4th generation curiosities

[WCFB-Russ]

(Note: I put this in here because I need people's help and not everyone reads the 4th gen areas...apologies if this offends anyone (double-posting))

So --- get a soda and some snacks cause I gotta run down the story really quick here and it might take a little bit:

Back in 2005 - driving my 1994 Camaro 3.4L V6 after having broken in the Spec Stage 2 Clutch and installed a Polyurethane Trans Mount to my 5-speed manual (t5) - I happened to be on the 110N freeway heading onto the 91W. The interchange there is a fun dip to a 90* turn on which I *always* down-shift, hit the apex and floor it out of the turn just for s&g.

On this particular occasion I did the same as I had always done, and upon hitting third gear an flooring the accelerator - I hear an *extremely* loud BANG (almost a BAM noise) and suddenly the entire car is shaking. I was probably going above 75-80mph when it happened...

I pulled to the side of the road, convinced I had blown a tire (that's what it felt/sounded like) - made sure it was safe, got out of the car and did a complete walk around. No issues. All 4 tires were inflated with no signs of distress, bulges or damage/wear. So I get back in the car and accelerate back up again, to find the vibrations around 60-65 mph. We (my wife and I) were headed to a friends house, so we got there and since he was a car guy, we talked the matter over with him, deduced it was probably the U-joints giving way, and I resolved to fix them.

Did that. Bought two new u-joints and melted the old nylon out of the factory ones on my Ls1 STEEL driveshaft and replaced the U-Joints with Spicer U-Joints I bought from pepboys.

Vibration seemed gone, until I hit 70-75mph - I tried pushing past the vibration but it seemed like the faster I went the worse the vibration got. Never did manage to find a place where the vibration vanished, and I have been on a quest to eliminate since.

Without making this story too much longer, to date I have:

• Replaced Axle Bearings/Carrier Bearings
• Replaced rear with LS1 Rear End (3.42 gearing / full disc - after causing the pinion to grenade - long story)
• Replaced Rear Tires
• Replaced both Front Wheel Bearing Hub Assembly
• Replaced both Outer Tie Rod Ends
• Replaced Front and Rear endlinks
• Replaced U-Joints
• Had driveshaft rebalanced
• Replaced transmission (another long story)
• Adjusted transmission mount height to bring to proper height w/poly endlink pieces

I cant adjust my pinion angle because I have a TQ arm made by MAC which JEGS now sells, looks like this:


(kind of auto-adjusting).

As of right now if I get the car up to 3500 rpm in 4th gear (about 80mph) or above 2500 rpm in 5th (around 80mph), the entire car vibrates. Vibration is felt in the pedals and the middle-back of the driver's/passenger seats.

Anyway - would appreciate any info anyone can give me or suggestions. I'm sure I've replaced more parts on the car but those are the only pieces I can think of. If you mention something and I've replaced it I will definitely add it to the list of replaced/repaired parts.

Also - in 2005 I had my entire steering system rebuilt and replaced the stock v6 rack with a Z/28 steering rack - however it does *not* look like they replaced the steering components other than the rack itself, and I'm a little concerned about that...(rubber on the outer tie rods was 1994 original and very rotted/falling off when i replaced them).

Thanks for any help you can give.

-Russ

[PfadtRacing]

Forgive me black34V6, I am not entirely familiar with the chassis. So my suggestions will probably be out of the blue based on general troubleshooting.

Is the driveshaft that is currently in the car 1 piece? or 2? Is there a bearing carrier? If so, have you replaced it?

Sounds like you have gone through quite a mess trying to diagnose this. Sorry to hear your troubles.

[PfadtRacing]

It sounds as though you are certain that this vibration is speed based, and NOT RPM based, correct? The wrong answer to this question would rule out a TON of troubleshooting steps. Just making sure you in fact are seeing this at multiple RPM values.

[WCFB-Russ]

Thanks for the kind response

Have been through a lot. The driveshaft is a Single Piece Steel driveshaft taken from a 1998 LS1 Trans Am (the previous owner (t/a) upgraded to Aluminum).

It is most definitely SPEED based - not RPM based. I can rev from 0-5000 rpm in 1st gear (or even in neutral) and get no vibrations whatsoever. However on a dyno, on the street, wherever I am driving, if i hit 3000 rpm in 5th gear (80+ mph), I feel a HUGE amount of vibrations..feels almost like the car is going to fall apart (I try very hard not to reach this speed ever)

Hope this helps to help me and thanks everyone

[viper,redz]

Its the poly mount get rid of it . I put one in my car an hated it you can feel everything . Throw it away an put a rubber tranny mount and that should solve the vibration you are feeling .

[wbdinger]

How about tire balance?

[RocketCutlass]

Check your driveshaft, I bet you flung a balancing weight. Check the tailshaft of the trans too.

Edit: scratch that, saw you balanced it and replaced trans.

[WCFB-Russ]

@viper,redz: Thought about going back to the stock tranny mount to find out if thats the cause...might just have to try that (i still have it and it was working ok - i just thought the poly mount would give me crisper shifts)

@RocketCutlas: hehe.. yea those were my first two theories...

@wbdinger: have had the tires balanced twice now - once right after it happened and then again when I had the rear tires replaced all of about 3 weeks ago (working on getting front tires replaced). But I had all 4 tires done when I had the rears replaced (paid a little extra to get that but it was worth it to know they were ok)