Understanding my syncro

[rctucker]

So, right after i bought my 87 syncro i drove about 300 miles and my rear drivers side cv/axle unbolted itself from the transaxle. (amazingly the bolts where all still there thanks to the cv boot) I have zilch (zero) knobs.

I went through all the gears reving the engine and there was no forward movement.

Does this say anything about my VC, I thought this ment that it was "stuck open"

based on this perspective... this disconnected axel should be detected as slippage and the other wheels should engage? if one of the rear wheels slips does the power get transferred to the other rear wheel or do both need to be slipping in order for the VC to heat and engage? this indicated to me that. all forward motion was driven through the rear drivers side wheel.

Obviously, I'm confused and don't understand the mechanics, if you can help me understand this better, next time in your town, ill buy ya a beer!

Thanks

[4Gears4Tires]

Your VC is bad. I had the same thing happen to me when a terrible shade tree mechanic didn't torque the cv bolts to 33ftlbs. My van drove just fine with the cv shaft clanking around in the trailing arm.
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'87 Syncro
Ferric Oxyhydroxide Superleggera Edition

[Sodo]

[Wildthings]

Assuming it was a rear CV that came undone, if you have a decoupler for the front and no form of locking differential in the rear, you are getting the expected results.

The torque on the CV bolt is supposed to be quite high and should be done with a torque wrench for best results. The torque is 33 ft*lbs and that is with moly grease on the bolt threads, though some will argue otherwise.

[4Gears4Tires]

He said he has zero knobs.
_________________
'87 Syncro
Ferric Oxyhydroxide Superleggera Edition

[Sodo]

[rctucker]

To parse the responses.

with no knobs, and the driverside rear axle disconnected, getting no forward movement is expected?

to clarify my understanding of what has been said.
Unless i have a locking dif in my transaxle, power will not be transfered to the other rear wheel, both rear wheels need to be slipping in order for the VC to engage.

looks like i need to do the 2x4 test, just need some flat ground and a jack on wheels.

[Sodo]

[4Gears4Tires]

[rctucker]

ok, lets eliminate the VC for a second bc that is confusing people.

lets focus on just the rear transaxle with NO decoupler.

If one axle is disconnected from the transaxle (let's say its the driver's side, but probably doesn't matter)

There should be no forward motion bc the transmission will give all power to the drive shaft that spins the fastest? (the disconnected driver's side)

If there was a locker, I could then lock that and then forward motion would result bc the power would be transferred equal (but this is probably not recommended)

If I disconnected the passenger side axle from the transaxle (now neither rear axles are connected) this would then enage slippage bc there now a differential dtwn front and back. (the 2x4 test)

sorry if im ignorant, im having a hard time understanding these systems from a top level from the bentley manual.

where does a peliquin limited slip come into play here?

thanks for any thoughts!

[Wildthings]

[Sodo]

Rtucker you are correct WRT the behavior of a rear differential and a locking differential.

A Peloquin would not drive the van forward if one rear CV was unbolted.
There is a locking Peloquin though.

3rd request for these 2 basic details that are relevant to whether or not power gets transferred to the front differential.

1) have you confirmed that your van has a (center) driveshaft installed?
2 ) you wrote that there’s no knobs but have you confirmed that your trans has no decoupler? Are there ANY vacuum actuators on your trans?

If you don’t know this (yet.....you will !), just post a pic of the forward end of the trans.
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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

[Sodo]

Here's an info-sheet pic I started working on a few months ago.
It seems on-topic for a thread titled "Understanding my syncro".
I don't remember why I started on it.
Just a Syncro-nut thing.

It's still in-work.
If anyone sees errors or omissions I'm interested.
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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

[syncro surf]

[Yellow Rabbit]

Or worse, someone blew up the syncro transmission and stuck a 4 speed in there.

[MarkWard]

Or

I think for many new syncro owners, the viscous coupling VC is difficult to understand or appreciate. Add multiple previous owners and 30 plus years it gets even more complicated to know for sure how it should work.

There’s also not an easy way to test it without setting up safe test conditions. That said, It’s a pretty cool piece of hardware.

I believe any new syncro owner can expect to go through the entire drivetrain at some point.
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☮️

[4Gears4Tires]