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gears
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Location: Bend, OR; Kailua, HI
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PostPosted: Sun Nov 11, 2012 12:44 pm    Post subject: Syncro transaxle service Reply with quote

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.
Image may have been reduced in size. Click image to view fullscreen.


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:
Image may have been reduced in size. Click image to view fullscreen.


Fortunately, the primary area of pinion engagement remained intact:
Image may have been reduced in size. Click image to view fullscreen.

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:
Image may have been reduced in size. Click image to view fullscreen.


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:
Image may have been reduced in size. Click image to view fullscreen.


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:
Image may have been reduced in size. Click image to view fullscreen.


.. compared to an engagement flank with almost no wear:
Image may have been reduced in size. Click image to view fullscreen.


The corresponding wear on the replaced operating sleeve:
Image may have been reduced in size. Click image to view fullscreen.


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.
Image may have been reduced in size. Click image to view fullscreen.


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:
Image may have been reduced in size. Click image to view fullscreen.


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:
Image may have been reduced in size. Click image to view fullscreen.


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:
Image may have been reduced in size. Click image to view fullscreen.


Threads of another manufacturer's nut:
Image may have been reduced in size. Click image to view fullscreen.


Threads of 3rd manufacturer's nut:
Image may have been reduced in size. Click image to view fullscreen.


Threads on pinion bearing:
Image may have been reduced in size. Click image to view fullscreen.


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:
Image may have been reduced in size. Click image to view fullscreen.


Debur and Chamfer both sides of any drilled holes:
Image may have been reduced in size. Click image to view fullscreen.


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:
Image may have been reduced in size. Click image to view fullscreen.


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:
Image may have been reduced in size. Click image to view fullscreen.

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.
Image may have been reduced in size. Click image to view fullscreen.


It can be seen how the retaining tang only contacts 40% of the bearing circumference:
Image may have been reduced in size. Click image to view fullscreen.


More to come ..
_________________
aka Pablo, Geary
9.36 @ 146 in '86
'90 Syncro Westy SVX
'87 Syncro GL 2.5

Needed: Stock 14" x 6" Syncro steel rim


Last edited by gears on Mon Dec 31, 2012 11:55 am; edited 2 times in total
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gears
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PostPosted: Sun Nov 11, 2012 1:04 pm    Post subject: Reply with quote

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.

Image may have been reduced in size. Click image to view fullscreen.



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

Image may have been reduced in size. Click image to view fullscreen.



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

Image may have been reduced in size. Click image to view fullscreen.


Such a simple solution to stuck drain plugs .. ALWAYS use teflon tape:
Image may have been reduced in size. Click image to view fullscreen.


It's probably all that rock-crawling (and Uber's ladders) that caused my loose pinion nut failure ..
Image may have been reduced in size. Click image to view fullscreen.


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
'90 Syncro Westy SVX
'87 Syncro GL 2.5

Needed: Stock 14" x 6" Syncro steel rim


Last edited by gears on Sun Nov 11, 2012 1:22 pm; edited 2 times in total
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insyncro
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PostPosted: Sun Nov 11, 2012 1:10 pm    Post subject: Reply with quote

Bravo.
Awesome pictorial Exclamation

Thank you.
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Jedi
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PostPosted: Sun Nov 11, 2012 1:25 pm    Post subject: Reply with quote

Applause Popcorn Applause Popcorn Applause VW Logo Popcorn Grey Vanagon Popcorn
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IdahoDoug
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PostPosted: Sun Nov 11, 2012 1:45 pm    Post subject: Reply with quote

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
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rubbachicken
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PostPosted: Sun Nov 11, 2012 7:29 pm    Post subject: Reply with quote

very cool, what camera are you using to take the picture
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kbeefy
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PostPosted: Sun Nov 11, 2012 7:44 pm    Post subject: Reply with quote

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


Great thread, thanks gears!
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'86 Syncro Westy. Stock for now.

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gears
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PostPosted: Sun Nov 11, 2012 8:56 pm    Post subject: Reply with quote

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
'90 Syncro Westy SVX
'87 Syncro GL 2.5

Needed: Stock 14" x 6" Syncro steel rim
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presslab
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PostPosted: Mon Nov 12, 2012 11:58 am    Post subject: Reply with quote

Great photos and explanation. Thanks!

Did you replace the mainshaft because of the 2nd gear pitting?
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gears
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PostPosted: Mon Nov 12, 2012 1:09 pm    Post subject: Reply with quote

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.
Image may have been reduced in size. Click image to view fullscreen.


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
'90 Syncro Westy SVX
'87 Syncro GL 2.5

Needed: Stock 14" x 6" Syncro steel rim


Last edited by gears on Tue Nov 13, 2012 3:18 pm; edited 1 time in total
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gears
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PostPosted: Mon Nov 12, 2012 4:29 pm    Post subject: Reply with quote

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
Image may have been reduced in size. Click image to view fullscreen.

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.
Image may have been reduced in size. Click image to view fullscreen.

_________________
aka Pablo, Geary
9.36 @ 146 in '86
'90 Syncro Westy SVX
'87 Syncro GL 2.5

Needed: Stock 14" x 6" Syncro steel rim
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snowsyncro
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PostPosted: Mon Nov 12, 2012 5:57 pm    Post subject: Reply with quote

gears wrote:


Time wasn't on my side for this rebuild .. it was admittedly a rush job. No more car work possible 'til Spring.
Image may have been reduced in size. Click image to view fullscreen.


Love this thread gears.
You need to come up here -- it was 15degC and sunny here today!

RonC
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PostPosted: Mon Nov 12, 2012 7:18 pm    Post subject: Reply with quote

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

Nice work.
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PostPosted: Fri Dec 07, 2012 3:08 pm    Post subject: Reply with quote

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.
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insyncro
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PostPosted: Fri Dec 07, 2012 9:55 pm    Post subject: Reply with quote

I miss the islands and my boards Crying or Very sad
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gears
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PostPosted: Sat Dec 08, 2012 8:16 am    Post subject: Reply with quote

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).
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9.36 @ 146 in '86
'90 Syncro Westy SVX
'87 Syncro GL 2.5

Needed: Stock 14" x 6" Syncro steel rim
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insyncro
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PostPosted: Sat Dec 08, 2012 8:33 am    Post subject: Reply with quote

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 Wink

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 Wink
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