NVH Issues

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

Postby TheHeretic » 27 Jun 2017 10:04

Much better now! When putting in the new KA24 transmission we were able to lower the rear of tranny quite a lot compared to the dogleg that was in there before. A significant decrease in vibration when accelerating. Still something very slight but that's before getting the car up on a lift again and measuring the pinion angle and making some adjustments.
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TheHeretic
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Re: NVH Issues

Postby TheHeretic » 15 Jul 2017 14:05

Working on trying to get every bit of vibration out of my driveline as I start to feel some during acceleration and at speeds above 75+mph. Was able to get my 510 on a lift this past week and measure what I believe are the right spots on the driveline but would love someone to verify that. As I write this I am realizing that I might be off a little on the technique. Basically raised the car on the lift using blocks under the rear pinch welds and then the front frame rails. So the back might be a little higher than the front when lifted. As zeroed out the digital angle device on the concrete floor. Do I need to do it again with a different method?

Measured at rear differential (Up 1.7 degrees)
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Measured at rear of transmission (Down 3.4 degrees)
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From what I have read online and here on the Realm, the working angles of a U-joints are what's important; they should be greater than 1 degree, both within 1 degree of each other, and 3 degrees maximum working angle each for common single cardon joints, resulting in long service life. Anything over 3 degrees will shorten their life and/or produce vibration.

So the first step I decided to make was to raise the transmission which did drop down the angle to down 3.1 degrees. I used a slim spacer that measures 4.5mm or 0.18 inches and placed it between the transmission mount and transmission. Downside is that the top of the transmission is now rubbing against the tunnel cover but I can always raise or modify that (KA24 tranny with bolted on, for now, Datsport tunnel cover).

Didn't think I could adjust the differential but after doing some reading I think that I can move the front shims from the bottom to the top which should tilt the differential down towards the middle of the car increasing the angle and getting it closer to matching the angle of the transmission. Already have the thicker poly bushings on the bottom of the mustache bar so swapping those would be decreasing the angle which isn't what I want to be doing. Any thoughts on increasing the rear diff angle?

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Also measured the angle of the valve cover to see how the engine was angling. L-Series motor measured on top of the Datsun letter. The result was 3.4 degrees down to the back of car. Not even sure if that is what it should be? Might be important if I continue to raise the transmission to get the driveline angle below 3 degrees.

Any help is super appreciated! Coming to realize that when it comes to fine tuning your car the only person who will truly take the time and cares enough to get everything perfect is yourself!
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Ryan

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zKars
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Re: NVH Issues

Postby zKars » 15 Jul 2017 15:11

I'm going through this as well.
As to where to measure the angles, I'd remove the drive shaft and measure the vertical face of the diff flange and the end of the output shaft on the trans. That works on a L trans anyway. Unless is very obvious that those yoke faces are in line with the shaft, but why chance it.

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66DUCE
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Re: NVH Issues

Postby 66DUCE » 15 Jul 2017 19:58

Easiest way to do this is by measuring with a magnetic angle gauge, typically drive line angles are measured at the yoke (output of transmission at right angles to road surface) to the driveshaft (yoke at right angles to road surface on the drive shaft). The ideal difference between the two should be within 0.5 degree. you can use a socket to extend the angle gauge for the 510 small "U" joint. If you don't take this into account you will have a noticeable vibration! Keep in mind that if you are using the original dog bone style drive axles that you will not totally eliminate the drive line vibration. Also keep in mind that if the drive line vibration go's away at about 62MPH (100KPH) you may have a wheel balance issue! This is the only tried and true way of eliminating drive line vibrations.

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bertvorgon
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Re: NVH Issues

Postby bertvorgon » 15 Jul 2017 20:45

I agree with 66Duce.

I spent the time and have mine within .5 degrees and my car is very smooth all the way to 130 MPH.

I also ultimately had Specialty make me a drive shaft in his lathe where I have NO balance weights on the thing, it runs dead smooth. I fought drive line shops for too many years trying to get a balance, I really don't know what the problem was, but after Andy made my driveshaft, the final vibration was gone.
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JordanTr
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Re: NVH Issues

Postby JordanTr » 15 Jul 2017 21:18

I ended up with lots of spacers above my moustache bar in the ka 510.

I'll say the goal 1 more time just to maximize confusion. You want the pinion shaft and output shaft of the trans to have parallel misalignment. This means that the working angles of both cardan joints are the same and opposite. Keep those angles equal (by ensuring the shafts are parallel) and ideally end up with a working angle in each joint of about 0.5* as Keith says would be the best case scenario.
Jordan | '72 2 door KA project | '94 240sx RB26DETT | '97 Silvia RB25DET | '90 Audi 90 Quattro 20V (DD)

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66DUCE
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Re: NVH Issues

Postby 66DUCE » 15 Jul 2017 21:57

Good points Kieth and Jordan. All Cardan joints ("U" joints) need the interference angle of 0.5degree to operate correctly, to properly keep lubricant moving throughout joint and articulate all the caps on the u joint. The idea of the interference angle is to cancel out the speed up and slow down of the cardan joint. We need at least 2 "u" joints to make this happen

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TheHeretic
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Re: NVH Issues

Postby TheHeretic » 17 Jul 2017 11:40

Drove the car today at highway speeds and just the slight decrease in angularity difference from 1.6 degrees down to 1.4 degrees made a difference at 80mph. Thinking of removing the spacer between tranny and mount and trying to adjust just using the differential. So to tilt the differential the right direction I should remove the shims from the lower front mounting points and insert them to the upper front mounting points? Please confirm. Byron?

Any other ways to adjust the angle of the diff? Shouldn't need to want to adjust it side to side, right?

Thanks in advance!
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Ryan

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66DUCE
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Re: NVH Issues

Postby 66DUCE » 18 Jul 2017 09:09

I see in your original post that you are using a frame contact hoist, there will be deflection on the rear suspension bushings which could affect your rear readings. to eliminate this I would suggest using a drive on type of hoist or using the drive on ramps for all 4 wheels. sounds like you are on the right track to put the shims on the top side, and yes you want to move them equally (on both sides). Again 0.5 deg is what is Ideal.

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TheHeretic
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Re: NVH Issues

Postby TheHeretic » 18 Jul 2017 10:37

Yeah my neighbor has a drive-on hoist I can use. Didn't think it would make a difference as being IRS the diff is locked in place and not moving whether the wheels are up or down. So when you say equally you mean both right and left front shims get moved to the top and the rear shims stay in place?
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66DUCE
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Re: NVH Issues

Postby 66DUCE » 18 Jul 2017 13:50

You will have some busing deflection on the rear suspension as the wheels hang free, as you are trying to eliminate a vibration that happens when vehicle is at curb weight you want to re-produce same conditions that this occurs, so the use of a drive on hoist is a must. Depending on how much movement you gain by moving the shims from bottom to top (I would do this and re-measure) also make one change at a time. If you are within the ball park then take for another drive. I would make sure that you are using the same route (road-wise) to test nice smooth stretch this way you do not have road surface as a factor. As I was driving in California last week there seems to be quite a variance in road quality/texture for most of the road ways!

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TheHeretic
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Re: NVH Issues

Postby TheHeretic » 18 Aug 2017 15:02

Worked on this again yesterday (took day off) and really didn't get anywhere. Dropped the driveshaft this time and fully supported the rear wheels so that there was no deflection. Measured the diff (0.9 degrees) and the rear of tranny (3.8 degrees). Clearly, things need to be adjusted. Based on the desire to decrease the downward angle of the transmission and getting confirmation that the transmission should be sticking up higher (showed the below pics to a bunch of KA/SR Datsun experts), I will be adding a large spacer between the mount and bottom of the transmission. Hoping to get it below 3 degrees. BUT also need to change the angle of the diff to get its angle higher. Goal is the 0.5 to 1 degree difference mentioned previously.

Got the front shims out of the diff but couldn't get the rear ones out without removing the mustache bar and just didn't have enough time to do that and put to back together. Probably should have left the car at Dean's house overnight. Assuming I am able to remove all the shims, what does everyone mean by "reshimming" the diff? Are you using the same shims just moving them around top to bottom?

I guess the best help I need is suggestions of what to do that would bring the front of the diff down.

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66DUCE
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Re: NVH Issues

Postby 66DUCE » 18 Aug 2017 21:44

Again I can't stress enough, to re-measure after you make a change (so you do not chase your tail) at the rear of the transmission. Is the change enough? is it going in the right direction? Then move on to the rear did you take a measurement with the shims out of the front of the diff (removing them and re-tightening diff mounting)? I know that you said that the mustache bar would have to be removed to add more shims, but as mentioned in an earlier post it is easier to do one step at a time. Looking at an old post (picture) looks like the shim was on the bottom already, so removing it should give you less angle at the diff (front) closer to 0 deg.

Yes you will need to change the trans tunnel to suit the KA trans height.My thinking here is to keep the shim on the front of the diff and increase (add) shims to the rear (mustache bar) to give you more angle closer to the angle of the trans.
Hope this is helping??? One change at a time (document both what you did and measurements) will help to avoid going in circles.

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Re: NVH Issues

Postby greenthumb » 19 Aug 2017 06:31

Any possibility to drop your engine mounts at all?
It's amazing how much difference that makes

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Byron510
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Re: NVH Issues

Postby Byron510 » 19 Aug 2017 06:48

I did spot the engine mounts in the Bronze and dropped the engine oil pan within 3/16" of the cross member when using the syocknNissan type motor mounts. So some geometry can be gained here.
Due to the distance between the motor mount and the tranny mount, that likely made only a small change to the driveshaft angle. In my case I was looking for more hood clearance from the valve cover.

Do keep us posted.

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because the opposite never works.


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