Engine Vibration Above 3000rpm

5.0foxbody91

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Dec 27, 2015
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Hey guys, I'm new to this forum, I've always loved mustangs, and I finally got one. It's a 91 lx hatch. I've had some trouble with it, but I have most of the problems fixed except for this vibration one. The shifter will vibrate like hell above 3000 rpms, whether I'm sitting still or going down the road. I'm not sure of what it is, I just bought the car about a month and a half ago. I'm thinking harmonic balancer, or an engine balance problem, but I'm not sure, any suggestions or tips, would be greatly appreciated, this car means a lot to me. Thanks in advance!
 
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Black1987

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Jan 9, 2011
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Is this a manual or automatic? I would inspect your transmission mount and mounting hardware first. If the car is lowered at all, also check the pinion angle. Is the vibration the whole car or isolated to the shifter? If the vibration is the whole car, I would then proceed to look at the motor mounts and harmonic balancer.
 

5.0foxbody91

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Dec 27, 2015
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It's a manual transmission, the trans mounts and motor mounts I already had checked, and they looked good. I had someone check the drive shaft and u joints, and they were good. I would think if I leave he shifter in neutral, and I'm sitting still, the problem is in front of the trans. I can feel major vibration in the shifter, but there is some vibration through the dash too. What would I check for on the harmonic balancer?
Thanks guys!
 

90sickfox

I didn't really have an issue with the stink...
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Mar 2, 2015
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If you have a stock fan check that also....I had one that had one of the plastic fins broken.....it would vibrate the hell out the car.
 
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90sickfox

I didn't really have an issue with the stink...
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Mar 2, 2015
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The harmonic balancers (factory) have a rubber insulator between the belt hub and the body. What I do to check is disable computer advance ( the plug by the distributer) and check number one tdc and put a timing light on it. The timing should stay constant at say 10 degrees or whatever its set at. If the rubber is poking out it also could indicate a bad balancer. There are alot of factors that can cause a vibration. I'm no expert . noticed it happens sitting still so no drive line issue will cause that. Its got to be ahead of the trans. Flywheel, clutch, balancer, fan, etc
 
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5.0foxbody91

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Dec 27, 2015
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Thanks for the input guys. I just checked the fan, it was okay. Then I noticed the balancer was wobbling at idle, is this normal? Or is that the problem?
 

5.0foxbody91

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Next I'm gonna disconnect the timing advance plug, and I'll check it that way, thanks 90sickfox!
 

90sickfox

I didn't really have an issue with the stink...
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Mar 2, 2015
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No problem....I don't know as much as a lot of these guys but I've been messing with these cars for a while now. Hope you find your problem.
 
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OneWheelPeel

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Dec 23, 2015
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Another thing you could check is the shifter bushing. My shifter would vibrate insanely at about 3k in neutral and in gear. I took out the hurst shifter and saw that the bushing was cracked. I put a new bushing in a pro 5.0 shifter and that fixed it.
 

5.0foxbody91

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I was actually about to ask if that was the problem, I ordered one awhile back but I never put it on, I think it is in the shifter now after looking at it. Do you happen to know how to install a shifter bushing? If so could you walk me through it? I appreciate it man.
Another thing you could check is the shifter bushing. My shifter would vibrate insanely at about 3k in neutral and in gear. I took out the hurst shifter and saw that the bushing was cracked. I put a new bushing in a pro 5.0 shifter and that fixed it.
pro
 

OneWheelPeel

Active Member
Dec 23, 2015
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I was actually about to ask if that was the problem, I ordered one awhile back but I never put it on, I think it is in the shifter now after looking at it. Do you happen to know how to install a shifter bushing? If so could you walk me through it? I appreciate it man.

pro
All you do is take your shifter boot off and the heat/sound rubber thing. Then you unbolt the four shifter bolts. Remove the shifter and then you will see a "bowl/cup" area that the bushing will go into. You will know when you see it. After that you just connect the shifter and bolt it back up.
 
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