64 transmission rear mount question.

[jwhunter]

I am having a vibration at about 55 mph and not above or below that speed. Tires and wheels check out ok. My old rear transmission mount appeared to be compressed so I replaced it. I still have the vibration and now I have noise from the transmission area. My question is could there be different mount heights that could cause this problem? I got the replacement from a local parts store. Should I get another from Corvette Parts place to see if there is a difference.? I have balanced the drive shaft and replaced the drive shaft u joints. that appeared to help some. I rotated the shaft 180 degrees at the rear end and that helped some. I plan to replace half shaft u joints next. Any suggestions. Sorry for the length of this.

 

[I_R_DA_ONE]

Have you changed the height of the car??? lowered it

You may have to force balance all four tires rather than just spin balance them..... this gives you a better balance on the actual running condition of the tires....

Does the car viberate or shake????? If it shakes , it's probably a tire that is out of round........If it viberates, it's probably a bad u-joint...

Mike

 

[IH2LOSE]

I am having a vibration at about 55 mph and not above or below that speed. Tires and wheels check out ok. My old rear transmission mount appeared to be compressed so I replaced it. I still have the vibration and now I have noise from the transmission area. My question is could there be different mount heights that could cause this problem? I got the replacement from a local parts store. Should I get another from Corvette Parts place to see if there is a difference.? I have balanced the drive shaft and replaced the drive shaft u joints. that appeared to help some. I rotated the shaft 180 degrees at the rear end and that helped some. I plan to replace half shaft u joints next. Any suggestions. Sorry for the length of this.

Check out this link

http://www.corvetteactioncenter.com/forums/showthread.php?t=65673

Some questions

do you have and original bell housing installed

When you say you now have a noise from the trans area,is that noise a scraping/hitting noise because the trans sits higher and now maybee the trans output shaft is touching something.

When you say your tires check out,does that mean you have had them all high speed balanced,A quick story My wife had a brand new Navaagator and it had a funny vibration in it as soon as you hit like 60 on a highway,it had it wheels and tire balanced/rotated and the vibration never left.Finally I had it and wanted a new truck from Lincoln.Lincoln suggested a Static balance? I think it was a hunter machine that actually weighted down the tire while it was being spun,Once the tires got on the machine they found a defective wheel and tire.They replaced that one wheel and the truck was perfect.I dont know why it made a difference when under a load but the tire was found bad with in 10 secounds.

Dont rule out a clutch or engine problem. See what your rpm is at 55 when the vibration come in, and then take it for a ride and pull first gear out to the specific rpm that you noted, this will determine if its engine or just in the suspention.

Good Luck

I share your frustration Chasing a fibration is very frustrating,

 

[jwhunter]

64 transmission rear mount question

Thanks for the suggestions. The bell housing is original. I have not had the wheels/tires balanced on a hunter weighted machine, but will try that next. The vibration and noise occur at 2500 rpm in 4th gear only. This also happen when decellerating in 4th. thru 2500 rpm. I don't think the yoke is hitting the body but will check. The noise sounds like something hitting the exhaust system. I checked this but did not find anything. I have one motor mount (passenger side) that the rubber is cracked. It doesn't appear cracked all the way thru. Could this possibly be the problem? Again thanks for your help.

 

[JohnZ]

The Hunter GSP9700 is the ONLY way to have your tires balanced; it not only balances precisely, it loads the tire, checks radial and lateral runout, measures radial force variation and shows how to re-orient the tire on the rim to reduce it. There's a locator on the Hunter Engineering site (www.GSP9700.com) that shows you where the nearest shop is to you that has the machine.

 

[IH2LOSE]

Jw For sure if the rubber is cracked the motor mount is probable bad and should be replaced.

have you ruled out the motor as your vibration and think its just in the suspention? If you think its just suspention I would start with the balance,

But this noise May also point to a problem.I think youwish2bme would be better off giving advice on this. to share what he actually checked on his car.I will drop him a PM incase he missed this post.

Good Luck

 

[youwish2bme]

Well I don't know how much better I'll be at giving advice but I always try to....

Jack, It sounds like you have done most of what anyone would do in the case of a vibration. Vibrations are very tedious to diagnose but can be found eventually... I see you live in Raleigh so it's always good to hear of someone else from the Triangle here on the forum.. Also I see that you are a member of Corvettes International I know there are two pretty knowledgible guys in that club, Frank Everitt and Greg Liscomb are two that I 've met. I'm always also willing to help anyone in the area so if you want another set of eyes just let me know.

Vibrations are never fun and I've disassembled my complete rear suspension chasing the one that I hopefully can say HAD.. Could you give us some more information on why you think that it's a driveline vibration? Previously I'd come right out and say a vibration at 55 mph I would suspect a tire imbalance. It seems most vibrations at this speed are tire/wheel related. I see you posted that you had the tires balanced but by whom.. I had my Torque Thruster rims balanced at THREE different shops in the area before I got someone that knew what they were doing. It turned out to be some younger guys that just opened a shop here in Clayton. Atlantic Tire on Atlantic is the shop that I have used in Raleigh before, the owner is a member of CI and his guys take the time with your vette.. I have no problem recommending that shop. They treated me like I worked there and gave me free rein while there.

Did this vibration just all of a sudden become apparent or have you had it since you've owned the car?

If you like you can email me at david.hitchens@na.biomerieux.com...

Hope this has been of some help.. Dave..

 

[jwhunter]

Dave, thanks for the information. I have had the vibration since I got the car. I put new tires (Goodrich radials) and had them spin balanced and required very little weights. I think I will try the hunter force weighted balance. I will email you and get the name of the guys in Clayton and try them since they are closer than shop in Raleigh.

 

[youwish2bme]

The guys in Clayton don't have a Hunter road force 9200 though.. The Atlantic Tire location has the road force machine and that will definately tell you if you have a bad tire. The guys in Clayton just take the time to properly balance a tire vs just throwing the weights on as I've seen else where.. Both shops are very good though.. Dave...

 

[allcoupedup]

Tailshaft bushing?

Brian

 

[jwhunter]

Thanks guys, as usual you are right on. Had wheel balanced with hunter force machine and had one bad rim. Changed rims and guess what the virbration is gone.
Thanks again.

 

[youwish2bme]

Man I'm glad you found it!!! To bad it's raining out now... I'm still wrenching on mine watching it rain... Dave...

 

[Viet Nam Vett]

Man I'm glad you found it!!! To bad it's raining out now... I'm still wrenching on mine watching it rain... Dave...

Keep at it Dave....I hope the problem you had is the yokes. I would stick with your stock SB yoke. It should be able to handel the power from your SB.

Let us know what happens when the ground drys up..and you can jump on it..

 

[JohnZ]

Thanks guys, as usual you are right on. Had wheel balanced with hunter force machine and had one bad rim. Changed rims and guess what the virbration is gone.
Thanks again.

Glad you found it! The Hunter GSP9700 road-force machine puts any other tire balancer to shame; think about it - even if the tire is triangular, egg-shaped or square, it can be perfectly balanced on any spin-balancer, but that doesn't mean it'll be smooth going down the road. Look for an article on precision wheel balancing in the September issue of "Corvette Enthusiast" magazine.

 

[00fxd]

Since I've had my car it has always had a bit of a irritating vib. It would be nice if it was gone. I'm going to try a different driveshaft tomorrow. In the past 2 years in my never ending work in progress, thinking back, for various reasons, I have changed the eng, clutch, flywheel, bell housing, front yoke, diff, 1 stub axle, wheel driveshafts, different wheels. That little vibration is always there making my sihfter rattle. The only thing left is the trans. I sometimes wonder about the driveshaft angle, but every thing is mounted on stock mounts in good condition.

 

[jwhunter]

00fxd,
My vibration is gone now after force balancing the tires on the hunter machine. I also have a rattle in the shifter. Mine is at 2200 rpms, none above or below that. I guess it is something you have to live with. If you find the cause, let me know and I will do the same.
Thanks
jwhunter

 

[JohnZ]

2200-2500 is the harmonic that excites the shifter, as it's bolted solid to the tailhousing; the high number of customer complaints about that issue resulted in the running change in early '66 production to move the shifter to its own separate support on the crossmember, and a TSB was issued to the dealers to install the '66 support bracket and relocate the shifter on complaint units.

 

[00fxd]

I should have mentioned that mine is a Hurst. The vib occurs at highway speeds and is quite noticeable. On long trips I spin my shifter ball off to stop the rattle. I stuck in the other driveshaft tonite, will spin 'er up tomorrow. There is no movement of the yoke in the tailshaft bushing. I've had worse movement in other cars with no issues..