Fisrt gear syncro out - need re-build?
 

Inspection of my 86 Carrera identifies grinding when shifting to first gear or reverse while moving as bad first gear syncro. Mechanic said not to worry about it, as long as I do not mind having to be stopped when shifting to first. Told me to wait until I need a clutch or other engine repair that required removing the engine.

Will changing the trans fluid/lube help at all, or is there an additive/flushing that could correct or minimize the problem?

Probably a dumb question, but I do not understand the mechanic's of the trans/syncro, so if anyone could explain the basics, I am curious to know.

Any idea on/if other gear syncro go out and how long (miles) til you think I will need a re-build?

:confused:

Welcome!

Many of our old beloved 915 boxes have pretty beat up first and second synchros by now. The 915 in general takes a bit of tenderness and smoothness to get along with. If you can live with it I would wait for a clutch work.

Make sure all the gear shift bushings are OK and the coupler is properly adjusted. Likewise the clutch.

New lube can be an improvement but will not change the fact that the synchros are worn. Many 915 owners like Swepco 201.

Also, please try the search button. The subject has been covered many times.

And post pics of your car.

SmileWavy

Welcome to the 915 trans. Few if any of us can downshift to 1st at any speed over 5 mph. Second gear will get you going easily from any rolling stop.

86911sc:
Do as your Mechanic says: Come to a full stop for first and shift gently into second meaning: Not too fast from 1st into 2nd.
The 915 never was a fast-shifting transmission even new.
Ensure that the bushings in the shift housing are good and the shift-coupler is good.
Changing oil doesn't hurt but worn synchros are worn synchros.
Do a search on this subject here, it's been covered many times.

Agreed on the search. The subject has been covered very thoroughly here and you will find a ton of info and pictures.

In the interim, you may try double-clutching also. It helps spin-up the gears to match speeds and takes away some of the work the synchronizer assembly must do. But, if your gear's dog teeth are thrashed, no amount of double clutching is going to help much. If two parts don't mate well because of misshapen metal......... you get the picture.

Here's a couple to get you started. The second one is VERY informative due to the replies from those who have been servicing these transmissions for MANY years.

http://forums.pelicanparts.com/porsche-911-technical-forum/300593-915-slider-teeth-how-worn-they-pic.html?highlight=sleeve

http://forums.pelicanparts.com/showthread.php?s=&threadid=276245&perpage=20&highl ight=sleeve&pagenumber=2

When you change your tranny fluid keep an eye out for little metal teeth. These would also be an indicator that it's time.

Grinding into reverse when stopped is not indicative of a synchro problem ... it is a clutch maladjustment or pilot bearing problem. Reverse gear has no synchronizer!

Thanks for all of the responses - got somethings to check now.

Here is the link to where I uploaded some pictures. This gallery requies images <100K, so they are a little grainy ......

OOPS, here is the link, sorry!

http://www.pelicanparts.com/gallery/86911c2/

Just noticed your reg'n date. Welcome aboard!