Vibration analysis expert opnion needed!
Thread Starter
Melting Slicks
Joined: Nov 2001
Posts: 2,214
Likes: 0
From: Casa Grande AZ
Vibration analysis expert opnion needed!
I've had a vibration in my car since I bought it. At first it was very bad and present most of the time above 45 mph. Before winter I had it whittled down to just 45 -50 mph but was present with or without the clutch depressed. So this winter I pretty much completely redid the front and rear suspension.
Now I still have the vibration although not as severe. It's still present between 45 and 50 mph. It is especially pronounced upon acceleration. It does not appear to be dependant on engine RPM but rather speed. It doesn't seem to appear until 3rd and 4th gears at the offending speed. AND it completely and totally disappears when I push the clutch in - even when reving the engine.
What's the likely culprits??
Thanks!
Now I still have the vibration although not as severe. It's still present between 45 and 50 mph. It is especially pronounced upon acceleration. It does not appear to be dependant on engine RPM but rather speed. It doesn't seem to appear until 3rd and 4th gears at the offending speed. AND it completely and totally disappears when I push the clutch in - even when reving the engine.
What's the likely culprits??
Thanks!
Race Director
Joined: Oct 2000
Posts: 16,477
Likes: 1
From: Enter Post Count Here
Re: Vibration analysis expert opnion needed! (lbell101)
Hmmm...I came in here thinking we could hook up the Chadwick-Helsmuth machine, but it wouldn't be of much use finding the vibration.
How are your U-Joints?
How are your U-Joints?
Le Mans Master
Joined: Sep 2000
Posts: 5,635
Likes: 4
From: Orlando Floriduh
Re: Vibration analysis expert opnion needed! (lbell101)
Check for bent or out of balance half shafts, drive shaft. or a bent transmission output shaft. May also be an out of true,loose or out of balance pressure plate
Thread Starter
Melting Slicks
Joined: Nov 2001
Posts: 2,214
Likes: 0
From: Casa Grande AZ
Re: Vibration analysis expert opnion needed! (NoWorries)
It's for sure not the U-joints. I replaced them right after I bought the car with no improvement. Then I replaced them AGAIN this winter just to be sure. Additionally, the previous owner said he had just changed them too. I'm thinking that the vibration elimination when depressing the clutch would rule out the u-joints too. I can't believe I still have this vib!
Drifting
Joined: Oct 2000
Posts: 1,825
Likes: 56
From: Shawano WI
Re: Vibration analysis expert opnion needed! (lbell101)
Larry;
Way back when I was running Muncies in my race car I had a problem similar to that. Only had a vibration when the car was under load and only in third and fourth gear. I suspected it to be the roller bearing between the input shaft and the main shaft. When I took the trans apart the bearing felt a little (very little) rough. While I was at it I also replaced the front input shaft bearing and the pilot bushing. The vibration was gone but I don't know which of the three was the problem.
Way back when I was running Muncies in my race car I had a problem similar to that. Only had a vibration when the car was under load and only in third and fourth gear. I suspected it to be the roller bearing between the input shaft and the main shaft. When I took the trans apart the bearing felt a little (very little) rough. While I was at it I also replaced the front input shaft bearing and the pilot bushing. The vibration was gone but I don't know which of the three was the problem.
Advanced
Joined: Mar 2002
Posts: 90
Likes: 0
From: Colorado
Re: Vibration analysis expert opnion needed! (lbell101)
:chevy Here's opinion to throw into the mix... Mine had a vibration I chased for the first 10 years I owned it... sound's like a long time, but it only showed up in speeds over 70mph so I would fix something, then drive it for awhile, then repeat. I replaced the u-joints, had the driveshaft and both half shafts spin balanced, replaced the transmission (suspecting the rear output sleeve & other life-wear possibilities) (kept the original one and am running it again now of course), replaced the output yoke, re-built the trailing arms, replaced the steel wheels, balanced them multiple times, and finally found the culprit all along....the mounting bushing on the front of the differential (snubber). Since then (15 years later), NO vibration...drives like it's new (because most of it IS). Good luck :smash:
Thread Starter
Melting Slicks
Joined: Nov 2001
Posts: 2,214
Likes: 0
From: Casa Grande AZ
Re: Vibration analysis expert opnion needed! (gsk@sprintmail.com)
Thanks for the ideas. I'm leaning towards the tranny/clutch area. I replaced the carrier front mount already (and it REALLY needed it). Looks like I'm in for a tranny pull, rebuild, and clutch / pressure plate check!
Team Owner
Joined: Aug 1999
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Re: Vibration analysis expert opnion needed! (lbell101)
Can you estimate the frequency of the vibration? That helps narrow things down a bit. Is it once per engine rev in 4th? (driveshaft spinning at the same speed as the engine with the 1:1 ratio). Or is it higher or lower?
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