Driveshaft help

[72HCODE]

I'm getting a vibration with my car over 65mph.

first thing i did was rotate the shaft 180 on the rear yoke to the 3rd member and put it back and that improved things.

however the vibration is still present,

Question:

1) would rotating the transmission yoke 180 have a similar effect to rotating the 3rd member yoke as far as balance?

2) are driveshafts bi-directional does it matter which side of the driveshaft is connected to the yoke and which is connected to the 3rd member yoke (assuming the U-joint caps are the same)?

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I'm thinking about having my driveshaft checked for balance as well.

possibly replacing the Yoke.

I'm also thinking about replacing the yoke and driveshaft with a new one and trying that route

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this vibration might not be a new thing, it could of been present before i'm just driving the car much faster then i used to on the highway now.

 

[jbojo]

How many miles on the drive shaft? Could be that the U-Joints are bad and need replacing

 

[72HCODE]

U joints are all new, and greased. i actually just checked them as well when i took the drive-shaft off.

mileage unknown, driveshaft might of been replaced in the past. I've had it for 10+ years and put about 14K on it.

when i drove the car i used to keep it around 55mph there is little to no vibration at 55-65mph after that it increases i have not gone over 80mph.

70mph is about 3000 rpms with my end ratio.

 

[Jeff73Mach1]

How is the balance on your wheels and tires? A vibration at that speed is often a tire out of balance. Perhaps you lost a wheel weight.

Phase of the driveshaft should not matter on a car with a 1 piece drive shaft with u joints on both ends.

Does the vibration go away if you shift into neutral and coast?

Does additional speed make it go away? If so at what speed does it disappear?

 

[jbojo]

Just throwing this out too, might want to check the rubber mount on the transmission tail housing. Could be loose or broken but most likely tire balance as Jeff has mentioned if the drive shaft is good.

 

[Jim and Jutta]

I'm getting a vibration with my car over 65mph.

first thing i did was rotate the shaft 180 on the rear yoke to the 3rd member and put it back and that improved things.

however the vibration is still present,

Question:

1) would rotating the transmission yoke 180 have a similar effect to rotating the 3rd member yoke as far as balance?

2) are driveshafts bi-directional does it matter which side of the driveshaft is connected to the yoke and which is connected to the 3rd member yoke (assuming the U-joint caps are the same)?

----

I'm thinking about having my driveshaft checked for balance as well.

possibly replacing the Yoke.

I'm also thinking about replacing the yoke and driveshaft with a new one and trying that route

-----

this vibration might not be a new thing, it could of been present before i'm just driving the car much faster then i used to on the highway now.

I had strange vibrations at higher speeds that would come and go, sometimes just letting off of the gas from high speeds caused a shutter; turned out my yoke was bad and the driveline was out of balance. Had it fixed vibrations gone.

 

[72HCODE]

Tires new replaced last week,

Wheels balanced same day.

Old tires and new tires had the same vibration over 65 mph

Trans mounts just checked it is good, as I rebuilt the trans last month.

Motor mounts good also checked.

Will do a test with the engine in nuetral and see if letting off power at speed makes the vibration go away.

Vabriation gets worse and worse over 75mph.

 

[72HCODE]

a yoke was 80$ so i took a chance and ordered one.

me swapping it should take an hour or 2.

 

[rocket366]

yes

kicking it into neutral at speed will eliminate the engines balance as the problem.

I bet it's wheel balance that is causing the vibration.

Back in the day I had a freind I could swap things with to try such as tire/wheel

to eliminate problems... and yes I miss those days.

Paul

 

[Bill73Ragtop]

I believe in having any drive shaft balanced (or at least checked) before installing for the long-term. Cost is usually $15 - $20 for a balance check.

Something of note: Back in 2007 when I was nearing the finishing stages of restoring my 69 convertible Reso-mod, I ordered a new drive aluminu shaft from Denny's Driveshaft (located here in Buffalo). I had purchased a new yoke (+/-$90) and took it to him (still in the box) to see if it would save me few $$. When I went to pick up the new drive shaft he gave me the yoke back saying he checked it and it was not machined very well and would have created big problems. He showed me how (and even I could see it when he pointed it out) it was machined too much on one side. He said it was not worth the effort to try to correct. The cost of the new drive shaft was $450 which included yoke, U-joints, etc. It runs perfectly true - as it should.

One additional item: I once failed to fully seat the u-joints into the rear 3rd member yoke. Big mistake. I did not compress the caps and nestle it tightly into the u-joint. Had similar vibration as you describe and then within 20 miles experienced catastrophic rear u-joint failure at 60 mph. Big problem with a convertible since the tunnel support plate won't let the shaft drop down and away. Beat the hell out of the rear sheet metal under the seat area. I have confidence you will never make the mistake I did....

 

[OMS]

Dan, I have a complete 71 C6 shaft

Won't be needing it for awhile.

If you want to borrow it to see if the vibration goes away.

Just cover shipping, let me know.

Don

 

[72HCODE]

well i'll be under the car the next couple days to recheck.

I know it isn't the tires or the rims. i know the vibration was REALLY bad just after i swapped transmissions. i turned the driveshaft 180 and things improved but it still isn't right. I know its not the engine or the balancer but i will check again anyway.

I'm going to check play in the driveshaft as well.

also i have a new yoke on the way should get here next week.

When i rebuilt the trans i checked for anything bent and nothing was.

thanks Don, I'll see what happens the next couple days.

 

[Mikes73]

You said it starting vibrating really bad after the transmission swap, maybe it is the transmission or torque convertor, or flexplate. You never know.

 

[72HCODE]

you are right, i'm hoping it is something easy.

the converter is a new TCI, flexplate i reused(could be a problem source), transmission nothing appeared out of balance when i assembled.

when i first got the trans in and test drove the vibration shook the entire car at 20mph, on the highway the vibration was moving my mirrors around on the doors LOL. I flipped it over and everything was good, but on the highway after 65mph it gets jiggly again.

things i did not replace besides the flex plate, the driveshaft and yoke and 9" 3rd member yoke.

 

[72HCODE]

just checked for play in the U-joints and both yokes; Nothing everything feels solid.

 

[jbojo]

As mentioned earlier I would just have the driveshaft balance checked. I would replace the yoke since you got that already and try driving it again and if you still have the vibration then have the driveshaft balance checked again.

 

[Don C]

I would rotate the new (and old) yoke around on a set of v-blocks and check the runout on the u-joint machining.

 

[72HCODE]

Just did a idle to 3000 rpm hold in nuetral with the AC compressor on and then off.

There was a vibration around 1500 that came and went then above 2500 it did vibrate more then I thought however the vibration was different then what I felt on the highway.

Still I was surprised by the vibration at 3000 sitting in nuetral.

New yoke gets here on Monday so I will swap it out next week after I check it over and make sure it is good.

The AC compressor did add to the vibration at 3000rpms

 

[mjlan]

Could it be something with the convertor pilot in the end of the crank?