I can see the bumps and preload spacer doing is compressing the polyurethane making it firmer and hence, more likely to transfer NVH (noise vibration harshness). The rubber mount had no preload on it and worked fine and the poly is so much more firmer and stronger that I see no reason to make it even more firmer. If anyone knows of a reason to use the preload spacer as is, let me know.
The other down side to using the preload spacer is that it will add height to the tranny mount. This will move the tranny higher and it could possibly come into contact with the floor board which will definetely create NVH. Even if the tranny doesn't touch the floorboard it does change the drivashaft angle slightly. Some people have said that the angle change can produce noise. I don't know, but it doesn't sound worth taking a chance on.
Now I believe the modded (no preload spacer, removed bumps) tranny mount is just about the same overall height as the factory mount which is good. If you find that your tranny is a little too high you can lower it by installing washers in between the trans crossmember and the car body. It's best to use large diameter, flat washers to help spread the load.
You can reuse the bolts that hold the mount to the tranny. For the mount to crossmember you can use one of the supplied bolts that come with the mount. You will use the center hole of course. I tightened everything up with red locktite just to make sure they don't vibrate loose.
Here are some pics to help describe what to grind off:
Once done, it will look like this:
______________________________________
Impressions:
Sound:
IF, IF I roll up the windows, turn off the radio, put AC fan on low I can hear a little more gear whine from inside the tranny. Under heavy acceleration I think there is more overall noise than with the rubber mount. I'm just guessing as I can't be sure. So basically there was almost no noise increase. Now if I roll the windows down, or turn on the radio, or open my exhaust cutout (exhaust was going through Magnaflow muffler during listening tests), or just turn the AC fan speed up I can't hear any increase in noise at all. So basically no noise increase in my case. Hip, hip, hooray!
Vibration:
Just cruising down the road I think I can feel a little more of the car. I can't say for sure. It's really a good feeling, nothing harsh. The car feels a little more solid.
Under heavy acceleration I can definately feel a little more vibration than before. Again, no big deal, it just feels more solid. It's so faint that I think I'm getting used to it already. So the vibration thing is practically a moot point. Hip, hip, hooray again!
Shifter Feel:
This was the big surprise (I have a Hurst Billet Pro). Previously I have been having a hard time getting nice smooth shifts all the time. Sometimes I'm in the zone and can be smooth, but other times I feel like I can't synch the engine to tranny worth a damn. I know I'm a good shifter, but I tend to shift quickly all the time. If I let the clutch out real slow the shifts get smooth, but who does that, right?
After the poly mount, my shifts have been smooth as glass. Both upshifting and heel/toe down shifting under braking. I mean the shifts feel so much better without all that slack that was in the driveline. This reason alone makes the swap worth it.
I'm so pissed that I didn't do this earlier. It wasn't me this whole time, it was the damn spongy mounts that were screwing up my shift feel. Sorry about the rant, but I have to vent.
Anyway, the shifter handle handle feels so much more solid in my hand and when shifting, it will only torque over a little and that's it. No more moving around. It feels solid and I have more confidence in my shifts. So hell yea, hip, hip hooray!
I couldn't be more pleased with this tranny mount change. I'm looking into swapping both the torque arm bushing and the motor mounts with poly as well.
If you have any questions, let me know.
Jason
I was looking all over the forums for some good info on the poly mounts but only found bits and pieces, so I decided to create this post in the hopes that it will help some people.
First of all, I have a 99TA M6 and recently needed to replace the tranny mount. I decided to get a poly one, but was worried of the noise problems I've heard other people post about. I still have the rubber TA (torque arm) and rubber engine mounts. I'm going to be changing those soon and will report back if I feel it necessary.
Our cars use a standard GM tranny mount, nothing fancy or exotic. Your local parts store will try and tell you they don't stock the ones for our cars, but just ignore them and get the standard GM universal mount. I picked up an Energy Suspension unit from my local speed shop, part number 3.1108R for red and 3.1108G for black.
The basic installation is described here at the Install University.
I will fill you in on the specifics concerning the poly mounts. I can't speak specifically to the Prothane mounts as I haven't seen those. The Energy Suspension mounts will come with a metal bar called the preload spacer, 2 bolts and various washers. After looking at everything under the car I decided that the preload spacer bar is not needed, I also removed the 2 bumps that the spacer would have compressed. I just used a bench grinder to remove the raised bumps. It was quick and easy to do. All that I can see the bumps and preload spacer doing is compressing the polyurethane making it firmer and hence, more likely to transfer NVH (noise vibration harshness). The rubber mount had no preload on it and worked fine and the poly is so much more firmer and stronger that I see no reason to make it even more firmer. If anyone knows of a reason to use the preload spacer as is, let me know.
The other down side to using the preload spacer is that it will add height to the tranny mount. This will move the tranny higher and it could possibly come into contact with the floor board which will definetely create NVH. Even if the tranny doesn't touch the floorboard it does change the drivashaft angle slightly. Some people have said that the angle change can produce noise. I don't know, but it doesn't sound worth taking a chance on.
Now I believe the modded (no preload spacer, removed bumps) tranny mount is just about the same overall height as the factory mount which is good. If you find that your tranny is a little too high you can lower it by installing washers in between the trans crossmember and the car body. It's best to use large diameter, flat washers to help spread the load.
You can reuse the bolts that hold the mount to the tranny. For the mount to crossmember you can use one of the supplied bolts that come with the mount. You will use the center hole of course. I tightened everything up with red locktite just to make sure they don't vibrate loose.
Here are some pics to help describe what to grind off:
Once done, it will look like this:
______________________________________
Impressions:
Sound:
IF, IF I roll up the windows, turn off the radio, put AC fan on low I can hear a little more gear whine from inside the tranny. Under heavy acceleration I think there is more overall noise than with the rubber mount. I'm just guessing as I can't be sure. So basically there was almost no noise increase. Now if I roll the windows down, or turn on the radio, or open my exhaust cutout (exhaust was going through Magnaflow muffler during listening tests), or just turn the AC fan speed up I can't hear any increase in noise at all. So basically no noise increase in my case. Hip, hip, hooray!
Vibration:
Just cruising down the road I think I can feel a little more of the car. I can't say for sure. It's really a good feeling, nothing harsh. The car feels a little more solid.
Under heavy acceleration I can definately feel a little more vibration than before. Again, no big deal, it just feels more solid. It's so faint that I think I'm getting used to it already. So the vibration thing is practically a moot point. Hip, hip, hooray again!
Shifter Feel:
This was the big surprise (I have a Hurst Billet Pro). Previously I have been having a hard time getting nice smooth shifts all the time. Sometimes I'm in the zone and can be smooth, but other times I feel like I can't synch the engine to tranny worth a damn. I know I'm a good shifter, but I tend to shift quickly all the time. If I let the clutch out real slow the shifts get smooth, but who does that, right?
After the poly mount, my shifts have been smooth as glass. Both upshifting and heel/toe down shifting under braking. I mean the shifts feel so much better without all that slack that was in the driveline. This reason alone makes the swap worth it.
I'm so pissed that I didn't do this earlier. It wasn't me this whole time, it was the damn spongy mounts that were screwing up my shift feel. Sorry about the rant, but I have to vent.
Anyway, the shifter handle handle feels so much more solid in my hand and when shifting, it will only torque over a little and that's it. No more moving around. It feels solid and I have more confidence in my shifts. So hell yea, hip, hip hooray!
I couldn't be more pleased with this tranny mount change. I'm looking into swapping both the torque arm bushing and the motor mounts with poly as well.
If you have any questions, let me know.
Jason
