NVH Issues

Suspension, including wheel, tire and brake.
Chickenman
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Re: NVH Issues

Postby Chickenman » 18 Dec 2016 14:37

bertvorgon wrote:Thanks for posting that link up Rob, that is without a doubt the best graphic visual example of what is going on.

I fought driveshaft vibration for years in the early days, then found out about the angularity and phase issue, never looked back after that and ever more so when Andy made me my driveshaft.

Derek, it stands for NOISE, VIBRATION and HARSHNESS...

Basically embodies our 510s as we stiffen things up and get rid of factory sound deadening.


Technically... it's Noise, Vibration and Harmonics. Not that we would be nit picky of course :lol:

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bertvorgon
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Re: NVH Issues

Postby bertvorgon » 18 Dec 2016 15:55

"Racing makes heroin addiction look like a vague wish for something salty" - Peter Egan

1973 2Door Slalom/hill climb/road race / canyon carver /Giant Killer 510
1968 Vintage 3HP Mini Bike
1971 Vintage 13' BOLER trailer


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TheHeretic
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Re: NVH Issues

Postby TheHeretic » 16 Mar 2017 13:08

Quick update here and hopefully the advice from the experts. So after a lot of work sound deadening the car I was able to take it out for a drive. While quieter for sure, the issue I am dealing with is still there. Basically something happened when the STI differential and coilovers went in. I'm thinking that it is the angle of the driveline (shaft) at this point but I would love your opinions.

So the vibration is mostly there when accelerating from light to full throttle but is the strongest at 5Krpm+. Exhaust rubbing has been eliminated after getting that checked out. I can be accelerating lightly and once the clutch is pushed in while accelerating, the rpms go up (duh) but the vibration goes away immediately.

Not sure what else I can do to "test" other things it could be. Gotta be between the tranny and diff, right?
Carpe Diem!
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RMS
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Re: NVH Issues

Postby RMS » 16 Mar 2017 13:30

when swapping my diff back in the fall I noticed a lot of play and slop and only the rust lines / paint lines helped in getting the diff back in the right place.

I would loosen the four mounting bolts and the mustache bar, give it a wiggle, tighten it back up and see what happens.
two_68_510s wrote:I guess our donkeys are quicker then your sled dogs!

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SteveEdmonton
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Re: NVH Issues

Postby SteveEdmonton » 16 Mar 2017 17:19

I chased vibration & noise for ages and finally found that the bolts holding the factory tranny mount to my 71B 5-speed were coming into contact with the crossmember (Experimental Engineering) when load came on and the driveline rotated ever so slightly on its axis. Bolts with a shorter head took care of the problem in short order.

Prior to this, though, I had replaced motor-mounts, tightened every nut & bolt in sight, separated brake & fuel lines so they couldn't touch anything-- you name it, I tried it. Of course nothing made any real difference until finally-- finally!-- I figured out what the actual problem was.

It'll be like this for you too. But hopefully you'll find the right thing sooner rather than later. :)
'71 4-door
'74 MGB-GT
'04 Miata

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RMS
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Re: NVH Issues

Postby RMS » 16 Mar 2017 21:47

yup the freshly plated stock bolts on the dogleg touched my ee member too
two_68_510s wrote:I guess our donkeys are quicker then your sled dogs!

Chickenman
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Re: NVH Issues

Postby Chickenman » 16 Mar 2017 23:52

Could very well be pinion angle. A small amount of mismatch can cause a substantial amount of vibration. You may have to shim your diff and the transmission to get the angles correct.

Even with IRS, there will be some upwards rotation of the pinion nose when accelerating. Poly bushings will reduce the amount of rotation, but there will always be some, unless solid metal bushings are used.

The following pictures illustrate the correlation of tranny, driveshaft, and pinion nose angles. When under high load. At rest, the ideal angle is slightly downward on the pinion shaft. The diff nose will then rotate upwards under load an align to a zero degree angle.

Image

akara
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Re: NVH Issues

Postby akara » 14 May 2017 20:31

TheHeretic wrote:I might be missing it but is there a topic or link to a more in-depth discussion around driveshaft angularity? Don't know if right now is the best time to mess with it but definitely will want to address it when I put in the KA24 transmission. Also what is everyone using to measure the u-joints angle? Was going to just download an app to the phone and use it...

This is something i am interested in as I am pretty sure the driveshaft angle is wrong on all of my cars. How does one take the proper measurements to check the angle the engine and differential are mounted at? I can level the driveshaft to the body, or to the rear crossmember, but there is nowhere flat on the differential itself or on the gearbox itself to ensure they are mounted flat in the car, anyone have any suggestions or do I need to buy special tools?

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Re: NVH Issues

Postby Three B's Racing » 16 May 2017 05:04

Place driveshaft in a position so two of the universal bearing cups are 90 degs. Take a socket that fits on the cup and place it and your phone with angle finder on it and measure at trans and diff. I have a digital angle finder with a magnetic and non magnetic base that works great.
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funwithmonkeys
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Re: NVH Issues

Postby funwithmonkeys » 16 May 2017 18:50

Three B's Racing wrote:Place driveshaft in a position so two of the universal bearing cups are 90 degs. Take a socket that fits on the cup and place it and your phone with angle finder on it and measure at trans and diff. I have a digital angle finder with a magnetic and non magnetic base that works great.

Thank you for that. I have been wondering if there was an easy way to do it and that looks like it.
If no one from the future comes back to stop you from doing it then how bad of a decision can it really be?

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JordanTr
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Re: NVH Issues

Postby JordanTr » 16 May 2017 21:29

funwithmonkeys wrote:I have been wondering if there was an easy way to do it and that looks like it.


I want to borrow some tools from work to do it. Pruftechnik Ultra Cardan Shaft Alignment
Jordan | '72 2 door KA project | '94 240sx RB26DETT | '97 Silvia RB25DET | '90 Audi 90 Quattro 20V (DD)

Three B's Racing
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Re: NVH Issues

Postby Three B's Racing » 17 May 2017 07:09

JordanTr wrote:
funwithmonkeys wrote:I have been wondering if there was an easy way to do it and that looks like it.


I want to borrow some tools from work to do it. Pruftechnik Ultra Cardan Shaft Alignment


Awesome and did you notice what they said? " Shaft offset to help with universals lubrication" because if the shaft is in perfect alignment of it's mating universals they don't properly lubricate themselves. I've alway been told the universals/driveshaft must have some angularity to them for proper lubrication of the universals.
"Lastnight the wife said oh boy when your dead you can't take nothing with you but your soul oh "Think"
- John Lennon

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JordanTr
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Re: NVH Issues

Postby JordanTr » 17 May 2017 07:24

Good catch Lou.

I think that point is confusing for a lot of people since oftentimes people measure the angle of the cardan shaft compared to the angle of the input/output shaft. This is an angle but if both angles are equal then the overall alignment is zeroed out.

If you look at OEM Nissan stuff, the diff pinion is offset from the center of the tunnel for just that reason--to allow for parallel misalignment to keep the u joints happy.
Jordan | '72 2 door KA project | '94 240sx RB26DETT | '97 Silvia RB25DET | '90 Audi 90 Quattro 20V (DD)

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funwithmonkeys
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Re: NVH Issues

Postby funwithmonkeys » 19 May 2017 13:55

I just measured mine and I have 2.4 and 4.5. After a bunch of fiddling I got it down to 2.7 and 4.0. My car is not level so a difference of 1.9 Down to 1.3. To get it any closer I would need to lower the front of my motor. My trans is really close to the tunnel and my CV's are getting really close to my exhaust. Looks like I will will just have to live with it.
If no one from the future comes back to stop you from doing it then how bad of a decision can it really be?


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