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Discussion Starter #1
We were first started racing the Tinyvette we had a resonance-type sounds coming from the whole car, it seemed, at around 4,000 rpm in fourth gear and only fourth gear. The whole shell of the car starts to sound like a vibrating drum. After we get past 4,000 rpm it dies out.

Back then we thought this was normal, having never driven a GT before, but maybe not, because it went away for a while and now it is back.

We have a Getrag and the drive shaft is essentially new. I'll check to see if it lost a balance weight. I'll check the u-joints and that they are tight. I wonder a bit about the shaft inside the torque tube and wonder if I need one of those fancy RallyBob shafts.

I plan to crawl under the car again soon to check everything for tightness, wear of bushings, etc.

Tires are new and have been balanced.

Has anyone experienced the same thing? Was the problem solved?

Mike
 

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... it seemed, at around 4,000 rpm in fourth gear and only fourth gear. The whole shell of the car starts to sound like a vibrating drum. After we get past 4,000 rpm it dies out.

...I'll check the u-joints and that they are tight.
You might need to take the front u-joint apart to find the problem.
 

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Discussion Starter #4
Thanks for the links. They help and pretty much convince me the propeller shaft is the culprit. That said, since the problem has come and go, and our speeds are not that much greater, I suspect that instead of the shaft itself it will be the bolts and all that hold everything together.

It may be a few days before I can check this. I'll let you know what I find.

Mike
 

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Discussion Starter #5
I finally got under the car to inspect and found that the torque tube donut is damaged and when I grab the drive shaft I cam move it up and down. It looks like I'll be pulling the torque tube tomorrow, or possibly tonight, depending on how other stuff goes.

I also noticed that the bolts securing the u-joint have been digging into the donut. There's a pretty stiff spring in the Getrag pushing the drive shaft back and it seems to have done it's job too well.

Interesting side-note, spell check doesn't recognize the word "donut", but does recognize donuts. I guess it thinks one donut in any context is not possible. That, or it wants me to be fancy and spell it doughnut.
 

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I also noticed that the bolts securing the u-joint have been digging into the donut. There's a pretty stiff spring in the Getrag pushing the drive shaft back and it seems to have done it's job too well.
When you remove the shaft inspect the trans main shaft for any shiny places.
The shaft could be bottoming out.
 

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Mike, install heavy duty donut if you already didn't. You may also reinforce it by threading old V-belt between donut and the housing.
 

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Discussion Starter #8
When you remove the shaft inspect the trans main shaft for any shiny places.
The shaft could be bottoming out.
I'm not sure what you are referring to. If the transmission, the spring would be pushing against it. For the drive shaft to move aft something on the other ends has to be giving.
 

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Discussion Starter #9
Mike, install heavy duty donut if you already didn't. You may also reinforce it by threading old V-belt between donut and the housing.
Thanks for the tip. I have a spare but I'll check with Gil before I install it.

I also have a spare rear end. I'll dig into it before I do that on the Tinyvette. Practice. It's been a long time since I messed with this part of the car.
 

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The torque tube, driveshaft, and differential are after the transmission, so the vibration should be speed sensitive not at a specific RPM. I had a similar problem with my recently restored 70 GT. it would vibrate the whole car at 50 MPH. I found that one of the ujoint caps had moved out of the yoke slightly causing the shaft to become off center. I replaced the ujoint and everything was fine.
 

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Discussion Starter #11
It was a bear getting the new doughnut in but with a little heat from the oven and various tools to use to slide the doughnut past the tab it went together. I finished everything around 1 PM Thursday and made it to the track and was set up that same night. For the race itself, there was good and bad, but the resonance/vibration is gone.

Thanks all for the tips and advice.

Mike
 

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It was a bear getting the new doughnut in but with a little heat from the oven and various tools to use to slide the doughnut past the tab it went together. I finished everything around 1 PM Thursday and made it to the track and was set up that same night. For the race itself, there was good and bad, but the resonance/vibration is gone.

Thanks all for the tips and advice.

Mike
Mike, did you do the v-belt trick, or was the Hi-Po donut deemed stiff enough by itself?
 

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Discussion Starter #13
I didn't use the v-belt trick. The Hi-po doughnut was really stiff and did a great job last weekend.

Our previous doughnut was a hi-po and it lasted us about 7 years, 25+ races. Not sure why if failed. Maybe they have a life expectancy, or we damaged it when we dropped the rear end to service the poly bushings.
 

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Since I replaced the original donut with the heavy duty OGTS one I get slight vibration in 2nd gear when accelerating. No problems with vibration in 4th gear at high rpms. Makes me think something is not aligned properly and that torque is causing movement of the prop shaft. Is there an alignment procedure for the shaft and/or donut?
 
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