[Joe Piro]

I removed the Mechatronics unit from my 2006 Jetta TDI DSG transmission so that I could replace the (G182 transmission input speed /G509 clutch oil temperature) sensor. When I loosened the ten Mechatronics retaining screws (that are supposed to be replaced and I have new ones) I accidentally loosened another T27 screw that looks like it is one of the many screws actually holding one of the eleven solenoids. (All the screw heads look alike.)
And now that I think more about it, I am not sure that they are solenoid screws. I did attach a photo for clarification. There's nothing in my manual about this.
Does anyone know the correct torque setting for these screws? This one is about an inch long whereas the ten Mechatronic screws are about an inch and a half.
Should these other screws be replaced also, like the ten Mechatronics unit screws.
I want to be precise about this because it took so much work to remove the transmission (for clutch pack replacement) and get to this point. Also don't want a failure because a screw failed.
The 2005-2007 Volkswagen Jetta Quick Reference Specification Book (found on eBay) has been a huge help with torque settings, but it has nothing about the solenoids.
(BTW I have checked the solenoid resistance and they are all as specified.)
Thanks for your help.....

 

[a1979corvette]

I’m going to look at the torque for that screw in my manual soon as I get back to my shop.

Information about your bolts, you are talking about TTY (Torque to Yield) bolts. They are easily recognized by having a greenish blue tint coating a greenish blue paint marking and several other manufacture specific markings or designs. Once the bolt/ screw has been torqued to its yield strength, it cannot be reused because the yield strength has diminished. Technically it’s weakened by plasticity elongation or stretch, and must be replaced, by engineering design.

 

[Joe Piro]

I really appreciate your taking a look. I'm being really cautious here because a failure can really create a problem.
At first I thought this bolt secured one of the solenoids but now I am not sure what it does. I now see how the solenoids are attached. I think probably the entire module is assembled in layers with hydraulic pathways in the casting and these bolts secure the lamination. I counted fifteen of them and there may be another one or two hidden under a solenoid, etc.
I loosened it by mistake when I took out the ten bolts that hold the Mechatronics module in the transmission. The original screws all had the greenish tint that you mention (or maybe brown-ish.... not sure) and I already replaced the ten long ones (module to transmission housing) per VW instructions. The new ones don't have any tint but they are well marked and are the correct part number. I have attached a close-up of the head and it definitely has a dark greenish (or brown-ish?) tint (as you suggested) but no legible markings on it as to manufacturer or grade. I'm not sure the tint is green and I wonder if they are just dark from being in transmission fluid for 16 years?
I torqued it to 10 Nm (88 inch lb). Then I considered taking it out and re-installing with Loc-tite.
Then I remembered how hard it was to take the transmission out so I decided it do it right.
It's pretty snug in there right now and I have thought maybe I should leave it as it is.
The VW dealer parts counter was not able to look it up for me because the screw is not a part that they service.
Thanks for any help you can provide...

 

[a1979corvette]

Unfortunately, I thought I had the tear down for the mechatronic itself. I don’t.
Apologies

 

[a1979corvette]

Everything you said is spot on, you’re on the right track. The black button head screw your referencing does hold the halves together and I agree with 88 lbs./in.
I don’t recommend using thread lock in this area period. It has is use and place. Just not here, especially with a small screw.
I use a purple or green ultra light thread lock for button head screws on a HD because they shake so darn much.

 

[Joe Piro]

Thanks again for your reply. I don't know who would have the Mechatronics teardown manual? The VW dealers (or Porsche or Audi) just don't service those. I read a good bit about torque settings this afternoon and concluded that I should be able to find a torque setting in charts that are published online, specifying the size, the grade of bolt, and the thread pitch. Two charts that I checked specified 7 ft lb and 8 ft lb. Another said 11.8 ft lb but I think they confused their Nm with their ft lb. and I don't trust that one. So I'm comfortable in that range (88 inch pounds) but your second opinion helps.
I have also concluded that this fastener is not torque to yield. The specification of torque plus angle gives a more accurate final torque but does not always indicate a TTY fastener. Torque plus angle is just a better way to get an accurate result. Someone over at the Garage Journal explained this to me. For a TTY, the bolt or screw must be able to stretch. A head bolt is a good example. These screws go into a totally threaded hole with 1 thread per mm and there is no way they can stretch. Conclusion: I think I'll leave it screwed in at 88 inch pounds... no thread lock... and not risk removing it again. It had a nice firm end point at 88. The good news is I don't have to remove the transmission if I have to access the Mechatronics again.
Thanks a lot for your help and interest. If you want another really good resource, check out the people at Garage Journal. I find them helpful and entertaining. They have a lot of experience over there from hardcore amateurs to professional mechanics.
I don't want to load up your mailbox with anything you might not be interested in, but a GJ member sent me links to two videos. One was the assembly of straight six diesel engines in the Cummins factory. The precision and complexity was impressive. Another video was about Torque and Fastener technology from Atlas Copco. I learned a lot! Just a short note and I'll shoot those over. If not, I won't be offended in the slightest.
BTW if you use ultra light thread lock on your Harley, what kind do I need to use on my BMW?

 

[a1979corvette]

A transmission shop would have access to manuals for that. It’s not a free service and copy write protected so passing those around a forum could be costly.

 

[Joe Piro]

I know one locally and i might give 'em a call tomorrow.
Thanks.

 

[Joe Piro]

transmission shop would have access to manuals for that.

Just to close the loop on this question:
As a result of your suggestion about transmission shops:
I typed "Mechatronics Repair Manuals" in my browser and hit a site called "Transmission Repair Manuals." It allowed me to download the "VW Self Study Course #851403" which is a very thorough analysis of the 02E transmission... details on operation and solenoid function etc. ...learned a lot!
It was not a repair manual which I can probably download for a nominal fee. But there was a link to a video by a mechanic in India who disassembled the Mechatronics completely, de-laminated the layers, then
replaced the solenoids, etc. He said the torque for these screws should be 5 Nm plus 1/4 turn. That equals 44 inch pounds plus 1/4 turn. Bottom line... I'm leaving the fastener in place... should be about right... maybe a little high but likely safe.

 

[Joe Piro]

And finally (maybe) the TDI Club recommended a site called "erWIN" which provides access to all VW printed literature. They have a subscription service including a one day subscription for $35 and you can print your downloads.