Syncronizers going out.

[Guest silverbullet]

I have a 77-280 with a 5 speed, about a year and a half ago I replaced my clutch with a centerforce dual friction unit, when I did that I found that I couldn't get the fill plug out so after taking the trans out I took it to a local trans shop and had them replace the front cover gasket and the input and output seals after they removed the plug, after installing I put Redline MTF in it along with a shot of Z-MAX friction reducer and I found that it shifted much better and after getting it on the freeway noticed much less heat buildup but shortly after that I noticed my 2nd and 3rd gear syncros were getting very weak where before they were just fine, do you think it was the Z-MAX getting into the syncros and reducing friction so much that I now have to replace them, and if so how hard a job is that(never worked on the inside of a manual trans)and what is the difference between a full blown rebuild and just an overhaul?

[Mike C]

The trans has to completely come apart to replace synchros. Get a factory service manual and decide it it is a project you can handle. The oil should not have affected it, just age most likely. I've never heard of anything being damaged from too LITTLE friction...(It's the 1-2 synchro on my ZX 5 speed) IMO, a rebuild and overhaul are the same thing. I guess the difference might be replacing what HAS to be replaced (like the first time you had your trans worked on) vs. replacing ALL of the wear parts: synchros, bearings, bushings, seals, etc.

[Guest silverbullet]

Originally posted by Mike C:

I've never heard of anything being damaged from too LITTLE friction

Thanks for the reply Mike, I was just wondering though I know that you do need a certain amount of friction for certain things to work properly: clutches/clutch packs(autos.)etc... aren't the syncronizers in a manual tranny basically just a small clutch pack? My theory was that if that is the case to much friction reduction would make it very hard for them to do the job, please let me know if I am wrong as I freely admit my manual trans experience is very limited

[Mike C]

I believe that the synchronizers use the viscosity of the fluid to help match speed on shifts and not the lubrication. They are not really clutch packs but lots of little teeth that just cause the sliders to fall into alignment when moving the shifter handle. They are made of brass in order to be the wear item so that when shifting gets notchy, you can replace synchros and not have to replace the sliders and speed gears.

[johnc]

Actually, the synchros in the 4 speed (and I assume the 5 speed too) need some drag from the transmission fluid to work correctly. Too little friction will cause exactly the sysptoms you describe. I lost the 2/3 syncros in one of my 4 speeds immediately after switching to Swepco low friction gear oil.

[Mike C]

Exactly what I was saying by the VISCOSITY of the fluid. Maybe I should have thought of a better way to phrase it... The most important factor is AMOUNT of fluid. Keep your trans full for best performance and life expectancy. Look at the T5 where they switched fluids from 80w90 to Dexron II ATF. This was done because the thicker oil could not adequetely penetrate the needle bearings used on the speed gears when they switched to the "World Class" designation. They changed the style of syncronizer as well (to paper cone) in order to have them function with the new characteristics of ATF.

[Guest silverbullet]

So it is fluid viscosity that lets the syncros do their thing, now that makes sense as to what was happening before, I had some very high quality conventional oil in before and at room temp. it seemed to be a little thicker than the Redline and would shift hard in the morning when it was cold untill I built up a little heat then shifted fine so maybe it was kind of masking some wear in the syncros? Anyway it is not to bad unless I am getting on it(speed shifting) so maybe I will just take it easy except for when I don't want someone to pass me .Thanks for the enlightenment guys

[pparaska]

It's not really the viscosity. It's the friction coefficient between the synchro and gear that you have with a particular fluid. This is not related to the viscosity (although that's a secondary effect), but the makeup of the fluid. The Redline MTL is a special higher friction formulation. It did wonders for my Eclipse GSX. I'm using BG Synchroshift now, as it was found by others that the lower weight of the MTL was not "thick" enough to stay in some bearings and some experienced premature wear.

 

In my Tremec, I'm using GM Synchromesh. That's what Tremec says to use, so I listen to them.

"Michael" Ol thinks it shifts worse than his worn out Doug Nash 5spd though . I'm used to it. Doesn't bother me at all. Much of my Tremec's shifting "stiffness" has to do with a very short shifter handle. Gotta address that too...

[Guest silverbullet]

Originally posted by pparaska:

it was found by others that the lower weight of the MTL was not "thick" enough to stay in some bearings and some experienced premature wear.

 

do you think that I should replace the Redline? It will probably be another couple of years till I can afford to put the chev. sml. blk. in it and I do need to make it last.