how much offset is it compared to the pinion? I've never even noticed, since it's not easy to tell looking up at it 6" from my face, laying on my back.
Harmonic vibrations in Jeeps: A new theory (please read!)
- Thread starter psrivats
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how much offset is it compared to the pinion? I've never even noticed, since it's not easy to tell looking up at it 6" from my face, laying on my back.
We have a thread somewhere with exact measurements, guy was doing LS swap and was asking for everyone measurements.
I don't have a ruler at the moment, but here is a quick snap of it. Front is more obvious, rear is a bit harder to see.
I had noticed the front before, but yeah, never the rear. and the way it is in that photo, seems like any squat due to acceleration, wind resistance, or extra weight would make things even worse due to the arc of the track bar. I might brainstorm on a good way to check the actual ride height of the rear at 70-75mph and add weight to simulate that height in the garage when I center the axle.
That said, my LJ's driveshaft is about 50% longer than that of a TJ, so the angles should be less pronounced.
Hello everyone! This is my first post, I found this thread while trying to source my vibration problems, but on my YJ.
I Read all thread and found some interesting moments.
I have 5,5" total lift (4,5" suspension and 1" Browndog rubber motor mounts and raised skid plate) and like the others my vibration problems start when I install 4,88 gears (revolution axle & gear brand) I had some vibrations before since I swapped ford 8.8 with flange adapter, but vibes appear only on 70+ and dont bothered me much. After regear I start feeling bad vibrations at 40+mph, it feels everywere, seats, shifters, steering wheel.
If I removed front DS vibes gets smoother, if I removed rear DS - vibes completely gone (in both ways I speed up to 70mph)
So here is what I did
- Move transfer case about 1/2" to pass side by rewelded skid plate holes for transmission mount to minimize side angle at F8.8 pinion
- Install JB conversions mega short SYE with new custom Adams driveshaft and 1350 yoke on f8.8
- set rear pinion about 0.5 degrees lower driveshaft (on Adams webside there is recomendations for leaf spring suspension to lower pinion about 2 degrees but that does not worked for me, I tried) with almost 0 degrees there is less vibes
- set front pinion from -3 degrees to almost 0 degrees to driveshaft (forgot to mention that I have CV style front Adams driveshaft, I install it about 1,5 years ago) by putting 2 degree shims on leaf springs
Also I have custom made 3/16" skid plate that weights around 50lbs but after reading this thread I'm planning to make one from 1/4" steel, the weight would be around 60lbs..
After all this movements theres is big improvements, but I still can feel a little vibes at 50-55mph, then they disapper till I hit 65+ and there is starting uncomfortable vibes and drone. There is consistent vibes and drone, not pulsating, like an incorrect pinion angle..
Ok so I put Jeep on the jack stands and hit 80mph on 2wd and there is no vibes at all (front DS not spinning) then I put it in 4wd and got vibes at 65+ (but 50-55 vibes are gone)
After that I unbolt the rear DS and in 4wd again speed up to 80 - vibes still persists. So there is some interesting fact that without load I have vibes on front end spinning, but no vibes under load..
Then just for the test I remove both driveshafts and speed up in 4wd - no vibes, so i believe transfer case is good (I have durango TC with 1,25" chain)
Also I noticed sometimes front DS splines have a little play and sometimes its rocksolid.. Dont know why, but I believe it cant wore out in 1,5 years and about 10 000 miles. At least blue glidecoat looks like new.
I add some pictures of my driveshaft angles.
First two - rear driveshaft.
3 and 4 - front driveshaft.
Is there a normal operating angle for double cardan?
5th picture is rear driveshaft with offset transmission mount.
And sorry for my English, I'm from Russia..
I Read all thread and found some interesting moments.
I have 5,5" total lift (4,5" suspension and 1" Browndog rubber motor mounts and raised skid plate) and like the others my vibration problems start when I install 4,88 gears (revolution axle & gear brand) I had some vibrations before since I swapped ford 8.8 with flange adapter, but vibes appear only on 70+ and dont bothered me much. After regear I start feeling bad vibrations at 40+mph, it feels everywere, seats, shifters, steering wheel.
If I removed front DS vibes gets smoother, if I removed rear DS - vibes completely gone (in both ways I speed up to 70mph)
So here is what I did
- Move transfer case about 1/2" to pass side by rewelded skid plate holes for transmission mount to minimize side angle at F8.8 pinion
- Install JB conversions mega short SYE with new custom Adams driveshaft and 1350 yoke on f8.8
- set rear pinion about 0.5 degrees lower driveshaft (on Adams webside there is recomendations for leaf spring suspension to lower pinion about 2 degrees but that does not worked for me, I tried) with almost 0 degrees there is less vibes
- set front pinion from -3 degrees to almost 0 degrees to driveshaft (forgot to mention that I have CV style front Adams driveshaft, I install it about 1,5 years ago) by putting 2 degree shims on leaf springs
Also I have custom made 3/16" skid plate that weights around 50lbs but after reading this thread I'm planning to make one from 1/4" steel, the weight would be around 60lbs..
After all this movements theres is big improvements, but I still can feel a little vibes at 50-55mph, then they disapper till I hit 65+ and there is starting uncomfortable vibes and drone. There is consistent vibes and drone, not pulsating, like an incorrect pinion angle..
Ok so I put Jeep on the jack stands and hit 80mph on 2wd and there is no vibes at all (front DS not spinning) then I put it in 4wd and got vibes at 65+ (but 50-55 vibes are gone)
After that I unbolt the rear DS and in 4wd again speed up to 80 - vibes still persists. So there is some interesting fact that without load I have vibes on front end spinning, but no vibes under load..
Then just for the test I remove both driveshafts and speed up in 4wd - no vibes, so i believe transfer case is good (I have durango TC with 1,25" chain)
Also I noticed sometimes front DS splines have a little play and sometimes its rocksolid.. Dont know why, but I believe it cant wore out in 1,5 years and about 10 000 miles. At least blue glidecoat looks like new.
I add some pictures of my driveshaft angles.
First two - rear driveshaft.
3 and 4 - front driveshaft.
Is there a normal operating angle for double cardan?
5th picture is rear driveshaft with offset transmission mount.
And sorry for my English, I'm from Russia..
Английский супер, все четко и понятно 
You have two factors that set you apart from most of what i have seen:
1. in 4wd vibes typically go away, yours is opposite.
2. typically removing front DS resolves the issue, but that is not to say that front DS is the issue. If there are no outside factors, front or rear DS by itself operate very smoothly, it is when they are both connected something is not in sync.
4wd or 2wd, your rear seems to be a common variable.
8.8 is known for its angle issues that result in vibes. There are guys on here who have been fighting with 8.8 angles and eventually have given up.
Have you tried to center rear yoke of axle with rear yoke of TC by offsetting rear axle to the side? It may look retarded, but that may eliminate inherent issue with 8.8 and provide more clarity on what exactly is going on in the rear.
You have two factors that set you apart from most of what i have seen:
1. in 4wd vibes typically go away, yours is opposite.
2. typically removing front DS resolves the issue, but that is not to say that front DS is the issue. If there are no outside factors, front or rear DS by itself operate very smoothly, it is when they are both connected something is not in sync.
4wd or 2wd, your rear seems to be a common variable.
8.8 is known for its angle issues that result in vibes. There are guys on here who have been fighting with 8.8 angles and eventually have given up.
Have you tried to center rear yoke of axle with rear yoke of TC by offsetting rear axle to the side? It may look retarded, but that may eliminate inherent issue with 8.8 and provide more clarity on what exactly is going on in the rear.
Thanks eastbloc!
In 4wd on the road with both driveshafts vibes gets a little smoother, but not much. Its on the jack stands with free spinning tires in 2wd I have no vibes at all, so I assume the rear end is good? but in 4wd with boths driveshafts and also with rear removed I have vibes (But on the road with only front DS its smooth) So I'm thinking something in front end vibrates without load. Also I tried this without tires just to eliminate vibes from them, but turned out that tires is perfectly balanced because there is no difference with or without them
I dont tried to move axle sideways, but on the leaf springs it means I need to reweld my perches, but I move my transfer case by 1/2" to pass side. This is that far I can move it without putting force on the motor mounts. Now i cant see much angle on the rear pinion u-joint, on the 5th photo on my previous post it looks straight from TC to rear axle. But there is minor side angle on the front driveshaft at front axle u-joint, i cant measure it, but this angle is deffenetly smaller that angle at rear axle before i moved TC.
So IF this is just nature of two double cardan driveshafts spinning together then I'm thinking about on-car balancing with hose clamps, I have good experience with this method on my previous CV rear driveshaft with flange adapter before I install megashort SYE and 1350 yoke to rear axle. It wasnt perfect but at least not terrible like it did before..
In 4wd on the road with both driveshafts vibes gets a little smoother, but not much. Its on the jack stands with free spinning tires in 2wd I have no vibes at all, so I assume the rear end is good? but in 4wd with boths driveshafts and also with rear removed I have vibes (But on the road with only front DS its smooth) So I'm thinking something in front end vibrates without load. Also I tried this without tires just to eliminate vibes from them, but turned out that tires is perfectly balanced because there is no difference with or without them
I dont tried to move axle sideways, but on the leaf springs it means I need to reweld my perches, but I move my transfer case by 1/2" to pass side. This is that far I can move it without putting force on the motor mounts. Now i cant see much angle on the rear pinion u-joint, on the 5th photo on my previous post it looks straight from TC to rear axle. But there is minor side angle on the front driveshaft at front axle u-joint, i cant measure it, but this angle is deffenetly smaller that angle at rear axle before i moved TC.
So IF this is just nature of two double cardan driveshafts spinning together then I'm thinking about on-car balancing with hose clamps, I have good experience with this method on my previous CV rear driveshaft with flange adapter before I install megashort SYE and 1350 yoke to rear axle. It wasnt perfect but at least not terrible like it did before..
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Watch out @Chris. The Russians are coming. Before we know it they'll be hacking your servers and find all the photos of you doing blow off a prostitutes ass in Vegas. Or, red dawn.... I can't accurately read the future.Английский супер, все четко и понятно
I’ll just do what mainstream media did with Hunter Biden and say it’s “Russian misinformation”
your English is actually quite good.
I couldn't quite tell from the photos, but does your front Dana 30 have the vacuum operated center disconnect? If so, we should take that into account as behavior will be different in 2WD...it would be more comparable to one of us that has installed a manual hub conversion.
I couldn't quite tell from the photos, but does your front Dana 30 have the vacuum operated center disconnect? If so, we should take that into account as behavior will be different in 2WD...it would be more comparable to one of us that has installed a manual hub conversion.
Ahh i misunderstood you
I read you saying "If I removed front DS vibes gets smoother, if I removed rear DS - vibes completely gone (in both ways I speed up to 70mph)", and figure that rear is the issue here.
And you being on leaf springs also makes it different than our TJ with coil springs.
When you shifted rear of transfer case to the side, there is a chance that you created additional horizontal angle between front transfer case output and front drive shaft. Did this extra angle have any effect on the vibrations? Hard to tell, maybe it is worth exploring.
This is my supa-dupa technical drawing to explain what i mean
https://wranglertjforum.com/threads/oscillating-harmonic-vibes.50345/page-3In this thread, post #46 i was thinking to do the same thing you did, offset rear of transfer case to the passenger side. With Dana 35 my rear is not perfectly aligned, but it is not as bad as with your 8.8
But then i thought to myself that shifting rear of transfer case will create extra angle at the front output.
I have not tried doing that yet, but i want to give it a try and see the results.
Further more, your front ds splines having a little of play can be a result of vibrations, really depends how long you had them.
I am not around my Jeep at the moment, so i cant verify, but i hope that someone else can check theirs.
This is the first time i hear of on-car balancing with hose clamps, but it looks very effective and you should definitely give it a try. However, have you tried to rotate drive shaft 180 degrees? Sometimes there is a conflict between the balance of yoke and balance of drive shaft, and if they are out of sync, it will create vibration.
If my drunk logic is correct, there are 4 ways a drive shaft can be mated between two yokes
No, I dont have vacuum disconnect, so my fornt DS spins everytime
Nice drawing!
Yeah, I thought about front DS horizontal angle but I dont think it's very bad due to double the length of the front shaft compared to the rear. But I'm willing to try and put stock skid plate to center the TC and lower it at 1" at the same time and see what happens, maybe try to lower my motor back 1". I made a quick sketch in solidworks and found out this would give me a 1-2 degree less on the CV joints.
I didn't noticed how long I have this play in front DS splines, but the whole driveshaft is about a year and a half old and that blue coating on the splines looks like new.
I only rotate whole front DS on the both yokes and it made no difference. But I thought that phasing DS to yokes doesn't matter..
"I read you saying "If I removed front DS vibes gets smoother, if I removed rear DS - vibes completely gone (in both ways I speed up to 70mph)", and figure that rear is the issue here." - you read this correct, but I forgot to mention that was before I put new rear driveshaft with JB conv megashort. The old shaft is definitely make bad vibes because I put an adapter flange on it without rebalancing
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That is what everyone says, and I thought so too, until that one time when I was changing rear tc output seal.
Assembled everything back together, and out of no where vibrations. I was pulling my hair out for a week while trying to figure out what went wrong.
Then all I did was rotate tc yoke - vibes gone like magic. If you read around, there are few of us on here who went through this.
Fact is, so far there is only one known solution to regear vibration issue - locking hubs.
Everything else is as the saying goes "гадание на кофейной гуще", maybe this - maybe that, who knows. Slowly go insane as you tear your Jeep apart in search of the mystical vibrating creature.
If you are already thinking about hose clamp balancing, might as well play with yoke phasing.
Looks like i am getting somewhere with my vibrations.
I had vibes with both driveshafts in, which would go away in 4wd or with one of (front or back) driveshafts removed.
So far in order:
Front Hub bearings and ball joints, 132000 miles on originals
Swap rear TC yoke incase one from Advance Adapters is out of balance too
Swap to super short SYE
Raised motor mount, concerned that result of extra angle at front DS will create issue, will see
I had vibes with both driveshafts in, which would go away in 4wd or with one of (front or back) driveshafts removed.
So far in order:
- Changed tc mount - no difference
- Changed driveshafts - no difference
- Endless balancing of tires - no difference
- Changed control arms from MC duroflex to SAVVY jj
- Some have reported duroflex joint not being able to keep axles squared away under load
- No difference
- Multiple goes at making sure alignment is squared away
- i think i lost a bit of my sanity with all the measurements, cant tell
- Changed rims and went up from 31 to 33 tires.
- This was the 1st notable difference, but vibrations were not eliminated, they became less severe.
- Possibility result of or combination of:
- rim or rims were bent
- bigger tires brought revolutions of driveshafts down
- i have always been skeptical of 1 tire being able to hold balance, but no amount of balancing could prove my assumption.
- Changed front TC yoke to a smaller one from Tom Woods
- this was the 2nd and most notable difference.
- Vibes are significantly dampened,
- I could get to 65mph with both driveshaft and not feel as if i am driving impact hammer.
- What have remained i would not even call vibes, it turned into a wobble
- Got new tires rebalanced again
- I am on the highway doing 70 mph 97% concern free
- a slight wobble will randomly appear and go away.
- lower speed vibrations are there that disappear after 35 mph
- i am confident it is rear pinion angle related
- i have compensated angle by setting it at 0 with full tank + extra weight
- no extra weight and lower fuel level seems to create difference of more than 1 degree.
- i am confident it is rear pinion angle related
- I am on the highway doing 70 mph 97% concern free
Front Hub bearings and ball joints, 132000 miles on originals
Swap rear TC yoke incase one from Advance Adapters is out of balance too
Swap to super short SYE
Raised motor mount, concerned that result of extra angle at front DS will create issue, will see
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This is the first I've heard of the smaller front output yoke. Do you have any more details about it that you can share?
smaller is a wrong word, shorter in comparison, which i dont think matters any.
Bad yoke with run out is bad yoke with run out.
Vtx531
TJ Addict
I recently noticed the heat shield above my muffler is coming apart and not mounted securely. I think this could be a source of resonating and “vibration”.
well that would have saved me about $250 on a new front driveshaft when mine ended up too long
. How much runout did you measure?Similar threads
