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livethevanlife
Samba Member
Joined: May 18, 2015
Posts: 191
Location: La Paz, Baja California Sur
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 Posted: Sun Jun 17, 2018 6:18 pm Post subject: Transmission Went out after 50k Pilot Shaft Backed out |
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My rebuilt transmission finally gave out today. Had the van all packed up and was heading to Sequoia when it started making lots of noises and popping out of gear. Mechanic friend and I pulled the trans this afternoon and found the Pilot Shaft had come loose. I’ve suspected that this rebuild wasn’t done right from the start as it never felt quite right to me (though I cant explain why). The Pilot Shaft is screwed in, and then sleeved and secured with a circlip. When done correctly it seems to be very unlikely it would back off the thread and come loose like it did. My question is how this could have happened and has anyone experienced similar? Not going to call out the rebuilder. It’s a air cooled transmission with upgraded thrust plate, steel cage bearings, South African oiling plates, and a peloquin. We pulled the back of the trans off for kicks. None of the splines are chewed up, the ring gear looks ok, and so does the Peloquin. I am going to have it all gone through and parts replaced where necessary, but am trying to understand what happened short of rebuilder error?
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www.LiveTheVanLife.com
www.VentureLibre.com
https://www.PeaceVans.com/baja
1991 Syncro Triple Knob Westfalia "Miki" 2.2WBX
1992 Syncro Triple Knob Tintop "Schnitzel" 1.9AAZ
1990 Syncro Rear Locker Doka Subi 2.2
1974 VW Thing 1835cc
1989 VW Carat |
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gears
Samba Member
Joined: October 28, 2002
Posts: 4391
Location: Tamarack, Bend, Kailua
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livethevanlife
Samba Member
Joined: May 18, 2015
Posts: 191
Location: La Paz, Baja California Sur
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| Posted: Sun Jun 17, 2018 7:20 pm Post subject: Re: Transmission Went out after 50k Pilot Shaft Backed out |
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Thanks, those are all referencing earlier VW models and not Vanagons, however im guessing its the same phenomenon? Should this have stud have been replaced when it was rebuilt? And I didnt read anywhere what would cause it to back out.
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www.LiveTheVanLife.com
www.VentureLibre.com
https://www.PeaceVans.com/baja
1991 Syncro Triple Knob Westfalia "Miki" 2.2WBX
1992 Syncro Triple Knob Tintop "Schnitzel" 1.9AAZ
1990 Syncro Rear Locker Doka Subi 2.2
1974 VW Thing 1835cc
1989 VW Carat |
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gears
Samba Member
Joined: October 28, 2002
Posts: 4391
Location: Tamarack, Bend, Kailua
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| Posted: Sun Jun 17, 2018 8:40 pm Post subject: Re: Transmission Went out after 50k Pilot Shaft Backed out |
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If you read the first two listed threads you'll learn the physics behind the phenomenon and you'll note that even very experienced builders aren't aware that the problem even exists.
The newly designed stud didn't come out until the waterboxer engine was introduced, so you really can't blame the rebuilder of an air-cooled trans for the issue.
On the other hand, once a builder has been informed of the problem, the cause, and the cure, there is no excuse to ever again use the old style stud.
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aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com |
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AndyBees
Samba Member
Joined: January 31, 2008
Posts: 2326
Location: Southeast Kentucky
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| Posted: Sun Jun 17, 2018 9:37 pm Post subject: Re: Transmission Went out after 50k Pilot Shaft Backed out |
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In December, 2015, I removed my tranny to install the upgraded pilot shaft for the larger TDI clutch disc. I found the circlip laying on the bottom of the transmission.
Fortunately, the only damage was the small screw stud. I replaced it with one like yours.
I rebuilt my tranny from scratch and have no idea how the circlip got off the shaft. That was at about 50k miles. The tranny now has a little over 82k miles on the rebuild
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'84 Vanagon Tin-top, ALH TDI. 1989 Tin-top
1983 Air-cool, 225k miles, 180k miles mine. Seven trips to Alaska from 1986 thru 2003. |
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Waldi
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Joined: February 28, 2014
Posts: 1752
Location: Germany
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| Posted: Mon Jun 18, 2018 1:04 am Post subject: Re: Transmission Went out after 50k Pilot Shaft Backed out |
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| The circlip cannot get off the shaft without breaking. |
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AndyBees
Samba Member
Joined: January 31, 2008
Posts: 2326
Location: Southeast Kentucky
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| Posted: Mon Jun 18, 2018 4:45 am Post subject: Re: Transmission Went out after 50k Pilot Shaft Backed out |
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| Waldi wrote: |
| The circlip cannot get off the shaft without breaking. |
Waldi, I agree 100%.
However, during the rebuild, I personally went through every inch of that transmission installing over $1,000.00 of new and upgraded parts. For the life of me, I have no clue how that circlip ended up there. In the photo, it's laying exactly where I found it and there was not one on the shaft.
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'84 Vanagon Tin-top, ALH TDI. 1989 Tin-top
1983 Air-cool, 225k miles, 180k miles mine. Seven trips to Alaska from 1986 thru 2003. |
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gears
Samba Member
Joined: October 28, 2002
Posts: 4391
Location: Tamarack, Bend, Kailua
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| Posted: Mon Jun 18, 2018 8:05 am Post subject: Re: Transmission Went out after 50k Pilot Shaft Backed out |
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Andy's circlip may have been a used one that got overly bent. I try to be as careful as I can installing 'em, but they always seem to bend a little.
The self-threading early stud issue really came to light with the 2-piece mainshafts we made for Porsche. I got the call from Germany that two out of 6 prototype shafts had come apart during an important race. I'd never heard of this happening before, and the only immediate answer I had was to send extra long 7mm Type I nosecone studs from an old trans I had in the garage.
Then I remembered seeing the newer style stud when I'd rebuilt my Vanagon transaxle, and immediately ordered 100 from the local VW dealer. Here you can even see the early style stud in first sequential GT3RSR transaxle parts breakdown:
https://www.thesamba.com/vw/gallery/pix/1069707.jpg
In Porsche racing, the engines are turning the 2-piece mainshaft @ 8,500 rpm, and engine braking occurs in every turn. The free-floating stud continually brakes against the forward threads in the mainshaft, and under certain conditions, eventually threads itself all the way forward. So, a process that took the OP's trans 50,000 miles to occur, happens after a couple hundred miles in a high-revving race car.
https://www.thesamba.com/vw/gallery/pix/1567185.jpg
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com |
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