Driveline vibration in 5th gear but not 4th

[dave6666]

2001 GTS with 27K miles. At speeds of 100 to 130 or so, I have normal (defined as slight) driveline vibration in 4th gear, but as soon as I push in the clutch to go to 5th, the vibration is much more pronounced (defined as "maybe I shouldn't be doing this"). It stays when I actually go to 5th after releasing the clutch. At speeds of 70 to 80 and thereabouts there is nothing different between the 2 gears. Have not tried 4th to 6th.

I don't like explanations that get really long, so I'll just list a few facts here about my car. I really have nothing in mind that stands out at this point, and also don't mind spending whatever it takes to replace whatever needs replacing.

-> Tranny mount recently replaced with Big Brakes billet x-member and poly mount.

-> Engine mounts are original although I have a set of Woodhouse mounts ready to go in soon. I can't really say I know the condition of the OE mounts right now. I did some searching and it seems like the poly mounts will account for even more vibration so I really don't know how all of this will come together.

-> Clutch was replaced by me recently with an ebay Luk kit.

-> All six u-joints and straps recently replaced with new Spicers.

-> All suspension and diff mounts to factory torque.

-> Tires and wheels good and well balanced.

-> Have typical driveline/tranny clunk when decel/accel under light load.

 

[Viper Wizard]

I've got it, you need to add a little more air to the rubber ring your sitting on!






I really couldn't stop myself from typing!

 

[Warfang]

I've got it, you need to add a little more air to the rubber ring your sitting on!






I really couldn't stop myself from typing!

Still haven't shaken off the celebratory champagne yet huh?

 

[treesnake]

My bet is a broken motor mount. Do you sometimes have a little trouble shifting (or missing) into third gear also?

 

[Tom F&L GoR]

Is it correct to say that the vibration occurs when the clutch pedal is depressed (disengaging the engine) but only happens when the vehicle speed is over 100 mph? (i.e. no load on the drivetrain?)

 

[dave6666]

Is it correct to say that the vibration occurs when the clutch pedal is depressed (disengaging the engine) but only happens when the vehicle speed is over 100 mph? (i.e. no load on the drivetrain?)

Partially correct Tom if I understand your question. Here is a sequence:

-> Driving in 4th at 120mph. Normal vibration.

-> Depress clutch to go to 5th. Vibration immediately increases.

-> Shift to 5th and release clutch. Vibration persists.

Looked at my engine mounts last night from underneath and they look OK. I realize that may mean squat.

Also, the vibration will occur just increasing speed to 120 or so if I'm already in 5th. It really has nothing to do shifting, it's just high speed in 5th gear. But not 4th.

In lieu of installing an on-board air system for my Wizard ring, I would prefer to either address an issue, or be impressed upon by others that this is normal.

 

[dave6666]

I've got it, you need to add a little more air to the rubber ring your sitting on!

I really couldn't stop myself from typing!

Chuck, get it right. The correct layout for smilies is 3x 6, or 666.

 

[treesnake]

"Looked at my engine mounts last night from underneath and they look OK. I realize that may mean squat."

Mine looked good from underneath also. After romoving them it was obvious that they were broken. The new poly mounts "feel" a lot better anyway

 

[FATHERFORD]

Hell dave I would just replace the mounts anyway. I'm not no genious, but 11+ year old rubber motor mounts on engines creating the torque these cars do can't be in that good of shape today.

If it just vibrates more in 5th, at the same speed as it does in 4th, that rules out anything past the tail shaft of the tranny in my eyes. Putting the car in 5th put's more load on the engine and tranny.

 

[Username]

-> Clutch was replaced by me recently with an ebay Luk kit.

Has this problem only been since you replaced the clutch?

Although rare, we see some bad clutch packs that cause vibration that is felt at higher speed. The higher gears seem to multiply the problem as the output and drive shaft are spinning faster.

 

[dave6666]

Hell dave I would just replace the mounts anyway. I'm not no genious, but 11+ year old rubber motor mounts on engines creating the torque these cars do can't be in that good of shape today.

If it just vibrates more in 5th, at the same speed as it does in 4th, that rules out anything past the tail shaft of the tranny in my eyes. Putting the car in 5th put's more load on the engine and tranny.

As mentioned above, I do have Woodhouse mounts waiting for me to get to them. Doing my Belanger headers here shortly, and will combine those projects.

Has this problem only been since you replaced the clutch?

Although rare, we see some bad clutch packs that cause vibration that is felt at higher speed. The higher gears seem to multiply the problem as the output and drive shaft are spinning faster.

Can't recall if there is any coincidence with the clutch replacement and this issue. Not very often do they close down Interstate 35W for me. You know, professional driver on closed course...

 

[FATHERFORD]

As mentioned above, I do have Woodhouse mounts waiting for me to get to them. Doing my Belanger headers here shortly, and will combine those projects.

What are you waiting for? more beer? Get after it!

 

[dave6666]

What are you waiting for? more beer? Get after it!

Quite the opposite actually. I was hoping to do this project sober!

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[ViperTony]

I think you need a Roe Supercharger Dave, that's the only solution.

 

[Tom F&L GoR]

Feel the vibration in the car or in the shifter?

 

[dave6666]

Feel the vibration in the car or in the shifter?

Both.

 

[Tom F&L GoR]

I'd put the car on floor jacks and slowly raise the engine with a hydraulic jack. And look under the hood for where the intake manifold may hit it. Do your air cleaner tube clips keep falling off?

 

[dave6666]

I'd put the car on floor jacks and slowly raise the engine with a hydraulic jack. And look under the hood for where the intake manifold may hit it. Do your air cleaner tube clips keep falling off?

I'll do that tonight with the jack and see if the mounts or anything else shifts. I have the car in the air right now anyway fitting my new side sills for side exhaust conversion. Autoform fun...

I have no problems with anything coming undone on the air intake system, like the airbox clips of smooth tube clamps. Have also not seen any marks on the hoodpad from rubbing. Which I got to know my hoodpad quite well with now 2 hoodpad painting write-ups in the Illustrated Upgrades section.

 

[FATHERFORD]

I'll do that tonight with the jack and see if the mounts or anything else shifts. I have the car in the air right now anyway fitting my new side sills for side exhaust conversion. Autoform fun...

I have no problems with anything coming undone on the air intake system, like the airbox clips of smooth tube clamps. Have also not seen any marks on the hoodpad from rubbing. Which I got to know my hoodpad quite well with now 2 hoodpad painting write-ups in the Illustrated Upgrades section.

Man you are going all out on your viper huh? New wheels, new exhaust, new mounts...

 

[dave6666]

Man you are going all out on your viper huh? New wheels, new exhaust, new mounts...

Oh, and like the "I want nitrous so I can do a zillion miles per hour in 3.2 seconds" is not all out too?



And you forgot SRT brakes in my list...

 

[FATHERFORD]

Oh, and like the "I want nitrous so I can do a zillion miles per hour in 3.2 seconds" is not all out too?



And you forgot SRT brakes in my list...

LOL ehh I guess.

 

[dave6666]

Driver side engine mount with engine elevated about an inch.

Mystery solved?

No need to adjust air in inflatable seat Wizard cushion ring thingy?

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[dave6666]

Wanted to follow up with the progress here. New Woodhouse motor mounts have gone in, but in the process of a much longer project so no road test yet.

First pic is driver side mount. Second pic is pass side OE header dented from banging frame rail.

I'm starting to feel warmer and fuzzier all the time that this was the problem.

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