Mrmerlin

My suggestion on MFG process ,
if your going for the exact fit protocol,
I would make the mount with it in a slightly loaded configuration.
IE the top and bottom would be closer together with less Urethane

NOTE if the mounts are tall like the factory new mounts are before fitting then they might be too tall,
this can lift the trans/TT and exhaust up farther than it was designed for.
NOTE fitting new Volvo mounts and lifted trans mounts could see these clearance issues happening.
Though a proper test fitting on a few cars would answer these questions

The parts you make should be made to look like a new loaded mount looks.

I find that just about every car I am inspecting is in need of new trans mounts, so its a viable operation if your going to go forward

Waldo928

Why the loaded (compressed) configuration? Because a solid mount won't settle as much as the stock mount with the space?

bureau13

Oooh, if this is to become a product, I'm in. I'm sure I need them. They can sit in the box next to my motor mounts that I haven't worked up enough courage to try to change...

Mrmerlin

well based on your report the mount your making is pretty much going to maintain its position.

A new factory mount will compress a bit to a running loaded condition, this is what I would aim for .

If the trans is lifted higher than it was designed for and then new motor mounts are also fitted and these also might be a bit higher than the originals,
then the drive line system could contact other chassis parts.
Remember the engine and trans are connected via the TT this also means the exhaust system is connected as well ,
raising the drive line will push the shifter higher in the 5 speed cars and compress the foam padding into the chassis,
this might be a good thing for the foam as it will offer a better seal.

The other thing to consider is that the exhaust system can also contact chassis parts like heat shields ,
the trans fluid lines will also be raised not much,
but careful inspection should be done to insure no running issues exist.

I want to try a few sets of these to see how the NVH shakes out.

The new factory mounts have gotten pretty expensive

Waldo928

I see what you are saying. Even though these are solid they do compress a little when they are installed. These are not like other solid (harder) racing mounts. When I was installing them I had to raise and lower the transmission several times to get the correct thickness measurement for the shims. I could visibly see the urethane compressing when I let the weight of the transmission rest on them. Maybe that is why I am not getting any adverse vibration even though they are solid. The urethane is pretty rubbery. When I get the stock mount I will compare the heights to see what the difference is. I'd be willing to make up different configurations for you to try out (solid Gen I, solid Gen II (factory height), Gen II with cutout, etc). I just don't have the time in my schedule to do all that performance evaluation, but if you want to I'll certainly entertain making several iterations.

dr bob

Stan --

I think the only place the exhaust connects with the driveline is at the header/manifold flanges, so the trans mount height is not an issue. If anything, having the trans at the correct height (vs sagged) the torque tube will have a little more clearance to the heat shields.

The running position with the factory mounts includes pretty much imperceptible compression of the rubber. In the factory design, the loading is a combination of compression and shear. In the subject rebuilt mounts, the shear component is all but absent due to the filled cavity at the top. Perhaps the easiest thing to do is measure the height of the gearbox from the crossmember with new mounts (I can get that sometime before New Years 2019 at the rate I'm going on car projects...) and compare with the same measurement with the OP's rebuilt mounts.

I wouldn't hesitate to use the OP's design to replace collapsed mounts. I made the executive decision to swap in the new factory mounts I'd already purchased, and found the isolation a bit better than either the cavity-filled-with-hose or rebuilt-with-urethane options I tried. It's easy enough for me to drill out some of the urethane in my own "rebuilds" to compare the isolation. But the car is hibernating and no test driving until spring, so that doesn't do much for this immediate cause.

Mrmerlin

FWIW some cars have an exhaust mount tied to the center of the TT this is just aft of the cat clamps ,
I find more than a few cars require the bending of the heat shields after fitting Volvo mounts,
not much but this is a needed operation.
I guess there is enough give in the exhaust system to have the rear higher

Mrmerlin

I am working on a good way to remove the old rubber from the old mounts I have been saving so far it looks like a sawsall might do the trick.

dr bob

Stan--

That's about what I used. Followed by a wire wheel then 40 grit flap disk in the angle grinder. The spacing and orientation between the two metal sections is critical -- measure a new mount carefully for correct height. The X-Y orientation maintains correct failure-mode positioning as well as the no-lateral-load bolt-up. Hence my high-tech routed-in-a-2x4 positioning jig.

Captain_Slow

Matt -
I'm up in Leesburg area. After replacing motor mounts with slightly taller Volvo mounts I noticed the clunk of the trans case on the cross member during hard acceleration while turing right. The Volvo mounts raise the engine a bit, so the trans went down a bit. Wanting to level the drivetrain I bought new Porsche trans mounts. Installation wasn't very difficult, but this is a challenge that seems to vary from one car to the next. I'm planning to put my 928 up on LiftBars in about a week so I can pull the front bumper cover for prepping and painting. If we have some nice weather coming I'll keep it on the ground and make a run down to your place to check out this great project. This is one of those things that seems well over due. Nice going making such a contribution to the 928 community.

Wisconsin Joe

Random thought:

Stan works on a lot of these cars, likely has one with reasonably new trans mounts on it that he will be under sometime soon.

Stan, can you find the "loaded height" of new(ish) mounts? And the difference between loaded and unloaded heights?

This project has a lot of appeal to me. I know my mounts are older and have to be at least somewhat squashed. But I don't know how much.

So finding out how much they are squashed and having proper measurements to reman them is very interesting to me.

I'd likely "borrow" the technique and materials list, and owe the OP a beer or something for passing on the info.

Imo000

Tried burning it off?

Mrmerlin

burning will melt the abrasion pad on the lower section

Waldo928

Stan,
I did burn mine to clean them off after removing the abrasion pad. I replicated the pad with solid urethane. I don't know how important it is that the face of the pad be nylon. If it is critical I can always cut a piece of flat nylon and put it into my mold so the new pad will have the same characteristics. Now I'll just have to find a source of 1/8" flat nylon. I stripped two more sets of mounts yesterday so I'll look to incorporate this change on my next set of pours. Since there seems to be interest in people knowing my method I will likely video the whole process and post to Youtube to save myself typing. But to be honest, for one set of mounts the juice isn't worth the squeeze. The only reason I did it was because I had three cars that needed mounts.

the flyin' scotsman

Im dropping the S4 trans this winter for the TT rebuild; very interested in having the mounts rebuilt