Syncro Propshaft Alignment Problem

[MarkWard]

Driveshaft critical speed also needs to be considered. The syncro driveshaft is actually pretty long for a one piece driveshaft. Something like this is fun to play around with. Try different values.

Critical speed calculator.
https://spicerparts.com/calculators/driveshaft-safe-operating-rpm-calculator
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[ALIKA T3]

[Sodo]

Sorry for making you crazy Alika.
I was typing on my phone, wasn’t able to look up the proper info to jog my memory.
There is no such thing as 90° driveshaft clocking (being useful for anything relevant).
That was a total brain fart.
I edited the posts with strikethru.
Good thing I found it before 10c did.
.....still somewhat vulnerable on that one...🤣🤣

Basically the u-joint angles must be equal in either Z or U configuration.
For Syncro it's U config, and 4° at each U-joint.
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'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[ALIKA T3]

[MarkWard]

My syncro sometimes makes a noise moving off from a stop. I thought it was an exhaust rattle. Decided to swap in a good used CAT. Found the installed cat had been hallowed. Checked all the other hardware etc. Nothing obvious.

Driving it more, I believe the noise is from the driveshaft. I had my driveshaft person make me a custom one. Nothing unlike what vendors sell. No quibo, but a slip joint and common replaceable u joints. It’s smooth, but I’d rather not have any noise. It seems to be related to how I move off. Weird I suppose. It doesn’t bother me enough to remove it and see if the noise subsides.
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[ALIKA T3]

[VikingWagen]

After installing a boxeer tdi engine, driveshaft vibrations have been driving me nuts. I tried the van cafe method twice and shimmed the rear of the diff up. No luck. In fact it is worse after the 2nd van cafe attempt. I’ve got a 15 year old gowesty slip yoke shaft that was fine before the install. I had it balanced and serviced anyway and nothing changed. I also have another variable. All 5 mounts for diff & transaxle were replaced with T3 poly yellow mounts. Other than getting my hands on a laser tool, I am at a loss.

Update: with my iphone level, the diff flange is pointing down 4.2 degrees, the middle of the shaft is at 1.2 down at rear and the transaxle flange is pointing down 1 degree. Looks like the rear of the diff should be raised more, but its already against the shift rod. Is there a way to lower the front of the diff instead ? As I understand from earlier posts, the transaxle needs to go down and diff goes up so that they are both close to 2 degrees, right? Is lateral alignment as important? If so, how to check for that?

Van cafe states that “The slip yoke end goes to the front differential.” I’m a bit confused by some mention to do the opposite.

Thanks for any help, guys!

[Howesight]

Going from memory, not experience, lateral alignment is also important. You want the driveshaft-to-flange angles, both vertically and laterally, to be numerically close. The factory setup, IIRC, has no lateral angle and therefore no specification for angle. In the Bentley at 39.43, VW says: "Align final drive [meaning the front diff] in longitudinal direction and tighten mounting bolts."

I get a slight vibration at speeds I rarely drive at (35 mph), and I have been too lazy to try to adjust the positions. I have the Van Cafe slip-yoke drive shaft as it was delivered back in 2008. As my rear VW motor mounts sag (three instead of two due to the SVX conversion), the vibration has diminished, so that gives me a clue for when I overcome my inertia in future. Your future involves a laser alignment tool.
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'86 Syncro Westy SVX

[VikingWagen]

[Syncro Jael]

[dkoesyncro]

Recently a post was made that the input shaft was said to be 10mm offset to the right assuming this means passenger side if at the back of the van?

If getting technical with finding centerline of the van and dropping plumb from various parts of the drivetrain, the center of crank pulley will land 10mm to the right of center.

I also used a phone app for finding angles but found it cumbersome and sensitive. I bought a Lazer and also question it's accuracy. I know the pain of sorting out the vibes and have pulled my prop shaft until I can devote a weekend or more to the challenge.

[4Gears4Tires]

It's definitely offset to the right/passenger side. This confused me many times when putting my van back together because I didn't notice when taking it apart. Very odd that the support beams are centered but the shaft isnt. Either do one or the other. Everything offset or everything centered. It really irritates me to look at it.
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'87 Syncro
Ferric Oxyhydroxide Superleggera Edition

[MsTaboo]

Here's the laser method I've been using; has worked very well for me on several different Syncros.

First off you want to make sure the van is level, both front to back and side to side.
Lateral alignment can be easily checked with a basic construction laser tool. They're not very expensive these days (or borrow one)
Using the case lines in the transaxle and the front diff get the two in line with each other (double check this after any up/down adjustments of the two).

With lights on:

Next is the vertical. I have the old GW laser tool they used to rent and sell (I bought one, it was expensive but has been worth it), a similar setup can be cobbled together with regular laser pointers. The hardest bit is figuring out the holder for the pen, it needs to be able to hold the pointer in the center of the output flanges, while allowing it to rotate and pivot (this would be a good candidate for a printed part, it doesn't need to be as massive as the GW pucks ).
The other part is a card with a small level and vertical line that is also attached to the flanges. This is the marker card. Both are held on with magnets.

And here's the laser pointer setup.

The way it works: mount the laser on the transaxle and the card on the front diff, make sure card is level (vertical line is perpendicular to floor), as you point the laser at the marker card rotate and adjust the pointer until it describes a dot instead of a circle, mark the dot on the card (a piece of tape works well for multiple tries).
Then swap the setup so the pointer is on the front diff and the card on the transaxle and repeat. This will tell you where the the diff and transaxle are pointing in relation to each other; you can then shim each as needed.
The dots should end up centered on the vertical line and slightly lower than the center of the flange.
Repeat until dots from each direction end up on top of each other.
Remember to double check the lateral alignment of the cases.
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Currently:
'90 Syncro Westy 3 knob w/Zetec

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[VikingWagen]

MsTaboo, excellent writeup! Lucky you to snag one of GW's alignment tools. I will try to cobble together something like that and see if I can get the vibes to go away. FYI, I called GW yesterday and found out they no longer do any service on customers vans. Bummer, because I was thinking about swinging down that way to have them align the drive train.

[ALIKA T3]

It is worth mentioning that the poly bushings are also less forgiving, some people couldn`t go anywhere with them and went back to rubber.

Also the torque for these rubber mount bolts is 45nm. I just dropped my transmission yesterday, you can still spin the metallic mount with donuts assembled ( makes sense bc of the plastic spacers, but still interesting).
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Silicone Steering Boots and 930 Cv boots for sale in the classifieds.
Syncro transmission upgrade parts in the Classifieds.
Subaru EJ22+UN1 5 speed transmission
http://www.thesamba.com/vw/forum/viewtopic.php?t=416343
Syncro http://www.thesamba.com/vw/forum/viewtopic.php?t=4...num+gadget

[joetiger]

[VikingWagen]

[VikingWagen]

[4Gears4Tires]

Probably not, but you probably moved everything around just enough when swapping in the old bushings that it is aligned properly now.

Either way, don't touch it!
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'87 Syncro
Ferric Oxyhydroxide Superleggera Edition

[VikingWagen]