Need help with vibration and shifting issues- 2005 GTO
05-30-2013, 08:01 PM
#1
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Need help with vibration and shifting issues- 2005 GTO Ok, so I'll be as descriptive as I can. The story begins-
Bought the car a year ago from the dealer I work at. I am a GM tech. Only mods were K&N intake, muffler deletes, some gay chrome wheels, and GMM Ripshift street shifter. 66k miles.
Bought it without even test driving it, had 3 bald tires and donut spare on rear. The 4th was in the trunk and had blown. Otherwise car was in pretty good shape for the money I paid.
Put on 4 new tires and drove it for a month. Had a minor vibration at 120, but nothing major.
Noticed my driveshaft center bearing was starting to tear so I found a used one piece aluminum Driveshaft shop shaft and adapter. Put and a Pedders rear diff mount insert in on a Friday at work and went to the local 1/8 mile track that night. Had bad wheelhop, enough that the driveshaft hit the rear seatbelt bolt.
Drove it on the highway the next day and had a severe vibration at 65 and faster. Over 100 shakes the car and makes loud humming type noise, but not a wheel bearing hum. It is speed related, not rpm or gear dependent. At 110 if you push in the clutch the vibration does not get worse but the hum noise is louder. Put the stock driveshaft and diff mount back in and vibration is still there.
Sometimes does not go into first easily, have to let the clutch out and push it back in then force it into gear. Clunks into gears when shifting, second is worse. Won't go into third sometimes when shifting at wot. Even with the car off, sometimes it clunks hard/loud or won't go into first. At a stoplight sometimes when I force it into first it feels like the car kind of lurches forward, but not like a clutch not disengaging.
WHATS NOT CAUSING IT:
Wheels/tires- road forced my gay chrome wheels and found one bent. Put on 4 different wheels and tires.
Driveshaft/adapter/yoke- I've tried the stock driveshaft, DSS aluminum shaft, local shop steel shaft, both with DSS aluminum adapter flange. Changed yoke to a GForce1320 billet yoke and a steel shaft.
Mounts/bushings- Did it with all stock bushings. Now have poly engine and subframe bushings.
Clutch- Just installed monster level 2 clutch w/ 18lbs flywheel, new slave and pilot. Input shaft was not worn at pilot bearing.
Anyone have a similar transmission issue? I've been chasing this for a year now and I'm sick of it. I don't like driving on the highway because its so annoying. I've read about issues with bent mainshafts and think that could be a possible cause. Any help with this is greatly appreciated.
Thanks, Josh
Bought the car a year ago from the dealer I work at. I am a GM tech. Only mods were K&N intake, muffler deletes, some gay chrome wheels, and GMM Ripshift street shifter. 66k miles.
Bought it without even test driving it, had 3 bald tires and donut spare on rear. The 4th was in the trunk and had blown. Otherwise car was in pretty good shape for the money I paid.
Put on 4 new tires and drove it for a month. Had a minor vibration at 120, but nothing major.
Noticed my driveshaft center bearing was starting to tear so I found a used one piece aluminum Driveshaft shop shaft and adapter. Put and a Pedders rear diff mount insert in on a Friday at work and went to the local 1/8 mile track that night. Had bad wheelhop, enough that the driveshaft hit the rear seatbelt bolt.
Drove it on the highway the next day and had a severe vibration at 65 and faster. Over 100 shakes the car and makes loud humming type noise, but not a wheel bearing hum. It is speed related, not rpm or gear dependent. At 110 if you push in the clutch the vibration does not get worse but the hum noise is louder. Put the stock driveshaft and diff mount back in and vibration is still there.
Sometimes does not go into first easily, have to let the clutch out and push it back in then force it into gear. Clunks into gears when shifting, second is worse. Won't go into third sometimes when shifting at wot. Even with the car off, sometimes it clunks hard/loud or won't go into first. At a stoplight sometimes when I force it into first it feels like the car kind of lurches forward, but not like a clutch not disengaging.
WHATS NOT CAUSING IT:
Wheels/tires- road forced my gay chrome wheels and found one bent. Put on 4 different wheels and tires.
Driveshaft/adapter/yoke- I've tried the stock driveshaft, DSS aluminum shaft, local shop steel shaft, both with DSS aluminum adapter flange. Changed yoke to a GForce1320 billet yoke and a steel shaft.
Mounts/bushings- Did it with all stock bushings. Now have poly engine and subframe bushings.
Clutch- Just installed monster level 2 clutch w/ 18lbs flywheel, new slave and pilot. Input shaft was not worn at pilot bearing.
Anyone have a similar transmission issue? I've been chasing this for a year now and I'm sick of it. I don't like driving on the highway because its so annoying. I've read about issues with bent mainshafts and think that could be a possible cause. Any help with this is greatly appreciated.
Thanks, Josh
05-31-2013, 01:03 AM
#2
Since you seem to have a spare, it would be easy to drill a yoke and bolt it to the mainshaft; see if you can find vibration there without the driveline.
It doesn't sound like 5-6 driven gear looseness (before someone suggests that) unless it partially goes away in 4th.
After that, look into the diff.
Address the clutch release (did you shim the clutch?) while you're at it.
It doesn't sound like 5-6 driven gear looseness (before someone suggests that) unless it partially goes away in 4th.
After that, look into the diff.
Address the clutch release (did you shim the clutch?) while you're at it.
05-31-2013, 05:27 AM
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Can you explain drilling the yoke to bolt it on?
Its not the diff, I put in a truetrac over the winter. Vibration still there before and after.
I don't believe it is a clutch release issue. Had the same problem with the stock clutch. I have a customers 05 GTO in my driveway right now and it bench shifts a lot easier and quieter than mine.
I did not shim the clutch, Monster said shimming was not needed with their clutches.
Its not the diff, I put in a truetrac over the winter. Vibration still there before and after.
I don't believe it is a clutch release issue. Had the same problem with the stock clutch. I have a customers 05 GTO in my driveway right now and it bench shifts a lot easier and quieter than mine.
I did not shim the clutch, Monster said shimming was not needed with their clutches.
05-31-2013, 11:08 AM
#5
The mainshaft is drilled and tapped. Take a 27 spline yoke and drill it. Bolt it on. That lets you test it at speed, safely versus a complete teardown, or a low-speed run-out check that may not show the same issue as a highway speed run.
You'd need to better qualify your statement of "lurches forward, but not like a clutch not disengaging." then. If on level ground in 1st, it moves forward with the clutch pedal down, it's a clutch release issue, or a really bad piloting issue.
Swap shifters around to rule that out.
Used cars. There is an exception for everything.
I don't believe it is a clutch release issue. Had the same problem with the stock clutch.
I have a customers 05 GTO in my driveway right now and it bench shifts a lot easier and quieter than mine.
I did not shim the clutch, Monster said shimming was not needed with their clutches.
05-31-2013, 07:12 PM
#6
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I guess a better way to describe the lurching is a loud clunk that you can feel in the shifter and throughout the vehicle. The car itself doesn't actually move.
