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#21
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First, I would determine if it was the engine or drivetrain, using the techniques already posted. Personally, my '65 had a mirror-blurring vibration for years. Turned out to be a worn front driveshaft yoke. A new yoke and bushing in the muncie fixed it. I have also run into cars where the locating tang was hammered/worn on the rear yoke, making it nearly impossible to center the driveshaft. My gut tells me you have a driveline issue. Also, check the weights on the rear brake drums, etc. A run-out gauge will help you check driveshaft run-out and wheel run-out, which is also not a bad idea. I feel your pain....vibration is a fun killer.
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Jeff |
#22
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iam sure you check this, e-brakes hangin up?
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#23
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Karl |
The Following User Says Thank You to 72LuxuryLeMansLa. For This Useful Post: | ||
#24
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But, in all seriousness, engine firing frequency is a 4th order disturbance of engine rpm (there are four firing pulses per revolution for a V8 engine). If it gets close to another distubance, like 2nd order driveline, it can result in the "boom/beat" phenomenon I described. Quote:
The hope is that if you can isolate the frequency of the disturbance you can back calculate which components are spinning at that same rate (either the base frequency or some harmonic of it), thereby pinpointing your suspect component. It virtually eliminates all this guesswork. It simulates on a smaller scale how we quickly diagnose and repair vibration problems at the GM Proving Ground, except we use power spectral density plots and/or order tracking on one of our Noise & Vibration dynomometers, analyzing several strategically placed accelerometers at the same time. Disclaimer: You do, however, have to be careful where you place the vibration tach. If you set it on the steering column, for example, and the column is going off on it's own resonant frequency rather than the forced frequency of the actual disturbance, it can cause some confusion. K
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'63 LeMans Convertible '63 Grand Prix '65 GTO - original, unrestored, Dad was original owner, 5000 original mile Royal Pontiac factory racer '74 Chevelle - original owner, 9.85 @ 136 mph besthttp://www.superchevy.com/features/s...hevy-chevelle/ My Pontiac Story: http://forums.maxperformanceinc.com/...d.php?t=560524 "Intro from an old Assembly Plant Guy":http://67-72chevytrucks.com/vboard/s...d.php?t=342926 Last edited by Keith Seymore; 10-10-2013 at 09:05 PM. |
#25
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pggto -
Did you do this yet? Quote:
This first step will eliminate half the car, so you know you don't have to worry about that part of it and can begin homing in on where you need to focus. K
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'63 LeMans Convertible '63 Grand Prix '65 GTO - original, unrestored, Dad was original owner, 5000 original mile Royal Pontiac factory racer '74 Chevelle - original owner, 9.85 @ 136 mph besthttp://www.superchevy.com/features/s...hevy-chevelle/ My Pontiac Story: http://forums.maxperformanceinc.com/...d.php?t=560524 "Intro from an old Assembly Plant Guy":http://67-72chevytrucks.com/vboard/s...d.php?t=342926 |
#26
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Is the tranny crossmember bent in any way? Another thing to check is how close your engine sits to the engine crossmember. (Does the fan come real close to hitting the bottom of the shroud?) Sometimes (especially on cars that have been drove hard or have a lot of miles) the engine crossmember tends to "spread out" ever so slightly, letting the engine sag and throwing off the pinion angles. Just something else to check. Still comes back to the basic pinion angle deal.
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#27
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Heres a question for you vibration guys since we are on the topic. Could it be a slightly bent pulley? I have a bad vibration that comes in after 2500 RPM and gets much worse with vehicle speed but its never present before 2500rpm in any gear and it only shows up strong in 3rd 4th and 5th.....I think I have a crank pulley that has a small bend in the outer portion of the ring from when I put in in a tire to haul it. Its not messing with the fan belt but the bend is obvious. Im going to tap it back in place tomorrow and report back. I guess im thinking out loud since we are on the topic.
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-1967 GTO HO Restomod. PKMM 433ci, SilverSport T56 Magnum 6spd, Moser 9", SC&C and a bunch of other pro touring goodies - Build Thread http://forums.maxperformanceinc.com/...615847&page=23 |
#28
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With the car on the ground, how much remaining 'slip' area on the yoke is showing? Same question when it's on jack stands and the suspension is drooping? When the shaft is out at this point, take a close up of the rear yoke and post it. Also, grab the rear yoke and wiggle it. A pinion bearing is also a possibility. .
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. 1970 GTO Judge Tribute Pro-Tour Project 535 IA2 http://forums.maxperformanceinc.com/...d.php?t=760624 1971 Trans Am 463, 315cfm E-head Sniper XFlow EFI, TKO600 extreme, 9", GW suspension, Baer brakes, pro tour car https://forums.maxperformanceinc.com...ght=procharger Theme Song: http://www.youtube.com/watch?v=7zKAS...ature=youtu.be |
#29
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Really ? I had to shim my engine mounts up slightly to get the fan to quit rubbing the bottom of the shroud. I tried everything trying to determine why after all these years it started rubbing. Shimming fixed the problem, but I never knew the cause. |
#30
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Trans mounts too, seen where the wrong trans mount causes issues. And now of course you need to verify your pinion angles. .
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. 1970 GTO Judge Tribute Pro-Tour Project 535 IA2 http://forums.maxperformanceinc.com/...d.php?t=760624 1971 Trans Am 463, 315cfm E-head Sniper XFlow EFI, TKO600 extreme, 9", GW suspension, Baer brakes, pro tour car https://forums.maxperformanceinc.com...ght=procharger Theme Song: http://www.youtube.com/watch?v=7zKAS...ature=youtu.be |
#31
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As seen in another "vibration" thread. Cliff Ruggles had reccomended that unknown vibrations can be found in the transmission bushings such as pilot bushing and tail housing. Have you checked these.
Tim john--- |
#32
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#33
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I'm on engine # 8 in the driver, and get about 100k+ out of each, and if you look at my crossmember, and the current headers on the car, you would agree that I don't baby that thing. So don't think miles has much to do with it.
I'm not convinced it's frame spread some are experiencing, because it takes a considerable amount to show up like that. It would more show in an alignment than in shroud or oil pan clearnace. On the shroud, my first thoughts would be the core support bushings are worn, and the bolts were tightened. That would raise the core support up to 1.5 inches or more, and cause shroud clearance issues. Pan to crossmember clearance, my first thoughts would be due to the engine mounts. I've seen such variations in mounts that cause all kinds of problems, wrong part (box/part swap), poor manufacturing, and incorrect application (cross reference wrong). Think about it, if it spread that much, don't you think it would show up in an alignment? Those front upper control arm mounts would have to move like more than an inch, and that would need like a stack of shims to get right. Second thought would be trans mount is too high, wrong app again. And that would show up as a vibration, since it would whack out the pinion angles. Original Poster - Guess we're all still waiting for you to complete the diagnosis as suggested, before we can continue. Have you isolated the area the vibration is coming from yet? .
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. 1970 GTO Judge Tribute Pro-Tour Project 535 IA2 http://forums.maxperformanceinc.com/...d.php?t=760624 1971 Trans Am 463, 315cfm E-head Sniper XFlow EFI, TKO600 extreme, 9", GW suspension, Baer brakes, pro tour car https://forums.maxperformanceinc.com...ght=procharger Theme Song: http://www.youtube.com/watch?v=7zKAS...ature=youtu.be |
#34
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#35
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#36
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Absolutely, all the little things do add up, and those seem to be tougher to isolate too. I have a bad habit of over-engineering stuff, and in a lot of cases am searching for complicated problems when it's something easy staring me in the face. So any chance I have to provide insight in some areas of thinking out loud, especially, I try to soften that logic/process. A bunch of times I've found solutions to my own issues in that process!
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. 1970 GTO Judge Tribute Pro-Tour Project 535 IA2 http://forums.maxperformanceinc.com/...d.php?t=760624 1971 Trans Am 463, 315cfm E-head Sniper XFlow EFI, TKO600 extreme, 9", GW suspension, Baer brakes, pro tour car https://forums.maxperformanceinc.com...ght=procharger Theme Song: http://www.youtube.com/watch?v=7zKAS...ature=youtu.be |
#37
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I suppose that is what I am doing to try and throw the original poster "a bone" is thinking out loud. In my case (only after I had installed my Gear Vendors unit) did I have a vibration that was driveline related at about 60-75 mph, that wound up being a lot of little things that added up. fixing each little thing made it "better", but in the end it was the fact that they had cut my driveshaft 1/2 too short (causing the yoke to wobble ever so slightly in the back of the GV unit). Had a new driveshaft made up at the correct length by Dennys, and that solved it. Over the years, I had developed a similar vibration in my Oldsmobile, and it wound up being the driveshaft had been "opened up" in the rear very slightly, by some improper u-joint replacement. You could slide the shaft back and forth in the caps ever so slightly. It would not allow perfect centering of the shaft when running. It was only about 1/32 of an inch, but that was enough to cause a vibration.
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#38
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I see that you replaced the trans already, but was it used? I had a terrible vibration in my car and after suggestions from ppl on this forum, including Cliff, I replaced the pilot shaft bushing in the output shaft and the tail housing bushing and it solved my problem.
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#39
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