5M 4th gear synchro, advice

[TonyF]

Hello people. I did a search and didn't turn up what I was looking for so I'd like to get some pointers on my 5M transmission.

 

The likely issue I believe is my 4th gear synchro is worn. It grinds a bit when warm and rpm's are over 3k shifting into 4th from 3rd or 5th.

 

The car runs sound, has good oil samples and to my knowledge is running all original parts and currently has 170000 miles, no tune. It was actually a good find, unmodified, but that's another story.

 

Anyhoo, I do autocross and it does fine but my OCD is kicking in and it's a spare car so I was thinking of first doing a compression test reading and pending the results this fall, drop the tranny, swap the clutch, check the snout and stuff, then let the experts at my local Subie shop crack the case and give the tranny a good once over, paying particular attn to said worn part(s).

 

I've already changed the banjo and it was clean, while I am in there, I'll probably drop the DP and check the turbo shaft.

 

I guess my question is, is this synchro a common weak point in the trans? Is it worth messing with (doesn't grind at low rpms or when cool)? What other stuff is economically worthwhile to dig into for a guy like me with a lift and tons of tools, just not that much experience but tons of sense?

 

I used to fix helicopters so this stuff seems pretty simple, just new to me.

Option B is just drive it until the wheels fall of and wait for a good deal on a 15+wrx or something else that's fun.

 

Expert thoughts anyone?

[DWCookster]

Honestly if it's just your daily driver and nothing else just deal with it until it goes. It'll cost the same when it comes to paying someone to crack open the transmission and replace parts. Might as well do it when it's fully gone. If it still works and it's not too much of an issue, I wouldn't worry about it. 5th gear was a problem for a bunch of friends of mine when I used to live in Anchorage, Alaska. Now if you're auto crossing quite a bit, good chance you're going to kill that transmission pretty soon with an already possibly failing synchro.

 

At this point it's more of are you willing to spend the bucks to have a shop fix the transmission or do you wanna wait? My personal opinion is if you're auto crossing, go ahead and get the transmission fixed so you're not stranded somewhere after your fun or some where in between.

[Max Capacity]

The 4th gear synchro is a common issue. Google Uncle Scott's cocktail. That may work.

https://www.google.com/search?q=uncle+scott%3Bs+cocktial&sourceid=ie7&rls=com.microsoft:en-US:IE-Address&ie=&oe=&safe=active&gws_rd=ssl

 

If your going to fix it right, I would suggest you invest in Moore Performance Blast Plates. My 5mt shifts so much better with them. it no longer fight's going into 3rd under high RPM and lots of power.

 

You will need special tools to get he gears apart and there are other things you should replace while the trannys apart. But any decent shop will know that. You can pull the tranny yourself, just make sure you put a 2x4 between the radiator and the front of the engine, because the block will tilt forward when the trannys off.

[TonyF]

I just changed the fluid not too long ago with the genuine Subaru stuff, acted the same before the fluid change and it was pretty clean so normal wear I think.

 

Another thing making it a tough decision, squeaking clutch. Operates smoothly but seems in need of grease in there. I don't need the car during winter so right now the plan is to drop it and make it right. The car is very sound otherwise. I have been doing a lot of little things to keep it up.

 

Appreciate the pointers.

[fahr_side]

Scotty's cocktail worked really well for me. Even I went 6MT later my old trans is still going strong in its current home.

[TheMonaLisa]

Grimmspeed sells the Scotty's cocktail on their web site. Takes the hassle away from ordering everything yourself. That mixture is magic.

 

 

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