replace sychro rings/gears?

[jeffc280sl]

Bought a replacement manual tranny which I'm rebuilding.  Plan to replace 4 large ball bearings, seals and gaskets.  Gears and synchros look fine to me.  I'd like to hear from experts concerning if I should replace the synchro rings.  Here is a pics, I hope it shows sufficient detail for an evaluation.

Thanks

Download Attachment: synchro2.jpg
40.88 KB

Jeff C.
1970 280SL 4-speed

[Benz Dr.]

Place the syncro cone on the gear with a little bit of trans fluid to lube the two pieces. Push down and try and twist the syncro ring in a radial direction. It should lock up right away and not spin at all. If it turns more than one or two mm it's probably no good.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[jeffc280sl]

Thanks Dan,

I'll give it a try and let you know.



Jeff C.
1970 280SL 4-speed

[jeffc280sl]

Dan,

I think you are asking me to put the synchro ring back in place and then slide the synchro body over the ring.  Then while holding the synchro body firmy try to spin the synchro ring assembly to see if there is more than 1-2mm of play.  I have a very small amount of play in the 1-2 mm range so I guess its okay.  This test would seam to indicate that the width of the teath on the snchro ring are not worn too thin.  If it were too thin there would be more radial play when you slide the synchro body over it.

Should all 4 synchro rings have the same size teeth?  Most importantly width?

Thank you very much!

Jeff C.
1970 280SL 4-speed

[jeffc280sl]

This picture, from a Porshe, would indicate wear of synchro rings takes place in the depth of the ring verses the width.  Is this the kind of wear we should be looking for?

Download Attachment: worn synchro1.jpg
62.42 KB

Jeff C.
1970 280SL 4-speed

[Shvegel]

For my money I replace first and second gear syncro rings on every trans I filet. If you don't know what you are looking for in regards to gear and slider wear I would suggest taking the gears to someone who rebuilds transmissions for a look.

Hint:

Guys who rebuild large truck transmissions usually know what they are doing. The one thing they like to avoid is a pissed off truck driver.

[Benz Dr.]

No. You do this test by simply dropping the ring on top of a gear cone and seeing if it will move sideways. If it moves at all ( as per the test ) the ring is worn out.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[jeffc280sl]

Thanks again Dan.  The ring fits very snuggly onto the gear cone.  The undersurface of the ring looks to be in very good shape and the grooves on are very defined.

Jeff C.
1970 280SL 4-speed

[jeffc280sl]

Looks like the sychronizer body 111 262 07 35 has some worn splines on top near the brass ring.  Pic attached.  Part is available at SLS for 86 euros.  I seems like the sliding collar which slides back and forth on the snchro body when shifting moved in one direction too far and ended up too near the end of the slines on the body causing wear.  I need to determine if a loose nut allowed for this kind of play.
 
 
Download Attachment: Manual tranny 055a.jpg
51.65 KB

Jeff C.
1970 280SL 4-speed

[jeffc280sl]

Here is one of George's pics of the sliding collar that slides when shifting gears.  The loose nut is the same one he speaks about in his write up.

Download Attachment: 2006123163849_trans-mainshaft-sml.jpg
46.54 KB

Jeff C.
1970 280SL 4-speed

[Benz Dr.]

The teeth and width is likely the same on all the syncros but 1st gear syncro usually has a wider piece or section on the oustside rim than the other ones.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[jeffc280sl]

Thanks Dan,

Now that I have it completely apart I can see that one of the rings has slots on the side that meets the gear cone.

Jeff C.
1970 280SL 4-speed