I rewelded my spring perches at what I thought was 1 1/2 degrees lower pinion angle. I thought all was fine driving around town until I got on the highway 3 months later and noticed vibration between 55 and 60. Re-checked the pinion angle and now it is a streight line with the driveshaft, both pinion and driveshaft are at identical degree. If I put 2 degree shims in backwards I should be perfect; but I can only find 6 degree steel shims at wild horses.
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Who Sells STEEL leaf spring shims
- Thread starter LouB
- Start date
70_Steve
Old Guy
- Joined
- Dec 13, 2002
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- 8,317
Dunno where Lou got them, but I included this link in the Pinion Angle tech article.
http://www.4crawler.com/4x4/ForSale/Shims.shtml
I need to know too - for my future files.
- Joined
- Nov 28, 2001
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- 10,105
For those of you with iPhones... This is somewhat tangential (which I guess makes this a thread hijack), but might be interesting because this thread started because of wanting to kill vibration.
I bought a cool app for my iPhone called "Vibration". It turns your iPhone into a vibration spectrum analyzer. More information here.
I have also been getting a vibration at around 50-55 mph. The software can capture up to about 10 seconds of data. It has a delay feature so you can press "start", then have enough time to set the device against something before it starts acquiring data.
So I got on a straight smooth road, ran up to 50-ish mph where I felt the vibration, and acquired a time series. Afterwards, I used the frequency transformation feature to identify the frequency peaks. Lo and behold the big spikes were at around 480 rpm (tire speed) and 2200 rpm (driveshaft speed; I have 4.56 gears). Testing at other speeds showed that the tire vibration got steadily worse with greater speed, but the driveline vibration was worst at around 2200 rpm.
I thought it was pretty cool to be able to positively ID where a vibration is coming from, instead of guessing. I mostly killed the tire vibration by getting them rebalanced. Still gotta deal with the driveline, but that's a separate issue- I have a fairly new driveshaft, and the pinion angle is good (2 degrees low). But I run a 17 degree drop at the CV and spend a lot of time at 70-ish on the freeway, which may be the killer.
Sorry about the hijack, hope someone finds this useful.
As for shims, I've bought a few pairs from 4crawler.com also. Good service, in my experience. When I bought from him he was making them to order. Probably still the case.
I bought a cool app for my iPhone called "Vibration". It turns your iPhone into a vibration spectrum analyzer. More information here.
I have also been getting a vibration at around 50-55 mph. The software can capture up to about 10 seconds of data. It has a delay feature so you can press "start", then have enough time to set the device against something before it starts acquiring data.
So I got on a straight smooth road, ran up to 50-ish mph where I felt the vibration, and acquired a time series. Afterwards, I used the frequency transformation feature to identify the frequency peaks. Lo and behold the big spikes were at around 480 rpm (tire speed) and 2200 rpm (driveshaft speed; I have 4.56 gears). Testing at other speeds showed that the tire vibration got steadily worse with greater speed, but the driveline vibration was worst at around 2200 rpm.
I thought it was pretty cool to be able to positively ID where a vibration is coming from, instead of guessing. I mostly killed the tire vibration by getting them rebalanced. Still gotta deal with the driveline, but that's a separate issue- I have a fairly new driveshaft, and the pinion angle is good (2 degrees low). But I run a 17 degree drop at the CV and spend a lot of time at 70-ish on the freeway, which may be the killer.
Sorry about the hijack, hope someone finds this useful.
As for shims, I've bought a few pairs from 4crawler.com also. Good service, in my experience. When I bought from him he was making them to order. Probably still the case.
Lars,
That's pretty interesting. A bit techie for me; but, maybe one of the young guys in our EB group will come up with the same piece of gear. I initially had a hard time determining if the vibration was tires or driveshaft.....
The thing that just kills my ego is I degreed the axel about 6 times and welded new perches on and thought I had it right on the money. I'm blaming it on the springs settling down a bit.
That's pretty interesting. A bit techie for me; but, maybe one of the young guys in our EB group will come up with the same piece of gear. I initially had a hard time determining if the vibration was tires or driveshaft.....
The thing that just kills my ego is I degreed the axel about 6 times and welded new perches on and thought I had it right on the money. I'm blaming it on the springs settling down a bit.
Monitoring machine (very large machine, in my case) vibrations is part of my job. It's pretty useful. Explaining/understanding/using the information is a bit tricky, since it's pretty math-intensive, but you don't need to be a PhD math whiz (I'm none of those things, believe me) to get a general grip on how it works. The crazy thing is that not too many years ago, the equipment to do what I did for barely over 100 bucks (cost of phone plus software) would've set you back over $5000 easy.
Don't beat yourself up over the spring perch measurement challenge. I've done the exact same thing, which is how I wound up buying shims from 4crawler.com
methcat
Sr. Member
you guys ordering his standard 2" wide shims? seems like ideally they'd be 2.25" wide...
Not to take away from your iphone idea but the seat of my pants tells me if theres a vibration or not and its free.
But still interesting how did you determine tire vibrations from driveshaft vibration with just this application? To me unless you can attach this equipment to a part then test all it told you was you had a vibration which you already knew. Then you had the tires rebalanced and ran the test again so that part of the vibration was gone which really only leaves the driveshaft and normal road vibrations.
But still interesting how did you determine tire vibrations from driveshaft vibration with just this application? To me unless you can attach this equipment to a part then test all it told you was you had a vibration which you already knew. Then you had the tires rebalanced and ran the test again so that part of the vibration was gone which really only leaves the driveshaft and normal road vibrations.
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- Nov 28, 2001
- Messages
- 10,105
I think that's what I got - I could go measure for sure. As I recall, I obsessed about the delta in width as well and then realized that 1/8" difference on each side probably wasn't worth worrying about.
Todd Z.
22213evl
Bronco Guru
ok this is getting too close to something like ( I can feel vibrations with my butt) maybe this should be moved to the perv forum.
sorry broncnaz but it is not very often that you set yourself up for something as good as that, I had to take a shot. ;D
- Joined
- Aug 23, 2007
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- 24,322
He knew his driveshaft rpm from a tach. Divide that by axle gearing to get wheel rpm. Just have to be careful about how you interpet the spikes on the spectrum analyzer. Whenever you have 2 or more vibrations (frequencies) at the same time you'll see spikes at the lower and upper difference frequencies also, which are meaningless.
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- Jun 11, 2004
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- 11,855
With spectral information you can even get an idea of what kind of driveshaft/driveline problem you might have since blance issues show up as a 1/shaft rev spike and u-joint issues, particularly u-joint alignment, show up as 2/shaft rev. Axle shafts are turning at different revs and so any spikes corresponding to axle rotational fequency then point in that direction..and so on.
Spectral vibration analyzers are very usefull..I ahve been using PC-based and handheld anaylzers for a long time; we sintall equipment in ships and craft whre machinery noise and vibration is a critical issue. Way cool that its now an iPhone app and not thousands of bucks in special equipment.
Any idea what the upper limit on the frequency range for that app is? I have to wonder what kind of filters are in place on the iPhone accelerometers.
Spectral vibration analyzers are very usefull..I ahve been using PC-based and handheld anaylzers for a long time; we sintall equipment in ships and craft whre machinery noise and vibration is a critical issue. Way cool that its now an iPhone app and not thousands of bucks in special equipment.
Any idea what the upper limit on the frequency range for that app is? I have to wonder what kind of filters are in place on the iPhone accelerometers.
No problem I figured someone would take a shot heck I even thought about it as I was posting. Have to give back sometimes. I know I've given a few shots.
Drive shaft speeds ect is the easy part. that much I understand. The part I dont quite get is how you can set a peice of "test equipment" on what the floor? and determine where your vibrations come from tires, driveshaft, street, engine ect.
I'm a simpleton I guess.
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- Aug 23, 2007
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The different vibrations will be present in any area that isn't completely isolated and dampened. Rubber body bushings would attenuate the vibrations to some extent but I can see how they would be measureable. From there it's just a matter of determining the frequencies of the different moving parts.
