Rear transmission mounts: SOLVED

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Martin Benade
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Rear transmission mounts: SOLVED

#1 Post by Martin Benade » Tue Jul 05, 2022 8:16 pm

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.
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Jim Liberty
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Re: Rear transmission mounts

#2 Post by Jim Liberty » Tue Jul 05, 2022 8:23 pm

Like you it seems counterintuitive. Does the rubber seal in the engine compartment seem lower. ........Jim.
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Martin Benade
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Re: Rear transmission mounts

#3 Post by Martin Benade » Tue Jul 05, 2022 8:30 pm

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.
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Re: Rear transmission mounts

#4 Post by John Brooks » Tue Jul 05, 2022 8:47 pm

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.
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Re: Rear transmission mounts

#5 Post by Mike Wilson » Tue Jul 05, 2022 9:06 pm

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.

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Re: Rear transmission mounts

#6 Post by John Brooks » Tue Jul 05, 2022 9:16 pm

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.
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Martin Benade
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Re: Rear transmission mounts

#7 Post by Martin Benade » Tue Jul 05, 2022 9:21 pm

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.
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Re: Rear transmission mounts

#8 Post by Mike Wilson » Tue Jul 05, 2022 9:33 pm

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

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Re: Rear transmission mounts

#9 Post by Vic Skirmants » Tue Jul 05, 2022 9:44 pm

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

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Re: Rear transmission mounts

#10 Post by Dick Weiss » Tue Jul 05, 2022 9:55 pm

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!

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Re: Rear transmission mounts

#11 Post by Martin Benade » Tue Jul 05, 2022 9:57 pm

My new mounts are clearly thicker than the oil soaked ones I removed, but somehow I now have less ground clearance. Makes no sense.
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Re: Rear transmission mounts

#12 Post by Daryl Bertram » Tue Jul 05, 2022 10:45 pm

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.

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Re: Rear transmission mounts

#13 Post by Martin Benade » Wed Jul 06, 2022 12:35 am

The only changes are a slightly heavier crank and flywheel, I’d guess 10 lbs
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Re: Rear transmission mounts

#14 Post by Harlan Halsey » Wed Jul 06, 2022 5:08 am

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.

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Re: Rear transmission mounts

#15 Post by Vic Skirmants » Wed Jul 06, 2022 7:29 am

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.

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