Difficulty: Intermediate | Time: 30 minutes active per mount + 24-72 hours cure | Applies to: 1982 to mid-1985 Porsche 944 (pre-85.5) and 1986-1988 Porsche 924S (same mount setup)
The early 944 and 924S use two rubber transmission mounts, one on each side of the transaxle. Porsche stopped making them, the NOS units left float around $250 each, and there's no proper aftermarket replacement for the dual-mount setup. The fix is to rebuild your existing mounts with polyurethane sealant. About half an hour of work per mount, materials from any hardware store, and the result holds up.
This procedure works whether the transaxle is out of the car or still in place. The photos here show the trans-out path. That's what we did, and most people end up doing this fix as part of a clutch or torque tube job anyway. Step 1 covers both ways.
What You're Replacing
Each mount is a rubber bushing seated in an L-shaped steel suspender bracket. Two mounts per car, plus two brackets. The brackets you're keeping; the rubber bushings you're rebuilding.
| Part Number | Description | Qty |
|---|---|---|
| 944 375 045 00 | Transmission mount (yellow paint mark) | 2 |
| 944 375 045 05 | Transmission mount (white paint mark, alternate) | 2 |
| 477 399 167 E | Suspender bracket, left | 1 |
| 477 399 168 E | Suspender bracket, right | 1 |
Failure shows up as rubber separating from the metal, oil contamination, visible cracking, or enough collapse that you can rock the transaxle side-to-side by hand. If you've broken CV joints more than once for no apparent reason, this is almost always the cause.
This is not the late-style mount (944 375 045 04, used 85.5 onward, including 944 Turbo, 944S, S2, and 968). That's a different part with different solutions.
What You'll Need
| Item | Notes |
|---|---|
| Polyurethane sealant | One caulk-gun cartridge of Sikaflex or similar. 10oz/300ml covers both mounts. Note: higher durometers will be a pour-based solution, not caulk gun tube. |
| Caulk gun | Standard, if using. |
| Masking tape | Enough to dam the openings on the underside of each mount. |
| Cardboard scrap | Backing surface during application and cure. |
| Brake cleaner or degreaser | Old mounts are oily. |
| Scuff pad or 80-grit sandpaper | Surface prep on the rubber. |
| Wire brush | Useful for the worst of it. |
| Sockets, 13mm and 17mm | Covers the mount and bracket fasteners. Long 3/8" extensions if doing this in-car. |
| Penetrating oil | The mount fasteners have been there a while. |
| Torque wrench | For reinstall. |
A Word on Durometer
This is the main decision you'll make. Shore A hardness (the "durometer") determines how much firmer the mount becomes:
- 60A. Closer to factory feel. Modest stiffness increase. Good choice for daily drivers, pampered weekend cars, and anyone keeping the rear seat and full carpet. You'll get rid of the slop without turning the cabin into a tin can. Caulk-gun polyurethane sealants live in the 40-55A range, which is close enough. That's what we used on this build (55A, because it was what we had on the shelf).
- 80A. The most commonly recommended durometer in the community. Significantly stiffer drivetrain, noticeably more vibration and noise transmitted into the cabin. A solid choice if you've already accepted some NVH (no rear seat, sport-mod interior, harder bushings elsewhere). Most 80A products are two-part pourable urethane. Different application process than the caulk-gun procedure below, so follow that product's instructions.
- 90A and up. Approaching solid-mount territory. Best for track cars or builds where shifter feel matters more than sound deadening.
Whatever you pick, more cars in the community run 80A than 60A, but the 60A crowd tends to be happier with their daily drivability. Pick based on how the car gets used, not how it makes you feel.
Fitment Notes
- Left and right brackets are different. Mark them when they come off.
- The 924S setup is identical. Same mounts, same brackets, same procedure.
- This does not fit anything later. 944 model year 85.5 onward, 944 Turbo, 944S, 944S2, and 968 all use a different design.
Step 1: Get the Mounts Off
With the transaxle out (what we did, what the photos show). The mounts are sitting right there on either side. One M10 bolt secures each mount stud to the transaxle bracket. Pull it to free the mount. Either separate the suspender bracket from the chassis or leave it; the rest of the work happens on the bench either way.
With the transaxle still in the car. You can get to the mounts through the rear wheel wells. No need to drop the trans just for this fix:
- Get the car in the air. Rear on jack stands, parking brake set, wheels chocked. You need real working room, and don't try this on ramps.
- Support the transaxle. Jack under the trans case with a block of wood to spread the load. Don't lift. Just take up the slack so the mounts aren't carrying weight when you start pulling fasteners. A transmission jack is better if you have one.
- Remove the rear wheels. With the wheels off, you've got direct access to the mount area through each wheel well.
- Pull the mounts. Penetrating oil on the fasteners first, give it a minute. Pull the M10 bolt at each mount with long 3/8" extensions through the wheel well; much easier than fitting a wrench in there. Then unbolt the suspender bracket from the chassis (M8s); usually easiest to pull the bracket and mount together and separate them on the bench. Pop the right-side fuel filter bracket if it's in the way (10mm, takes 30 seconds). Stiff aftermarket rear springs may not drop the right trailing arm enough for clearance; disconnecting the lower shock bolt buys the extra inch.
Step 2: Clean and Scuff
Forty years of road grime and oil weep will keep sealant from bonding. Don't skip this.
- Wire-brush off loose grime.
- Hit the rubber with brake cleaner. Multiple passes until rags come away clean. Let dry fully.
- Scuff every rubber surface that will see sealant. 80-grit paper or a coarse pad. You want matte, not glossy.
If chunks of rubber are falling out, dig those out so there's solid material left for the sealant to bond to.
Step 3: Mask
Run masking tape across the bottom face of the mount (the side that seats in the bracket recess) and over any holes or seams where you don't want sealant escaping. Most caulk-gun polyurethanes are thick enough that this is a much lighter-touch masking job than a pourable two-part urethane would need. You're sealing edges, not damming a liquid.
Set the mount on a piece of cardboard with the bottom face supported.
Step 4: Apply the Sealant
Cut the cartridge tip to a bead width slightly narrower than the gaps you're filling. Pierce the inner seal. Run a heavy bead into every void in the rubber and work it in with a gloved finger or the cut end of a popsicle stick. Push down. You want the sealant packed into the cavities, not floating on top. Overfill rather than underfill.
One 10oz cartridge does both mounts with leftovers. Working time before the surface skins over depends on the product. Check the tube before you start so you know how much pace to keep.
Step 5: Cure
Most caulk-gun polyurethane sealants are moisture-cure: they set up from the outside in. Typical timing is touch-dry in a few hours, surface-cured by the next day, and fully cured at 3-7 days depending on temperature and humidity. Your product's tube has the specifics. Read it.
Don't reinstall before full cure. The middle of a thick section can stay soft well after the surface feels solid. If your application is deep in spots, err on the longer side of whatever cure time the manufacturer lists.
A Word on the Cosmetic Outcome
The cured result is not pretty. The sealant sets up matte black with whatever ridged, stringy texture it picked up coming out of the caulk gun and being pushed around. It does not look like a finished OEM part.
This is fine. The mount is doing structural work, not styling work, and once the trans is back in the car nobody sees it again. Don't waste time trying to smooth it out. You won't improve the function and you'll just frustrate yourself.
Step 6: Reinstall
Bolt the mount back into the suspender bracket if you separated them, then bolt the bracket back to the chassis. Reasonable torques for the fasteners involved:
| Fastener | Torque |
|---|---|
| M8 bracket-to-chassis (8.8 grade) | 18-22 ft-lb (25-30 Nm) |
| M10 mount-to-trans bolt (8.8 grade) | 35-40 ft-lb (47-54 Nm) |
These are conservative starting points for the bolt sizes. If your workshop manual has a specific factory spec, use that instead.
Troubleshooting
Sealant didn't fully cure in a deep section. Moisture-cure products struggle with thick pours. The middle takes a long time to get exposed to enough humidity. Give it up to two weeks. If a section stays gummy indefinitely, dig it out and re-apply in thinner layers.
The fill pulled away from the rubber in one spot. Prep issue. That area didn't get degreased or scuffed properly. Dig out the loose piece, prep the local area, and patch.
One mount went in fine, the other was a fight. Brackets are L/R-specific and not interchangeable. If you've got the wrong one on the wrong side, that's why.
Vibration after reinstall. Some increase is expected. Even at the softer end of the durometer range you'll feel it. Significant new vibration usually means a CV joint that was damaged from years of running on dead mounts and is now showing itself. Inspect the joints.
Wrap-Up
Once the trans is back together, you should notice a tighter drivetrain immediately: crisper shifts, no transaxle wander, no more CV-joint death spiral.
If you did this with the trans out, take ten minutes while you're in there to look at the shift linkage. The rod ends and bushings in the early 944 shifter wear out and contribute to the "loose shifter feel" that often gets blamed on the trans mounts. If yours feels sloppy, refresh it now. It's also the easiest moment you'll ever have to install a short shifter if that's on your list.
Got questions? Tag us on socials or hit us at info@treedylabs.com. Show us the build when it's done. We actually want to see it.