Syncro transaxle service

[gears]

During my recent off road pre-run for our Lost Burritos GTG, I began hearing a R&P whine from my transaxle. The sound came on rather suddenly, so I suspected either a damaged pinion bearing or a failed pinion bearing nut. Because I didn't want to miss any Lost Burritos fun, I decided to chance running the transaxle "as is" the following off road weekend. Thankfully, everything held together during our outing, and I was able to remove the transaxle for inspection the following week.

Because this was something of a rush job to get my van back on the road before snowboarding season, I didn't have time to do a full rebuild pictorial (refer to James Pate's excellent Vanagon transaxle rebuild thread: http://www.thesamba.com/vw/forum/viewtopic.php?t=491932 ) .. but I will some time in the near future, hopefully in conjunction with more meaningful upgrades. Mostly, I was happy to find I could take photos through one lens of my binocular microscope .. so while these shared photos lack 3D clarity, the detail is still better than naked eye.

Removal of my two magnetic drain plugs confirmed the need for tear down .. SOON.

What I found upon disassembly was a loose pinion bearing nut. Had I taken a bit more time, I probably could have determined whether the nut had come loose and backed off, or if it had literally expanded and popped a thread before backing off further. In any case, the result was a pinion shaft free to thrust forward, causing loss of proper R&P mesh. I was lucky. I recognized the problem soon enough not to ruin too many parts.

My main area of concern was the pinion tip. With load shifted from proper flank engagement to improper tip-only engagement, wear accelerates rapidly at the tip:

Fortunately, the primary area of pinion engagement remained intact:

ha ha .. yeah, I know that blurry tooth in the background looks terrible, but it's an optical illusion .. I promise.

Further general inspection revealed areas of wear unrelated to the failed nut.

VW's low-loss, fine-toothed, 3rd and 4th gears are considered a weak point to performance tuners. I have no complaints, considering this gear held up to SVX power for almost 30,000 miles, but it's quite evident that surface scuffing has left the gear unserviceable:

Along with 3rd gear damage, I expected so see something going on with 2nd gear. Sure enough, I found a narrow band of micro pitting on the lower half of the mainshaft's 2nd gear teeth:

Eight years ago, I had found a somewhat rare .78 Euro 4th gear with borderline engagement teeth. Normally, I would have rejected any gear with this sort of wear, but because of the rare ratio, I opted to install the gear with a new operating sleeve. The combo worked out nicely. Under normal circumstances, this gear would be popping out of engagement .. but because it had a new operating sleeve and I've kept my shifting sympathetic, the geometry remains crisp and the complimentary angles (between sleeve and gear) remain true. Once again, I merely fed this gear another new operating sleeve (and inner hub) and hope to find these angles nice & crisp the next time I disassemble.
Worn drive flanks on 4th gear engagement teeth:

.. compared to an engagement flank with almost no wear:

The corresponding wear on the replaced operating sleeve:

During the rebuild process, I checked the South African housing that I had originally installed and found almost no wear (.0005"). It really helps to zero the bore gauge on a new housing first for maximum accuracy.

Because I do put quite a bit of demand on both 2nd and 3rd gears during on-ramp acceleration, I expect greater wear on these two gears. While all gears received new idler bearings, 2nd gear bearing was upgraded slightly:

Back to the loose pinion nut .. my original problem. The weight of our vehicles certainly enters the equation when considering weak points within our Syncro transaxle. The chromoly nut upgrade is almost a requirement for race cars, but not generally for street cars. Yet there's a huge grey area with vehicles that sometimes race or go off roading.

Ironically, I had cautioned James Pate when he built his Vanagon transaxle about using an aftermarket chromoly pinion nut during his trial assemblies. (There's a long history of thread seizures when using hardened chromoly threads on hardened bearing race threads, so normal procedure for me is to use a stock nut for all trial assemblies, and the chromoly nut on final assembly only.)

I had even suggested to James that he didn't need a Chromoly Pinion Nut at all, despite his SVX power. My bad. Here I am with a failed VW pinion nut. Hard to say with certainty what caused it, but off roading and SVX power certainly contributed. Fortunately, the solution had been sitting in my storage locker for years:

The true irony for me is that this nut is an item my company had introduced to the U.S. off road market back in 1989. Jeff Field's Transaxle Engineering was the first to use our Chromoly Pinion Nut, and it solved the problems many his off roader racer customers had with failed stock VW pinion nuts. Other manufacturers & vendors soon jumped on the bandwagon with their own nuts .. some not so good (because they seize on the bearing).

Threads of one manufacturer's nut:

Threads of another manufacturer's nut:

Threads of 3rd manufacturer's nut:

Threads on pinion bearing:

Anyhow, in 1990 Jeff came up with a little service trick for our first style of chromoly nut, the beefy Type II nut. Because this nut replaces both stock nut and washer, the lip is MUCH thicker and beefier than the more popular Type I version. (Compare top two nuts in the pile above.) The two bonuses of the Type II nut are 1) One or two additional threads over the OE nut 2) a locking pin can be used with the Type II nut, eliminating the need for Loctite on the threads. Not only does this aid in disassembly, but it lessens the possibility of seized threads when oil and/or antiseize can be used rather than Loctite.

Drill nut for locking pin:

Debur and Chamfer both sides of any drilled holes:

After installing the Chromoly nut at proper torque, use the predrilled hole as a guide to drill 8mm deep into the case alloy with a very slightly smaller diameter drill bit:

The tiny dowel's shiny surface is roughed up on a stone, the hole in the housing is filled with Loctite, and the dowel is then carefully tapped into place. Enough of the dowel is left to grasp with a vicegrip:

Placement of this dowel is important. It should be on the right side of the case as shown. Should the dowel ever fracture, it can be severed with a Dremel .. but only if properly located.

Further along in the rebuild, we pause to inspect the original retaining tang for the mainshaft ball bearing. This one had very little wear because I had surfaced the housing on the last rebuild. This area will be properly beefed up on my next transaxle, using either Daryl's plate or Weddle's insert.

It can be seen how the retaining tang only contacts 40% of the bearing circumference:

More to come ..
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[gears]

While the 4th gear splash plate was reinstalled, I do NOT feel that this is the solution for heat build-up in the 4th gear & mainshaft ball bearing area. We need to follow Alaric's lead with proper oil cooling, and perhaps go further with specific oil delivery points.

Every failure is a learning experience. Thanks for sharing, Jon ..

It's incredibly straightforward to check backlash on a Type II:

Such a simple solution to stuck drain plugs .. ALWAYS use teflon tape:

It's probably all that rock-crawling (and Uber's ladders) that caused my loose pinion nut failure ..

New parts in this rebuild included:
4 synchro rings
double taper pinion bearing
mainshaft ball bearing
mainshaft needle bearing
3 idler bearings
mainshaft
2nd idler
3rd gear set
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[insyncro]

Bravo.
Awesome pictorial

Thank you.

[Jedi]

_________________
1961 Westfalia SO23 Mango Green/Seagull grey
1961 Westfalia SO34 T/BW
1961 Westfalia SO34 SWR
1964 Westfalia SO33 pearl white
1965 Westfalia SO42 Velvet green
1986 Syncro Wolfram grey with black int GL
1986 Syncro Doka
1987 Syncro Sevana beige Adventurewagen
1987 syncro Sevana beige GL
1973 Pumpkin orange Thing
2 1963 Rag top bug's
1965 Manx
1970 Single cab
1971 combi
1990 Vanagon GL
2007 Audi A4 3.2L quattro

[IdahoDoug]

As someone who has been inside this rare transmission and gotten some excellent advice from you - bravo. What I appreciate the most by far is your balanced perspective on things. For instance, pointing out that some modifications like the pinion nut are not perfect. Too often whatever people change on their Vanagon becomes the "coolest and most perfectest ever." So, when excellent followup like yours is provided it is worth gold, and also worth holding up as an example of furthering the passion.

Regards,
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

[rubbachicken]

very cool, what camera are you using to take the picture
_________________
lucy our westy

lucy's BIG adventure

meet 'burni'


markswagen {mobile mechanic} san diego area all early VW's cared for.

619 201 0310 or 617 935 4182

[kbeefy]

theres such a thing as a 3D microscope? Thats awesome and I want one!!


Great thread, thanks gears!
_________________
86 syncro CHC, NorthWesty subbie 2.5, decoupler, locker, custom interior, 225/75r16 Duratrack's on CLK's, Toyo cabin heater, ARB fridge, 300w Zamp Solar, Gowesty bumpers/skid/rails, Fiama awning

'86 Syncro Westy. Stock for now.

2000 F350 7.3 CC LB 11' Northland Cabover

2006 Subbie OBXT

2002 Tacoma DoubleCab 4x4

1969 Mustang Basket Case 351c/FMX/9

http://kbeefy.blogspot.com/

[gears]

My jewelers 20-40X binocular microscope is indispensable for close-up parts inspection .. and the lens from my new Sony Cyber-shot pocket camera seems to fits up against a single eyepiece. I wish I'd done this before ..
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[presslab]

Great photos and explanation. Thanks!

Did you replace the mainshaft because of the 2nd gear pitting?
_________________
1986 Vanagon Westfalia EJ25
1988 Subaru GL-10 EJ20G --- 2000 Honda XR650L
2010 Titus El Guapo --- 2011 On-One 456 Ti

[gears]

This was honestly a total rush job, and not a full rebuild. While I installed many necessary new parts, I neglected to resleeve the main case and install a new R&P. But .. this spare trans should easily last 30K, while my "real" transaxle will be ready for installation long before that.

I had coincidentally pulled all my tools and trans parts out of storage recently, with plans to build an oil-fed/cooled transaxle (with other minor upgrades).

I may take and add a few photos to this thread showing the effects of heat build-up around 4th gear. Both the mainshaft ball bearing and 4th gear needle bearing suffer from poor oil circulation/overheating, while 4th gear race on the mainshaft requires polishing at the very least.

This shows a .011" step worn into the race face by 4th idler gear. Such dramatic wear isn't usually seen around 3rd gear.

2.06 2nd gear is a pretty stout ratio. VW mainshafts almost never fail in this ratio (it's always the idler that fails first) .. and yet that narrow band of micro pitting made me a bit nervous (so far as reinstalling in an SVX application). Changing out the 2nd gear idler was a no-brainer. I picked out my best used 1st & 2nd idler gears, aided by my microscope.
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[gears]

I went back for a closer look at the mainshaft I had rejected, and found the bearing race is actually in good condition. The sole reason I rejected this mainshaft is a potential fracture zone visible as a bright line just below the band of micro pitting.

40X close-up of potential fracture zone

While this mainshaft would probably survive forever if paired to a stock 2.1, it is most certainly compromised.

Time wasn't on my side for this rebuild .. it was admittedly a rush job. No more car work possible 'til Spring.

_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[snowsyncro]

[bac914]

What address do I send my transaxle to for you to inspect/rebuild?

Nice work.

[derekdrew]

How can somebody move so many times recently between Hawaii and the mainland and yet be able to find his tools????

You guys better make him feel loved on the mainland or he'll move again and get distracted.
_________________
Derek Drew
derekdrew - a t - derekmail - dott - com

[insyncro]

I miss the islands and my boards

[gears]

My snowboards are leaning against my trans workbench, overlooking a small ski area .. so, I've got it pretty good this winter. Ride hard in the mornings .. fiddle with parts in the afternoons (if I can still stand).
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[insyncro]

Nothing like first chair in the AM after fresh snow.
Ah the good old days.
My best season ever had me on snow 286 days of that year with three Golds at Junior Nationals for my riders and a Gold for Ross Powers at the Olympics.
I'm still using some of the frequent flyer miles

I will be putting a HiTop on one of my Syncros this Spring to build the ultimate Surf and Snowboard destination vehicle.

making time to get out and use is a different story all together.

Shred some pow for me