Bad first gear synchro
Thread Starter
Pro
Joined: Jul 2005
Posts: 573
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From: Wichita KS
Bad first gear synchro
Looks like the first gear synchro is bad in my '03 Z06. What's odd is that it seemed to just go all of the sudden. It only ground a couple of times previously downshifting to 1st and then it just pretty much stopped working. I can only downshift to first at a very low speed (like 5 or below) or at a dead stop.
All other gears are fine, there is no other apparent problem. I drained the fluid and it looked very clean (I changed it about a year ago).
My question is, is there anything else that could have broken in the transmission to have caused this somewhat sudden failure? What I'm really wondering is if I should drive it like this, or is there a chance of doing further damage??
Thanks,
Dave G.
All other gears are fine, there is no other apparent problem. I drained the fluid and it looked very clean (I changed it about a year ago).
My question is, is there anything else that could have broken in the transmission to have caused this somewhat sudden failure? What I'm really wondering is if I should drive it like this, or is there a chance of doing further damage??
Thanks,
Dave G.
Former Vendor
Joined: Oct 2006
Posts: 278
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From: Auburn/Dacula/Lawrenceville Georgia
If you have the means to do so, flush your clutch fluid and put something back in of good quality. A good DOT 4 fluid. Afterwards, install 4.5 qts of GM Synchromesh and/or the Pennzoil equivalent (that's what we use) in the trans. I like to call Synchromesh "transmission guy in a bottle", stuff is amazing.
If those 2 together do not smooth out your problem, you've got a boogered up 1st gear and the trans needs to come apart. With the T56 having to be broken down from the rear forward, it would be a good time to have the entire transmission refreshed. If it comes to that I'd highly recommend doing the following: Rebuild kit with carbon fiber blocker rings, billet synchro keys for 1-2 and 3-4, bronze fork pads, Steel 3-4 shift fork, and make sure whoever builds it now's how to properly shim the entire assembly while checking it with a dial indicator to make sure it's within spec.
Good luck!
Thread Starter
Pro
Joined: Jul 2005
Posts: 573
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From: Wichita KS
Thanks for the detailed response. I had seen some mention of synchro key failures in searching the forums. All I know is there has been no indication of stuff floating around (clean oil, no sparkles, no noises, etc...). It may be just typical wear. The slave cylinder has been a little marginal for a while. I've been flushing it regularly with Dot 4 fluid which has kept it working ok, but not perfectly (typical increase in free play after high revs). So that may be the real cause.
I did do a lot of searching before posting this thread and already have 4 bottles of GM Synchromesh FM on the way. As bad as it is, I doubt that will fix it, but maybe help enough to get me by for a while until I can get the issue resolved over the winter. It must still work partially as I can (carefully) slide it in to first at low speed.
Dave G.
I did do a lot of searching before posting this thread and already have 4 bottles of GM Synchromesh FM on the way. As bad as it is, I doubt that will fix it, but maybe help enough to get me by for a while until I can get the issue resolved over the winter. It must still work partially as I can (carefully) slide it in to first at low speed.
Dave G.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
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From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
WHY,,,,,,,,,,
,,,,,,, would you down shift to first gear. I can’t say that I have not done the same BUT,,,,,,,, I do not make a habit of down shifting to first. I would call it a VERY rare action.
It’s a really short gear and the synchros work HARD when down shifting to that gear.
As long as you can still shift into first when very slow or stationary, I would worry too much about it.
I would change the ATF because you KNOW that there are wear/tear pieces parts of that synchros in the fluid. Switch to ANY Synthetic AFT and you will improve the shift quality of the trans in the remainder of the gears.
,,,,,,, would you down shift to first gear. I can’t say that I have not done the same BUT,,,,,,,, I do not make a habit of down shifting to first. I would call it a VERY rare action.It’s a really short gear and the synchros work HARD when down shifting to that gear.
As long as you can still shift into first when very slow or stationary, I would worry too much about it.
I would change the ATF because you KNOW that there are wear/tear pieces parts of that synchros in the fluid. Switch to ANY Synthetic AFT and you will improve the shift quality of the trans in the remainder of the gears.
Thread Starter
Pro
Joined: Jul 2005
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From: Wichita KS
Bill, that is actually one reason I posted this thread. I was considering just letting it go for now, but didn't want to do further damage if there was some other issue. Heck, just for street driving you really don't need to use first at all. I do run a lot of Solo events with the car, but same story. Never use first except at the start and sometimes I start in second when the start is fairly slow/tight.
And if I do decide to let it go for a while, I'll likely put a synthetic back in it. I changed it last weekend to just some dyno stuff, but was going to try the synchromesh partly just out of curiosity since I read in various places that it made a decent synchro band-aide. I never intended to leave it in long term since it's not really the correct spec oil.
Dave G.
And if I do decide to let it go for a while, I'll likely put a synthetic back in it. I changed it last weekend to just some dyno stuff, but was going to try the synchromesh partly just out of curiosity since I read in various places that it made a decent synchro band-aide. I never intended to leave it in long term since it's not really the correct spec oil.
Dave G.
Team Owner
Joined: Mar 2002
Posts: 24,160
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My car won't drop into 1st unless I'm at a crawl or stopped, and every manual car I've driven has been similar. I had an Acura that I swear had a interlock on 1st until you were completely stopped. Trying to go into that gear with any movement at all felt like you were hitting a wall with the shifter.
Originally Posted by talon95
nd if I do decide to let it go for a while, I'll likely put a synthetic back in it. I changed it last weekend to just some dyno stuff, but was going to try the synchromesh partly just out of curiosity since I read in various places that it made a decent synchro band-aide. I never intended to leave it in long term since it's not really the correct spec oil.
Thread Starter
Pro
Joined: Jul 2005
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From: Wichita KS
Well using a synchromesh fluid in my case is a band-aid for my worn synchro. I wasn't saying it was junk or anything. The downside is it is a dyno oil. The Friction Modified version is supposedly a hybrid though which is the one I ordered. Nothing wrong with them at all except a good synthetic is supposed to hold up better over time.
A lot of cars shift hard in to first. Mine just grinds big time if I try to downshift at any significant speed. Not the same thing (unfortunately).
Dave G.
A lot of cars shift hard in to first. Mine just grinds big time if I try to downshift at any significant speed. Not the same thing (unfortunately).
Dave G.
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Team Owner
Joined: Mar 2002
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Well using a synchromesh fluid in my case is a band-aid for my worn synchro. I wasn't saying it was junk or anything. The downside is it is a dyno oil. The Friction Modified version is supposedly a hybrid though which is the one I ordered. Nothing wrong with them at all except a good synthetic is supposed to hold up better over time.
Thread Starter
Pro
Joined: Jul 2005
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From: Wichita KS
).
Thread Starter
Pro
Joined: Jul 2005
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From: Wichita KS
Safety Car
Joined: Dec 2011
Posts: 4,704
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From: Redondo Beach CA
Wow I never would have guessed that a complex gearbox like this one could tolerate any failed parts. Good old yank tank designs.
I also want to thank the guy with the rebuild list. Good for me, my car is getting some good miles and transmissions don't grow back after you wear them down.
I once had a car with a non syncro first gear. After I blew that gear up trying to impress a girl, the trans guy showed me how lucky I was, since I drove it around for a good bit more. There was a small collection of metal bits of parts on a magnetic drain plug, but the big items were just lying in the bottom of the case, just waiting to jump up and cause mischief. Old sports car were more down to earth. THe 1962 car that had a non synco first also came with a hand crank stowed in the body work, and a starter button under the hood, because the cars needed a lot of tune up type attention back then.
I also want to thank the guy with the rebuild list. Good for me, my car is getting some good miles and transmissions don't grow back after you wear them down.
I once had a car with a non syncro first gear. After I blew that gear up trying to impress a girl, the trans guy showed me how lucky I was, since I drove it around for a good bit more. There was a small collection of metal bits of parts on a magnetic drain plug, but the big items were just lying in the bottom of the case, just waiting to jump up and cause mischief. Old sports car were more down to earth. THe 1962 car that had a non synco first also came with a hand crank stowed in the body work, and a starter button under the hood, because the cars needed a lot of tune up type attention back then.
Melting Slicks
Joined: Apr 2009
Posts: 2,479
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The best thing I ever did was put in Mobil 1 synthetic ATF. It is a Dex III fluid and it is still manufactured and readily available. I highly recommend it. It definitely smoothed out gear engagement in all gears.
Thread Starter
Pro
Joined: Jul 2005
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From: Wichita KS
I put it in today and made a few laps around the neighborhood. Definitely helped. Not fixed, but noticeable improvement. If you get it, make sure you get the "Friction Modified" version. At least that's the one everyone recommended on various forums when I was Googling it. Not cheap though.
Drifting
Joined: Jan 2000
Posts: 1,660
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From: Charlotte, NC
It generally takes about a month for me to reap the benefits of transmission fluid change. So it should get better within the next few weeks.
Oh, and be sure to rev match your downshifts. Not only is it fun and a good challenge to do correctly but it saves your tranny!
Oh, and be sure to rev match your downshifts. Not only is it fun and a good challenge to do correctly but it saves your tranny!
Advanced
Joined: Jan 2007
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I put it in today and made a few laps around the neighborhood. Definitely helped. Not fixed, but noticeable improvement. If you get it, make sure you get the "Friction Modified" version. At least that's the one everyone recommended on various forums when I was Googling it. Not cheap though.
Thread Starter
Pro
Joined: Jul 2005
Posts: 573
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From: Wichita KS
Some dealers carry it. Although I couldn't find one locally so I ordered it from Amazon.
(told you it wasn't cheap)
(told you it wasn't cheap)