Anyone ever "fix" a scratchy synchro with fluids?
 

I have a 6-speed running MTG but it's a huge POS crunch-box. 3rd gear does not like to downshift. Can I add some GM friction mod or AMSoil slip lock and get any improvement?

Synchros need friction to function properly. Adding friction modifiers (ie slipperiness) will make them worse.

I never knew what FMs did, never researched it. I thought they made things more slickery. I guess I can over-fill and see what that does.

Never, ever buy a transmission from an auto-x'er, even if he says he only drove it a couple times.

wait didn't you yell at a n00b for suggesting the same thing?

LOLOL

oh the ironing

Never. Again, I don't understand how the slip-lock works so I'm not going to troll anyone over it.

Friction is used to accelerate/decelerate the input shaft to make the next gear slide in smoothly. Blipping during downshifts makes this process faster.

At least that's my understanding and I'm content with that level of detail (ignorance is bliss :)).

What fluid are you running in the trans?

Oh goody, answers to questions I didn't ask. Tell me more.

Half AMSoil MTG, half pterodactyl ejaculate.

friction modifier is used to reduce friction between parts.

synchros NEED FRICTION to work.

gohead and add it and complain more?

I was on board with slip-lock reducing friction from post #2 of this thread.

this stuff? AMSOIL - Synthetic Manual Transmission and Transaxle Gear Lube 75W-90 (MTG)

Seems like it would work well, although I'm using this ford motorcraft fluid and noticed a huge difference from whatever the fck was in there previously.

Motorcraft MTX-75 IB5 transmission fluid XT-M5-QS

Although since that Amsoil stuff is GL4 fluid it should be good from what i've read. I LOVE amsoil and it's all i run in my Buell.

The Motorcrap posted above was a step up from my redline, it noticeably improved shifting.
If not, I have a synchro or two if yours are out of spec I could mail you.

This thread is perfect timing. my new to me, sat on a garage floor for a year or two 80,000 km 6 speed shifting was/is horrendous as well.

I might try the motorcraft if we can get it here BUT have noticed in the past week as i use the car more, the gearbox is improving. Perhaps sitting around wasn't the greatest and using it is wearing any rust or whatever off.....

I race national MX here in NZ, the Motul "Pro" gearbox oil is shithouse. Jumps out of gear, won't go in to gear etc....(life threatening on a MX track!)"Downgrade" to the bog standard Motul transmission oil (1/2 price) and shifts are perfect.

I came to the conclusion the "Pro" shit was too slippery and the synchros etc were not coping....told my friends who were haivng the same problem and they all ended up with the same conclusion.

Who knew, oil can be too slippery....!

You may find your self diving into the art of tranny rebuilds. Put on your happy face. ;)

STFU about the Motorcraft shit gear lube. This is not that thread, go away.

You have a GL5 lube in when a GL4 is required, no wonder it shifts like shit. the AMSoil MTG is for extreme use, Motorcraft and Synchromesh for dialy driving.

Thanks but I'll just dump this trans and get another...from my garage.

I just changed the shift boot from the old vinyl one to a leather boot. Do you think that will increase my homosexual lust?

I have been running Royal purple for the last 14k miles, id say its pretty good. Then again my shit only has 34k miles.

Just switched to MTG in my 6speed as of 30 min ago: already feel a difference. Feels Goodman

Has anyone proven this with a UOA?

My Motorcraft fluid shifts *much* better on the track than the GM Friction Modified fluid which made shifts into 3rd a crunchy mess. I'm tempted to try the AMSoil MTG but I'm reluctant to abandon something that works for me.

hustler, is this your daily or your race car?

If daily, the BG SynchroShift is also pretty smoov.

Daily. I may try that, but I'm really tempted to dump this off and consider it "experience". $600 down the shitter.

what does it do specifically? Grind? Tough to push it into the gate?

Mine is an absolute clunk box when its cold. I have to seriously put effort into shifting smoothly, but when I do, its totally fine. I'd keep revs from dropping too fast between shifts and that seems to avoid any notchi-ness or roughness. It doesn't grind though, just tough and rough switching between gears.

When its up to temp it shifts like butter. Flawless.

Is yours the same way or always clunky?

I basically have to shift without the clutch when cold and 3rd gear always grinds miserably on the downshift. At this rate and severity, the trans won't last long.

Any chance the previous owner put something too snotty in there? I'd say it's worth the cost of a trans fluid flush and a refill with one of the synchro fluids.

It's already been flushed. I started with cheap-o synchromesh. Junk oil from the old trans I pulled, drove it for a week, swapped to MTG.

Once a synchro is worn enough that it no longer has the ability to act as a brake and slow the gear, there's no reviving it with fluid. You can potentially change the way the trans feels/shifts with a different viscosity gear oil, but if the synchro is worn out and grinding, it's done. There is literally material worn away from the inner contact area, or the teeth are deformed enough, that it can't function properly any more.

And make sure your clutch is properly adjusted. I'll assume you know how to do that and that your clutch is not dragging. Which is the #1 killer of synchros.

you could try some synchromesh fluid, but the reality is even if it helps at all, it is a bandaid. you could also try revmatching your downshifts to help with smoother engagement.

Oh god, are you serious? Could I really try that?

hahaha!

Are you serious? Why the sarcasm? You are asking if a fluid could fix your trans... All I was doing was making a suggestion. Lighten up. I didn't say it in a condescending way. Why ask questions and then shit on the answers? We ALL know if the trans is acting as you describe the only real fix is to replace the failed parts. Maybe next time just don't reply to posts that you think are stupid? Sorry if I am coming off as a dick, I just don't understand why people ask questions then get pissed off when they don't get the type of answers they want. Feel free to weed out / delete my posts if you find them unrelated or not helpful in any way.

As much as I would like to say some smart ass comment, I will refrain. We are all enthusiasts here, and interenet bs aside, no one like busted cars. I hope you sort out your trans problems. Take care.

I can translate sarcasm for you:

This is why I called you out on it in the for sale thread. Because it's annoying and most people don't have the patience to deal with people who come here to post a bunch of one-liners that are barely relevant just so they can whore their car parts without otherwise participating.

Actually the original problem lies in the fact that i was on my phone and i did not realize this thread had 2 pages so i missed the whole mention of synchromesh. I was not spamming. I personally used synchromesh with good results on one of my previous cars so i suggested it.

I had no luck with additives. I had to replace tranny in my 99. Had to put it on blocks, took 1 day to remove and replace. Wasn't too bad.

The vast majority of "bad syncros" are actually the result of a bent shift fork. Its pretty unusual for a syncro in a good, modern transmission to just get shitty out of nowhere. Typically a shift fork gets bent, it starts grinding, then after a year of that shit, the syncro is torn up so when someone opens the transmission they go "oh, look at dat der syncro dats all tore up, ders yer problem".
So no, I dont think any kind of fluid is going to help. Going to a different weight might make it shift better so you dont bend the fork in the first place, but thats about it.


In the mean time, double clutch...

Did Motorcraft change their labeling on the MTX bottles?

Bought a shelf full of what the counter guy says is the right stuff. The part number contains MTX but the label just says synthetic transmission fluid.

Is this statement based on direct observation, or anecdotal information? I've been rebuilding transmissions for a shop off and on for 3 years, and a dragging and improperly adjusted clutch is the #1 reason we see worn synchros, followed by bearing failures due to inadequate lubrication. And I've never seen a bent shift fork, only broken ones.