Tranmission mount failure

[juiceman]

What are the signs that a transmission mount is failing?

Does it happen all of a sudden?

Does it happen over time?

What damage can be incurred if not fixed immediately?

I have been at my whits end trying to determine the slowly growing hum/vibration I have been having and can only get it to the transmission area. transmission ships and functions fine. I can remember something on the old site saying that a transmission mount can cause a vibration but cannot exactly remember

Thanks for refreshing my memory

[greg_atlanta]

The only way to fully understand the benefit of a new transmission mount is to have it installed!!!

Very good bang for the buck. It aligns the transmission and driveshaft better.

A bad mount causes unnecessary drivetrain vibration. It's doubtful the transmission will fall out if you don't replace it, but why not?

Part is $80-100??

[aaacomp]

With a delayed replacement you could damage the motor mounts and the driveshaft... The transmission mount is inexpensive compared to the the replacement of the other two. From what you're feeling now would indicate that it was the transmission or driveshaft.....:thumbup

[juiceman]

With a delayed replacement you could damage the motor mounts and the driveshaft... The transmission mount is inexpensive compared to the the replacement of the other two. From what you're feeling now would indicate that it was the transmission or driveshaft.....:thumbup

transmission or drive shaft? Do you mean the transmission is going or just the mount? The car only has 64K.

I will be replacing the mount next week

[aaacomp]

Just transmission mount.. not enough miles for either really,, sounds like something else.....:thumbup

[Q45tech]

You look at the mount on a lift if there is not 1/2" or more of head space [air] between the rubber and the the metal top of the mount, the weight of the car [on the ground] will allow the metal to contact and squish the rubber flat allowing drive train vibrations to transmit to the body.

It is all a system: motor mounts, sway bar mounts, shock mounts, transmission mounts, rear subframe mounts, drive shaft center bushing [doughnut]. a failure of any will result in vibration.

The failure mode is salt, heat and ozone changing the strength of the rubber to support [hang] and isolate the transmission.

In Atlanta they seem to last 90-140k I just replaced mine for the second time after 118k on the second one.The upper links last 30k, the tension rods 60k, the suspension arm rubber bushings 120k, the motor mounts, transmission mounts, diff mounts have a similar life.....the rear subframe mounts can last 240k or fail at 4k if a rear end [or severe rear fender] collision occurs usually somewhere in between...

...many don't fail at the body shop but a year later so they never get repaired!

We have more than a dozen [90-95] Q with failed rear subframe and no matter what you do to the other things a certain amount of extra vibration is always there but they won't spend the $1100 to correct it!

[aaacomp]

.....:thumbup

[Qdog]

How much of a rear end bump does it take to damage the sub-frame bushings ? Just got rear ended at a light by a mini van, plenty hard but not enough to show any bumper damage to either vehicle. How can I check for possible bushing/sub-frame damage ? 92Q, 153K mi. I've read about Wurth on the bushings to extend their life, what about generic silicone, same thing ?

[PalmerWMD]

How much of a rear end bump does it take to damage the sub-frame bushings ? Just got rear ended at a light by a mini van, plenty hard but not enough to show any bumper damage to either vehicle. How can I check for possible bushing/sub-frame damage ? 92Q, 153K mi. I've read about Wurth on the bushings to extend their life, what about generic silicone, same thing ?

QDog:

I just asked the same question in the infiniti onlinbe mechanic section of thois board.

See answer there..

Fred...

[juiceman]

Had an ac belt squeel for sometime, actually whne the belt was changed by the mechanic I had a squeel. He adjusted the belt. When I looked under the car he had it at the stops and so much the retqaining clip was bent. I do not think this is normal. Whne replacing the belt it had the same squeel but did not want to over tighten belt. Pulled the pulley and found that the bearing is not smooth operating and catches at areas. I am going to be getting a replacement this week.

Since all this started with the ac "on" some time ago, I think that this may have been causing my resonant hum.vibration. Do you all concer?

Upon looking at the transmission mount, I do not see 1/2 inch of air between the top of the rubber the mount. Maybe a quarter inch. I think I will order this part at the same time and replace anyway.

Thanks for the input and will post when done.