Source of vibration? '66 Transmission Mount?

[blink182house]

Hey guys; so I love driving the cadi around but I'm trying to get all the little bugs worked out from the years of use. When I'm driving I'm getting some sort of driveline vibration. My u-joints feel good and aren't making any noise, and I just had the wheels all checked and balanced. I am yet to do any wheel bearings or turn the drums, but while it was on the lift I couldnt get any play out of the bearings by grabbing the drum and trying to move it. All the drums still have the original factory mounted weights on them, so they should be balanced as well. I'm wondering if possibly the transmission mount is creating a lot of this?

When I'm cruising the car has a shake front and rear, I think the front may be just simple bushings/joints/bearings all combined and will come out with all my future maintenance. The rear however is doing it as well, cause I can feel it in the seat more than the steering wheel. Cruising speeds its at different speeds worse than others, similar to a unbalanced wheel. At interstate speeds it creates a good bit of 'drone' in the cab, specifically when you start to go down a decline and are barely on the throttle (like when you'd expect your exhaust to kind of start sputtering from letting off the throttle).

The only other issue I've come across is that I've noticed if I'm at a stop or like 5mph, very low speeds, and I just FLOOR the throttle I get some big driveline jumping. It's as if the rear tires (brand new) are too sticky and the motor cant spin them, so the rearend is hopping... but it feels to me like the stress is going back to the transmission and the transmission is jumping or moving. I go nowhere, gas floored, and its a large shake/thump feeling/sound. This doesnt happen though if I roll into the throttle and floor it, or even if I'm rolling at like 20mph and ROMP the throttle to make the car torque.

I'm new to this chassis and working on a tight schedule, so I figured it wouldn't hurt to pick everyone's brain since my finger is too large to get to my own (lol)! Let me know what you brainstorm or suggest! If I can get this car to smooth out like it was 40 years ago, it is going to be the ultimate ride! THANKS!



Also, on the transmission mount was wondering if anyone has ever used one of these:
http://www.streetsideauto.com/p/lakewood-24350/?utm_source=GoogleShopping&utm_medium=GoogleShopping&utm_term=GoogleShopping&utm_content=GoogleShopping&utm_campaign=GoogleShopping

It seems like a universal polyurethane mount, but it looks like the original design... so wanted to know what the past experience was with that. The only other option I've come across is a much more expensive oem replicated polyurethane from caddydaddy:
http://caddydaddy577.corecommerce.com/1965-1966-1967-Cadillac-Transmission-Mount-New-Core-Fee-Not-Included-See-Details-FREE-shipping-in-the-USA-p2014.html

[kevo]

how's the carrier bearing look?

[blink182house]

There is not one at all; is there supposed to be on a 4dr 66? The driveshaft is very large and is a solid 1pc, doesnt look as if there would be one.

[kevo]

ah, I'd have to look that one up... I know on my 62 coupe when the carrier bearing was jacked, I had a weird vibration and sounds identical to your problem

[blink182house]

A bad carrier bearing sounds like a great source, but i'm not certain this car requires one. I just stuck my head under it to check, have to crawl beneath it to see if there're any mounting holes on the bottom for a bracket to hold a bearing. Hopefully someone else will chime in though before I do, it's been raining today haha dont want to get all wet!

[Cadillac Kid-CLC #15364]

Drive shaft is a single piece with two CV joints, one at each end.  Sounds like you have lots of "kinks" to work out.  Regarding the rear transmission mount, see if there is at least 3/8 of an inch clear between the crossmember and the transmission tail shaft.  If not some of the contact vibration is comming from that metal to metal contact.
You have bushings in the rear suspension as well as the front, so any looseness back there will add to the melody.
I might suggest starting from the front of the car and working back.  Get the front suspension and steering  checked and up to specs, check the rear transmission mount (as well as checking the front engine mounts), have a good driveshaft company check and balance the driveshaft/CV joints, and then work to the back suspension.
Greg Surfas

[pdxmose]

No carrier bearing, just one piece.

Suspecting the tranny mount is a great guess once you get past wheel balance, CV joints, etc.  They all seem to fail after 40 years.  That could also explain the clunk on torque.  Take a look at the mount in the center of the tranny crossmember.  It's likely ripped around the entire edge.  Mine was and so was my parts car.

They cost about $125 to have them rebuilt and you need to send a core as they specific to only '65 and '66 (pretty sure).

Instead, I converted mine to accept the BIGGER mount from the later years, which were common to lots of GM vehicles and WAY cheaper. I'll try to find the post from when I did mine.

                ...mose

[pdxmose]

Found it.  

http://www.modifiedcadillac.org/forum/index.php/topic,3135.0.html

RockAuto is closing them out at $4.75!

          ...mose

[Chris Conklin]

RockAuto is closing them out at $4.75!

So buy a bunch of 'em... being "closed out" kind of infers lack of need and maybe end of production? Give it a few years, they could be at the c-note plus benchmark. 

[pdxmose]

I should have been more clear.  They are closing out one manufacturer. 

And this is for the later year mount, not the one for the 65/66/67.  The later year mounts are readily available for about $12.

              ...mose

[The Tassie Devil (Bruce Reynolds)]

And probably getting the next ones from China?

Bruce.

[EZ]

In your other thread you said you had "bent rims"  Did you replace them already?

If I were you I would plan in replacing every single rubber bushing in the suspension/ steering/ mounts from front to back on the car.
45 year old rubber will be rotton especially after sitting for 30 years.

[Gary]

I would be hesitant to use a polyurethane mount. They are known to transmit more vibration than a rubber mount.
For $ 12  its hard to beat factory vibration engineering.
I do agree with Greg's approach of systematically eliminating the problem. How many times have I "diagnosed" a problem and thrown money at it, when I should have used the K.I.S.S. approach.
And I was the final "S."

Gary

[blink182house]

Yes, I have replaced all bent rims.
Gary, I agree on the polyurethane, wasn't aware of the ability to use a later model as Greg has informed me now! I'll be buying one of those asap, as mounts are an important item to replace imo.

I am going to get the front bushings/joints all replaced and do the brakes, as well as front bearings. Afterwards, I think I'll drop the driveshaft and have it balanced and do u-joints regardless that they 'feel' good. I hope it's not something in the rearend like pinion bearings lol!

[Cadillac Kid-CLC #15364]

No, I did not recommend amodifying a "later" mount.  I've bitten the bullet  on my '66 and gotten the correct year's replacement mount. 
Regarding the drive shaft, there are two Constant velocity joints.  I would strongly reommend that you take your driveshaft to a good DS rebuilder so they can re-do the joints and balance the shaft.
Greg