Dan Fletcher Super Stock Videos - Opinions

[Mark Ugrich]

Originally Posted by joespanova

Change engines..........may not even be driveline related.

One possibility would be a bad thrust bearing allowing the crank to move and bind against the converter.One of my cars had a "whine" only on coast.I found the flywheel bolts had printed the face of the converter.ARP bolts with thinner heads solved the problem.

[Don Sofranko]

Seems like the vibration starts as soon as the coasting begins, then gets so bad he feels it in the shifter, and the rest of the car at the end.

I would have the gear changed right away. In a stick car, with a 6.50 screw, we would crack pinion teeth after 45-50 runs. Then after 50, you could barely touch the shifter in the shutdown coast. We found a better gear oil helps a bunch, on gear life. A new gear should make it whisper quiet in the shutdown.

I know you guys get more gear life than that. But there is always a limit...
Mark Williams knows drivelines, and sells the better gear oil. Regular gear oil isn't good enough... get the torco for longer gear life.

www.markwilliams.com/Catalog/pg23.pdf
torco sells for 10.70 a quart now, what are you using currently?

[Mike Taylor 3601]

Usaully driveshaft will vibrate at two points on a run,a certain rpm which it will vibrate when passes that rpm accelerating then at that rpm when decelerating.
I still think sounds like gear noise.
Dan,
If can mount dial indicator and check driveshaft for run out on each end, if it runs around .015''or less should be smooth.
Built driveshaft awhile back that couldn't be made smooth,had to build another one with bigger od tube and thinner wall thickness to fix it
Mike Taylor 3601

[joespanova]

Originally Posted by Mark Ugrich

One possibility would be a bad thrust bearing allowing the crank to move and bind against the converter.One of my cars had a "whine" only on coast.I found the flywheel bolts had printed the face of the converter.ARP bolts with thinner heads solved the problem.

The only reason I suggested that was because it eliminates anything wrapped around and including the crank. He probably has spares as much as he races ,

[Don Sofranko]

Reading back a few pages, it says you are ready to switch back to the 6.20 gear.
That should provide evidence of the problem. Really though, a bad pinion would be all it takes. The pinion teeth do crack and deform, which can be hard to see.

I had one gear wear out after 35 hits, when I had Quaker State gear lube in the 9 inch.
That pro gear was found with rolled metal on the pinion. The pinion is more important than the ring gear. If the gear has too little backlash, its going to push out the heavy lube also.

I sure would hate to be your gear set, watching how hard you wheel that Camaro at the stripe!

[ss3011]

The Engine/Transmission shafting needs to be parallel to the rearend pinion shaft. This will allow each of the u-joints to run at the same angle which cancels the acceleration and deceleration the driveshaft sees each revolution. That is why the u-joints are phased to each other. If you crank too much pinion angle into the rearend, then the u-joints will get out of phase, and you will have a vibration. The pinion angle will change as the rear suspension moves because on a 4 link the upper and lower bars are typically not run parallel. Might be worse in this case when slowing down.

[Greenlight]

Install a high frequency accelerometer on the car and make a run.

Use FFT (Fast Fourier Transform) software (you can find some free versions on the internet or I'm sure ATI has this software) to break down the vibration to individual frequency and amplitudes. Then take the high amplitude readings and see what frequency is associated with it.

For example, if the high amplitude vibration frequency is 13.3 Hz (13.3 times a second) at a time when the engine RPM is 7000, the alternator RPM is 10000, the trans. output shaft is 4800 RPM, the rear axle RPM is 800 (13.3 revs per second), you can focus on things that turn the same RPM as the rear axle (ring gear, side carrier bearings, axle bearings, brake rotor, wheel, tire).

Whatever you do, don't change the roof. That's not it.

Here is a cheap accelerometer that works great. I've used mine for analyzing vibrations in high speed machinery as well as vibrations when a putter hits a golf ball.

http://www.gcdataconcepts.com/x16-4.html

[tpoh815]

Originally Posted by Mark Ugrich

One possibility would be a bad thrust bearing allowing the crank to move and bind against the converter.One of my cars had a "whine" only on coast.I found the flywheel bolts had printed the face of the converter.ARP bolts with thinner heads solved the problem.

This is caused by Dan treeing his opponent so bad he has time to whomp the gas so many times he literally makes ten passes for each run causing premature thrust bearing wear! Hence the "virbation".025 end play aint nothin !

[Mark Ugrich]

Originally Posted by tpoh815

This is caused by Dan treeing his opponent so bad he has time to whomp the gas so many times he literally makes ten passes for each run causing premature thrust bearing wear! Hence the "virbation".025 end play aint nothin !

Actually the situation I had was that the converter was tight against the flywheel bolts.It bound up the trans enough that I found shavings of thrust washer in the transmission pan.Not saying that's what's happening here,but I'm sure Mr. Fletcher will figure it out.

[Larry Hill]

If Dan can't fix it, he will spend enough time searching and finally worry it to death. He works very hard at his chosen craft!