[Hank's 68]

I was having work done on my transmission and I was told my drive shaft was out of phase. I searched for the term "phase" on this site and read that an out of phase drive shaft could lead to a bumpy ride.

Can someone explain what the term out of phase means?

Thanks.

[rojo]

It means the u-joints are not aligned up with other. GM did this on purpose to take out some sort of harmonic vibration. There's a good post somewhere with some pretty high tech explainations. I had mine put back in phase when I had is shortend and balanced. I could not tell any difference.

Edit: I did a search on "driveshaft phase" and got some good hits.

[JimM]

ditto. my yokes were originally out of phase, when i had the driveshaft shortened tit came back in phase, no difference that i can tell.

[Fred Ficarra]

Ditto-ditto. I'm on my second overdrive. No difference, damn-it! Solution? I just bought a new aluminum shaft. It's in phase AND I raised the rear-end yoke 6 degrees. Now it's only off 1.5 degrees. In-gear, on the road should be perfect. Fingers crossed. I'll know in the spring.

[Fred Ficarra]

UPDATE!!
First drive on the road yesterday. Since new, my car vibrates at 70mph and beyond. NOT any more! Butter smooth. Success.

[kustomwerker]

drive shafts in the older cars had a ton of runout from the factory...(i just had the 1 in my 79 done...it was out 70 thousanths!!!)when you run an overdrive, the shaft is spinning far faster than with a th350/40/pg, because final drive in them is 1:1...overdrive is .70:1 or even less, so the shaft is spinning up to 30 % faster than it used to...my d/s guy is a really cool old timer that retired from designing and manufacturing custom machinery...he made his balancer from scratch...its pretty frikken cool to see the process done,,,mine had a bad vibe from day 1, but after the 2004r, it really shook...even wiped the rear bushing out of the trans!!!now its like glass through the driveline...now i just gotta get new front tires...lol...

[Fred Ficarra]

Thanks for that Mike. Just one thing. The drive shaft speed doesn't change with overdrive. Only everything forward of the OD gear slows down.

[kustomwerker]

my point was taken backwords, probably because of how i worded it...i tend to drive a lot faster with the od because i can...at 100 miles an hour, my driveshaft is spinning aprox 30%faster than my old cruising speed of 70 mph...therefore the vibration is far more pronounced...i can go faster therefore i do go faster...lol...u r absolutely right fred...everything internally, and up to the motor spins slower to make the same speed...