Drive shaft balance

[1970Moparmann]

Trans looks in line.  drive shaft angle looked good.  I dropped it off at the shop today and it will be ready tomorrow.  The main guy said "most likely" my heavy vibration is due to the drive shaft out of balance. 

I'll report back tomorrow.

[Cooter]

Obviously maximum, you must have the only perfect Charger that doesn't shake. As for the rest that open numerous threads about vibrations, these mostly weren't  'supposedly' "jumped"and vibrate all to hell.
2.76 gears do not spin the driveshaft as fast with 3spd auto as fast as a set of 3.55 or 4.10 gears in OD.
Therefore, you have less problems with vibrations that seem to creep up.
Btw:I'll have to take your word as to no shaking. (No proof or links)

[Paul G]

Maxim what are your pinion angles? Can you measure those? Bone stock angles, or at least angles from a car that has no bad vibs would be great info.

[flyinlow]

Paul,

Any road construction around you. Maybe tar or contaminate on driveshaft. When they shortened the shaft did they look inside it? good condition ,no  rust or mud?

Just a couple unusual thoughts on things that might cause the balance to change.  

Craig

[MaximRecoil]

Obviously maximum, you must have the only perfect Charger that doesn't shake. As for the rest that open numerous threads about vibrations, these mostly weren't  'supposedly' "jumped"and vibrate all to hell.

You didn't read my post so well. Let's see:

"maximum"?

"Perfect Charger" ... who claimed that? The imaginary "maximum" fellow?

"Only one that doesn't vibrate"? Who first determined that all other Chargers vibrate and then made such a ridiculous claim?

"Supposedly"? ... there is no "supposedly" about it; the car was jumped, or it sustained an impact with identical mechanics to a nose-forward landing from a jump of significant height. Either way, the end result is the same.

2.76 gears do not spin the driveshaft as fast with 3spd auto as fast as a set of 3.55 or 4.10 gears in OD.

First, they are 2.71 gears, not 2.76. Secondly, your claim is false with regard to the 3.55 gears in OD, and is only barely true for the 4.10 gears in OD. The A518 has a .69:1 gear ratio in OD, which effectively turns a 3.55 rearend gear into a 2.45. It effectively turns a 4.10 gear into a 2.83, which isn't much lower than my 2.71 gears.

Therefore, you have less problems with vibrations that seem to creep up.

See above.

Btw:I'll have to take your word as to no shaking. (No proof or links)

Do whatever you want. Given that I drive the car and you don't (nor have you ever), it follows that I know whether it vibrates or not, and you don't.

Maxim what are your pinion angles? Can you measure those? Bone stock angles, or at least angles from a car that has no bad vibs would be great info.

There's an angle finder at the garage. When I next get a chance I will.

[Cooter]

Again, you do not understand what your talking about regarding driveshaft speeds with OD trannies. I dismiss you out of hand. Please try again when you understand a little better. Maybe ask the guy that does all your work for you. And Maximum, as in maximum ass.

[ottawamerc]

Wow Cooter who pi$$ed in your cheerios this morning

Scott

[MaximRecoil]

Again, you fo not understand what your talking about regarding driveshaft speeds with OD trannies. I dismiss you out of hand. Please try again when you understand a little better.

Are you seriously trying to argue with basic math? In any event, you're flat out wrong. 3.55 × .69 = 2.4495. That's a fact. You obviously don't understand how to calculate a final drive gear ratio. A 3.55 rearend gear ratio is only effectively a 3.55 final drive gear ratio if the final drive gear in the transmission is 1:1 (such as with a 727, 904, A833, etc). Want to know why? Because 3.55 × 1 = 3.55, obviously.

Maybe ask the guy that does all your work for you.

There is no guy that does "all my work for me"; only a guy that does work involving fabrication. I do electrical and mechanical work myself.

And Maximum, as in maximum ass.

Dyslexia? Don't worry, it is nothing to be ashamed of.

[Cooter]

Ashamed? Once again, John was right. When you graduate from that briefcase you call a toolbox, then you might learn something other than what you think  you know.

[XH29N0G]

I'll jump in here with possible misunderstanding of the discussion. 

I have been running an OD gear for a the past 30 years, first with a 3.23 rear and now with a 4.30.  The OD makes it so the engine does not rev as high, by changing the ratio of the transmission.  This does not change spinning rates downstream of the transmission.  Since the driveshaft is between the transmission and the differential, it spins at a rate determined by the rear gears. 

When I switched to 4.30s, it was smooth until I stomped on it one time and believe a weight came off the driveshaft.  Then it vibrated like all get out.  I took it to a truck shop (big trucks, dump trucks, buses, semi's).  They balanced the driveshaft and the vibration went away.  I also believe that if I had a minor imbalance that I might not have seen it with the 3.23 gears, but would see it with the 4.30s.

More recently, I had another transmission installed with a new driveshaft and am tracking down a vibration at higher speed that changes depending on whether I am on or off throttle.  My first try is related to pinion angles, which I have now adjusted.  If that cures it, I will sign on again and let everyone know.  My understanding is that basically for pinion angles, the vibrations come about when the axis of the transmission and the axis of the differential are not parallel, and it is best not to have working angles that are too large (some say less than 3.5 degrees).

That is all I know.  As I understand it, other sources of vibration can be the rear of the transmission, a u joint, and tire balance.

[flyinlow]

Yea with OD trans and lower axle ratio's the driveshaft rotational speed gets up there. With 3.91 gears and 28" tires at 130mph I figured the driveshaft was spinning over 6000 rpm.

So with a .50 OD six speed with a .78 GV behind it and 5.13 gears do I need a carbon fiber driveshaft to go 200mph?   

[ws23rt]

I'll jump in here with possible misunderstanding of the discussion. 

I have been running an OD gear for a the past 30 years, first with a 3.23 rear and now with a 4.30.  The OD makes it so the engine does not rev as high, by changing the ratio of the transmission.  This does not change spinning rates downstream of the transmission.  Since the driveshaft is between the transmission and the differential, it spins at a rate determined by the rear gears. 

When I switched to 4.30s, it was smooth until I stomped on it one time and believe a weight came off the driveshaft.  Then it vibrated like all get out.  I took it to a truck shop (big trucks, dump trucks, buses, semi's).  They balanced the driveshaft and the vibration went away.  I also believe that if I had a minor imbalance that I might not have seen it with the 3.23 gears, but would see it with the 4.30s.

More recently, I had another transmission installed with a new driveshaft and am tracking down a vibration at higher speed that changes depending on whether I am on or off throttle.  My first try is related to pinion angles, which I have now adjusted.  If that cures it, I will sign on again and let everyone know.  My understanding is that basically for pinion angles, the vibrations come about when the axis of the transmission and the axis of the differential are not parallel, and it is best not to have working angles that are too large (some say less than 3.5 degrees).

That is all I know.  As I understand it, other sources of vibration can be the rear of the transmission, a u joint, and tire balance.

You are right about transmission final drive ratio vs the rear end ratio. Cooter was as well and said basically the same thing.

We are after all talking about drive shaft vibration and the final drive at the axial affects this not the engine rpm.
A 4-10 gear takes 4.1 turns of the drive shaft for one turn of the wheel. A 2-76 gear takes only 2.76 turns for one wheel rotation.

As for pinion angles. And just to be helpful.
1. Question? Why even have universal joints. -- The rear axial on leaf springs moves way to much in two directions for another type of coupling to be practical.

2. Question? Why the need for an initial offset (pinion angle).---The needle bearings in the joint need a minimum movement in order for them to roll completely. If they did not get that amount of movement they would just wiggle in place and take a set in the race. As well as not be able to circulate their grease. (premature bearing failure)

Another item not mentioned in the discussion about drive shaft vibration is "critical speed".

Any rotating member has a critical speed that when met will vibrate regardless of how well balanced it is.

Example of this is a long small dia. shaft for the purpose of a mental visual.
A shaft will sag from it's own weight.  As it starts to turn it will still have sag. As the speed increases the sag will creep toward the up side in the direction of rotation. The critical speed of this shaft will be the rpm at which the sag goes over the top. The shaft now looks like a jump rope.
This is a point that will cause much vibration.

There are other things that affect the "critical speed" rpm such as loose bearings , out of balance, induced vibration from another source (harmonics).etc.

A pulsing vibration could very well be a shaft moving in and out of critical speed.
A vibration that settles down as the speed increases could be that the shaft has passed first critical speed and is now moving towards the next critical speed. The next one is generally greater than the first. Eventually something will fail.

A limber shaft will have a lower critical speed than a stiffer one.
Also of course no vibration makes the bearings happy.

[Cooter]

Ever been under your newer truck? Wanna guess why that. 6"aluminim driveshaft is that big?


As mentioned,  and as was pointed out to me in another thread, gear ratios in the rearend stay the same whether you are cruising as they did back in the day with 4.10 gears and engine screaming at 4000rpm...
You didn't notice the vibration as much because you were concerned with the engine revs. Kinda like you expected a little shaking at those rpms...

Too many today seem to think that if their engine isn't turning the rpms, then the rest of the drivetrain isn't as well..

You are still turning 4.10gears, only difference is your tranny has made it a lot easier on your engine, but is killing your pinion bearings.

This is why most newer vehicles have synthetic oil in them. It's to try and keep bearings and the oil from breaking down from higher temps.

I see LOADS of Explorers in the shop with pinion bearings GONE due to an OD and 4.10 gears for like 150k miles.

[ws23rt]

Ever been under your newer truck? Wanna guess why that. 6"aluminim driveshaft is that big?


As mentioned,  and as was pointed out to me in another thread, gear ratios in the rearend stay the same whether you are cruising as tgey fid back in the day with 4.10 gears and engine screaming at 4000rpm...
You didn't notice the vibration as much because you were concerned with the engine revs. Kinda like you expected a little shaking at those rpms...

Too many today seem to think that if their engine isn't turning the rpms, then the rest of the drivetrain isn't as well..

You are still turning 4.10gears, only difference is your tranny has made it a lot easier on your engine, but is killing your pinion bearings.

This is why most newer vehicles have synthetic oil in them. It's to try and keep bearings and the oil from breaking down from higher temps.

I see LOADS of Explorers in the shop with pinion bearings GONE due to an OD and 4.10 gears for like 150k miles.

Absolutely correct   Maxim was so quick to dismiss something he failed to read what was said and understand it. A clue to what the topic is is at the very top of the thread. It however is not colored or in "bolding"? a made up word but we know what he was talking about anyway.

[cdr]

if my car ever goes down the road,with my 4.57 & .69 overdrive,engine at 6000 rpm,my drive shaft rpm will be right at 8700 rpm. i will need an alum 3.5 shaft.

[MaximRecoil]

I'll jump in here with possible misunderstanding of the discussion.  

I have been running an OD gear for a the past 30 years, first with a 3.23 rear and now with a 4.30.  The OD makes it so the engine does not rev as high, by changing the ratio of the transmission.  This does not change spinning rates downstream of the transmission.  Since the driveshaft is between the transmission and the differential, it spins at a rate determined by the rear gears.  

This is all correct. I was only considering how the effective final drive ratio affects engine RPM, which was an error on my part, given the context of this thread.

So for example, a car with a 3.55 rearend at ~65 MPH in .69:1 OD will have an engine RPM of ~2000 and a driveshaft RPM of ~2900.

My car's engine and driveshaft, with its 2.71 rearend and 1:1 top transmission gear, would both be at ~2200 RPM when going ~65 MPH.

By the way, both of those examples assume an average size tire, something like a 215/70R15. My engine and driveshaft's actual RPM at 65 MPH is a little lower than that, about 2100, because my tires are 235/70R15.

[Cooter]

What are most driveshaft shops balancing driveshafts to??
I know back in the day it was only around 3000rpms.

[ws23rt]

I'll jump in here with possible misunderstanding of the discussion.  

I have been running an OD gear for a the past 30 years, first with a 3.23 rear and now with a 4.30.  The OD makes it so the engine does not rev as high, by changing the ratio of the transmission.  This does not change spinning rates downstream of the transmission.  Since the driveshaft is between the transmission and the differential, it spins at a rate determined by the rear gears.  

This is all correct. I was only considering how the effective final drive ratio affects engine RPM, which was an error on my part, given the context of this thread.

So for example, a car with a 3.55 rearend at ~65 MPH in .69:1 OD will have an engine RPM of ~2000 and a driveshaft RPM of ~2900.

My car's engine and driveshaft, with its 2.71 rearend and 1:1 top transmission gear, would both be at ~2200 RPM when going ~65 MPH.

So is this an admission that you misread/misunderstood a post and proceeded to explain something that was off topic?

OOps I see that you changed your post to that effect.    

[Paul G]

What are most driveshaft shops balancing driveshafts to??
I know back in the day it was only around 3000rpms.

Denny's website states they can balance up to 10,000 rpm. It does not say they do balance every shaft to 10,000 rpm though. The last shop that balanced mine had it on a jig that was spinning at a very low speed. I would guess no more than 1500 rpm imo. So I doubt my DS has ever been high speed balanced. 

quote from Denny's;
Is driveshaft balance really necessary?

YES!  Driveshaft balance is necessary for smooth driveline operation and to eliminate the destructive effects that an unbalanced or poorly balanced driveshaft will have on your transmission and rear end.   At Denny's Driveshafts we High Speed High RPM Balance every driveshaft to meet or exceed the top rpm requirements of your engine and transmission, especially in the case of an overdrive transmission where the driveshaft rpm is greater than the engine rpm in high gear.   This is very important and should not be overlooked when purchasing a new driveshaft.  We can balance and test to 10,000 rpm so whatever your requirements are we can meet them.   This will ensure that you will have the smoothest ride at all road speeds and track speeds and also a quicker ET.  You won't be limited by rear end gear ratio and you will experience smooth running especially when using an overdrive transmission.    True high speed balance means balancing at a High RPM. 

[ws23rt]

What are most driveshaft shops balancing driveshafts to??
I know back in the day it was only around 3000rpms.

Denny's website states they can balance up to 10,000 rpm. It does not say they do balance every shaft to 10,000 rpm though. The last shop that balanced mine had it on a jig that was spinning at a very low speed. I would guess no more than 1500 rpm imo. So I doubt my DS has ever been high speed balanced. 

quote from Denny's;
Is driveshaft balance really necessary?

YES!  Driveshaft balance is necessary for smooth driveline operation and to eliminate the destructive effects that an unbalanced or poorly balanced driveshaft will have on your transmission and rear end.   At Denny's Driveshafts we High Speed High RPM Balance every driveshaft to meet or exceed the top rpm requirements of your engine and transmission, especially in the case of an overdrive transmission where the driveshaft rpm is greater than the engine rpm in high gear.   This is very important and should not be overlooked when purchasing a new driveshaft.  We can balance and test to 10,000 rpm so whatever your requirements are we can meet them.   This will ensure that you will have the smoothest ride at all road speeds and track speeds and also a quicker ET.  You won't be limited by rear end gear ratio and you will experience smooth running especially when using an overdrive transmission.    True high speed balance means balancing at a High RPM. 

This sounds great if that is indeed what they do.

[Paul G]

Paul,

Any road construction around you. Maybe tar or contaminate on driveshaft. When they shortened the shaft did they look inside it? good condition ,no  rust or mud?

Just a couple unusual thoughts on things that might cause the balance to change.  

Craig

That shaft is clean, painted and polished..... on the outside. Never saw the inside. Last spring when I broke the trans was the last time the DS was off the car, and in the machine shop for a balance and new u joints. I am probably going to pull the DS this weekend or next and get some measurements for a new DS. It sounds like the thing to do next, maybe?

Denny's says stock drive shafts are not intended for race applications.

Quote from Denny's
Why did my driveshaft tubing twist or break?

There are many reasons. If you are using a stock driveshaft in a racing application then you already know the answer. Stock shafts should never be used for racing. If you had a driveshaft built by a driveline shop and it has broken or twisted the tubing then you should take it back to where you bought it. They apparently built your driveshaft with tubing that was similar to stock driveline tubing or possibly selected a tube diameter or thickness that was not correct for your application. Just because the shop builds dump truck shafts does not mean it can handle the requirements of a race car.
[end quote]

My Charger is not a race car by any means. But it does do a lot of this. And with the recent carb swap and tweeking it can do a decent second gear burn out. That only puts more load on the shaft at higher rpm when it tends to wobble around any way. I don't know?

[ws23rt]

Paul,

Any road construction around you. Maybe tar or contaminate on driveshaft. When they shortened the shaft did they look inside it? good condition ,no  rust or mud?

Just a couple unusual thoughts on things that might cause the balance to change.  

Craig

That shaft is clean, painted and polished..... on the outside. Never saw the inside. Last spring when I broke the trans was the last time the DS was off the car, and in the machine shop for a balance and new u joints. I am probably going to pull the DS this weekend or next and get some measurements for a new DS. It sounds like the thing to do next, maybe?

Denny's says stock drive shafts are not intended for race applications.

Quote from Denny's
Why did my driveshaft tubing twist or break?

There are many reasons. If you are using a stock driveshaft in a racing application then you already know the answer. Stock shafts should never be used for racing. If you had a driveshaft built by a driveline shop and it has broken or twisted the tubing then you should take it back to where you bought it. They apparently built your driveshaft with tubing that was similar to stock driveline tubing or possibly selected a tube diameter or thickness that was not correct for your application. Just because the shop builds dump truck shafts does not mean it can handle the requirements of a race car.
[end quote]

My Charger is not a race car by any means. But it does do a lot of this. And with the recent carb swap and tweeking it can do a decent second gear burn out. That only puts more load on the shaft at higher rpm when it tends to wobble around any way. I don't know?

You could be the quality control tester for their drive shafts.   They should pay you for the service.

[Cooter]

I would think as long as you ain't trying this, you'll be ok with one of theirs.

I wonder who does Sean's [Farmtruck] Drive shafts?

[ws23rt]

I would think as long as you ain't trying this, you'll be ok with one of theirs.

I wonder who does Sean's [Farmtruck] Drive shafts?

[chargerbr549]

Here is a good read on a driveline vibration problem that he finally solved. He ended up balancing the shaft on the car.
http://www.dodgecharger.com/forum/index.php/topic,63413.0.html

I had a driveline vibration problem on a dodge dakota that I had, at lower speeds it was fine but when it got up to speeds above 30mph it would start to vibrate so I took it to a driveline shop to get it balanced and it didn't really change the vibration much so I figured out the rpm that the driveshaft was spinning when it started to vibrate and it was around 3000 rpm so I talked to the shop that balanced the shaft the first time and their machine didn't spin it anywhere near 3000 rpms and told me that it should be fine at the lower rpms that they balanced it to, it wasn't, so I finally found a shop that could balance it well above 3000 rpms and presto the problem was solved!!!