Worn synchros - fluid change good or bad?

[Rand]

The best fluid in my 2007 Focus with MT was the ford fluid

Redline MTL?(iirc) was good but not quite as good.

If you have old nasty fluid in there just changing it might help quite abit.

You dont want an api gl-5 or any dual rated fluid.. it will be notchy.

 

[aquariuscsm]

Some fresh mtf might be all you need. Unless the previous owner pounded the holy [censored] out of the tranny,I could never see synchros wearing out with that little mileage.

 

[Short_Bus]

Originally Posted By: aquariuscsm
Some fresh mtf might be all you need. Unless the previous owner pounded the holy [censored] out of the tranny,I could never see synchros wearing out with that little mileage.


I will freely admit I beat the snot out of it. The 3rd gear synchro problem is a fairly common problem with this trans though.

When I bought the car with about 100k miles on it i would only get a slight "nik" going into third when shifting fast at 6k+ rpms. Now it is happening at more typical situations when hustling into traffic and is now a solid crunch. I'm know how to avoid it, but as shifting a manual trans becomes a "muscle memory" affair, it is easy to forget to slow the shift down.

So nobody thinks my "new fluid will be too slippery" theory holds any water? My rudimentary understanding of synchros is that there is some kind of clutch material that grabs to get the gears to match speed. I am wondering if new fluid would just make these clutch surfaces slip more.

 

[MolaKule]

Quote:
I really don't have any idea how synchros work but I wonder if they need some "traction" to operate.
And for what it's worth, I was planning to try the Motorcraft manual trans fluid (honey) that is spec's for the MTX and costs ~$25/qrt.


http://www.bobistheoilguy.com/forums/ubb...sio#Post1231182

It might increase longetivity a tad but it won't bring back ole Synchro.

 

[jhellwig]

Originally Posted By: HerrStig
Originally Posted By: jhellwig
Stop using the clutch in that gear if you wanna keep getting by.
Just exactly how does THAT work?


You only need the clutch to get the vehical going. When you let off the gas you can slip it out of gear and when the next gear matches the input speed it will slip in without much force. Truckers only use the clutch to get the truck moving. You never clutch when shifting a splitter or a two speed rear end.

 

[Short_Bus]

Originally Posted By: jhellwig
Originally Posted By: HerrStig
Originally Posted By: jhellwig
Stop using the clutch in that gear if you wanna keep getting by.
Just exactly how does THAT work?


You only need the clutch to get the vehical going. When you let off the gas you can slip it out of gear and when the next gear matches the input speed it will slip in without much force. Truckers only use the clutch to get the truck moving. You never clutch when shifting a splitter or a two speed rear end.


I do this fairly often, typicaly when I am trundling along in slowish traffic. People should not confuse this with normal shifting when accelerating up to speed. You pull it out of gear when you are right at that equilibrium point between acceleration and deceleration. At that point there is no tension on the gears and it will slide right out. You then push gently into the next gear. You will feel the synchros start to spin up and when the engine rpms match up it will drop right in.

 

[Brybo86]

I've never done it but how much work is involved in replacing the bad synchro?

 

[Jetronic]

complete strip of the gearbox internals.

all in all a day or 2 of work.

 

[MolaKule]

There are many rebuild kit makers out there such as this one:

http://www.manualtransmissionkits.com/nv4500_bk308ws_bearing_kit_rebui.htm

You get new seals, bearings, and best of all, new synchro assemblies.

 

[dailydriver]

Originally Posted By: rooflessVW
Originally Posted By: Leo99
I'm in the don't change ATF camp but if the tranny is on its last legs, changing it might help. What do you have to lose?


The key word in his post is "synchro."

His transmission is a manual.


Yes, anything MTX in Ford speak is a MANUAL gearbox.

 

[OMCWankel]

I'm going to propose something radical that worked for me. I had a high mileage Miata with the 6 speed box and VERY worn 2nd and 3rd synchros from a previous owner. I dumped the gear oil from the box and filled with a blend. 50% conventional Valvoline GL-4 75W-90 and 50% Redline Heavy Shockproof. It cured the bad shifting. This was with 185K miles on the Miata. When I just recently sold it at 255K miles the transmission was still shifting fine (one fluid change in that interval).