Losing my mind- pinion angle

[Anonymous]

Where does it "feel" like the vibration is coming from?

Put the car on stands, put someone in it, put it in second gear and look closely at the rear wheels, then crawl under and look closely at the driveshaft. If that looks okay, swap the front wheels to the rear and look at those as well.

If you have a bent wheel (front or rear) it should be able to be seen, if it looks bent and you swap the front to rear and it still looks bent, then you likely have a bent axle flange. Also, I believe you should be able to see that the driveshaft isn't running true as well.

Finally, get a auto-stethescope (they are better than screw drivers and vacuum hose), they aren't that expensive at the auto parts stores, and put it up to the gear case and see if you can hear anything that doesn't sound like a smooth gear-2-gear action and smooth bearings. Also put it at the end of the axle tubes to listen to the axle bearings.

If all this doesn't find the issue, put the front on stands and check play on the front wheels (tie rods and ball joints) and check the front wheel bearings.

If the above doesn't find your issue, I'd be surprised.

 

[cleetus]

Took it to a local DS shop today and the guy spun it right there. He got up to 2500 RPM and it sounded like a helicopter taking off.

Hopefully the new balance will fix the problem. It STILL does not explain why it happened with the old DS however. The chances of having 2 DSs out of balance is very low. I believe the first DS got bent after the explosion of parts, and not before it.

We'll see tomorrow when I get the DS back if it solves the problem or was just one of the factors.

 

[80montecarlo]

was that on a lathe at 2500 rpm, I have never seen or heard of shafts being spun up that fast for a balance, they are always balanced at 500 RPM.

 

[cleetus]

Aye, was on a lathe or lathe-like machine. It was a long narrow machine, and the DS bolted in. And I'm almost positive he said 2500.

 

[10secBu]

Dynotech can balance up to 8000 rpm.

http://www.dynotechengineering.com/driveshafttech101.htm

 

[80montecarlo]

hmmmmmmmm the company I work for and all the others locally all balance ours at 500-550

 

[cleetus]

How fast is the DS spinning with 410s at 100 mph and a 1:1 gear ratio?

500 RPM is awful slow isn't it? Won't I be spinning 500 DS RPM at like 30 mph?

 

[80montecarlo]

yeah but that is where the balancer is designed to take the most accurate readings

 

[cleetus]

Problem not totally solved.

The new balance made an enormous difference, but the slightest vibe is still there. I'm going to monkey with the angle so more and see if I can figure this out.

I put jackstands underneath the spring perch on the rear, took off the tires, and tested some different angles. I eyeballed the DS as it spun. It appears the vibration is coming from the rear yoke area, as the front of the DS was tight when spun, but the rear sort of egged. I looked at the rear yoke from the side and saw it is slightly out of round (judging by the shield in front of the seal). I don't if that's normal or not.

Could the bolt on piece that holds the rear u-joint on go bad? And where do you get one of those?

Anyone ever have a fcked up brand new Richmond pinion set?

 

[cleetus]

Also found another issue. In neutral, I revved up to 3000 RPM, where the vibration starts. Apparently, SOME of the vibration is in the engine. I'm going to check the flexplate and retorque the converter to see if that makes a difference. It is entirely possible the engine is running too lean though as the last time I had it at the track with open headers, it was breaking up like mad at 3k.

Seems like 3k is my arch nemesis.

FWIW, the vibration is present only between 3000-3400 rpm. Below or above that is smooth both with and without a load.