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Discussion Starter #1
I have owned my 87 Graduate for about 5 years and have been plagued by the thumping while starting off in 1st gear. After replacing the transmission mout bushing, the carrier bearing rubber, the bushings in the rear trunion(?), the guibo(?) and reading numerous posts from other BB members with the same problem I decided to try something a little different. I removed the plate spanning the frame rails that the transmission mount bushing attaches to. I then completely filled the voids in the bushing with silicone caulk. Put it in from both sides to make sure it was filled. Let it cure for a day and then re-installed the mounting support. I realize this is probably a temporary solution but was just trying to see if it made a difference. It has been 2 months now and not a single thump. Taking off straight ahead, turning left or right, lots of throttle or just a slow rolling start, not one thump. I have not tried a 4 grand and dump the clutch start and am not planning to, but in all other instances the thumping is gone.
 

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But Mad North-Northwest
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Interesting. I've had that thump for ten years, even after replacing all the driveshaft bits as they wore out.

No issues with vibration? They sell a poly reinforcing insert for that bushing, but reports are that it causes nasty vibration problems.
 

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Discussion Starter #3
No bad vibes

Tom,
No noticeable vibration at any speed in any gear, just the absence of the thump on start. Even the better half noticed.
 

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You can buy a heavy duty transmission mount from Centerline. I have one in my Spider.
 

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But Mad North-Northwest
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I'll probably just try putting a piece of hose in the opening of the stock one. Same effect but less work.
 

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You can buy a heavy duty transmission mount from Centerline. I have one in my Spider.
Ed, I need to replace the transmission mount on my car and was hesitating between the original mount and the heavy duty one. The heavy duty bushing looks much more durable but I am a little afraid of vibrations etc compared to the standard one. I drive my Spider fairly hard but no track days for me.

Opinions?
 

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Hi Marc,
I aligned my drive shaft at the same time that I replaced the mount. I posted about it. I had to lower the center support a little to make the U-joint angles equal. The drive shaft seems to be a bit smoother now than it was with the weaker bushing.
 

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Hi Marc,
I aligned my drive shaft at the same time that I replaced the mount. I posted about it. I had to lower the center support a little to make the U-joint angles equal. The drive shaft seems to be a bit smoother now than it was with the weaker bushing.
Hummm, thanks for that Ed. This is a project for next spring so plenty of time to weight the pros and cons. I will track down your post when the time comes.

Cheers,

Marc
 

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Hosob,

You did not mention engine mounts.

Could they be weak links in the drivetrain whose failure has overwhelmed even a new tranny mount and your silicon fix simply papered over the problem?

All the best.
 

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Discussion Starter #11
Engine mounts

No, I replaced the engine mounts about 3 years ago after reading dire warnings on this bb.
Didn't start trying to find the thump gremlin til this summer.
 

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You can buy a heavy duty transmission mount from Centerline. I have one in my Spider.
Before taking things apart I had this issue at about 1500 rpm before and after replacement of bushing. When I look at my new bushing-tranny now out-it looks like the bushing for a 115 not 105. I know from looking I ordered the right part but got the wrong one it seems. But, I don't see a "high performance" one on their site, they rec metal dowels in the round holes for GTAs with the 105 mount. Can you provide a link for what you have I couldn't find it.
 

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That's what I saw too but it seems to read that it is the stock mount not upgraded or stiffened for the 105s. The one listed for 115s is the one I got with the center bushing lower.
 

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The early and late cars have interchangeable mounts. The early ones are heavy duty.
 

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I had that on my 87 Quad. The PO installed a new trans mount bushing but was upside down.
It can easily be put in the wrong way, which will reduce the clearance between the bushing mount and the support cross member, then when the rubber compresses you get metal to metal contact between the two. I removed it, turned it over, .....thumping gone!
 

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1984 GTV6, 1973 Berlina, 1987 Milano
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I have a poly trans mount in our Berlina. I do get a little bit of a drone around 4000 RPM but otherwise it's nice and firm, especially compared to others I have driven.
 
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