NVH Issues

[Chickenman]

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

[bertvorgon]

Not to be picky..but I got this from the Web...

https://en.wikipedia.org/wiki/Noise,_vi ... _harshness

http://www.frost.com/sublib/display-mar ... d=35405241

http://www.ricardo.com/en-GB/What-we-do ... hness-NVH/

far be it for me to argue with the Pro's....heh heh....

[Chickenman]

With gear noise and rotational noises, it's often referred to as Harmonics. Shall we agree that it can be called either? Merry Christmas.

Vehicle Gearbox Noise and Vibration: Measurement, Signal Analysis, Signal ...
By Jiri Tuma

https://books.google.ca/books?id=xy_qAgAAQBAJ&pg=SA2-PA49&lpg=SA2-PA49&dq=Noise,+Vibration+and+Harmonics&source=bl&ots=9JoJUglRNY&sig=_Q2nLO6hasw2S0l1TW6lW67xGGs&hl=en&sa=X&ved=0ahUKEwjd9veJkP_QAhVBW2MKHTLTDB8Q6AEIbjAQ#v=onepage&q=Noise%2C%20Vibration%20and%20Harmonics&f=false

Handbook of Noise and Vibration Control
By Malcolm J. Crocker:

https://books.google.ca/books?id=46NvrvpHIxEC&pg=PA1&lpg=PA1&dq=Noise,+Vibration+and+Harmonics&source=bl&ots=OYfrGpQjiU&sig=3qsSfaghRGJe2OmhuVrgs6e0b3w&hl=en&sa=X&ved=0ahUKEwjd9veJkP_QAhVBW2MKHTLTDB8Q6AEIcTAR#v=onepage&q=Noise%2C%20Vibration%20and%20Harmonics&f=false

Fundamentals of Noise and Vibration Analysis for Engineers
By M. P. Norton, D. G. Karczub:

https://books.google.ca/books?id=jDeRCSqtev4C&pg=PA515&lpg=PA515&dq=Noise,+Vibration+and+Harmonics&source=bl&ots=dGk7wm09W-&sig=RMV57v7N9qocBaiMHe8uEJCm8J0&hl=en&sa=X&ved=0ahUKEwjd9veJkP_QAhVBW2MKHTLTDB8Q6AEIWzAM#v=onepage&q=Noise%2C%20Vibration%20and%20Harmonics&f=false

[TheHeretic]

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?

[RMS]

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.

[SteveEdmonton]

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.

[RMS]

yup the freshly plated stock bolts on the dogleg touched my ee member too

[Chickenman]

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.

[akara]

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?

[Three B's Racing]

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.

[funwithmonkeys]

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.

[JordanTr]

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

[Three B's Racing]

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.

[JordanTr]

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.

[funwithmonkeys]

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.