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Thu Jan 27, 2005 8:59 am

For about the past couple of weeks my '91 Syncro has been experiencing some strange vibrations. It occurs at higher speeds (above 30 mph) and only during acceleration and while maintaining speed. It goes away when decelerating or when I take my foot off the accelerator.

The vibration is at a higher frequency, and comes across like a low hum. It makes things like the windows and items in the glove vibrate too.

I am thinking that it is in the engine rather than the transmission because the vibration doesn't change enough with a change in speed. At least it doesn't seem proportional. I am wondering if there might be a slight miss in the engine, or the FI system is putzing a bit.

I realize trying to diagnose this issue in a forum is difficult with out seeing/hearing, but I am hopeing someone has either had a similiar issue, or there is some known "Famous Vanagon Vibrating Problem"
Probably not.

Other things... I have checked the cv joints, and recently replaced transmission oil (problem was there before). I also recently replaced the starter which required removing axle from trans.

Thu Jan 27, 2005 9:31 am

Of the little I know of Syncros, I might know what it is. The "u" joints on your center shaft are loosening up. Now I haven't paid much attention to Syncros, since I am just an admirer not an owner, but This is a known problem that POs seem to stick new owners with. Does this sound like you?
read the link here:
http://vanagon.com/syncros/technica/Driveline/index.html

Thu Jan 27, 2005 9:32 am

Dumb question:

Do these things have a "carrier bearing" like my 4 WD truck? I of couse know nothing about Syncros, but if they have some other CV or U-Joints for the driveshafts, I would have a look at them to make sure they are still able to flex correctly.

Thu Jan 27, 2005 10:54 am

mightyart, that sounds exactly like what I am experiencing. The article said that it is hardly noticable at first, and gradually gets worse. For a while I thought my speakers were humming strangly, but as time has gone on, its getting worse.

I am going to take out that driveshaft and see if the vibrations are still there. Then go from there.

The syncro doesn't have a "carrier bearing" but does have U joints. From the article mightyart linked, it looks like the entire shaft was designed to be replaced. I love my Syncro but sometimes VW's propensity towards "job security" is a little irratating.

Makes for interesting Saturday afternoons though.

Sat Jan 29, 2005 4:53 pm

When you drop the shaft move the ujoint in your hand. You will find, probably only one is bad. It will be stiff not loose. They rust and get crunchy before becoming loose. It sounds very much like a ujoint problem. and any time you want to sell that van or see one for sale let me know. I'm searching for a synro. Good Luck

Sat Jan 29, 2005 5:58 pm

U joints are going bad. Remove the short shafts and have them rebuilt PRONTO :roll:

Mon Jan 31, 2005 12:57 pm

What is your experience with getting the u joints rebuilt? From the research I've done, it doesn't look like its a great option... success reported from about half of thoes who try it.

I also spoke with a local VW guy (he's reportedly good, and claims experience with Vanagons, and even Syncro's) and he said that the prop shaft is actually a double shaft with one inside the other, and that there could also be other reasons for shaft failure. He recommended replacing the whole thing. (My normal intuition is to distrust a mechanic, because OF COURSE its the most expensive option that is proposed. But then the name of the shop is Good Carma, so maybe they live by it...)

I am really looking for a way to do it without putting in a $700 rebuilt shaft. But at the same time, I don't want to go on the cheap just to save some money. This is my van (Sorry BavarianWrench, no sale for the forseeable future) and I have made a commitment to keeping her up and running GOOD.

Mon Jan 31, 2005 2:44 pm

GoWesty has a new type of prop shaft that eliminates the guibo, which i guess is pretty pricey.

Mon Jan 31, 2005 4:01 pm

ProvoCyclist, thanks for the tip. It looks like this could be the answer I am looking for.

For anyone else interested here is the link from GoWesty!
http://www.gowesty.com/syncro_driveshaft_replacement.htm

Tue Feb 15, 2005 11:45 am

I put in the new prop shaft from GoWesty! and it works great. If you are a Syncro owner and you are starting to hear a strange buzz, this is the answer.