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Will work for parts
Join Date: Oct 2002
Location: Silicon Valley
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weird vibes
I just replaced all the belts and rollers on my 88'. The belts went on alright and when I took it for a test drive I noticed a vibration on deceleration. I took into account all the vibrations that were there previously but this was new and you can feel it in the floor boards and the shifter. I thought that i might have gotten the balence shafts just sllightly off but they seem to be lined up correctly. The marks were dead on. I also had noticed the sway bar was very close to the AC compressor and indeed it was hitting and I unhooked the bar. the vibes are less but it is still there. There is some of this vibration on aceleration but mostly is is when you let off the throttle at speed with the clutch engaged. It idles perfectly and from the outside you dont hear any strange noises like rubbing or anything out of the ordinary. Any suggestions?
-Greg
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'88 944 240,100 miles -race car '05 Boxster 110,000 - Daily Driver '74 911 Targa - long term project |
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06-07-2005, 10:08 PM
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Are you sure the bal. shafts are insink? Larry
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06-08-2005, 07:44 AM
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Will work for parts
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Well, on Clarks garage the lower balence shaft should be aligned to a raised plastic line in the rear housing. Unless there are two it should be correct. The vibration is not enough to suggest that it is not 180* out.
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'88 944 240,100 miles -race car '05 Boxster 110,000 - Daily Driver '74 911 Targa - long term project |
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06-08-2005, 09:42 AM
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IF it was 180* out, you'd have vibration above about 3500 RPM no matter what you were doing (accelerating, holding stead, or decelerating).
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Ryan '84 944 moneysucker edition (SFR, Corbeaus, etc.) '02 Jetta TDI 280Lb/Ft 145Hp @ wheels. RC2 PP357's |
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06-08-2005, 10:21 AM
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Check it with this diagram.
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Hugh - So Cal 83 944 Driver Person NOT a 'real' Porsche -- Its Better!!!! When was the last time you changed your timing and balance belts and/or cam chain and tensioner? New Users please add your car's year and model to your signature line! Never break more than you fix! |
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06-08-2005, 12:28 PM
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why is the AC hitting the sway bar??? what kinda condition are your motor mounts in
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1986 951, Stock for now. ]87 924S Gaurds red- SOLD after 11 years of ownership |
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06-08-2005, 01:41 PM
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Will work for parts
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The motor mounts are probibly shot. The pulleys appear to be on correctly and I was looking at the right mark. I was very careful to mark and keep all the timing as it was. IF it was off by a tooth what kind of diffrence would it make? This is getting confusing. With the car sitting you can rev the engine and it seems ok but its when you drive it that it vibrates. sometimes turning can even seem to make it worse. Im sure its something stupid too and ill kick myself when i find out what it is.
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'88 944 240,100 miles -race car '05 Boxster 110,000 - Daily Driver '74 911 Targa - long term project |
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06-08-2005, 02:27 PM
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Well i rotated it 180 and it does it less but the bad vibe is still there. Now i get other vibrations as well. I also dont seem to notice a huge diffrence with it spun 180 to where the marks are, I thought that there would be a major improvment. I guess ill just keep trying things.
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'88 944 240,100 miles -race car '05 Boxster 110,000 - Daily Driver '74 911 Targa - long term project |
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06-08-2005, 04:15 PM
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I'd say it is your motor mounts, not the b'shafts. If it were the shafts, you would have vibes on accel as well as decel at a given rpm. Mounts are torqued differently on accel and decel.
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Still looking for the right deal on another P-car 1968 BMW 1600 2 liter 1956 Ford F250 1955 BMW R69 1999 Range Rover Callaway #011 of 220 (Yeah, as in Callaway Corvette...) |
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06-09-2005, 06:51 AM
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What Pokey said sounds right to me. If your bshafts are insink that would be the next place to check. Sitting and out of gear there isn't much torque transfer to the body, even if you reve the engine while parked you wont get much vibration. If it is the bshafts you would notice it anytime the engine was running. Larry
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06-09-2005, 07:24 AM
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If you can stick your hand between the oil pan and the cross member the engine mounts are good. If you can only get to the middle of the fingers or your knuckles then replace the engine mounts.
As to the balance shafts; getting the pullies back on 170 degrees out happens. You need to confirm where the keyway is in reference to the alignment notch. Either use a small wire to probe or take off the nut and outer washer/flange to reference the O and U.
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Hugh - So Cal 83 944 Driver Person NOT a 'real' Porsche -- Its Better!!!! When was the last time you changed your timing and balance belts and/or cam chain and tensioner? New Users please add your car's year and model to your signature line! Never break more than you fix! |
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06-09-2005, 08:38 AM
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Ok, Ill check both of those things.
thanks!
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'88 944 240,100 miles -race car '05 Boxster 110,000 - Daily Driver '74 911 Targa - long term project |
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06-09-2005, 11:43 AM
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1983 Porsche 944 2.5 liter
1987 Porsche 924S 2.5 modified
