Sam Buchanan

Here's the one I have:

Per the schematic the start button isn't hot until the ignition switch is turned on. It's wired into the same circuit as the fuel gauge. This is the way my P15 is wired, starter pushbutton is dead until ignition switch is turned on.

Drilling the holes is a reasonable idea. Now......who wants to do the prototype work (buying several sets and removing and reinstalling the transmission several times for road tests until the right combination of holes is found)? I'm convinced an undesirable spec is being used to manufacture our mounts. That spec may work ok in other applications.

https://www.jegs.com/i/Champion-Cooling-Systems/166/CC4749/10002/-1

Wow.....this is discouraging. But you are committed now and I'm confident you will eventually make it work. I may just tolerate the small leak between manifolds for a while. On a brighter note, the new battery cables are a great upgrade, hots starts are no longer reason for concern. Thanks for the tip!

Excellent! Glad the thread was helpful for you. Wish my car was as clean firewall-forward as yours.

Frank, definitely not a purist, my car has been modified to make it as reliable as I can (electric fuel pump, alternator, etc) because its purpose is to be driven. Just got back from the 22 mile trip to the airport. The mounts are a closed chapter as far I am concerned......I ain't pulling that transmission again anytime soon! The purpose of this thread is to inform those who are yet to consider changing mounts and let them know there are things to consider. I close my part of this thread with the following scan from the Service Manual: The mounts I have don't have a white stripe......and they sure aren't pliable........but......they do transmit vibration.......

Frank, the new mounts have restored the angle to what it should be with new mounts...... I'm a bit perplexed as to why there seems to be a resistance by folks accepting......that these mounts are just too firm.....simple as that. Softer mounts (lower modulus of elasticity) wouldn't ride lower, they would just absorb vibration instead of transmitting it. But I do appreciate the efforts to find a smoking gun.

I've looked for any places where exhaust or drivetrain could be touching the car. Keep in mind the ONLY thing that changed other than the mounts is the bellhousing is riding maybe 3/8" higher than before (probably where it would have been with the mounts it came with out the factory). The driveshaft is not a problem--at 45mph I disengaged the clutch, allowed the engine to go to idle, and the vibes went away even though road speed hadn't changed. That eliminates the driveshaft. Getting Ole Bessy started and feeling under the car (nawww...don't think I'll be doing that!) won't do any good, I've reduced the vibes except in mid-rpm range by removing all compression of the mounts. Please keep in mind this engine ran VERY smoothly with the old mounts, never noticed any issues until the mounts were changed. Lots of ideas have been presented as to what is now wrong (driveshaft, damper, interference) but EVERYTHING points to the new rear mounts being too hard. I looked at the front mount and it still has rubber in place (but why would that have changed overnight when the rear mounts were changed??). A very experienced member of the forum has stated that there are new mounts out there that are too firm. I'm convinced I got a set of them. I'll drive the car as is and don't intend to mess with this any more unless someone finds mounts that are soft enough to convince me to pull the transmission again. All the suggestions and feedback is certainly appreciated even though the root issue still exists. One bright spot is the transmission leak that started this whole process is FIXED.

Just got off the phone with Berbaum, was told the mounts I received were from stock they received about a year and a half ago. I asked if they had gotten any feedback about too-firm mounts or if any other mounts were available and the answer to both inquiries was "No".

Joe, I think by having the bolts loose enough to not compress the mounts I've accomplished pretty much the same thing as leaving out the bottom mount. But it might be worth a try.

Those mounts "look" identical to what I have and to all the other mounts I found. Steele's revulcanization service is the only exception I've seen. Compare the bottom mount to what is in the Service Manual illustration.....it ain't the same. But they should work fine with a longer bolt if they are soft enough.

@Dodgeb4ya stated the following in posts in a different thread: "Some new replacement mounts have rubber that's way too hard. Will cause vibration." "The rubber should be soft enough to push a thumbnail into it." The mounts I installed are much firmer than that. I think it is obvious that the mounts are just too hard.

The diagram does not match the mounts that are sold for our application. The tube is not long enough to extend all the way through the thick bottom mount. Tightening the bolt compresses the mounts and makes them "harder". I have the bolt set now so the mounts aren't compressed. Yes, the mounts now available appear to be different from what was originally installed. The photo Don posted is what is now shipped if you order mounts from any of the sources I found. Compare the bottom mount with the one in the manual illustration and you will see it is very different. The education continues. ?

Looks very similar to what I installed. I had to use a 4" bolt instead of the shorter one that was removed. There was no bottom mount, I assumed it had deteriorated to the point it had fallen out. But maybe it never was there since the old bolt was shorter?? The illustration in the manual doesn't show a "thick" bottom mount.

Interesting thought. The front mount has not been changed. But not the driveshaft, can depress clutch at speed and vibration goes away as engine rpm decays.

Were they soft enough??????? ?

No stripes. Interestingly, the mounts I have and all the ones I've seen listed in ads except for Steeles, don't match the illustrations in the manual (which I now have memorized...). The bottom mounts are so much larger than the ones in the manual that I had to use longer bolts. I'm wondering if whoever makes these mounts is shipping combinations of mounts that are different than they were in the original installation. Or maybe the illustration in the manual is for a different installation than the '48? I've learned (?) far more about engine mounts than I ever wanted to know...... ?

I haven't seen any hardness info in any of the listings. All the ads I've seen except Steele look like the same mounts. Inconsistency batch-to-batch would make this a real crap shoot....

I don't have any reason to think these are NOS, they looked very fresh to me, were not in any marked packaging. Price was about the same as other sources I checked, just figured AB would be more likely to sell more of them and not have any problems. But...... I have not contacted any other vendors....yet. Just looked at Steele, they only offer revulcanization service for the upper mounts. Not sure what you use for the lowers....or if you even use a lower, maybe just the big washer.....I'm kinda confused on this.

Andy, I have not, and I don't have any interest in throwing a vendor under the bus. This entire situation is still unfolding for me and my learning curve is steep. I didn't realize there were issues with some mounts until two days ago (had never purchased or installed old Mopar mounts) so I'm still in the process of evaluating my options. There are Mopar guys on the forum with far deeper background on this matter than I and I'm waiting to see what alternatives are available for those who need engine mounts. For some reason there doesn't appear to be much firm info bubbling to the surface, folks are laying low. I don't know how many manufacturers of mounts there are and how many of the mounts seen on various ads are coming from the same sources. Without definitive details I'm kinda in the dark. But I will contact AB soon.

Joe, I'll check out the bushings....did you find them at a local store (I haven't searched yet)? The new mounts did eliminate most of the clutch chatter.....now it just vibrates......

I relieved the torque on the bolts to the point where the washers on the bottom are just barely captured and the ride isn't too bad. Still enough vibes to feel but not enough to keep me from driving and enjoying the car. But, yes, buy soft mounts if you can find them....and let us know!

The information in this thread is scattered over multiple threads with unrelated titles. For archiving purposes the info is condensed in this thread so future owners can more easily find it. The rear engine mounts in my '48 P15 were totally shot so I ordered new ones from Andy Bernbaum. They arrived promptly and looked like the mounts I've seen advertised from other vendors. The lower mount was thicker than my old set so longer, 4-inch bolts were necessary to install the mounts. The engine could be jacked up sufficiently to insert the upper mount into the frame crossmember. I noticed the new mounts were quite hard....it wasn't possible to press a thumbnail into the material. I pulled the bolts up snug and everything looked as it should. As soon as the engine fired for the first test drive it was obvious a large amount of vibration was being transmitted into the car. Matter of fact, it was really unpleasant. After the first test drive I backed off the torque on the bolts and tested again. Significant vibration was still present, especially around 40mph in third gear. The engine smoothed out at higher speed. I have changed to nyloc nuts on the bolts so they can be torqued only enough to hold the mounts and lower washers in place. There is still more vibration that I like....but it seems obvious these mounts are made out of a material that is much firmer than needed. The reason for this thread is to caution owners that hard mounts are out there.....and you don't want them! Posts on the forum have indicated that softer mounts are available and if anyone knows a source for softer mounts it would be greatly appreciated if that info could be provided. This is another case of replacing worn-out parts but ending up with a situation that is not what we expected.....old cars can be a character-building process..... UPDATE; See post #54 for the remedy to the harsh mounts....the lower mounts were the problem.

After a few short test trips around town it appears the transmission leak is fixed. I think the key was getting the bearing retainer sealed so it will drain oil back into the transmission instead of on the shop floor.