Rear CV Joints problem Sudden "Klonk" on Acceleration

[jan.01]

Hi all,

We have a T3 Syncro 16 and I've started noticing a distinct "klonk" sound from the rear when I go from coasting to hard acceleration. It does not happen all the time, but sometimes almost with every accelerations, and sometimes never during a 40km ride. The noise is metallic.

While inspecting underneath, I noticed the rear driveshafts can move 2–3 cm in and out axially (not rotationally). That amount of movement seems excessive to me, and I'm starting to suspect the rear CV joints (inner or outer) may have a problem? We would like to use the van in the weekend, but nut sure this is safe..

The play that I have: https://www.dropbox.com/scl/fi/xuuzcmr81eu11pnkmfq...e&dl=0


Any insights, tests, or things to check next would be highly appreciated.
Thanks in advance!

Jan

[MarkWard]

New member today. First post and a link to click on to what appears Dropbox. I don’t click on links, but this seems suspect to me. Dropbox appearing links can be ransom wear. I’d caution anyone against till we have more details.

For Jan, in and out movement when the van is on the ground is expected. If you don’t know when the CVs were last serviced, it’s a straightforward dirty job. Get some peace of mind and do all 8.

[jan.01]

Hi,

Correct, new user as of today, but long-time viewer . Thanks for the reply!

Regarding the Dropbox link: it is just a plain video I recorded it with my phone showing the play I noticed. I don't know what the custom way is to upload a video.

The gearbox and rear diff were overhauled last summer, and the CVs were inspected at that time, broken rubbers replaced. Since then, I have only driven about 5,000 km. The front CVs have no noticeable play, even when the van is on the ground, it is only the rear that shows this kind of in-out movement.

Appreciate your input!
Jan
[vimeo][/vimeo]

[Wildthings]

Drive one side up on a curb to get more room underneath, set the parking brake, and put the tranny in neutral. Grab one of the CVs at a time and see how much you can twist it. New there will be no rotational movement, but with time an 1/8" is typical, while more than that is apt to be problematic. You should get a torque wrench and the correct hex or triple square adapter for your bolt heads (buy a 4" or longer adapter instead of a short one with an extension) and check the torque on the bolts. The spec torque for the bolts is 33 ft*lbs and it's common to find them loose.

[Backtotheeightiesagain]

If there is a sliding joint in prop to front diff I would grease that.
If not fitted sorry I don't see synchro now.
Be aware sound can be deceiving in direction.
If you not bothered about the smartphone, tape it to , around the bus on video/sound and gain hard evidence.
Any rubber mounts about 40yrs old suspect today

[?Waldo?]

CV shafts MUST have enough axial play to accommodate the movement of the tires up and down relative to the trans/chassis and the resultant larger/smaller distance between the drive flanges on the trans and the drive flanges at the wheels. With very tight new joints sometimes that play is not obvious.

[dhaavers]

[MsTaboo]

Hi jan.01 Welcome to the Samba.

First off here's a link on posting pictures and videos to the Samba:
https://www.thesamba.com/vw/forum/viewtopic.php?t=6

Next, don't worry about in/out play unless there is crunching associated with the movement. The CVs need some in/out slack.
Of course the CVs could always use attention if not done in a long time. Repacking the CVs is a messy job but not very hard if you have some decent tools. Lots of threads about this job, do a search (be sure to click "title only" button). Often the hardest part is just getting the axles off the rig.
While apart you can check the condition of the cages and balls for wear.
(edit, just saw your second post) When you say the rubbers were replaced do you mean the CV boots? If so, hopefully whoever replaced them did a proper repack.
On the front the outer CV is a bit different and usually less play.

With a Syncro you also need to check the driveshaft to the front diff. Grab the shaft and twist, checking for noise/movement in the U-joints. If the rig still has the original driveshaft it's not uncommon for the internal bushing to wear and you will get a sort of clang on acceleration. Or the Giubo donut could be failing.
The Syncro driveshaft can be tricky, read up before attempting removal. Again, do a search. If your rig is running smooth then you need to be careful not to change the alignment of the shaft. Need to make witness marks so it can be reinstalled exactly.

A few questions: How long have you owned the Syncro? What's your level of mechanical skill? Do you do your own maintenance?

We love pictures (and vids) so that we can get an idea of overall condition. Please post up a few.
_________________
Currently:
'90 Syncro Westy 3 knob w/Zetec

The information age has morphed into the age of disinformation and willful ignorance. Agnotology!
All that's needed for evil to prevail is for good people to do nothing.
Resist Kleptocratic Oligarchy (and Idiocracy)!

[jan.01]

Thanks for the detailed reply, really appreciate it!

In and out: no crunching at all, just the play, so sounds like that part is okay.
Rotational: no play

Link



Rubbers: yes, I meant the CV boots. Two of them were replaced about 5k km ago when we had the transmission and front diff overhauled. Local garage did the work. Pictures:

Front driveshaft: I have attached an extra video showing the driveshaft going to the front diff. There is quite a bit of play there, more than I expected. Definitely something I’ll look into further based on your suggestions.
Link



We have owned the Syncro for about a year now. We do the basic maintenance ourselves (fluids, filters, etc.), but leave the more advanced stuff to a trusted local garage.

Really surprised by all the feedback and support here, thanks again!

[dhaavers]

“Private Video - Sorry, you don’t have permission to watch.”

EDIT: FIXED!

- Dave
_________________
86 White Wolfsburg Westy Weekender
"The WonderVan"
<EDITED TO PROTECT INNOCENT PIXELS>

[MsTaboo]

I couldn't see the pictures (it really helps to load pictures to the Samba), but the video of the driveshaft is normal.
Sorry, I should have offered more info on that test. There will be that amount of twist as the shaft gears catch up from each direction.

What you want to check for is abnormal movement within the u-joints and the donut showing wear. Example: when you twist the shaft, after the slack is taken up, is there any flexing of the u-joints, or any cracks opening up in the rubber Giubo donut? You will need to put a bit effort into the twist.
This is just a basic test to look for very obvious signs of wear or loose hardware.

Clunks and other noises are very hard to diagnose from a distance, there could be a bunch of different sources. Are the transmission mounts secure? Engine mounts? Are the CV bolts tight? All the lug nuts tight, etc.

As I noted before, a clanging sound can come from the driveshaft itself, there is an internal yoke stub axle and bushing as part of the Giudo side of the shaft. It's purpose is to provide some movement within the shaft. It's not uncommon for these to make noise as the shaft ages.
Unfortunately the Syncro driveshaft is very difficult to rebuild and the usual course is to replace.

Are you experiencing any driveshaft vibration? This usually shows up at about 25-45 mph but can be present all the time; from a slight buzz to pronounced vibration that changes with speed.

It might be difficult, but maybe try and record the sound with the help of someone hanging (carefully) out the side door?

Also, have you done followup oil changes on the rebuild? Did the garage offer any advice about a break-in schedule? If not an oil change would be a good idea and a careful examination of the magnetic drain plugs for debris.
Do you know who actually did the rebuild? The Syncro transmission is pretty finicky and even experienced rebuilders can make mistakes. The front diff is more basic but still needs to done correctly.
_________________
Currently:
'90 Syncro Westy 3 knob w/Zetec

The information age has morphed into the age of disinformation and willful ignorance. Agnotology!
All that's needed for evil to prevail is for good people to do nothing.
Resist Kleptocratic Oligarchy (and Idiocracy)!