I just put new synchro/blocker rings on my aging tranny. Figured I'd share the results with everyone.

Tranny: 1992 LS
Miles: ~150k
Synchro rings: 1-2- brass, 3-5 carbon coated

Shifting before the "rebuild":
1st - Had to double clutch to get in gear above 2mph. Occasional grind.
2nd - Would grind on high rpm speed shift. Grinded about 5-10 times total.
3rd - would grind on every shift. Grinded about 30-40 times total (I started skipping 3rd)
4th - no grinds
5th - no grinds

Shifting after the "rebuild"
1st - Don't have to double clutch anymore, but still an occasional grind when barely rolling.
2nd - Downshifts are smoother, but still grinds at high rpms.
3rd - Grinding is completely gone. A little notchy on downshifts, but I can slam it into gear at 60mph with no problem
4th - Same
5th - Actually they sent me the wrong size ring. It's smaller. if anybody wants it I'll mail it to them for $15

So I guess the moral of the story is if you've got 2nd gear grinding issues, get the whole assembly (~$250 for each gear), but if 3rd,4th or 5th are grinding, just get carbon coated synchro rings from gearspeed (~$150 total).

Oh yeah, I used 10w40 gear oil, if anyone's wondering.

 

Hi, my 3rd gear doesn't work at all; it doesn't even go into gear. So i shift from 2nd to 4th. I was thinking of doing this, but is it worth it? Or should i just get a new tranny. Tranny probably has 270kms on it. If you recommend of changing the synchros, can you provide steps?
Thanks

 

Grinds usually aren't caused by synchros.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Aquafina &raquo;</TD></TR><TR><TD CLASS="quote">Grinds usually aren't caused by synchros.</TD></TR></TABLE>

Synchro sleeve or engagement teeth on gear worn?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by greasemonkee &raquo;</TD></TR><TR><TD CLASS="quote">

Synchro sleeve or engagement teeth on gear worn?</TD></TR></TABLE>

80% of the time it's the sleeve....these are prone to quicker wear than the synchro or the gear.

OP should have replaced the sleeve as well- please edit your post to keep misleading information legible

 

did u look at the teeth on the gears at all? u found bad gears alot and synchros were ok.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 97grnrs &raquo;</TD></TR><TR><TD CLASS="quote">did u look at the teeth on the gears at all? u found bad gears alot and synchros were ok. </TD></TR></TABLE>

yeah, most of the time I see the synchro sleeve to be severely mangled, but the synchro teeth on the brass synchro and the gear to be pretty solid usually

 

I agree, the sleeves are usually in shitty shape with the synchros being in fair condition. Also its important to get the synchro springs from gearspeed. They are sold seperately.

 

The springs are the most crucial part of that whole rebuild. Without proper tension on the sliding collar to synchronizer, the gearshift will simply move from the hub, to the gear, resulting in no gear slowdown/speedup and a grind. The spring is there so that the shift collar catches it, and presses it on the face of the gear, thus slowing it down.

Even with gears that have bad engagement dogs/collar splines on them, a blocking ring and synchro spring is all that is really needed, unless they are so smashed that it shifts rough/has a hard time getting into gear, like a physical blockage, not a grind.

After many many fast shifts, the springs can develop notches over time courtesy of the collar that cannot get into gear, this normally starts the grinding, and in turn leads to synchro burnout.

 

I am bumping this thread as I am having an issue after a Gearspeed Carbon install. I had a tranny built for my car and I bought a new 3/4 sleeve set and the Gearspeed Carbon 3/4/5 set. After about 1k miles I started to get a grind in the 3/4 shift and the 5/4 shift, fuild used is GM syncromesh and the car has a Quaife. It would do it just driving normally out of boost and in boost. I did not buy the syncro rings as I had no idea I needed to replace them until now when I came across this thread, do you think this could be the culprit?

I was told by someone that the issue could also lie in the friction cone, and that in time the surface becomes glazed and does not provide a proper surface for the syncro to brake, and help on my issue is greatly appreciated.

 

Ok, but as long as there is a spring between the sleeve and ring, then does it really matter how much tension it has? It's completely compressed between the two.

I've read that it's important to replace the sleeve, because the teeth get worn down from constantly moving over the spring. I assume once it gets worn down enough it can't put enough pressure on the spring(and ring) because of the increased clearance. This is probably why people say replacing the sleeve will fix most grinding issues.

Unless the spring has notches in it, then it wouldn't need to be replaced, right? I replaced just the ring on my 3rd gear, and the grind went away. The teeth on the sleeve were worn(though not much more than other gears) so I'll bet as soon as the ring gets worn down a little then the grind will come back because the sleeve can't put enough pressure on the spring to slow down the shaft.