Transmission 'insulator'?

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Bailey28

Not-quite-so-new-guy
Feb 16, 2017
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Been having minor driveline vibration issues at highway speeds. I had a new driveshaft with new U joints installed and it solved some of the vibration. There is a rubber pad for sale on e bay that I don't have in place, could this rubber part be the difference in the output shaft to the pinion angle thats causing the vibration? I have a new transmission mount already on the car (TH350) but no rubber pad between the mount and the trans. It appears to be at least 1/4" thick... I didn't know this pad existed until I saw it for sale.
s-l1600 (5).jpg
 

oldsmobile joe

Royal Smart Person
Nov 12, 2015
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welcome to the forum. i haven't seen the rubber pad before. is/was your car a v6?
how long has the vibration been there? and why do you think its driveshaft related?
other items that can cause vibrations are axle shafts, brake drums and of course wheel/tires.
 

565bbchevy

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Aug 8, 2011
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Clone TIE Pilot

Comic Book Super Hero
Aug 14, 2011
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Galaxy far far away
Not all G bodies used rubber bushings in the crossmember frame mounts. Some were jyst bolted directly to the frame.
 
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CopperNick

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Feb 20, 2018
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Have seen that type of rubber insulator before, along with the metal tube insert plate that goes with it; think I even have a few of them stashed away in a too box under the work bench Don't recall them being used under the tail shaft housing of a 350. The one on my Monte is poly-U and at least 1-to 1-1/2" thick. Also seem to recall that they were placed to sandwich a middle solid plate or bracket with one of the rubbers on each side of the plate and the tube insert pushed through the whole mess to trap it all together. Just can't remember what it all was for. Bother...……..
 

565bbchevy

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Aug 8, 2011
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I have a new transmission mount already on the car (TH350) but no rubber pad between the mount and the trans.
Isn't your trans mount rubber? The pad you posted looks like the isolators that go on the end of the trans crossmember on each side where it bolts to the frame and it seems not all gbodys had them.
 
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Bailey28

Not-quite-so-new-guy
Feb 16, 2017
24
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3
Thank you for the replies. My car is a 1984 El Camino that came with a 305 and a TH350C trans. When I bought the car it had a regular TH350 trans in it and a new trans mount. Someone prior to me attempted to make a driveshaft by cutting a longer one down. Their workmanship was poor as the yoke was welded off center by .050" causing a buzzing vibration at speed. I had Southwest Speed make a brand new driveshaft.

I still have a minor vibration after replacing a few brake drums, both axle shafts, all control arm bushings, trans was rebuilt with new output shaft bushing and balancing wheels and tires.

After seeing how the pad was advertised as 'TRANSMISSION CROSS MEMBER INSULATOR U 78 -87 EL CAMINO MONTE CARLO MALIBU' I began to wonder if the height difference might cause the vibration.

If not all cars came with the insulator I will have to look to other sources for the vibration. At this point I am starting to think it may be the pinion bearing or something inside of the differential. It has a 2.41 open 7.5" 10 bolt. I don't hear any obvious whining from the rear but I'm betting it has well over 100k on it at this point.
 

fleming442

Captain Tenneal
Dec 26, 2013
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Thank you for the replies. My car is a 1984 El Camino that came with a 305 and a TH350C trans. When I bought the car it had a regular TH350 trans in it and a new trans mount. Someone prior to me attempted to make a driveshaft by cutting a longer one down. Their workmanship was poor as the yoke was welded off center by .050" causing a buzzing vibration at speed. I had Southwest Speed make a brand new driveshaft.

I still have a minor vibration after replacing a few brake drums, both axle shafts, all control arm bushings, trans was rebuilt with new output shaft bushing and balancing wheels and tires.

After seeing how the pad was advertised as 'TRANSMISSION CROSS MEMBER INSULATOR U 78 -87 EL CAMINO MONTE CARLO MALIBU' I began to wonder if the height difference might cause the vibration.

If not all cars came with the insulator I will have to look to other sources for the vibration. At this point I am starting to think it may be the pinion bearing or something inside of the differential. It has a 2.41 open 7.5" 10 bolt. I don't hear any obvious whining from the rear but I'm betting it has well over 100k on it at this point.
If you've done ALL this, the vibration is either very minor or the wheels are still not right. Have you tried swapping wheels around? "Road Force" balancing? How old are the tires? Are they flat spotted from sitting? Rims in good shape? Unilug or hub centric?
I don't think crossmember pads will fix it.
 
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69hurstolds

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Jan 2, 2006
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Not all cars had them. Mainly V6 and Diesel engines did. They're on the end of the crossmember. Parts #2, and #3 on the diagram below. I know none of my VIN 9 Oldses have them.

Frame crossmemember 82-88 G-body.jpg
 
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565bbchevy

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Aug 8, 2011
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My 83' Monte came with them and my 86' Regal came without them and both are V8 cars, 305 and 307.
 
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