Picking up on a new "bad vibe"
12-18-2011, 06:30 PM
#1
Burning Brakes
Thread Starter
Picking up on a new "bad vibe"
Previous owner replaced motor mounts (solid) about 3K miles ago.
On a recent hard run, suddenly I have a serious engine vibration when I rev up over 5,500 RPM. Sounds like metal on metal. It's definitely tied to engine rev as this happens in all three lower gears.
I've heard some discussion about bands/straps that go over the top of the motor mounts perhaps hitting the heat shielding?
Being that it's tied to revs, I'm thinking it's not transmission mounts.
Any suggestions on figuring out exactly where this is coming from (assuming the motor mounts haven't collapsed as they are solids and reasonably new)?
On a recent hard run, suddenly I have a serious engine vibration when I rev up over 5,500 RPM. Sounds like metal on metal. It's definitely tied to engine rev as this happens in all three lower gears.
I've heard some discussion about bands/straps that go over the top of the motor mounts perhaps hitting the heat shielding?
Being that it's tied to revs, I'm thinking it's not transmission mounts.
Any suggestions on figuring out exactly where this is coming from (assuming the motor mounts haven't collapsed as they are solids and reasonably new)?
12-18-2011, 06:46 PM
#2
Rennlist Member
So if I understand correctly you have MM (solid) which have the straps. Do the straps only come on solid MMs? If so, when I had my MMs replaced at Sharktoberfest I received solid mounts. Bummer for me as I wanted the hydraulic.
Thomas
Thomas
12-18-2011, 07:30 PM
#4
Burning Brakes
Thread Starter
Supercedar - I don't think the solids are unique with respect to the strap. I need to research that a bit further as I didn't actually do the MM replacement work.
Maleficio - I have not checked hi-rev in neutral. Need to do that asap. Thanks for the suggestion.
Maleficio - I have not checked hi-rev in neutral. Need to do that asap. Thanks for the suggestion.
12-18-2011, 08:15 PM
#5
Team Owner
first some checking should steer you in the right direction
Lokk at the trans and see if you can fit your finger between the crossmember and the bottom of the trans, there should be about an inch of clearance ,
next look under the front crossmember and see if the pan is flush with the crossmember if its hanging below it then the MMs may have collapsed.
Jack up the front see if the fingers of the MMs are touching the fingers edge should be parallel to face of the crossmember sometimes they can get turned and thus one side of the finger can tap on the other finger.
Also look at the exhaust manifold to see if they might be hitting the side brackets of the crosmember
Lokk at the trans and see if you can fit your finger between the crossmember and the bottom of the trans, there should be about an inch of clearance ,
next look under the front crossmember and see if the pan is flush with the crossmember if its hanging below it then the MMs may have collapsed.
Jack up the front see if the fingers of the MMs are touching the fingers edge should be parallel to face of the crossmember sometimes they can get turned and thus one side of the finger can tap on the other finger.
Also look at the exhaust manifold to see if they might be hitting the side brackets of the crosmember
12-19-2011, 06:19 AM
#7
Former Vendor
Join Date: Feb 2004
Posts: 2,139
Likes: 0
Received 0 Likes
on
0 Posts
Trending Topics
12-19-2011, 09:26 AM
#8
Supercharged
Rennlist Member
Rennlist Member
Join Date: May 2002
Location: Back in Michigan - Full time!
Posts: 18,925
Likes: 0
Received 63 Likes
on
36 Posts
Here's a good way to test:
Rev car in neutral foot off the clutch pedal. Feel the shifter to see if there is a noticeable vibration. My guess is that you feel it.
Now try the same trick, but this time depress the clutch pedal. If the vibration is gone, it's coming from somewhere behind the clutch. My guess would be the torque tube. If the vibration is still there then it's in the engine.
BTW, this is exactly how I tested my torque tube. The front bearing had moved back some 20" leaving the front of the drive shaft unsupported allowing it to vibrate like crazy.
12-20-2011, 02:55 AM
#10
Burning Brakes
Thread Starter
There is no torque converter in a GT since it's a 5-speed. But it could very well be that the bearings have shifted in the torque tube.
Here's a good way to test:
Rev car in neutral foot off the clutch pedal. Feel the shifter to see if there is a noticeable vibration. My guess is that you feel it.
Now try the same trick, but this time depress the clutch pedal. If the vibration is gone, it's coming from somewhere behind the clutch. My guess would be the torque tube. If the vibration is still there then it's in the engine.
BTW, this is exactly how I tested my torque tube. The front bearing had moved back some 20" leaving the front of the drive shaft unsupported allowing it to vibrate like crazy.
Here's a good way to test:
Rev car in neutral foot off the clutch pedal. Feel the shifter to see if there is a noticeable vibration. My guess is that you feel it.
Now try the same trick, but this time depress the clutch pedal. If the vibration is gone, it's coming from somewhere behind the clutch. My guess would be the torque tube. If the vibration is still there then it's in the engine.
BTW, this is exactly how I tested my torque tube. The front bearing had moved back some 20" leaving the front of the drive shaft unsupported allowing it to vibrate like crazy.
12-20-2011, 06:36 AM
#11
Former Vendor
Join Date: Feb 2004
Posts: 2,139
Likes: 0
Received 0 Likes
on
0 Posts
There is no torque converter in a GT since it's a 5-speed. But it could very well be that the bearings have shifted in the torque tube.
Here's a good way to test:
Rev car in neutral foot off the clutch pedal. Feel the shifter to see if there is a noticeable vibration. My guess is that you feel it.
Now try the same trick, but this time depress the clutch pedal. If the vibration is gone, it's coming from somewhere behind the clutch. My guess would be the torque tube. If the vibration is still there then it's in the engine.
BTW, this is exactly how I tested my torque tube. The front bearing had moved back some 20" leaving the front of the drive shaft unsupported allowing it to vibrate like crazy.
Here's a good way to test:
Rev car in neutral foot off the clutch pedal. Feel the shifter to see if there is a noticeable vibration. My guess is that you feel it.
Now try the same trick, but this time depress the clutch pedal. If the vibration is gone, it's coming from somewhere behind the clutch. My guess would be the torque tube. If the vibration is still there then it's in the engine.
BTW, this is exactly how I tested my torque tube. The front bearing had moved back some 20" leaving the front of the drive shaft unsupported allowing it to vibrate like crazy.
Sorry for the confusion, I was responding to Maleficio's post about his new rear rattle in his 1982 Auto. That's why I qouted his post in my response.
As far as what you found, that is a classic TT bearing migration problem. We have gotten in TTs with the front bearing more than 25" in.
If one does suspect the TT as the cause of vibrations, safely raise the car, drop the front flywheel lower cover and take a look inside the TT. A coat hanger or other device can be used to find out how far the front bearing is down the TT.
Happy Holidays,
12-20-2011, 09:12 AM
#12
Basic Sponsor
Rennlist
Site Sponsor
Rennlist
Site Sponsor
For clarification - only the Volvo hydraulic MM's come with a tethering saftey strap which should not be used on our cars. If the Volvo MM was purchased from us it would not have the strap as we remove it before shipping.
The 928 has its own tethering system using two large hooks to retain the engine in place during a crash.
The 928 has its own tethering system using two large hooks to retain the engine in place during a crash.
__________________
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
12-20-2011, 10:52 AM
#13
Rennlist Member
For clarification - only the Volvo hydraulic MM's come with a tethering saftey strap which should not be used on our cars. If the Volvo MM was purchased from us it would not have the strap as we remove it before shipping.
The 928 has its own tethering system using two large hooks to retain the engine in place during a crash.
The 928 has its own tethering system using two large hooks to retain the engine in place during a crash.
Mine were installed with the straps. Should I attempt to remove them?
They were not purchased from 928rs, but I am sure they are the Volvo's as I picked them up and delivered to shop when work was performed.
Stay Warm,
Thomas
12-20-2011, 10:59 AM
#14
Team Owner
Superceder I have not ever seen these straps how much did you save buying from another vendor
12-20-2011, 12:17 PM
#15
Rennlist Member
I hurried to 928 Int to buy the parts and within a 24 hour period I had my car back for the trip home to Seattle.
I believe the mounts were $75.00 each.
Thomas