Vibration and Noise Issue

[Map63Vette]

So I just finished swapping in my new 8 3/4 and have run into some new issues. The first issue I noticed was that the driveline seemed to make a pretty nasty noise around 40 mph or so. It is most evident just cruising around town in 4th, but if I wind it high in 3rd you can start to hear it as well. It sounds kind of like cast metal scraping. I initially thought it might be the brake drums skimming the backing plates (the brakes were pulled from a different housing), but when I jacked the car up and let it run with the wheels off the ground it doesn't really sound like it's coming from the wheels and it's mostly speed based. The second problem is the car has a horrible vibration to it at highway speeds, like vibrating chair bad. I took a look at the driveshaft while it was running and it doesn't look like it's turning around center, however, it was the same driveshaft that was on the car before with the old rear end and it never shook like that before and I put brand new U joints in it a few weeks ago. My dad and I were guessing that maybe it's a pinion issue, but does anyone else have any ideas what it might be more specifically? The car also just got brand new wheels and tires with the axle swap, so everything should be all balanced up.

 

[Demon 408]

...new 8 3/4 ...sounds kind of like cast metal scraping ...it's mostly speed based ...has a horrible vibration to it at highway speeds ..."I took a look at the driveshaft while it was running and it doesn't look like it's turning around center" (explain please) ...I put brand new U joints in it a few weeks ago ...guessing that maybe it's a pinion issue (have you checked pinion angle?) ...car also just got brand new wheels and tires with the axle swap.

Wow! Lots of possibilities. Have you tried jacking up the rear and turning the rear tires by hand (car in neutrel) and listening for noises? What rear was in it before 8 3/4? You swapped the entire rear, not just the center section, correct? ..."I took a look at the driveshaft while it was running and it doesn't look like it's turning around center" (explain please) ...guessing that maybe it's a pinion issue (have you checked pinion angle?)

 

[pettybludart]

Maybe your u-joint isn,t centered in the yoke?Would cause a vibration.Something to check.

 

[Supershafts]

however, it was the same driveshaft that was on the car before with the old rear end and it never shook like that before and I put brand new U joints in it a few weeks ago. My dad and I were guessing that maybe it's a pinion issue, but does anyone else have any ideas what it might be more specifically?

Im going with you put the joints and didn't index anything and now the shaft needs to be balanced....

 

[whitey]

It sounds kind of like cast metal scraping. I initially thought it might be the brake drums skimming the backing plates (the brakes were pulled from a different housing), but when I jacked the car up and let it run with the wheels off the ground it doesn't really sound like it's coming from the wheels and it's mostly speed based.

Does it sound like when you were a kid and you taped a baseball card to your bicycle and it is hitting the spokes of the wheel? If so I had the same problem...pinion depth was off.

I have a problem now that sounds like your second problem...once I get to around 60-65 it sounds like something is loose or vibrating around? not sure what this problem is.

 

[fishy68]

Well if it didn't do it with the old rearend it must be a problem with the new one. Possibly a bad pinion bearing. Don't drive it anymore until you figure it out or you'll probably do more damage.

 

[fishy68]

Im going with you put the joints and didn't index anything and now the shaft needs to be balanced....

Huh! Index what? The u-joints don't have to be indexed except for putting them in so you can access the grease zerks. I've replaced so many U-joints I couldn't even begin to count them and never had to re-balance the driveshaft.

 

[Map63Vette]

It was some F body rear end before, pretty sure 8.25 from what I've found with measurements. The sounds is more of a scrape then the baseball card noise, it's sort of hard to explain. As for the driveshaft thing, if I hold a screwdriver lightly against it while it turns you can see that the driveshaft pulls away and goes back and touches the screwdriver like a u joint isn't centered, but wouldn't they center themselves? They worked perfectly in the old setup, and the caps all look even with the C clips to keep them all where they need to be. And it's not just like some piece vibrating, the whole car starts rattling your teeth. The steering wheel doesn't shake, but if my hand is on the shifter it's like holding a very powerful vibrator. I plan to pull the shaft and check angles the best I can today and see if the pinion yoke has any play in it. My dad and I were thinking maybe a bad pinion bearing that has enough play to cause an issue.

 

[Supershafts]

Your problem is with the shaft..
The only way your pinion can make a issue is if you can physically move it.


Changing joints can throw a shaft out of balance, putting the slip yoke on opposite of the way it was balanced with the shaft will make a vibration.
Dropping some driveshafts can and does knock them out and need to be balanced.

The screwdriver method in the car isn't perfect since there is some movement at the slip and your arm is not a fixture, I don't care how still you think your arm is... No good..

Angles directly effect load and unload and rpm.

If your angle is way out you'll have a load vibration, or a decel vibration.
If you exceed the rpm for the angle of the joint it'll progressively get worse or burn the joint up and vibrate.

 

[Map63Vette]

Just pulled everything and checked stuff out. How much play should there be in the back U joint? If I have it so that the straps on the pinion yoke are stacked on top of each other (both horizontal to the ground, so one high and one low), I can move the driveshaft up and down some amount, maybe 1/16 to an 1/8, but hard to really tell precisely. There is obviously movement though. I can physically see there there is a lot of runout on the shaft at rpm, the screwdriver thing was more to try to explain what I'm seeing. If I look perpendicular to the shaft while it is rotating it looks "warped", but progressively more at the rear than the front, so I assumed the problem was somewhere around the back yoke, but that's really all I could come up with. Anyone know what the stock pinion angle is for an E body 8.75? That's what's in the car and I set everything level when I moved the perches in, so that's where the pinion is sitting now.

 

[Map63Vette]

Also, from the best I could determine with my angle finder, the transmission is currently sitting down 2 degrees and the pinion is about 4 degrees up. The problem I have is that I have F body springs in the car complete with the spring isolation setup. Does anyone make shims for these? The center hole on the perch is something like 1 5/8 inches big. I could possibly just take out the rubber spacers and put in solid wedges in their place, but I'm not terribly fond of the idea right now.

 

[Supershafts]

Huh! Index what? The u-joints don't have to be indexed except for putting them in so you can access the grease zerks. I've replaced so many U-joints I couldn't even begin to count them and never had to re-balance the driveshaft.

You either never realized the vibration or just ignored it or got lucky..
I'll go with you ignored or didn't realize that noise, hum, buzz was the joints you changed..
Not all vibrations are physical to feel.
Every part of a shaft is balanced as it sits, so if you do not index the parts of the shaft as it is, it'll have a balance issue.
Just changing joints can throw a shaft out..
I see it a lot, very rarely do people get it right.

 

[Map63Vette]

Also, from the best I could determine with my angle finder, the transmission is currently sitting down 2 degrees and the pinion is about 4 degrees up. The problem I have is that I have F body springs in the car complete with the spring isolation setup. Does anyone make shims for these? The center hole on the perch is something like 1 5/8 inches big. I could possibly just take out the rubber spacers and put in solid wedges in their place, but I'm not terribly fond of the idea right now.

I guess I should clarify that this is with weight on the axle. The car may have also been at a slight angle (sitting on a driveway), but that should cancel out of both measurements right? What should this angle be? From what I could gather at Moparts tech archives I should shoot for around zero difference between the two to maybe a degree or two low on the rear?

 

[Supershafts]

Lose that isolator crap.... You should have tossed that when you pulled it from the other car..

As long as you are within -4 degrees of the shafts angle you are ok..

Again angles are load related, 90% of the time..
Your shaft is in need of some attention.
There will be some minute amount of movement side to side, that is not uncommon

Also, from the best I could determine with my angle finder, the transmission is currently sitting down 2 degrees and the pinion is about 4 degrees up. The problem I have is that I have F body springs in the car complete with the spring isolation setup. Does anyone make shims for these? The center hole on the perch is something like 1 5/8 inches big. I could possibly just take out the rubber spacers and put in solid wedges in their place, but I'm not terribly fond of the idea right now.

 

[Map63Vette]

Believe me, I would tossed the junk if I could have found a way around it. I bought the car that way and just swapped in the new axle a week ago. The centering pins on the leafs are way bigger than stock and the shock plates sit on the top instead of the bottom of the spring, so I really couldn't find a way around it without buying more stuff that I don't have the money for at the moment. I think I'll probably be swapping springs some time down the road, so I'll get it all set up the right way then, right now I'd really just like to get the car on the road again. I think I may try to pull the pinion yoke off the old axle and see if it fits the new one. There just seems to be way too much play in the one that's on the new axle to be right.

 

[Map63Vette]

Well, i think I got most of it figured out. There is still some noise, but I think it's because the pinion snubber appears to be loose. They may have just worked out some from all the shaking, but that might be the scraping noise, we'll see. The shake is down from car rattling bomb to very slight buzz. It turns out I may have had the wrong U joint straps installed. i was thinking I may have just had too small of a U joint on and needed a conversion joint since the driveshaft would turn just slightly in the pinion yoke, but the bearing cups seemed to fit snug enough, they just weren't being held down tight enough. Took the straps off the old axle and bolted it back up and it seems to run much smoother now.

 

[green1]

Are the same u joints used on both rear yokes?

 

[fishy68]

Your problem is with the shaft..
The only way your pinion can make a issue is if you can physically move it.

I've seen a bad pinion bearing cause a vibration and not have any movement. It had a flat spot on a roller. Changed the bearing and race and the vibration was gone.

Changing joints can throw a shaft out of balance, putting the slip yoke on opposite of the way it was balanced with the shaft will make a vibration.
Dropping some driveshafts can and does knock them out and need to be balanced.

I agree dropping a driveshaft can definitely mess it up but no way is putting the yoke on backwards going to throw it out of balance. The driveshaft is balanced independent of the yoke.

The screwdriver method in the car isn't perfect since there is some movement at the slip and your arm is not a fixture, I don't care how still you think your arm is... No good..

Angles directly effect load and unload and rpm.

If your angle is way out you'll have a load vibration, or a decel vibration.
If you exceed the rpm for the angle of the joint it'll progressively get worse or burn the joint up and vibrate.

I agree if the pinion angle is off it can introduce a vibration

You either never realized the vibration or just ignored it or got lucky..
I'll go with you ignored or didn't realize that noise, hum, buzz was the joints you changed..
Not all vibrations are physical to feel.
Every part of a shaft is balanced as it sits, so if you do not index the parts of the shaft as it is, it'll have a balance issue.
Just changing joints can throw a shaft out..
I see it a lot, very rarely do people get it right.

I can't agree with you. I am very aware of even the smallest of vibrations and I especially don't ignore vibrations or any odd noises for that matter. Been a mechanic for nearly 30 yrs. now. Don't claim to be the best but I have had a ton of experience with drivetrains. As I said above I do not agree the driveshaft is balanced with the yoke attached. A buddy and me just had to shorten his driveshaft for a trans. swap we did in his truck and they didn't balance the yoke and driveshaft as an assy. Just the driveshaft. That's how all the shops I've dealt with did it. I have seen people leave off the inside C-clips which center the U-joint and that'll cause a vibration but it's not really all that common in my neck of the woods.

 

[redfastback]

Well, Fishy, my driveshaft guy tells me to always include the front yoke so he can balance it. I have watched him balance them as well. Pretty neat to see how it gets done. He is an older guy that does it all by the book and I have never had a driveshaft built by him that was bad, other places YES. One place even put a 62 Impala shaft out of phase and swore that it would be fine.... yeah right.

 

[fishy68]

Well, Fishy, my driveshaft guy tells me to always include the front yoke so he can balance it. I have watched him balance them as well. Pretty neat to see how it gets done. He is an older guy that does it all by the book and I have never had a driveshaft built by him that was bad, other places YES. One place even put a 62 Impala shaft out of phase and swore that it would be fine.... yeah right.

Ok Red. Are you saying he actually assembles the yoke onto the driveshaft and balances it as an assy. or he balances the yoke then balances the driveshaft? All the shops I know of around me balance them independently. I have never had one that was built wrong so I guess I've been lucky. I can certainly understand not aligning the U-joint yokes on the driveshaft properly (which I believe is what you mean by having it out of phase) causing a problem. Other than that I can't for the life of me see how you can install the yoke onto the driveshaft or install the driveshaft itself out of phase. Other than installing the U-joint(s) wrong so you can't access the grease zerk which doesn't actually cause a problem except making it difficult or impossible to grease the U-joint. If I'm missing something one of you guys please enlighten me.

 

[Map63Vette]

Are the same u joints used on both rear yokes?

Yeah, I was pretty sure they were. I bought new U joints for the old setup because it had a bit of a shake to it and while I was at it I checked the bearing caps against the new yoke and they fit snug. I thought that might have been my problem when I got to looking at it, but the yokes are the same width between the mounting points. The difference in bearing size diameters was only like, .050 inches, but the widths are different by a fair bit. Pretty sure the straps I got with the new rear were for the bigger U joint. The difference is almost impossible to see when compared side to side, but when installed and clamped down it's evident since one set lets the U joint move slightly and the other keeps the caps in place.

 

[Supershafts]

<------- That screen name is my nickname given to me by a customer after i was the only person to straighten out his issue, it then became Supershafts racing, and then it stuck and is now associated with my shop www.supershafts.com

At my shop i do driveline, mostly driveshafts, diffs, gv splitters....some performance suspension work.. all day, all week, all year....

I do not agree the driveshaft is balanced with the yoke attached

That is wrong and bs...
IF anyone tells you OTHERWISE there a bs shop.... Everything that is part of the shaft NEEDS to be assembled to the shaft when it is finished for balancing and NEEDS to be there when the shaft is being set up prior to welding...

I won't do anything without all parts of the shaft present..

I agree if the pinion angle is off it can introduce a vibration

I can't agree with you. I am very aware of even the smallest of vibrations and I especially don't ignore vibrations or any odd noises for that matter. Been a mechanic for nearly 30 yrs. now. Don't claim to be the best but I have had a ton of experience with drivetrains. As I said above I do not agree the driveshaft is balanced with the yoke attached. A buddy and me just had to shorten his driveshaft for a trans. swap we did in his truck and they didn't balance the yoke and driveshaft as an assy. Just the driveshaft. That's how all the shops I've dealt with did it. I have seen people leave off the inside C-clips which center the U-joint and that'll cause a vibration but it's not really all that common in my neck of the woods.

I have seen the inside clips left out millions of times.
Balanced thousands of shafts after the customer changed the joints, and then bought new tires, had the rear diff rebuilt, and had another yahoo group of mechanics make him spend close to $5k before they found me..

I have seen that more times every year then you could imagine... just last week with a cts v caddy

I would bet the shop doesn't even have a balancing machine.....Or they have a very simple balancing machine and it can not balance a shaft correctly (you'll be surprised how many driveline shops are a machine shop with a lathe, trust me) (we have 3 shops in NY like that, i get balancing work from them that they can't do since they can't balance shafts complete, but they fuk the customer anyway)


Any shop that will tell you they do not need the slip yoke of flange yoke though....I'll tell you once.... RUN ! ! !

 

[Supershafts]

The difference in bearing size diameters was only like, .050 inches, but the widths are different by a fair bit. Pretty sure the straps I got with the new rear were for the bigger U joint. The difference is almost impossible to see when compared side to side, but when installed and clamped down it's evident since one set lets the U joint move slightly and the other keeps the caps in place.

You had the 7290 straps on the 7260 yoke.

 

[fishy68]

<------- that screen name is my nickname given to me by a customer after i was the only person to straighten out his issue, it then became supershafts racing, and then it stuck and is now associated with my shop www.supershafts.com

at my shop i do driveline, mostly driveshafts, diffs, gv splitters....some performance suspension work.. All day, all week, all year....



That is wrong and bs...

ok. It may be wrong according to the way you do it but i don't bs. I tell it the way i see it. Anyone on this board that knows me knows i'm not perfect but i don't bs anybody. Ok.. I disagreed with you but i did it respectfully.

if anyone tells you otherwise there a bs shop.... Everything that is part of the shaft needs to be assembled to the shaft when it is finished for balancing and needs to be there when the shaft is being set up prior to welding...

I won't do anything without all parts of the shaft present..


I have seen the inside clips left out millions of times.

wow!! Millions of times. That's about 27,000 per year.. Lol

balanced thousands of shafts after the customer changed the joints, and then bought new tires, had the rear diff rebuilt, and had another yahoo group of mechanics make him spend close to $5k before they found me..

I have seen that more times every year then you could imagine... Just last week with a cts v caddy

i would bet the shop doesn't even have a balancing machine.....

no, they had a balancing machine. I'm not a "rigger" nor allow anyone to do work for me that is.

or they have a very simple balancing machine

that is a possibility

and it can not balance a shaft correctly (you'll be surprised how many driveline shops are a machine shop with a lathe, trust me) (we have 3 shops in ny like that, i get balancing work from them that they can't do since they can't balance shafts complete, but they fuk the customer anyway)


any shop that will tell you they do not need the slip yoke of flange yoke though....i'll tell you once.... run ! ! !

:-d <---supposed to be a smiley face but apparently it isn't working right.

 

[Map63Vette]

You had the 7290 straps on the 7260 yoke.

Yup, that's what I was thinking. At least I got it figured out finally. Happy to have the car back on the road =P.