Friday, June 12, 2009

G and Reverse synchronizer

A problem that shows up in the Syncro gearbox after installing a TDI diesel is that the original bronze synchronizer rings get loose on the pins, which break and fall down in between the rotating gears.
They then end up smashing a hole in the transmission housing.

I made some stronger steel rings and brazed a bronze layer on, milled the grooves in the back side where the small springs fit in and finished the friction surface.
I then made a set of pins out of a special steel bolt and tapped internal thread in it.
The new steel synchronizer rings are then bolted to the pins with flat head Allan type bolts which have a tapered seat. I have put a small spot weld on it to prevent it from loosening itself.

I think that this problem is caused by the harsh vibrations of the TDI engine running without a dual mass flywheel, this causes the pins to loosen off in the softer bronze synchronizer rings and eventually it will break.

If you have problems shifting into Low or Reverse don't wait too long and take your transmission apart, it could self destruct within a 1000 KM.
Time will tell if this mod will work.


Jan said...

Hi Herman, I am glad to see that you are still actively making improvements. I am a regular at this site even although the discussions held where a long time ago. regards, Jan SA

Scott said...

Hi Herman,
Fantastic fabrication and finish work, just excellent. Respectfully, wondering if you would consider emailing me as I have some specific questions for you regarding possibility of fabbing parts or peronsal assist in a Syncro restoration (I'm in the US). Sorry to impose. completely unintended, just genuinely appreciative of your crafstmanship. Kind regards, Scott [smcquilkin _at_ gmail _dot_ com]

Herman said...

Thanks Jan, sorry for the late reply, just got back from a trip. I am still at it.
I have a few projects on the go, I will post pictures when I am finished.

Thanks Scott, I have send you an E-mail.


Shaun Supanich said...

Hello Herman, I am having the same problem with my transmission. I did not catch the problem until the tranny became junk. I am now building a new tranny and would like to have you make a set of these gears if possible. My van is running a 2004 Pumpe Dues BEW diesel and I only got 16,000km before it blew. Thanks, Shaun Supanich

Herman said...

Hey Shaun, I have send you an Email.

In short, I have removed the G and Low synchronizer from my transmission, I could hear it rattle while idling, I just used the slider of the synchonizer without the rings, the only drawback is that I have to double clutch or stop before going into Low.
The unit is fine for gasoline engines, but the diesels will eventually rattle it to pieces.

Yiannis said...

Dear Herman
Iwould like some assistance regarding my T25 Syncro gearbox. I have exchanged my engine from 1.6 TD to 1.9TD and after that I had a gearbox problem.

Herman said...

Hi Yiannis, If you have a high mileage Syncro your transmission will have to be rebuild sooner or later, it was probably worn and the switch to the 1,9 TD was the last straw. A good transmission should be able to handle the 1,9 TD without problems.

Cheers Herman

Noel said...

Hi Herman,
First I would like to comment on your craftsmanship, you are truly talented. Keep up the excellent work. Secondly, I built a TDI (ALH) rig for a friend including the transaxle two summers ago and now with 50K miles the reverse/gelande syncronizer let go, the only hole was in the alloy side cover, but the loss of oil prompted a failure of 3rd and 4th gear. I was curious how your new syncronizer is holding up and if you are willing to produce another? Or if you could share your thoughts on this subject. Regards, Noel
noel dot b dot lewis @ gmail

Herman said...

Hi Noel, thanks.
If you have a hole in the side cover, the Allen head bolt that is behind the cover may have come out and got jammed in between the gears and broke the cover, make sure that you use Locktite on that bolt.
It is fairly common for the Low/Reverse synchronizer to fail in a TDI conversion, although I made a few custom ones that seem to last, I have left the synchonizer out of my own transmission, I rather double-clutch when I go into low than run the risk of splitting the transmission housing and get stuck in some remote area.
Also I could hear it rattle at idle and I didn't like that.
No, I don't make them anymore, I just leave it out.

Cheers Herman