"grinding" noise

[elwesso]

THis has been going on for a little while... It sounds to me like its coming from the transmission.....

Whenever i hit the gas from a stop, i hear what sounds like a grinding noise... Its hard to describle, but it sounds like its coming from right behind the stereo but from the drivetrain... I can sort of feel it in the body of the car... It kind of sounds like if you take a bolt or something with threads, and scratch it along the corner of something.. Its very fast and once the car gets moving, say over 5 MPH, its fine.

The transmission shifts fine, fluid is fairly fresh and full.....

Any ideas??

[911/Q45]

Bad motor mount?

[elwesso]

THe motor mounts were replaced at T3 (i think?) approx 30k ago

[driverdriver]

It could be that on of your calipers are still engaged when you accelerate. It would grind before releasing. I've had that experience in a couple of non-Nissan/Infiniti's. The grinding sounded as if coming up through the drivetrain from the rear.

[squeefoo]

Heat shield vibration, rubber mallet test.

[elwesso]

Hmm

This did it equally before and after my brake swap

It feels as if something is out of alignment or something isnt catching, because it doesnt roast the tires off the line like it should

[qship96]

look very closely at the top of stillen bar{cover with chalk if need be} could be barely rubbing hoodliner as engine twists from initial torque-mine occasionally does and you can hear it,and feel it through the body of car.

[gniknave]

If you didn't feel it in the drivetrain I'd say it's the ABS unit, which would make total sense to me since you just went through some bleeding of the brakes with your Z32 upgrade. At our shop, after bleeding brakes on a car with abs, from time to time we may hear a grinding like sound coming from the abs unit indicating there's air in the system. Easy fix....hopefully your case is this minor.

[elwesso]

actually it looks as if mine is hitting the plenum... There is a TINY wear spot, maybe 2in long...On the drivers side of the plenum. Might explain why it does it worse when its hot...

It does do it when stall testing... Im glad to hear that my transmission isnt bad!!!

Ill verify this later when someone else is around and I can stall test and see if the engine is hitting the strut brace.. or maybe ill just take it off and see if it fixes it.....

Thanks a million Q ship!

[911/Q45]

If the plenum is hitting the strut brace, you've got a bad motor mount. Perhaps someone made a mistake with the replacement.

[elwesso]

If the plenum is hitting the strut brace, you've got a bad motor mount. Perhaps someone made a mistake with the replacement.

T3 did it when they swapped in the engine... hmmm

I tested it out tonite and Im fairly sure thats whats happening... Its hard to tell though but the engine moves quite a bit.....

[maxnix]

Maybe too much nitrous oxide has worn them prematurely?

[elwesso]

ACtually this engine has not seen nitrous.. I know it hasnt since ive had it and I dont know if we can trust Fred

[Q451990]

I had my motor mounts replaced on Q1 and the guys at T3 thought that there was more-than-normal movement for a '90. There was some speculation that the mounts for the 90-93 may have been superceded by the softer 94-96 mounts... so the movement you're getting on a 94 may be normal vs. Dennis' descriptions of how much is normal (almost none) for a 90-93.

Heath

[maxnix]

There was some speculation that the mounts for the 90-93 may have been superceded by the softer 94-96 mounts...

Heath

First I have heard that.

Are they silicon filled? If so, a lot of trouble and expense to change the specification.

[elwesso]

Id like to think my motor mounts arent shot by now.....

They were replaced on 8/1 at approx 87k... Car now has 116k