Ashley P

2005 "GTO" driveshaft

14 posts in this topic

Posted (edited)

Customer brings me a nice, 21k mile 2005 GTO (M6!) for a carrier bearing and diff mount "stiffener".  Test drive before work was good, no noticeable vibration.  Test drive after install, moderate to strong vibration at 40 mph.  Instructions with the carrier say shimming carrier and/or trans mounts can fix vibrations, but many (every possible?) shim attempts all result in no noticeable change.  Nice.:smirk:  (The only other thing I did was add a "rubber" spacer to effectively solidify the rear diff mount.)

I'd never even touched on of these reprobate "Goats".  It drives nice and rides nice.  I suppose the smooth ride deceives me into thinking the car isn't very quick.  (I thought cracking the throttle would scare my Corolla DD butt.)

(And FWIW, a REAL GTO has a driveshaft that's much stronger. :) )

Edited by Ashley P

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Might just be NVH increase due to stiffening things up.  I remember when those 5.7 and 6.0 Grandams used to mess with the BlueCoupe back in the day and would murder me.  I also remember when the tables turned and I used to look forward to seeing them come up next to me and walk off on em.  Now I don't think twice about them anymore really.

Matt

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After seeing your timeslips, I KNOW you wouldn't think twice about one of these cars!   lol

I wonder about the increase in NVH, but still there is a source.  Maybe that source is why the factory rubber mount was sloppy loose.  The vibration is strongest at 40, then remains noticeable 'til 80 when it's back as strong.  And it's too rough to ignore.  When not bolted down, the carrier housing tends to float about 1 bolt width to the passenger side of the bolt holes.  I'm not sure how to tell if that's due to the trans and/or diff aiming off course.  I noticed the oil pan/bellhousing seam is not parallel with the rack and pinion.  At least it LOOKS like it's not.  That would point the tailhousing in the direction it's off.  But engine mounts and subframe mounts look stock, car doesn't look molested in any way.  Weird.

(After spending too much time shimming and driving, I had a coworker hold the driveline at 40 mph while I used a muffler stand to raise/lower (and a pry bar to move left/right) , he said nothing changed the vibration.

I think it need slicks and clutch dumps till it breaks. ;) 

The learning curve of the independent repair shop is steep.  And/or I'm 'tarded.

66sprint6 likes this

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Yes, but understand "consumer psychology"...dealing with the public.  I wanted to use a little of my time to fix the underlying problem so the customer would have no complaints, logical or otherwise.  Now the simple facts are:  no vibration, I worked on it, vibration.

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If it bothers you that much, return it to stock and give it back to him. Explain how the parts caused a bad vibration and you couldn't stand to send a GTO out like that. $1 says he will tell you to put the vibrating parts back on. 

JohnC likes this

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Posted (edited)

Well, a new day and I latched on to it like a pitbull on a toddler and figured it out....U-joint has play side to side.  At least I ASSUME that's the cause, customer to provide 1 piece shaft later.

Edited by Ashley P

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The customer would normally do the work himself, but didn't have a way to press the bearing in.  He's a pretty good dude to work with.  I wouldn't worry about him screwing anybody over.

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59 minutes ago, Ashley P said:

I'm not worried about the customer.  It's just been a headache.

You might actually ought to be worried considering who he works for. LOL

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This week the customer supplied a G-Force engineering carbon shaft.  Problemo fixto.  (Puny LS needs a torque adder, though...)

JohnC likes this

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