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bac914
Samba Member
Joined: August 11, 2008
Posts: 112
Location: Denver
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 Posted: Mon May 12, 2014 8:11 pm Post subject: Syncro Driveline vibrates when decoupled, but not coupled |
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My setup: svx conversion with RMW parts, 1 year on rebuilt tranny with decoupler, 2 years on rebuilt front diff with new VC, new or serviced CVs in the last 6 months, new van cafe slip yoke driveshaft (purchased in the fall of 2013, just rebuilt and balanced last week).
Symptoms: Vibration at 30 and 75ish mph when decoupled. No vibrations when coupled.
Does this mean that something inside the decoupler is bad? Or is there still something else amiss in the driveshaft? I have read all the posts on both driveshaft alignment and angles and have tried the van cafe method to align front diff, but have not done fancy laser alignment procedures. I have experimented with different angles of the front diff, shimming up or down with no change.
The vibration on and off with the decoupler leads me to believe it's something with that. I will email the manufacturer, but curious if others have seen this before and have thoughts.
Thanks,
Brian. |
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insyncro
Banned
Joined: March 07, 2002
Posts: 15086
Location: New York
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| Posted: Mon May 12, 2014 8:32 pm Post subject: |
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Yes, others have had similar issues and it was in fact the decoupler that was the issue about half the time.
If your driveshaft has the rubber donut, try flipping it around to the other end and see if that changes anything.
Marking the flanges first is recommended so that they can be mount back to where they were if there is no change. |
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alaskadan
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Joined: January 09, 2013
Posts: 1857
Location: anchor pt. alaska
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| Posted: Tue May 13, 2014 8:14 am Post subject: |
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| A friend of mine is tring figure out a vibe too. If it is the decoupler are they rebuildable? |
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Jon_slider
Samba Member
Joined: April 11, 2007
Posts: 5091
Location: Santa Cruz, Crowdifornia
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| Posted: Tue May 13, 2014 9:01 am Post subject: Re: Syncro Driveline vibrates when decoupled, but not couple |
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| bac914 wrote: |
| Symptoms: Vibration at 30 and 75ish mph when decoupled. No vibrations when coupled. |
I dont know the cause of your vibration, but here are some things you might check.
1. determine what RPM the vibration happens at when driving. Then stop the Van, in neutral, rev back to that RPM, got vibration? If so, its not the transaxle, decoupler, driveshaft or CVs. If no vibration, go to test #2
2. Remove the driveshaft, go driving, vibration gone? if so its the driveshaft or decoupler
sounds like your driveshaft is new and verified balanced... that would leave the decoupler.
about angles, depending how your SVX is mounted, it may sit at a different height than a stock motor
while you have the driveshaft out, measure your flange angles relative to true vertical. I use an iPhone app called Clinometer. There are many different tools available to measure angles.
Your goal is to have the same angle front and rear, or within 1 degree of each other, and for neither angle to be bigger than 4 degrees. The easiest adjustment other than motor position and tranny ears, is to add shims to the front diff to reduce the angle that the front diff flange points at the ground.
it is OK for the front flange to point down at the ground, and for the rear flange to point up at the sky, as long as the angles are close to the same. Also OK for both flanges to point at the ground...
get back with your flange angles and test results, curious minds want to know 
good luck
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My Soapboxes: Inflation; Handling; Gearing; Decoupling; Swepco |
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zeohsix
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Joined: August 31, 2012
Posts: 501
Location: United States
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| Posted: Tue May 13, 2014 9:05 am Post subject: |
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The 2 sections of the decoupler are located in the nose piece......some kits ( IE....Long Enterprises ) use a bushing between the 2 shafts. If your bushing was shot, I could see where it would cause this problem. I used a German sourced kit with needle bearings that keep the 2 shafts located while decoupled a much better solution.
Decouple the trans....crawl under your Syncro and see if you can get any motion out of the front output flange....there should be no movement....if you can wiggle parts around and have free play....time to remove the front housing and inspect parts.
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I'm Cheap! I'll build that Syncro Westy myself and save money but, my labor is "FREE" especially if I ever go to sell it! One thing is I will know the quality of the parts and labor that went into the build and rest better when I'm actually driving said Westy down the road! |
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bac914
Samba Member
Joined: August 11, 2008
Posts: 112
Location: Denver
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| Posted: Tue May 13, 2014 9:39 am Post subject: |
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Thanks for all the great feedback.
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2. Remove the driveshaft, go driving, vibration gone? if so its the driveshaft or decoupler
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With the driveshaft out, now that I have new CVs, I get a nice vibration free ride at all speeds.
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....there should be no movement....if you can wiggle parts around and have free play....time to remove the front housing and inspect parts.
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I definitely have play in the output shaft of the decoupler. I noticed it when I put the rebuilt driveshaft back in. It concerned me but given I just had the tranny rebuilt and specifically asked about the condition of the decoupler (which was reported to be okay), I was hoping the play was okay. It is a Long Enterprises decoupler, so it sounds like I need to get it serviced? Can the bits be rebuilt? If so, who does that kind of thing?
Finally, can I run it as is in the coupled mode to eliminate the vibrations until I get it serviced? Is there some additional damage that would be done? Or should I remove the driveshaft again?
Thanks all,
Brian. |
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zeohsix
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Joined: August 31, 2012
Posts: 501
Location: United States
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| Posted: Tue May 13, 2014 9:54 am Post subject: |
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The end of the main shaft bearing surface could possibly get damaged if enough wear is allowed to happen. My opinion, get a German decoupler with the needle bearings and enjoy a long life expectancy I would never use bushings in this application if I were engineering the part.
FYI the main shaft has the pinion gear on it....it's a $1200 item!
I would remove driveshaft until you have problem looked into.
_________________
I'm Cheap! I'll build that Syncro Westy myself and save money but, my labor is "FREE" especially if I ever go to sell it! One thing is I will know the quality of the parts and labor that went into the build and rest better when I'm actually driving said Westy down the road! |
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Jon_slider
Samba Member
Joined: April 11, 2007
Posts: 5091
Location: Santa Cruz, Crowdifornia
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| Posted: Tue May 13, 2014 9:59 am Post subject: |
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| bac914 wrote: |
| should I remove the driveshaft again? |
that is not enough to solve the problems
very bad idea to keep driving with bad decoupler bushing, coupled or not, even with driveshaft out
I would replace the decoupler for one with needle bearings
http://www.aatransaxle.com/price_list.htm
and try to improve your flange angle match, since the mismatch likely caused the bushing failure
my guess is mismatched angles are putting pressure on the decoupler bearing, thats why it failed.
if you measure your flange angles and they match, I am mistaken. You need to know your flange angles so you can determine if that caused the bushing failure..
you are a good candidate for laser alignment, so you dont destroy another decoupler
the wallowed bearing is allowing your pinion shaft to wobble, very bad idea to keep driving an improperly supported shaft..
Flush drain, and check your tranny drain plug magnet for excess metal shavings coming off your ring and pinion..
How many miles (distance, not time), on the tranny? I hope your R&P is still OK
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gears
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Joined: October 28, 2002
Posts: 4391
Location: Tamarack, Bend, Kailua
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| Posted: Tue May 13, 2014 11:33 am Post subject: |
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It has to come apart for inspection. Yes, the German type with needles is better (than the shaft-against-shaft arrangement), but the play you feel is probably just a bad nose ball bearing. Unless excessive shaft wear is evident, I'd just replace the bad bearing.
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aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com |
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bac914
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Joined: August 11, 2008
Posts: 112
Location: Denver
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| Posted: Mon May 26, 2014 5:57 pm Post subject: |
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So I chatted with the manufacturer. He spent an hour on the phone with me explaining in detail all the other things it could be and somewhat mocking me for conceiving an idea as complicated as the decoupler causing my vibration. I think I'll just leave it at that...so back under the van with a clinometer.
Tranny angle was 5.1, front diff was 2.8. I was able adjust the tranny angle by removing the giant washers. The tranny angle after that was 3.6ish. After a nice vibration free test drive coupled and uncoupled, I'll concede that 'twas not the decoupler.
Now if I can only remember how my custom tranny skid plate that I took off 3 years ago goes on, I'll be a happy camper. 
So another syncro driveline vibration story ends happily by correcting flange angles. Can't wait to go four wheeling now and break something else.  |
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Jon_slider
Samba Member
Joined: April 11, 2007
Posts: 5091
Location: Santa Cruz, Crowdifornia
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| Posted: Mon May 26, 2014 7:30 pm Post subject: |
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| bac914 wrote: |
| Tranny angle was 5.1, front diff was 2.8. I was able adjust the tranny angle by removing the giant washers. The tranny angle after that was 3.6ish. After a nice vibration free test drive coupled and uncoupled |
thanks for following up
congratulations!
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My Soapboxes: Inflation; Handling; Gearing; Decoupling; Swepco |
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Syncro Jael
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Joined: December 19, 2013
Posts: 2204
Location: Utah
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| Posted: Mon May 26, 2014 7:56 pm Post subject: |
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Yup, I also learned the flange angles make a huge difference. Alignment of the front diff and transaxle is very important too!
Congrats on finding your issue. 
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1987 Syncro Westfalia Hightop - NAHT
Subaru EJ25 Forged Frankenmotor, Triple Knob.
Jael = (Mountain Goat) |
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bac914
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Joined: August 11, 2008
Posts: 112
Location: Denver
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| Posted: Mon May 26, 2014 8:17 pm Post subject: |
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Syncro Jael, Now that the driveshaft vibes are behind me I can get on with learning some Phillip Phillips songs for next years syncro solstice campfire.  |
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Syncro Jael
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Joined: December 19, 2013
Posts: 2204
Location: Utah
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| Posted: Tue May 27, 2014 8:20 am Post subject: |
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| bac914 wrote: |
| Syncro Jael, Now that the driveshaft vibes are behind me I can get on with learning some Phillip Phillips songs for next years syncro solstice campfire. |
We had a great time at the Solstice with your family as neighbors. Thanks again for singing us to sleep each night. It was great!
See you next year! 
_________________
1987 Syncro Westfalia Hightop - NAHT
Subaru EJ25 Forged Frankenmotor, Triple Knob.
Jael = (Mountain Goat) |
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