chaoscreature

Over the course of Friday night, Saturday and Sunday I made and installed transmission mounts in my car without removing the engine or transmission. In hindsight I am not sure if I would have taken on this projct had I known how difficult it would be.
There are some things that I probably could have done to make things easier on myself but I was trying to get everything done in time because I needed the car finished by tonight and I had no idea how long the machining would take.

First things first, jack up the car high enough so you can crawl around underneath and have enough room to lie on your side and twist around.
Next remove everything that is in the way, mainly the plastic and metal protective panels. I also removed the shift linkage going from the transmission to the shifter mechanism. This was to gain access to the bolts holding the metal tube transmission mount braces.

Next I removed the small rubber dog-bone transmission mount. The inner mount is pretty ingenious, little metal bits in there allow for side to side movement and rotation but very little fore-aft movement. I am still not entirely sure why this mount was needed, my guess was it was an afterthought.
After the rubber mount is removed you can place a jack-stand or a jack underneath the transmission. I used both because I don't trust my hydraulic devices to hold overnight. The transmission mount crossmember is pretty straightforward except for one stubborn bolt. I started by unbolting the tubular front pieces and the long 12mm bolt that goes through the transmission mount, but I couldn't drop one of the tubular supports out because the 12mm bolt was held captive by the trasmission. A sawzall freed everything up but obviously I got a little nervous about my ability to get everything done over the weekend when 2 hours into the job I had a saw out. Once the 12mm bolt was cut in half I had plenty of room to get the other half out and finally free the other tubular support.

Next I dropped the rest of the crossmember and got to removing the transmission mount. I got frustrated at first because I had the bolt in backwards through the removal tool. I foresaw getting the bolt stuck and not being able to add the second "cup" to the tool. The tool worked very well. The mount was in there pretty tight but I put some muscle into it and I heard a Pop and it started to come out. Halfway throgh you need to stop, disassembly the tool, install the second cup to the mount and then keep wrenching the mount out.
CupCar, thank you for making such an awesome tool and lending it to me!

Once the mount was out I took some more measurements and got to work on the second set of transmission mounts (I botched up the first set...). The TurboKraft mount installation should be very much the same as mine. You just pound in one side, then install the other side by tightening the bolts that go through it. The crossmember went back in with a little bit of pounding (the rubber mounts had some pre-load built in). This should have been pretty straightforward but I ended up installing and reinstalling everything two times because I kept missing stuff, like the tubular suport bars, or a washer or...

In the end I think the new mount is going to be perfect. I was concered that the poly bushes wuould be too stiff but I think they will have just enough compliance to absorb some vibration but still keep things in place. I also took a picture of my rod end shift linkage. I did this about 3 months ago, it made the shifting better but I am hoping the stiffer trans mount will make it perfect. I will give a report in a few days on how things worked out.

chaoscreature

More pics.

chaoscreature

I was aked why I had to cut the bolt.
There was a clearance issue and I could not get the bolt to come all the way out without cutting it. I tried pushing the transmission to the side as far as possible and the botl would just run into the transmission tunnel.
There is more room on the passenger side of the transmission. Had the factory installed the bolt on that side I would have been able to get it out. Notice the bolt heads are always on the passenger side when I use the tool for the same reason, I just couldn't wedge the bolt in from the other side. I was leary to drop the engine mounts OR use much force to twist the transmission for fear of damaging something. I did my best to feel around for stuff that was getting pinched or pulled, but I was being very cautious.

chaoscreature

Just an update.
I drove the car about today and the feeling is about what I was expecting. There is a slight vibration that you can feel in the pedals mostly when you first start engaging the clutch but it goes away for the most parts once you start driving. The shifting feel is much crisper now, the shift lever itself is rock solid and the feeling is more precise than it used to be, even though I had the heim joint linkage for a while now. I love it, but I know my wife is going to complain about the vibration next time she rides in the car. I kept my original mount just in case though!

Jeff96-993

I'm next, will use all your good instructions to get this done. I'm installing an RS mount, not quite as nice as the one you designed, but hopefully as effective

chaoscreature

I attended a DE event at the Pomona Fairplex yesterday and I thought I would post my thoughts on the new transmission mounts. I am very pleased with them. Between the new transmission linkage and the stiffer mounts the shift feel is greatly improved in the car. The whole chassis feels stiffer as well, not just the shifting... I am not sure how... maybe its because before i had stiff motor mounts so the engine/trans assembly was pivoting around behind me and now it stays put?

I would not recommend this for people who like to listen to their radios and enjoy a quiet ride though. You hear everything, every correct shift and you hear a satisfying "click-click", and you can hear the gears whirring around especially in 1st and 2nd.

trophy

Greta write up, and nice job on your fabrication.......

Jeff96-993

Finally got a chance to use Cupcar's handy dandy tool, and followed Peter's instructions above. Mount came right out, no problem. Have decided to go to a solid mount, and am waiting for the Wevo tranny mount to arrive.

Only thing I did different from above, I didn't have to cut the bolt to remove it. I removed the cross brace that holds the transmission cover, and then lowered the nose of the tranny some. There's enough flexibility in the mount that it's possible to pull down on the bolt and get some angle on it. Once it's angled a bit it clears the body and brake/clutch lines that are in the way. Luckily my son was helping, so one could do the jack and the other could keep an eye on that bolt. We didn't want to risk lowering the nose any more than necessary.

Jeff96-993

Another update. it's done, Wevo solid mount installed. A couple of secrets we employed to do it:

1) Follow chaoscreatures instructions
2) Use Cupcars removal tool
3) When you get to reinstall, put the solid aluminum mount in the freezer for a few hours.
4) When you get to reinstall, loosen the subframe mounts. and loosen the forward mounts the most.
5) Put protective supporting under the subframe since you'll have the mounts to about their last thread before you can sneak the bolt through.
6) Put the bolt through on the passenger side... there's more room, as chaoscreature mentioned.
7) Use a helper... if the subframe drops, you're hoping the protective supporting catches it... we had to go to the last thread before the bolt snaked through.
8) Use a helper... if you guessed wrong on which bolt thread was the last one, you're still alive.
9) Once the bolt snakes through, you're good. bolt it all back, you're done with the hard part.

chaoscreature

Jeff,
You went with totally solid mounts? I am curious about the noise transmittance.
Post your thoughts when you are done. I hope CupCar will allow the tool to stay in circulation, but I completely understand if he wants it back too. If he needs the tool back I will have a new one made.
Congrats on the install!

- Peter

Jeff96-993

Hi Peter, the test drive is today. I also installed solid subframe mounts too. I'll let you know what I think of the combination, and what the missus thinks of it, after that.

I was amazed at the amount of flexibility in the subframe bushes. When we were doing the tranny mount removal you could push/pull the nose of the tranny quite easily in any direction you wanted. After the solid subframe mounts, the nose didn't move noticeably.

And I installed an RS shifter with solid front bar from FDMotorsports. Testing everything should make for a fun drive today.

osugasman

Any way to tell when your tranny mounts are going bad?

Jeff96-993

The stock tranny mount I removed looked like new, so for me it wasn't a matter of it going bad, it was a matter of it sucking to start with. I can understand why they'd use a rubber mount for NVH issues, but since I don't consider the 993 a luxury car, it was an easy trade.

With a solid mount, there's a bunch of difference. I think I can feel each cylinder firing.

osugasman

Any write up for this on the AWD versions? I couldn't find an RS or Wevo version for the AWD car transmission mounts, only the motor mounts. Would folks just replace with the originals?

chaoscreature

Osugasman,

I am going to be helping another Rennlister develop a C4 semi-solid mount which will be similiar to the one I mounted on my car.
I will start a new thread once I get the ball rolling on that project.

I think the swap is pretty straightforward. The main mount is held onto the transmission by three small bolts and the one large bolt. You press the old mount out and press a new one back in.