Syncro driveshaft balancing jig?

[MsTaboo]

I've been going blind from reading Syncro driveshaft vibration threads, but one item that shows up once in a while is this mention of the balancing shop needing the correct jig to properly balance these shafts.

However I have yet to read an explanation of just what kind of tooling this is.

I'm still fighting a frustrating vibration at 25-35 mph that disappears at higher speeds. I dropped the driveshaft again tonight to double (quadruple) check the alignment with my GW laser tool. It's spot on to within maybe a 1/2 degree. (about an 1/16" between dots on marking board) dead centered, and very slight downward drop. Same orientation I've used many times.

Back story: slip-yoke driveshaft from VanCafe, was working perfectly. Removed both front diff and transmission for rebuilding. Reinstalled the driveline along with brand new OEM type rubber transmission / diff mounts and aligned with laser tools in both vertical and horizontal axis.
With the everything buttoned back up discovered new vibration as noted. Pulled driveshaft and went through checklist of possible causes. Reworked the alignment multiple times.
Decided maybe one of the u-joints was a bit worn - replaced both with Spicer joints. Had driveshaft balanced; shop said the results looked good. Still had vibration.

I have had four Syncros and replaced driveshafts on three of them, never had a problem getting smooth operation first try using the GW laser tool.
My Syncro is in top condition, new CVs, bearings, tires, etc. Tried with different set of rims/tires.
Runs perfectly smooth without driveshaft installed.

So I'm left with the possibility the shop did not balance the driveshaft to Syncro specs. I have read that the factory required a ISO G6.3 standard not the usual G6.16.
And this mention of some kind of jig or fixture. Can anyone provide a clear explanation of this tooling so I can ask a shop if they are so equipped?
Also, is this jig required only for the original driveshafts with the Giubo joints or does it include the slip-yoke style?
The shop seemed to think there was no problem dealing with the shaft; said "we know what we're doing".

Only other explanation is something wrong with either the transmission or front diff rebuilds, but wouldn't a problem there show up as vibration at all speeds?

This is an older picture from when I redid my suspension bushings, but shows the laser marking board I'm talking about. The new dots are in almost exactly the same location.

_________________
Currently:
'90 Syncro Westy 3 knob w/Zetec

The information age has morphed into the age of disinformation and willful ignorance. Agnotology!
Help the fight against Truth Decay.
Defend democracy, support Ukraine.

[Sodo]

I think the shop tool is simply a pair of "equivalent syncro flanges" - to bolt the shaft to.

You are showing the tool on the front diff.
And the laser hits the same dot when you put that tool on the rear diff?
So same angle?

What angle do you have?

I had lots of chats with a guy in Oklahoma who was having trouble with his Bostig-Syncro.
He had to do a LOT of adjustments, shimming mounts, but he claims victory and is looking forward to driving from Oklahoma to SyncroFest.
He would be glad to help you I bet.
He ended up at 2.5°.

MsTaboo maybe you need to accost a smooth Syncro and trade driveshafts for a test drive.
_________________


'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]

Desperate comment, but have you weighed the hardware ?

A friend in Costa Rica was having vibrations issues too. Turns out he had a different bolt and nut. He corrected it and it solved it on the spot.
Worth mentioning; maybe there's discrepancy there, and their order on the flange got mixed up from what you have before?

Or like you said, not correctly balanced, which wouldn't be the first time I read this on the forum. That's a hair pulling situation you got!
_________________
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

[Pchill2]

Those Bostigs have a lot of cantilevered engine weight. Is it possible the engine/trans is rotating rearward under acceleration causing driveshaft misalignment? Could be as simple as bad motor mounts.

I had that issue with my motor swap but didn’t notice until I pulled the driveshaft and heard the power steering pulley contacting the rear body. I’ve redesigned my engine mounts because of that.
_________________
87 Syncro Westy
Honda K24 swap

[MarkWard]

An old trick was to use hose clamps. Driveshafts are usually balanced at both ends. You could add a hose clamp to the front of the drive shaft and drive the van. Then rotate the clamp marking the starting point a few degrees and retest. It would be tedious, but you might get a feel for changing it.

Repeat with the rear end of the driveshaft. If you find the sweet spot assuming its a balance problem and not a runout problem, you could decide to weld washers in place of the clamps.

You should check both ends for run out with a dial indicator. A magnetic stand should probably hold the indicator for you. Measure both ends installed.

No affiliation.
Link

_________________
☮️

[Sodo]

[MsTaboo]

[MarkWard]

I was trying to suggest measuring runout with the driveshaft installed. You wouldn’t do this running in gear. You would at a minimum need the rear tires off the ground. Zero the dial indicator and manually turn the driveshaft. There are different arrangements that would cause you to test differently. Decoupler installed, VC or fixed stub. You just need to be able turn the driveshaft.

My in-line 4 cylinder at the pulley end was moving down under load visibly from a following car. I fabricated a mount to limit this movement. A torque mount of sorts. I imagine it would really change your operating angles if the engine is dropping at the pulley end under load. There are a couple pictures under my username showing the torque limiter.
_________________
☮️

[MsTaboo]

[ragnarhairybreeks]

Ms taboo…

When I took my original drive shaft to shop in Victoria they had to make adapter for the balancing lathe.

Also, the said right away the lathe didn’t spin as fast as they wanted for this shaft.

They did as best they could. But weren’t satisfied . I spent a lot of time with angles and gear clamp weighting and new u joints etc. still have that shaft ( maybe one day it will have Cv type joints ) . But got a cast off shaft and it’s pretty well fine installed in same set uo as the old one .

It’s frustrating I know

Alistair
_________________
'86 7 passenger syncro, converted to westy pop top, project still in progress
'82 westy, diesel converted to gas in '94, now gone...
https://shufti.blog/
Old address still works...
http://shufti.wordpress.com

[essjayarr]

I’ll share what “surprisingly” worked for me.
I had a sunroof Syncro which I had converted to Subaru 2.2 and went thru all the same frustrations with vibration. I had even built this elaborate laser alignment tool.
This was a lot of years ago, so I don’t recall who made the suggestion that worked. It may have been someone at VanCafe, since I did most of all my buying from them at the time.
The Fix: Loosen the front diff mounting bolts just a bit, not sloppy loose. Drive the van and let the drivetrain find its “happy spot”. Then go back and tighten it all back down.
My Syncro was silky smooth at any speed from then on.
I miss that one!

[MsTaboo]

Thanks for the suggestion essjayarr, but I've been around long enough to know that trick.
Been there, done that.
_________________
Currently:
'90 Syncro Westy 3 knob w/Zetec

The information age has morphed into the age of disinformation and willful ignorance. Agnotology!
Help the fight against Truth Decay.
Defend democracy, support Ukraine.

[MsTaboo]

[MarkWard]

@mstaboo. No difference coupled or decoupled? Assuming yes. VC or stub shaft up front?
_________________
☮️

[MsTaboo]

[MarkWard]

So, decoupled you should be able to turn the driveshaft enough to measure runout with a dial indicator. That saves jacking the van unless you'd like the room to work.

Where do the Ztec mounts attach to the engine block in comparison to the front pulley? Just curious. Not familar with that install.
_________________
☮️

[MsTaboo]

The engine hangs out there a bit, but like I said, the vibration is there even coasting.

If the vibes got worse under load I might suspect problem with engine shifting position, but they don't.
I've got close to eighty thousand miles on this conversion, first time having problem with driveshaft vibration.

I can turn the shaft with it decoupled but it's pretty stiff. I'll be getting the wheels off the ground. May not get to it today, partner is beating on me about time spent working on Syncro .
_________________
Currently:
'90 Syncro Westy 3 knob w/Zetec

The information age has morphed into the age of disinformation and willful ignorance. Agnotology!
Help the fight against Truth Decay.
Defend democracy, support Ukraine.

[bheins]

MsTaboo, did you get this issue sorted? If so, what did you find?

Bernie

[4Gears4Tires]

[MsTaboo]