Transmission mounts

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James OBrien
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Transmission mounts

#1 Post by James OBrien » Mon Jul 09, 2018 7:40 am

After installing a new clutch and pressure plate on my 1964 356C, I seem to have a vibration at about 2000 rpm. I am now considering replacing the front transmission mounts. Does that require removal of the engine and trans? Is there a way to tell whether the mounts are bad before removal of the engine?

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Vic Skirmants
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Re: Transmission mounts

#2 Post by Vic Skirmants » Mon Jul 09, 2018 7:47 am

James OBrien wrote:After installing a new clutch and pressure plate on my 1964 356C, I seem to have a vibration at about 2000 rpm. I am now considering replacing the front transmission mounts. Does that require removal of the engine and trans? Is there a way to tell whether the mounts are bad before removal of the engine?
Sounds like a balance problem at the engine. Front mounts last pretty much indefinitely. You CAN change them without pulling engine and trans. Support the engine, take off all the mount nuts, pry the trans back a bit, slide out the old mount; note the position of the shims and re-install new mount.

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Re: Transmission mounts

#3 Post by James OBrien » Mon Jul 09, 2018 7:53 am

So maybe I need to pull the engine and balance the clutch, pressure plate and flywheel together?

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Re: Transmission mounts

#4 Post by Tim Berardelli » Mon Jul 09, 2018 6:24 pm

James,

It has been my experience that new Pressure Plates are "out of balance" by a ton! Competition Engineering, Gene Berg Ent. and other machine shops can balance your F/W, P/P w/o a crankshaft to hang them on. I have a machine shop in N. VA that provides that service-If you're in this are and need help with that with issue help give me a call.
Last edited by Tim Berardelli on Tue Jul 10, 2018 8:23 am, edited 1 time in total.

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C J Murray
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Re: Transmission mounts

#5 Post by C J Murray » Mon Jul 09, 2018 6:35 pm

I have used pressure plates out of the box without problems in the past but I just put a new one into my Speedster that is vibrating, I HOPE! Tim, how long have they been out of balance by a ton?
'57 Speedster
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'60 Devin D Porsche Race Car - Finally Finished!
'63 GS 2133 coupe
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Re: Transmission mounts

#6 Post by Tim Berardelli » Mon Jul 09, 2018 6:42 pm

CJ
Based on my contact with these engines only about the last 45 years.

Dick Weiss
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Re: Transmission mounts

#7 Post by Dick Weiss » Mon Jul 09, 2018 8:22 pm

Viewing all the pressure plates (and even the discs) I've worked with, it's hard to imagine that all the drilled holes were added
"for the heck of it" and were done by the MFG? Being as a replacement part to be done after broken (or age?), I never needed
to rebalance everything from the flywheel out and the result was OK.
Of course, the flywheel would be rebalanced if there was some metal removed or lightened.

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Re: Transmission mounts

#8 Post by Steve Douglas » Mon Jul 09, 2018 11:37 pm

I recently had the same thing, does your flywheel have a locating pin for a hole in the presser plate? If you have to carefully look for the stamped marks on the flywheel and pressure plate, (plate maybe a paint dot) . I put mine on and it vibrated like yours, 2000-2500rpm. Pulled the motor rotated the pressure plate 120 degrees and everything was good. This was a 180mm setup, Some flywheels have a small pin and many pressure plates have around or square hole, note that hole in many cases will not to be lined up with the stamping on the flywheel

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Re: Transmission mounts

#9 Post by Dick Weiss » Tue Jul 10, 2018 9:35 am

I've found that the clearance holes for the 6-mounting bolts are very close to the bolt diameters which tends to align the P/plate
to the rotation axis of the flywheel.
The 200mm P/plate(s) have 2-pin holes along w/the 180, but I have a 180 P/plate w/5-holes in each mounting flange/face
(for lightening?) and there are @ least 2-different rivet thicknesses added for balancing.

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Re: Transmission mounts

#10 Post by James OBrien » Wed Jul 11, 2018 10:53 am

Dick-I didnt understand your post and its import-sorry. Could you elaborate? Is there a right way to align those holes to avoid imbalance?

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Re: Transmission mounts

#11 Post by Dick Weiss » Thu Jul 12, 2018 10:06 am

James,

If you're referring to all the extra holes in the P/plate I described, only 6 mounting holes are used which are thru
the 3-mounting face/flanges; All the extra holes (2-on each side of the mounting holes) are NOT thru the face surfaces.
Maybe for a little lightening(?). (If there are 2-pin holes in the flywheel to locate the P/plate--both are used, not just 1.)
Final balancing was done by adding the various rivet weights to certain holes suit--involving a little more labor vs. just drilling holes.

Dick

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Re: Transmission mounts

#12 Post by James OBrien » Thu Jul 12, 2018 2:37 pm

Thanks Dick and others. Going to pull engine and recheck pp and all trans mounts, hoop attachment and engine bolts.

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Re: Transmission mounts

#13 Post by Dick Weiss » Fri Jul 13, 2018 12:00 pm

A CORRECTION:

There are 2-bolt holes in each of the 3-mounting face/flanges --the extra holes are between them to add various rivets for final balancing.

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