Syncro Propshaft Alignment Problem

[ragnarhairybreeks]

sorry for my delay in responding to pm Landsailer.

-first off, I believe the flange angles should be equal, greater than 0 degrees (according to the "books", you need a little bit of angle on the joints to allow the needle bearings to wear properly).

- I disagree with Jon about his 4 degree recommendation. With high speed shafts (as we have on syncro), 4 degrees is the very upper limit. I think 2 degrees is better.

- angles should be the same and under 1 degree. I've seen recommendations of 0.2 degree max. difference between flanges.

- the balancing shop has to be familiar with high speed balancing. The runout tolerance has slipped my mind right now, but it is in the thous of inch when shaft spun at 3000 rpm. Some shops are more used to doing slower, less fussy shafts.

- almost needless to say, but shaft should be straight. Good shop can straighten shaft.

- the U-joint bearing cups must be a press fit into the joint ears, not a finger push fit.

- the internal bushings at the giubo end of shaft have to be tight, no slop. One can feel for the condition of those bushings when shaft installed by yanking up and down on shaft at giubo end. The giubo does disguise any slop to some degree, but I have felt looseness in bushings this way. With shaft out of van, the giubo can be removed and the yoke-shaft re-installed and the bushing slop (if present) easily felt. Sometimes worn bushings cause the propshaft to ring a little when starting out and slightly lugging the engine.

- the trick of having the three nuts and bolts (holding the front diff on the rubber mounts) slightly loose for a few miles does work to laterally align the front diff. But it won't do anything to help an unbalanced shaft.


hope this helps

alistair
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'86 7 passenger syncro, converted to westy pop top, project still in progress
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[Landsailer]

[Jon_slider]

> I disagree with Jon about his 4 degree recommendation. With high speed shafts (as we have on syncro), 4 degrees is the very upper limit. I think 2 degrees is better.

I don't know if 2 is better than 4, but in my case, I could not get 4, so I use 2 degrees front and rear. I agree the most important goal is to have both front and rear angles the same.

For background, the 4 degree info, is not my idea, it came from here:
http://vanagonsyncroproject-herman.blogspot.com/2007/03/drive-shaft.html
"On the Syncro, it is important that the drive shaft is well aligned, both the tranny and the front diff flanges have an angle of about 4 degrees. If you do an engine conversion, and the engine hangs too low, you could end up with some vibration. Another thing to watch out for when doing a conversion is that the original VW engine is slightly offset towards the driverside, about 17 mm, if the new engine is installed in the center of the engine compartment, it will put another angle on the drive shaft that is not compensated for by the front diff and it may cause a vibration also. "
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My Soapboxes: Inflation; Handling; Gearing; Decoupling; Swepco

[insyncro]

I know of three different DC shafts available.
One of them is much much heavier than the other two available.
Its weight becomes an issue if any "movement" is present in driveline mounting.
If the engine carrier has movement, I would mark the slip yoke with a line of grease and drive the van...trying to make it vibrate.
Second gear starts will lugg it enough.
What I would be looking for is smeared grease.
If so, not only is the trans flange angle changing, but the length of the shaft as well.
That combination on pavement is not ideal.
I will caution that failures of transmission nosecones and decouplers have happened, more than once with DC driveshafts.
The vendors are aware of this and have lightened the units since the first prototypes.

I own all three versions of the DC driveshaft and have tested them with my converted Syncros and bone stock ones.

Long story short, my $400 driveshaft.com unit out performs all of them and doesnt make a sound or a vibe.

I am not an advocate of shimming but have no experience with a Bostig in a Syncro.

Hope this helps.

[ragnarhairybreeks]

I disagree on the 4 degree angle. From Spicer driveline document, concerning flange angles (their caps, not mine):

RULE 1: UNIVERSAL JOINT OPERATING ANGLES AT EACH END OF A DRIVESHAFT SHOULD ALWAYS BE AT LEAST 1 DEGREE.

RULE 2: UNIVERSAL JOINT OPERATING ANGLES ON EACH END OF A DRIVESHAFT SHOULD ALWAYS BE EQUAL WITHIN 1 DEGREE OF EACH OTHER (ONE HALF DEGREE FOR MOTOR HOMES AND SHAFTS IN FRONT OF TRANSFER CASE OR AUXILIARY DEVICE).

RULE 3: FOR VIRTUAL VIBRATION FREE PERFORMANCE, UNIVERSAL JOINT OPERATING ANGLES SHOULD NOT BE LARGER THAN 3 DEGREES. IF THEY ARE, MAKE SURE THEY DO NOT EXCEED THE MAXIMUM RECOMMENDED ANGLES.

ref: http://65.170.161.218/~spicerpa/sites/default/files/pdf/driveshaft_installation.pdf

It is a worthwhile read.

alistair

[Landsailer]

So, flipping shaft around is no help. It was the last easy fix anyway. So my plan is to mess with the engine/trans angle now because I can't get any higher on the diff side right now. I am going to shoot for both down angled at 2 degrees. I think if I get longer bolts on the yoke, I can shim the yoke up to get a 2 degree down angle. If I shim the motor up (which I need to do anyway for contact on the skid plate) and I mess with the torque strap on the back to prevent/restrict engine dive (equalling trans flange upswing), and I shim the trans down slightly (which is going to suck, there are some heater lines and I am already crying about it), then maybe, maybe, maybe I can get the 2 degrees down angle I need back there.

insycro, I think this driveshaft weighs as much as an elephant.

I do believe matching angles are what's going wrong here, or mismatching angles in my case. The thing I don't understand is what's so great about the DC shaft if I have to get it perfectly perfect? I could have bought VW shaft for cheaper and had these same problems. Hell, it vibrated less with the busted VW shaft I already had.

[rowan]

insyncro wrote:

[Landsailer]

I have one you could buy

[insyncro]

[insyncro]

I will throw this out there....I have only had reports of amazing, vibration free driving with the GW donut less driveshaft.
I ragged them and it hard when first released.
The Syncro owners I have discussed it with love it.

I am not affiliated with Go Westy in any way.

Eating crow tastes like shite

[IdahoDoug]

I also agree with Allistair on the possible balancing issue STILL not being right. I drove 100 miles round trip to the "best and biggest" driveshaft shop in another state to have my drive shaft serviced. He gave it back to me so unbelievably out of balance I nearly drove all the way back to demand my money back.

So consider that it may be out of balance STILL. Here's an easy way to check. Get a simple hose clamp that will fit around the drive shaft near the joint. Make a reference mark where the clamp (which is your weight) is when you snug it on. Go for a drive and you'll feel a difference either better or worse. Pull over, move the clamp 90 degrees and make another reference mark and drive again. Do this 4 times and if you find a position it is suddenly smooth then all the other jerking around is going to be a waste of time - the shaft was not properly high speed balanced. Should take you about 10 minutes to do. If you find no change, do the same at the other end of the shaft and blow another 10 minutes. Wear old clothes. Use your 4 way flashers when you stop on the freeway to move the clamp.

I found another shop that specifically could to the high speed balance and he had built a jig to hold the Syncro shaft in his machine thanks to another buddy who had him do this for his Syncro.

DougM
_________________
1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader

[snowsyncro]

IdahoDoug alluded to this point early on, but I haven't seen it reinforced. With a true double Cardon joint, flange angles is not important at the ends of the shaft, as long as they keep the DC joint within specs. The reason flange angles are important in the standard Syncro propshaft is this...

A standard universal (Hooke) joint is not a constant velocity joint. When the input is being driven a a constant velocity, and there is an angle in the joint; the output velocity is not constant -- there is a rotational 'wobble'. To compensate for this, a second universal joint is used at the other end, and mounted 90 degrees out of phase with the first. So, input is constant velocity, middle part (propshaft) wobbles, output is constant.

The reason the flange angles are important is because it is essential to insuring the second joint properly compensates the first joint. There are several possible configurations to accomplish this, but in a Syncro the front and back joints are (or should be) in the same plane. For two U-joints in the same plane, the mounted angles must be the same. If they are not, then the second joint will not fully compensate the first, and there will be some wobble at the output of the second joint. Whether the angle is 2 degree, 4 degree, or 6 degrees is immaterial as long as the angles are the same, and within spec. However, smaller is better, because the intermediate shaft wobble is less, so the cyclical rotational forces are lower.

In a DC joint, the same principle applies, but the two joints are moved closely together. Now, the 'wobbling' propshaft is just the short little bit between the two yokes. There are still limits on the angles, but for small angles you can get away with using a single DC joint, even though both ends have an angle. So you can think of a DC joint as a constant velocity joint, as John Wessels pointed out when he introduced this shaft.

The reason you don't aim for a 0 degree angle with a universal joint is that the joint is designed to work with movement. There are needle (roller) bearings in there, and if the angle is 0 degrees, there is no rolling and the bearing does not work as designed. This recommendation has nothing to do with vibration, it is to maximize the life of the joint. But, if you have 0 degrees at one end, and (in a conventional propshaft) you then need 0 degrees at the other end, and in that case you don't need u-joints at all!

RonC

[rowan]

Snowsyncro wrote:

[snowsyncro]

[insyncro]

Some time ago there was a very heated debate about how well the DC would work with a Syncro van.
I am only rehashing some of the facts here so people actually understand why these are not readily available currently.
IIRC, there were two builders of DC driveshafts, Tom Woods and Burley.
John didnt actually build a shaft, but helped design it and sold them via Tom.
The generation one units were over built and way to heavy.
I personally have discussed the issues with owners of the gen 1 shafts.
Gen 2 was lighter weight and Burleys even lighter.
Still, issues presented themselves, hence, no production runs of DC driveshafts.
I am doing my best to keep this description fair and on point.
I bought each shaft when available.
Each was built incredibly well and the design made sense at the time.
After experimenting with each on my vans, it was clear that the DC unit would work well in conditions that would normally not happen in stock or converted vans close to stock, in reference to flange angles.
My understanding of the DC is that it will work with multiple varying angles...N-S, E-W and all in between.....under extreme load.
The DC works well in heavy duty machinery and offroad Baja trucks pushing 700hp.
IMHO, it is overkill in a Syncro and its actual weight causes issues in our lighter duty drivelines.

Feel free to search the various Syncro forums and you will find some more info.

If any of the named in this post have issue with my description, please let me know.
I am trying to ease the situation not throw gas on a fire.

[hans j]

Has anyone tried adapting small VW rabbit (90mm) CV joints to a propshaft yet? It seems like it would work well and even has slight axial play if needed.

Actually it looks like there are even smaller options out there after searching for a minute! All we need are easily machined adapters from the 4 bolt pattern to what ever size joint is used. I know driveline shops can lengthen/shorten propshafts.

Hmmmm I think I'll dig around at the shop and start measuring. I know we have some Audi propshafts lying around. I'm thinking it would be pretty cool if the '97-'98 carbon fiber B5A4 shafts would work!
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1986 Canadian Syncro Westy TDI - 1989 Syncro Single Cab - 2001 Audi S4 - 1981 VW Caddy ABA - 1980 VW Caddy EV - 1973 VW T-181

[insyncro]

Yes, CVs were experimented with before the DC units.

[Landsailer]

snowsyncro, thanks for the excellent info. I was hearing what everybody said before about angle, but for some reason I heard your explanation better.

Planning on fully tackling this problem this week or fully committing myself to finding an alternative after I have exhausted all my efforts. But I have some ideas after a little exploring yesterday and I will begin tonight (pending frostbite in my fingers).

Thanks to all who know way more about this stuff than I do.

[Jon_slider]

> In a DC joint, the same principle applies, but the two joints are moved closely together. Now, the 'wobbling' propshaft is just the short little bit between the two yokes. There are still limits on the angles, but for small angles you can get away with using a single DC joint, even though both ends have an angle. So you can think of a DC joint as a constant velocity joint, as John Wessels pointed out when he introduced this shaft.

thanks for the excellent explanation
I use a double cardan joint shaft, from Burley, to compensate for the fact that my motor is mounted in the center of the van, instead of 17 degrees to driver side as in the stock configuration. So Im counting on the Cardan to account for lateral alignment offset. fwiw, besides the Cardan joint, the other end of the shaft also has a U joint.

here is a pic from the Spicer pdf that Alistair linked to above, to help visualize the source of wobbling that snowsyncro explains

Based on all that, I would say I agree completely with Alistair that the smaller the angle the better, as long as it is not Zero.
_________________
My Soapboxes: Inflation; Handling; Gearing; Decoupling; Swepco

[insyncro]

I guess the added weight and wobble doesnt have any effect on internal transmission bearings than.
Something to think about....especially if multiple transmissions have gernaded shortly after rebuilds....hmmmm.
Also nose cones and decouplers shearing off.....hmmmX2.

Well anyway, my DC units are mounted to the wall of my shop as art.