I'm sorry if this has been covered thousands of times like every other topic on this board, but I need help quick. I changed my transmission mount today replacing destroyed stock unit with Energy Suspension Polyurethane. Well, I now have a vibration. It appears all throughout the speed range from stop to 80 MPH without getting worse. I didn't have this before the switch. Could the vibration be just that I'm more connected to the car and I'm supposed to feel more vibration? Or is the driveline out of whack?

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91 TA 5.7 TPI Automatic.
w/WS6 and 3.23 rear.
K&N Air Filter,Hypertech Coil,Moroso Blue Max Wires, Bosch Platinum plugs gapped at .050,
JET fan switch,JET air foil,Dual cats with Flowmaster 3" exhaust (Headers coming soon),
Complete PST components on front suspension, Spohn LCAs/Panhard bar.
It's not much, but it's a start and I have a Summit catalog! :-)

 

Also, I replaced installed my Spohn LCAs and Panhard bar. Could this be a problem? Trans mount, Panhard bar, and LCAs all with polyurethane bushings at the same time? Thanks.

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91 TA 5.7 TPI Automatic.
w/WS6 and 3.23 rear.
K&N Air Filter,Hypertech Coil,Moroso Blue Max Wires, Bosch Platinum plugs gapped at .050,
JET fan switch,JET air foil,Dual cats with Flowmaster 3" exhaust (Headers coming soon),
Complete PST components on front suspension, Spohn LCAs/Panhard bar.
It's not much, but it's a start and I have a Summit catalog! :-)

 

Many people who have replaced the stock tranny mount with one of the poly units have experienced this vibration. These mounts seem to be about 1/2" taller than the stock ones, changing the driveshaft angle.

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1985 Yellow IROC-Z 5.0 HO, T-5 3.73 Torsen, 4 wheel disks
PFCM pads, GTA wheels, Koni yellows, B&M Ripper, Dynomax

 

I have the ES polyurethane tranny mount too, and I do experience a little vibration, but only at speeds exceeding 80 MPH, and I have 3.73s in the back. At speeds less than that, the car is rock solid with no noticeable vibrations.

Possible causes for this could be poorly balanced wheels or driveshaft, and that the vibrations just weren't being transferred to you before with the rubber mounts. If those are determined to be ok then I don't know where to send you, except maybe a pilot bearing, but I wouldn't think that would occur at all RPMs.

I doubt the mods you described would cause vibration, at least not due to the polyurethane bushings. If you find a new flat road somewhere you should still have a good ride with the polyurethane. Just because it's stiffer than rubber doesn't mean it'll cause vibration, it just means road imperfections are transmitted to the chassis and your butt more than they would be with rubber.

If you had done polyurethane motor mounts then maybe you'd have vibration from the engine, but otherwise the engine should be fairly well isolated as far as vibration goes.

Hope this helped a little, probably stuff you already knew,

Jason

 

I also changed my Tranny Mount in my TH200 and i have experienced a rough vibration but i guess the mount have to accomodate or something...i hope this problem go away soon cause im fearin this will affect my Tranny internally.one time my park spring return broke and you could hear a big ratatatata like an helicopter cause i drove more then a week with a complete destroyed tranny mount

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1982 Pontiac firebird s/e 2bbl..Club organizator in chile southamerica.https://www.thirdgen.org/rides/index.tgo?action=view&rideid=3280

 

Does GM make a harder rubber mount for 3rd gens? Fourth gen's have a 1LE mount which uses a harder rubber compound, but is considerably taller than the 3rd gen. and won't fit. I know this from personal experience. If not I'll just replace it with a stock one. Anybody know the GM part number for the stock mount?

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'91 Formula
383CI Superram, Sportman II's
SLP Cam 214/224 .470/.490
Vortech V1 S-Trim
5-speed
3.42
12.34@117.04, 1.91 60Ft.
on Drag Radials

 

Last time I broke my tranny mount I replaced with a Energy Suspension mount and had the same problem with all the vibrations. I drove it for 2 days like that and that was enough. Pulled that one and put in another stock rubber one, all the vibrations went away.
Now running on the 4th tranny mount. Light the tires up around a corner and if they grab then *snap*.

 

Anybody know GM part number for the tranny mount? The stock 3rd gen one.

------------------
'91 Formula
383CI Superram, Sportman II's
SLP Cam 214/224 .470/.490
Vortech V1 S-Trim
5-speed
3.42
12.34@117.04, 1.91 60Ft.
on Drag Radials

 

I had heard of this vbration with the mount from energy suspension , that is why I went a stock one . I have not broken it since which was a week ago.

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383 86 Camaro Z28 ---1/4 mile et>13.65@103mph,,
10.5:1compression Dart Pro 1 Aluminum heads 215cc>2.05/1.60 valves,400 steel crank,cam specs:224/234 at 050 525/525 lift,3500 stall converter,shift kit,4.10 gears,770 Holley Avenger,Victor Jr. Intake,true dual exh,Hooker headers with 40 series Flowmasters,MSD Coil and Module.ALSO SECOND GEN Z28---mods:454 BBC,.546 max lift(doug herbert cam ) 750 Holley vac sec. ,Edelbrock Performer manifold,Holley electric fuel pump,Hooker headers,Flowmaster mufflers,beefed up 700r4 tranny, 3.90 gears, powertrax unit, B&M console shifter.

 

Can the transmission mount be bad without being broken?

I have a 91 T/A, 305, TPI and I'm getting a vibration coming thru the shifter when RPM's reach 3,000 rpm and higher. I've been suspicious of mount and checked it visually and with a crowbar but it appears to be in one piece.

 

For the GM rear tranny mount, it is #17990869

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1989 IROC-Z 5.7L
NOS 5151 150HP kit
ProBuilt 700R4, PI Vigilante 2800 stall lockup
Baer Brakes 12" Sport System

 

One thing I noticed w/ the the Poly bushings, is alot of them are pretty much universal, so they come w/ a thick shim in case you need it. Most people don't know better, and think they need it because it came w/ it, and there are no instructions. Once this shim is installed, it kills the driveline angle and induces a vibration. If you installed this shim, REMOVE it! If not, then I guess you need to keep searching, good luck!

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GM Master Tech
ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
Whatever chip I feel like burning,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
3.73 Posi
4wheel Disc Brakes
Summit 1-5/8" headers, 2.5" Dynomax catback.

Best 1/8: 9.519@72.74

'97 Bonneville SSE

 

I think I remember the ES poly bushing instructions say that you have to install the shim. Is it possible that an aftermarket parts supplier could be wrong? Sorry, I am just sick of crap "upgrade" parts.

------------------
92Z28
89GTA

 

I posted on this topic a few weeks ago when I replaced my worn stock mount with a new ES polyurethane mount. The instructions that come with the mount say the shim is not optional, it should be installed. So I followed the instructions and put it in, and noticed vibration that hadn’t been there before. I drove it for a couple days and decided to remove the shim. When I did, the vibes stopped.

 

Thats what I was saying. I don't know why they would tell you it had to be there, arn't they supposed to R&D this stuff before marketing it?


------------------
FREE CARFAX Record Check

If you live in Southeastern US, check us out!
South East Thirdgen

GM Master Tech
ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
Whatever chip I feel like burning,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
3.73 Posi
4wheel Disc Brakes
Summit 1-5/8" headers, 2.5" Dynomax catback.

Best 1/8: 9.519@72.74

'97 Bonneville SSE