How do I know if Synchros are bad?

[bbbngowc]

My 91 GT is grinding only in 3rd gear.

How can I test/check to know if it's the synchros or something else? I've changed clutch, clutch cable, clutch fork, adjusted clutch and changed to GM Synchromesh. Still grinding.

 

[AustinFoxBody]

I would think that that would be your problem. Does it grind more when the tranny is cold and get better once it warms up or is it all the time?

 

[Mustang5L5]

Most likely the blocker ring is wearing out.

BTW, GM synchromesh eats the linings and is not recommended in a T-5

 

[Ike83]

MY gears grind when they're cold, but then seem to get better when the car warms up. THAT would be a sign of bad synchros, right?

 

[Mustang5L5]

Yup, early signs of blocker ring wear.

Are you running synthetic fluid? If so, replace it with conventional ATF. It's less slick so it will grab more and help prevent grinds. It could fix the issue if minor enough

 

[Ike83]

Yup, early signs of blocker ring wear.

Are you running synthetic fluid? If so, replace it with conventional ATF. It's less slick so it will grab more and help prevent grinds. It could fix the issue if minor enough

Makes sense to me.

 

[bbbngowc]

I would think that that would be your problem. Does it grind more when the tranny is cold and get better once it warms up or is it all the time?

Does it all the time. If I'm cruising and I shift below 2000RPM it doesn't grind. Once I'm at 2000+RPM it grinds.

 

[bbbngowc]

Yup, early signs of blocker ring wear.

Are you running synthetic fluid? If so, replace it with conventional ATF. It's less slick so it will grab more and help prevent grinds. It could fix the issue if minor enough

I had synthetic fluid in, but I changed it to GM Synchromesh.

 

[Ike83]

Does it all the time. If I'm cruising and I shift below 2000RPM it doesn't grind. Once I'm at 2000+RPM it grinds.

See, that's kind of strange.

With mine, the vehicle shifts fine as long as you shift HARD into each gear. However, if I'm cruising below 2,000 rpms, and ONLY if I'm going from 1st gear to 2nd gear, the shifter will sometimes pop out of 2nd gear and back into neutral. It's like I have to man-handle the shifter in order to get it into 2nd gear without popping right back out at me.

 

[lx93notch]

may seem dumb but check the shifter an see if its tight cus mine was loose and it was only grinding 1st to 2nd. pulled the bolts out put some loc-tite on them and its been fine since

 

[Mustang5L5]

See, that's kind of strange.

With mine, the vehicle shifts fine as long as you shift HARD into each gear. However, if I'm cruising below 2,000 rpms, and ONLY if I'm going from 1st gear to 2nd gear, the shifter will sometimes pop out of 2nd gear and back into neutral. It's like I have to man-handle the shifter in order to get it into 2nd gear without popping right back out at me.

It's all related to the friction material ont he blocker rings.

With grinding over 2K RPMs, it's due to greater speed differential between gears. When you shift at 2K, it needs to drop maybe 1000 RPM. Less than that and you only need a 500-700RPM drop. There is a magic point where the synchro simply cannot match the speed quickly enough and you grind.

Same goes for shifting fast. Fast shirts put more force on the blocker ring and the initial "hit" can cause it to grab. When you shift slowly, it tends to slip a little bit more.

All signs of synchro's wearing.

And like i said before...it's cheaper to replace it now as you only need to replace the soft parts. Start consistently mashin gears and it gets expensive