Transmission wear from P&G (pulse and glide)?

[Piotrsko]

The cannister works but takes a while to get to vacuum even at idle and assorted leaks will make you crazy since everything now-a-days is cheap 3rd world manufacture. It won't recharge if the process is engine off coasting. My issue is the KOSTOV motor isn't a vacuum source

[EcoCivic]

Well I unfortunately may have my answer. While distracted by arguing with a passenger, I shifted from neutral back to 5th gear without blipping the throttle first (something I don't normally do) and the trans didn't appreciate going back into gear at 60 MPH from idle RPM. Although it didn't grind in the typical way, it kicked me out of 5th gear as soon as I tried to select it.

I think perhaps the 5th gear synchro may have been worn when I installed the trans as I don't think there's any way I could have caused any appreciable wear in just 6 months. It was from a junkyard after all. Although none of the gears grind while shifting from one to another, it seems that shifting back into 5th gear from idle at highway speeds is more than the 5th gear synchro can take.

I should have just replaced the synchros when I had the trans apart to replace the input shaft bearing before I installed it.

[Piotrsko]

Traditionally, the synchros look burnt or obviously worn, so if you looked, there was probably nothing major amiss. AFAIK, thrashing a synchro only takes about 5 minutes of goofy driving, even on a brand new one. Once they get hot enough to refine the lube oil, they are done. Ask me how I know.

[EcoCivic]

Originally Posted by Piotrsko

Traditionally, the synchros look burnt or obviously worn, so if you looked, there was probably nothing major amiss. AFAIK, thrashing a synchro only takes about 5 minutes of goofy driving, even on a brand new one. Once they get hot enough to refine the lube oil, they are done. Ask me how I know.

I did have the trans apart before installation to replace the input shaft bearing and inspect it and I did not see anything obviously wrong, none of the synchros were noticeably discolored. But I don't know that much about transmissions, so I didn't really know what specifically I was looking for. I didn't take the shafts apart either, I just took them out to get to the input shaft bearing.

I don't doubt that ruining a transmission within minutes is possible but I really don't see how I could have worn it out that quickly, I'm not at all an abusive driver. The only unconventional thing I do is shift in and out of 5th gear frequently, but as I said I always raise the RPM to where it needs to be before shifting back into gear to prevent synchro wear. For all I know this trans may have been that way since I got it. Not sure since I normally don't shift back into gear without first blipping the throttle.

[Piotrsko]

Has nothing to do with babying between gears, but everything to do with dissipated heat energy. Take a piece of brass, heat it up to some high temperature, drop it in a cooling oil. Does it cool immediately? Nope. While its still hot, repeat process.

They synchros get hot, that gear speed matching energy has to go somewhere like the attached parts or the oil. What we used to call crash shifting means you have to speed up or slow down the entire gear set and shaft perhaps the clutch disc also.

If your process was harmless......we wouldn't need to have this conversation. Ever buy a commuter car with hard to get into first or reverse issues? Ever notice a commuter car has dirty trans oil?

[EcoCivic]

Originally Posted by Piotrsko

Has nothing to do with babying between gears, but everything to do with dissipated heat energy. Take a piece of brass, heat it up to some high temperature, drop it in a cooling oil. Does it cool immediately? Nope. While its still hot, repeat process.

They synchros get hot, that gear speed matching energy has to go somewhere like the attached parts or the oil. What we used to call crash shifting means you have to speed up or slow down the entire gear set and shaft perhaps the clutch disc also.

If your process was harmless......we wouldn't need to have this conversation. Ever buy a commuter car with hard to get into first or reverse issues? Ever notice a commuter car has dirty trans oil?

That makes sense, thanks for explaining! The only doubt I have with that explanation is that since I always manually match the gear speeds to within 100 RPM or so before going back into gear, the synchros shouldn't be having to do that much work I wouldn't think? Normal gear shifts force the synchros to match many times larger speed differences than that all the time.

[Piotrsko]

That is why I thought they were bad when you had it apart.

Bit of better advice: 20 years ago chevy was having problems with newbies burning up their new to them manual trans pick ups. They have a pretty expensive fluid exactly for this problem, but it isn't ECO thin. Might get a couple quarts and try it.

I have found the only way to not fry synchros is to no clutch shift and allow the shafts to speed adjust with throttle and no more than extremely light shifter pressure. If it doesn't go easy it ain't right yet. Doesn't respond to quick shifting but I can get 400,000 miles out of a tranny. Takes me about a year to learn the car and makes my wife crazy. Double win.

[EcoCivic]

Originally Posted by Piotrsko

That is why I thought they were bad when you had it apart.

Bit of better advice: 20 years ago chevy was having problems with newbies burning up their new to them manual trans pick ups. They have a pretty expensive fluid exactly for this problem, but it isn't ECO thin. Might get a couple quarts and try it.

I have found the only way to not fry synchros is to no clutch shift and allow the shafts to speed adjust with throttle and no more than extremely light shifter pressure. If it doesn't go easy it ain't right yet. Doesn't respond to quick shifting but I can get 400,000 miles out of a tranny. Takes me about a year to learn the car and makes my wife crazy. Double win.

I use the Amsoil Synchromesh fluid. At nearly $20 a quart it's pricey but fortunately I only need 2. From the testing I have done, it seems to be about the same viscosity as OEM Honda fluid when cold but a bit thicker when hot.

Interesting suggestion, I always thought floating gears was hard on synchronized transmissions and mostly only a viable option for unsynchronized transmissions. I don't intentionally float gears, but one time I forgot to use the clutch shifting from neutral into 5th gear and it slid in no problem.

[Piotrsko]

Originally Posted by EcoCivic

Interesting suggestion, I always thought floating gears was hard on synchronized transmissions and mostly only a viable option for unsynchronized transmissions. I don't intentionally float gears, but one time I forgot to use the clutch shifting from neutral into 5th gear and it slid in no problem.

Bada bing, there you go. I learned manuals on truck style non synchro boxes where being able to do this was a necessity. If the shifter slides with no issues it means the synchros aren't doing very much to alter gear speed.

After they synchro go bad you either have to do this or pull and rebuild it anyways.

[Gasoline Fumes]

Originally Posted by EcoCivic

Interesting suggestion, I always thought floating gears was hard on synchronized transmissions and mostly only a viable option for unsynchronized transmissions. I don't intentionally float gears, but one time I forgot to use the clutch shifting from neutral into 5th gear and it slid in no problem.

Yeah, I'm pretty sure shifting without the clutch makes the synchros try to change the engine speed, versus just the input shaft speed. Of course if you can perfectly match revs every time, there won't be any wear. Rev matching with the clutch (and double-clutching) would be the best. My Insight demands this to downshift into 1st or 2nd gear. It'll growl at me if I don't!