Rear transmission mounts: SOLVED

356 Porsche-related discussions and questions.
Message
Author
User avatar
Martin Benade
356 Fan
Posts: 12179
Joined: Wed Nov 23, 2011 10:52 am
Location: Cleveland, Ohio

Rear transmission mounts: SOLVED

#1 Post by Martin Benade »

I just replaced my rear mounts, and now the muffler hits the ground when I back out of my steep driveway. For the last 15 years it only hit if I went faster than a creep. It seems like new mounts which raised the bell housing 6-8 mm should only have improved my situation- either by raising the engine a touch, or by raising the inner ends of the axles should raise the car a very tiny amount. Does anyone have a different explanation that places the muffler lower? And any recommendations for a good paving company in Cleveland Ohio?
Last edited by Martin Benade on Wed Jul 06, 2022 10:46 pm, edited 1 time in total.
Cleveland Ohio
62 Cabriolet
56 VW
02 IS 300
04 Sienna

User avatar
Jim Liberty
356 Registry Member
Posts: 4312
Joined: Tue May 06, 2008 3:47 pm
Tag: Jim
Location: Orange Co., CA
Contact:

Re: Rear transmission mounts

#2 Post by Jim Liberty »

Like you it seems counterintuitive. Does the rubber seal in the engine compartment seem lower. ........Jim.
Jim Liberty

User avatar
Martin Benade
356 Fan
Posts: 12179
Joined: Wed Nov 23, 2011 10:52 am
Location: Cleveland, Ohio

Re: Rear transmission mounts

#3 Post by Martin Benade »

Not sure because my rear shelf has been kind of a mess for the last forty years. I just took it apart, straightened the pieces, and welded it back in.
Cleveland Ohio
62 Cabriolet
56 VW
02 IS 300
04 Sienna

User avatar
John Brooks
356 Fan
Posts: 2146
Joined: Tue Jul 08, 2008 11:50 am
Location: Whidbey Island WA.
Contact:

Re: Rear transmission mounts

#4 Post by John Brooks »

It’s a little Nose High at the mounts. Loosen the bolts, lift the rear of the engine, so it pivots a little in the hoop. Then tighten the front bolts with the rear lifted.
John Brooks

62 Roadster
66 912
84 Cab
getting pushed around in porsches since 1965

User avatar
Mike Wilson
Classifieds Monitor
Posts: 11490
Joined: Tue Apr 15, 2008 4:37 pm
Location: SW Los Angeles

Re: Rear transmission mounts

#5 Post by Mike Wilson »

John, by doing so are there any requirements to readjust the suspension? I 'm thinking that now only can the engine be adjusted to address Martin's issye but also adjust the engine tin to tray fit.

Mike
Mike Wilson
Lomita, CA
'63 B coupe

User avatar
John Brooks
356 Fan
Posts: 2146
Joined: Tue Jul 08, 2008 11:50 am
Location: Whidbey Island WA.
Contact:

Re: Rear transmission mounts

#6 Post by John Brooks »

Mike. No the axel has a pivots at the trans. It’s the angle of the trans from the front mount to the hoop. The nose is a little high in the front. That drops the back of the engine. It’s not too hard to adjust. It’s been a long time since I was under there but I think there is 10-12mm to play to adjust in the front mount.
John Brooks

62 Roadster
66 912
84 Cab
getting pushed around in porsches since 1965

User avatar
Martin Benade
356 Fan
Posts: 12179
Joined: Wed Nov 23, 2011 10:52 am
Location: Cleveland, Ohio

Re: Rear transmission mounts

#7 Post by Martin Benade »

John, besides shimming aren’t the front mounts non adjustable? I didn’t touch them when I did the rear mounts, and if they are too high now they would have been even more so before with the old mounts.
You mean the bolt holes have that much play? Does the service manual cover this?
It kills me to scrape my fairly fresh Leistritz, especially now that I repainted it.
Cleveland Ohio
62 Cabriolet
56 VW
02 IS 300
04 Sienna

User avatar
Mike Wilson
Classifieds Monitor
Posts: 11490
Joined: Tue Apr 15, 2008 4:37 pm
Location: SW Los Angeles

Re: Rear transmission mounts

#8 Post by Mike Wilson »

Thanks, John. I'll give it a try.

Mike
Mike Wilson
Lomita, CA
'63 B coupe

User avatar
Vic Skirmants
Registry Hall of Fame
Posts: 9278
Joined: Tue Oct 27, 2009 5:02 pm
Location: SE Michigan
Contact:

Re: Rear transmission mounts

#9 Post by Vic Skirmants »

John Brooks wrote: "I think there is 10-12mm to play to adjust in the front mount"
I don't think so!

Dick Weiss
356 Fan
Posts: 4181
Joined: Sun Apr 20, 2008 12:54 am

Re: Rear transmission mounts

#10 Post by Dick Weiss »

Years ago, aftermarket rear mounts were somewhat thinner w/the rubber + both sides of the metal bonding
being less than 30mm overall thickness which allowed the engine to be lower when bolted up.
Also, when the rubber gets wet w/oil leakage from the bell housing/transmission shaft and flywheel seals,
the rubber will get squashed and the engine will sit lower. I can't imagine new mounts would be as thin
as bad ones unless they were made somewhere like India; etc. Ollies had them, but they were returned!

User avatar
Martin Benade
356 Fan
Posts: 12179
Joined: Wed Nov 23, 2011 10:52 am
Location: Cleveland, Ohio

Re: Rear transmission mounts

#11 Post by Martin Benade »

My new mounts are clearly thicker than the oil soaked ones I removed, but somehow I now have less ground clearance. Makes no sense.
Cleveland Ohio
62 Cabriolet
56 VW
02 IS 300
04 Sienna

User avatar
Daryl Bertram
356 Fan
Posts: 244
Joined: Fri Oct 07, 2011 11:54 pm
Location: San Diego, Ca

Re: Rear transmission mounts

#12 Post by Daryl Bertram »

OK don't laugh at me with this thought: new tires different diameter while doing the trans mounts? Lower tire pressure after then before? Deep thoughts by Jack Handy lol.

User avatar
Martin Benade
356 Fan
Posts: 12179
Joined: Wed Nov 23, 2011 10:52 am
Location: Cleveland, Ohio

Re: Rear transmission mounts

#13 Post by Martin Benade »

The only changes are a slightly heavier crank and flywheel, I’d guess 10 lbs
Cleveland Ohio
62 Cabriolet
56 VW
02 IS 300
04 Sienna

User avatar
Harlan Halsey
356 Fan
Posts: 2339
Joined: Fri Mar 02, 2012 2:05 pm
Location: No Cal SF Peninsula

Re: Rear transmission mounts

#14 Post by Harlan Halsey »

Think about it this way: The only way the muffler ground clearance can change is if the angle of the transmission/engine unit changes or the height of the unit changes. The height is determined by the axle angle, the ride height. If the ride height determined by the torsion bars is unchanged then the angle has to change. There's no adjustment at the front to speak of but if the rubber mounts were asymmetric and they were not replaced exactly as they were there could be a very small angle change. If the thickness of the new hoop mounts were different that would cause an angle change. If the hoop were riding on the mounting bolts rather than on the bosses that would cause an angle change. That's about it. The muffler to hoop distance is greater than the hoop to nose mount distance so changes in the mounts resulting in angle changes will be amplified at the muffler.

User avatar
Vic Skirmants
Registry Hall of Fame
Posts: 9278
Joined: Tue Oct 27, 2009 5:02 pm
Location: SE Michigan
Contact:

Re: Rear transmission mounts

#15 Post by Vic Skirmants »

Harlan wrote " If the hoop were riding on the mounting bolts rather than on the bosses that would cause an angle change."
Bingo! Definitely something to check.

Post Reply