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Discussion Starter #1
I had FRPP gears installed recently, with the full installation kit (all new bearings, etc).

The gears are not whining at all. However, I have noticed a slight vibration at exactly 65 mph. The vibration disappears at 64.5 or 65.5 mph. It is only right at 65 that I experience a brief low-pitched humming vibration. Like I said, it isn't real bad. It actually took a while for me to decide whether it was new or whether it was a figment of my imagination, or whether it was a sound that has been there all along. My car has quite a bit of interior resonance as it is with all my exhaust mods (longtubes, stingers).

I have the stock driveshaft. I am used to hearing about aftermarket driveshafts causing vibration and bad gear installs causing whining and other noises, not a vibration.

Could the gear install have caused this very momentary vibration and, if so, how?

Is it normal for aftermarket gears to cause some increase in NVH?

Is this something I need to worry about? It is actually not that bad, I could probably live with it, as long as I knew it wasn't just going to cause major problems down the road.
 

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Discussion Starter #6
Would it be possibly to develop the vibration simply from installing the gears (correctly), or would they have had to re-install the driveshaft in a different orientation (or done something else wrong during the gear install)?

I guess I'm just trying to figure out if this is caused by something the installers did wrong, or if it is just one of those things that might pop up once you start changing parts in the drivetrain.
 

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Discussion Starter #7
Also, do you guys think I'm OK driving around with this vibration for another three weeks or so?

Is this the kind of thing that signals an imminent failure where I have to stop driving the car and take it to the shop ASAP, or am I OK driving it around for a bit?

Should I try to avoid the speed where I get the vibration in the meantime?

Not sure I should be in panic mode or not and just trying to get an idea of how severe this problem is.
 

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There's is a possibility that it's the gear install so I'd get it looked at sooner than later.
 

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I guess I'm just trying to figure out if this is caused by something the installers did wrong,
I would try finding what's causing the problem instead of blaming it on someone.

Try what I said, just rotate the D/S 180* to where its on the pinion adapter.
 

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Discussion Starter #10
I would try finding what's causing the problem instead of blaming it on someone.
That's exactly what I'm trying to do...First, I'm just trying to get a feel for what might have caused this BEFORE I start blaming the installers.

I will probably take it back to them to have the driveshaft rotated, so I wanted to get some second opinions so I know how to handle the situation once I'm back in there.

So, if rotating the driveshaft does fix the vibration, what does that mean the cause of the problem was? Bad luck and I just changed the drivetrain harmonics somehow by swapping gears and by experimenting with the DS orientation it fixed the problem? Bad install? Neither? Is it even standard to install the DS back in its original orientation or does it USUALLY not matter?
 

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That's exactly what I'm trying to do...First, I'm just trying to get a feel for what might have caused this BEFORE I start blaming the installers.

I will probably take it back to them to have the driveshaft rotated, so I wanted to get some second opinions so I know how to handle the situation once I'm back in there.

So, if rotating the driveshaft does fix the vibration, what does that mean the cause of the problem was? Bad luck and I just changed the drivetrain harmonics somehow by swapping gears and by experimenting with the DS orientation it fixed the problem? Bad install? Neither? Is it even standard to install the DS back in its original orientation or does it USUALLY not matter?
Some times a small piece of dirt with get in between the C/V joint and the adapter or just the balance of the parts will cause it. Rotating the D/S will fix the problem. Yes its the harmonics that is causing it unless you had them rotate your tires....
Let us know how you make out.
 

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Sorry guys, noob question- what does this even do??
All driveshafts no matter how well balanced and straight will have one way of being installed that makes the tolerance stacking of the U-joints the smoothest. The “offset” in the D/S is caused by the small amount of slop in the U-joints, clips and how they sit in the driveshaft. The pinion no matter how perfect everything was machined will be a little “out” too. By rotating the D/S its possible to get the tolerance stacking of the D/S, U-joints, clips and pinion working with each other instead of against.
 

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That's exactly what I'm trying to do...
No your not. If you are not going to work on the car you don’t need to compile a list of possibilities at all. What are you planing on doing? Handing them a list and then standing over their shoulder the entire time?

First, I'm just trying to get a feel for what might have caused this BEFORE I start blaming the installers.
You can only asses blame after the problem is found. You can't "get a feel" for it before hand.

I will probably take it back to them to have the driveshaft rotated, so I wanted to get some second opinions so I know how to handle the situation once I'm back in there.
Yeah, I’m sure they will appreciate that. Technicians love nothing more than an internet jockey with a list. Secondly if you need to hand them a list of potential problems/solutions you don’t want them touching your car. Take your car in, explain the symptoms and go away and let them do what they do for a living. If you don’t feel comfortable doing that, don’t take the car to them.

You have two choices. You either trust your shop or you don’t. There is no middle ground. Customers that try and play the middle ground and want to “help’ me do their work I get rid of. I don’t have the time for that and its insulting. Why would a tech want to take advice from someone who is clearly unqualified. If you were qualified he would never meet you because you would be doing the work yourself.

I used to have my labor rates posted behind the service counter at my dealership (has to be there by law). It read:

Labor rate $75/hr
Labor rate with customer watching $110/hr
Labor rate with customer helping $225/hr

….and it was not a joke.


So, if rotating the driveshaft does fix the vibration, what does that mean the cause of the problem was?
No problem, just tolerance stacking.

If the orientation is the problem sure

I just changed the drivetrain harmonics somehow by swapping gears and by experimenting with the DS orientation
Could be the problem

Bad install?
Unlikely, bad gear jobs usualy maifest as a high pitch noise

Could be

Is it even standard to install the DS back in its original orientation or does it USUALLY not matter?
Standard but by changing the gear the center if the pinion could have moved just a bit so the origonal spot would no longer be good.
 

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Discussion Starter #15
While the technical information is certainly appreciated (you gave me the exact kind of information and answers I was looking for), some of the unnecessary internet forum back talk certainly is not. A perfect example of how internet forums can be incredibly helpful, while at the same time frustrating because you get some guy who doesn't even know you giving you crap and questioning your motives and reasons for posting in the first place.

I certainly wasn't planning on going in and handing them a list and then standing over their shoulder and trying to "help him do their job". I don't see any problem with trying to get some technical background information before going in to a shop and that is all I was trying to do.

Before I posted, I really had not idea what might be causing this. It showed up right after the install, so did they do something wrong? Should I expect them to cover the labor (that's what I meant by "handle the situation")? I suspected, as you've now confirmed, that this could simply be a result of messing around with the drivetrain. Not the installers fault, not a problem with the parts, just a simple consequence of changing the drivetrain from it's initial configuration (although I did not have this problem with previous gear installs).

I am now more informed than I was before I posted. Who knows, if I take it in to a shop and say "I'm getting a vibration, please fix it", they might have suggested some other costly form of diagnosis or repair (believe it or not, not all mechanics have the customer's best interest in mind). Now, I might simply ask if them if they can try rotating the driveshaft first. Hell, based on all your input, I may ask them to do that right off the bat. And, thanks to your help (and my persistent questioning), now I know WHY I would ask that and HOW that might fix. I'm hardly an expert now, but I am a little more informed. Why are you so opposed to that?

The first half of your post was a completely unnecessary rant, the second half was extremely helpful. I thank you for the latter half.
 

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While the technical information is certainly appreciated (you gave me the exact kind of information and answers I was looking for), some of the unnecessary internet forum back talk certainly is not. A perfect example of how internet forums can be incredibly helpful, while at the same time frustrating because you get some guy who doesn't even know you giving you crap and questioning your motives and reasons for posting in the first place.

I certainly wasn't planning on going in and handing them a list and then standing over their shoulder and trying to "help him do their job". I don't see any problem with trying to get some technical background information before going in to a shop and that is all I was trying to do.

Before I posted, I really had not idea what might be causing this. It showed up right after the install, so did they do something wrong? Should I expect them to cover the labor (that's what I meant by "handle the situation")? I suspected, as you've now confirmed, that this could simply be a result of messing around with the drivetrain. Not the installers fault, not a problem with the parts, just a simple consequence of changing the drivetrain from it's initial configuration (although I did not have this problem with previous gear installs).

I am now more informed than I was before I posted. Who knows, if I take it in to a shop and say "I'm getting a vibration, please fix it", they might have suggested some other costly form of diagnosis or repair (believe it or not, not all mechanics have the customer's best interest in mind). Now, I might simply ask if them if they can try rotating the driveshaft first. Hell, based on all your input, I may ask them to do that right off the bat. And, thanks to your help (and my persistent questioning), now I know WHY I would ask that and HOW that might fix. I'm hardly an expert now, but I am a little more informed. Why are you so opposed to that?

The first half of your post was a completely unnecessary rant, the second half was extremely helpful. I thank you for the latter half.
Thank you for confirming my observations. You are 100% “That Guy”.:bigthumbsup
 

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Discussion Starter #17
Yet another completely innocuous thread turned into a pissing match.

So, you recommend I have the driveshaft rotated as a first step, then scoff at the fact that I might take it in to a shop and ask them to do just that, instead of handing them a blank check and telling them to fix it. (After all, why would I want to try such a simple fix as a first troubleshooting step?!)

And you are on an internet forum sharing your vast knowledge of automobiles with others, yet you find it ridiculous to think that anyone might actually use this information in the real world. (After all, no one on an internet forum knows what the hell they’re talking about, right?!)

And you seem miffed at the fact that someone might want to do a little research and become more informed about the subject matter on which they will be spending their hard earned money. "Just take it to the shop! They'll make it all better." (Because there is no such thing as a busy/bad/dishonest/inexperienced mechanic. They don't exist. Anywhere.) Don't get me wrong, I trust my mechanic, I just want to know more about what he's doing and why.

Feel free to leave a witty come back, however, I won't be checking back on this thread to read it.
 

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Yet another completely innocuous thread turned into a pissing match.

So, you recommend I have the driveshaft rotated as a first step, then scoff at the fact that I might take it in to a shop and ask them to do just that, instead of handing them a blank check and telling them to fix it. (After all, why would I want to try such a simple fix as a first troubleshooting step?!)

And you are on an internet forum sharing your vast knowledge of automobiles with others, yet you find it ridiculous to think that anyone might actually use this information in the real world. (After all, no one on an internet forum knows what the hell they’re talking about, right?!)

And you seem miffed at the fact that someone might want to do a little research and become more informed about the subject matter on which they will be spending their hard earned money. "Just take it to the shop! They'll make it all better." (Because there is no such thing as a busy/bad/dishonest/inexperienced mechanic. They don't exist. Anywhere.) Don't get me wrong, I trust my mechanic, I just want to know more about what he's doing and why.

Feel free to leave a witty come back, however, I won't be checking back on this thread to read it.
Don't look now but I think you are the only one that has done any pissing.;)
 

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It seems by the way you posted your info request that you either don't have the skill or want to do the work your self. That's fine but it's helpful is you say that. We also have a sense of humor here, not a requirement but it helps......:hihi:
 

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I'm sure that everyone on here can appreciate a good sense of humor and a little ribbing every now and then but constant sarcasim and condesending replies is going to wear on anyone. The wealth of knowledge to be had on this site is great! but if you possess that knowledge and are unable to be tolerant of those who do not and are unable to respond to those questions without condesending sarcasim then why bother? This is a place where there should be no stupid questions because there is going to be people who have no idea what the right course of action is when attempting to diagnose a problem.
 
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