Vibrations starting around 4k RPM...
09-05-2013, 12:14 AM
#1
Thread Starter
Join Date: Sep 2013
Location: California
Posts: 10
Vibrations starting around 4k RPM...
So my 95 GT has a vibrating/rattling problem. When I drive past 4k RPM it's starts to vibrate. When I shift it goes away, and then comes back around the same RPM again. If I avoid those RPMs, it does not vibrate. This rattle does not occurs when revving in neutral either, well maybe a tiny bit, but nothing like when in gear. I have a rubber engine mount, and a polyurethane tranny mount that the previous owner installed. My auto tech told me a good place to start would be the transmission mount. I bought a stock replacement (rubber) and will be installing it next week. I am aware of a few things that it could potentially be, but am overwhelmed with the possibilities. Please let me know if you guys have experienced this and/or fixed this issue. Thank you!
09-05-2013, 01:12 PM
#2
6th Gear Member
Join Date: Mar 2010
Location: Wisconsin
Posts: 5,061
Just to understand better, this is only rpm based, not vehicle speed? It'll vibrate at 4k in every gear?
I'm not a mechanic by trade but I play one on here lol. Sounds like its engine related if it only does it at a certain rpm / load. You say it won't do it as bad in neutral. When was the last tune-up done, could be a miss in a cylinder, bad plug or wire etc. I think your engine-tranny mounts arent causing the vibration, but won't hurt to make sure they're tight. How bad is this vibration, can you feel it in the steering wheel or dash, or center counsel, is it slight or does the whole car shake apart?
Sorry for all the questions but it helps to be as detailed as possible so the next guy with more knowledge will narrow it down better. And be sure to post back when you find the problem, helps the next guy with similar troubles.
I'm not a mechanic by trade but I play one on here lol. Sounds like its engine related if it only does it at a certain rpm / load. You say it won't do it as bad in neutral. When was the last tune-up done, could be a miss in a cylinder, bad plug or wire etc. I think your engine-tranny mounts arent causing the vibration, but won't hurt to make sure they're tight. How bad is this vibration, can you feel it in the steering wheel or dash, or center counsel, is it slight or does the whole car shake apart?
Sorry for all the questions but it helps to be as detailed as possible so the next guy with more knowledge will narrow it down better. And be sure to post back when you find the problem, helps the next guy with similar troubles.
Last edited by 88 orangepeel notch; 09-05-2013 at 01:29 PM.
09-06-2013, 11:15 AM
#4
Thread Starter
Join Date: Sep 2013
Location: California
Posts: 10
Just to understand better, this is only rpm based, not vehicle speed? It'll vibrate at 4k in every gear?
I'm not a mechanic by trade but I play one on here lol. Sounds like its engine related if it only does it at a certain rpm / load. You say it won't do it as bad in neutral. When was the last tune-up done, could be a miss in a cylinder, bad plug or wire etc. I think your engine-tranny mounts arent causing the vibration, but won't hurt to make sure they're tight. How bad is this vibration, can you feel it in the steering wheel or dash, or center counsel, is it slight or does the whole car shake apart?
Sorry for all the questions but it helps to be as detailed as possible so the next guy with more knowledge will narrow it down better. And be sure to post back when you find the problem, helps the next guy with similar troubles.
I'm not a mechanic by trade but I play one on here lol. Sounds like its engine related if it only does it at a certain rpm / load. You say it won't do it as bad in neutral. When was the last tune-up done, could be a miss in a cylinder, bad plug or wire etc. I think your engine-tranny mounts arent causing the vibration, but won't hurt to make sure they're tight. How bad is this vibration, can you feel it in the steering wheel or dash, or center counsel, is it slight or does the whole car shake apart?
Sorry for all the questions but it helps to be as detailed as possible so the next guy with more knowledge will narrow it down better. And be sure to post back when you find the problem, helps the next guy with similar troubles.
09-06-2013, 12:54 PM
#6
6th Gear Member
Join Date: Mar 2010
Location: Wisconsin
Posts: 5,061
I could be anything that rotates when running, but pressure plates…… eh. Id say maybe flywheel lost a weight if you don't think it's motor related. You say it doesn't vibrate when rev'd in neutral, that tells be engine load plays apart in this too. Like petrock said, check your balancer for wobble first, that's the easiest right now.
The wheel out of balance would only be felt at certain speeds. Not based off rpm. Hard to tell with out driving it myself. That's why its important to be as detailed as possible so we get a clear picture of problem.
The wheel out of balance would only be felt at certain speeds. Not based off rpm. Hard to tell with out driving it myself. That's why its important to be as detailed as possible so we get a clear picture of problem.
Last edited by 88 orangepeel notch; 09-06-2013 at 01:12 PM.
09-06-2013, 10:57 PM
#7
Thread Starter
Join Date: Sep 2013
Location: California
Posts: 10
I'm trying to be as detailed as possible but the more I drive it lately the less I seem to notice it. Maybe because I'm getting used to it, idk. But not sure. How would I check the harmonic balancer? And for the flywheel I would take out the driveshaft and transmission etc?
09-07-2013, 06:54 AM
#8
4th Gear Member
Join Date: Nov 2006
Location: CA
Posts: 1,670
Start the motor and watch the pulley on the harmonic balancer and the harmonic balancer itself. If either wobbles at all, even slightly, the balancer is bad. Check it at idle, after pulsing the throttle a couple times, and when holding at or above 2k RPMs.
09-23-2013, 12:34 PM
#10
Thread Starter
Join Date: Sep 2013
Location: California
Posts: 10
Okay guys thanks for all of your help! The vibration was because of the poly transmission mounts. I replaced them with oem replacements for the time being just eliminate the vibration factor so I can assess one more noise I'm hearing. It's like a clicking/clinky/patter sorta noise when the engine is under load. Usually occurs around 75%-WOT. Most noticeable in around 3rd gear and higher. I put my ear to the shifter, and seemed like that's where the noise was coming from. I have a MGW short shifter and it looks like I may have a different transmission other than the stock. I bought the car and he didn't tell me that it wasn't stock. It doesn't line up correctly with the crossmember so installing an oem tranny mount took a little bit of cutting the mount with a separate steel plate to secure it. Not sure which tranny it is. Anybody who might have some insight on any of this let me know! Thanks!