Like I mentioned in one of my first posts, I thought the 1st gear synchronizer was worn until someone altered me that the 1st gear has no syncronizer.

Sometimes when I downshift from 4th to 3rd, the gearbox wants to grind. But I don't think has ever grinded when going from 2nd to 3rd.

So I'm afraid 3rd gear syncro maybe like the infamous 2nd gear syncro that always seems to fail on Fiat 124/SEAT 5 speed gearboxes.

When this occurs, it's usually if I down shift slowly. I even tried double clutching to no avail.

However I found a trick to avoid grinding. If I go from 4th to 3rd quickly without pausing, it engages like silk without any grinding. I'm not trying to be rough on my gearbox or speed shift it without the clutch or anything. I also don't want to bend any of the shifter forks. Another known notorious issue with Fiat RWD gearboxes.

I once had a Fiat X 1/9 with a knackered gearbox where just about all the synchronizers were worn. 4th may have been the only gear that was not worn.

3rd gear was particularly bad. But I found if I shifted at just the right RPM, I could get it to engage without any grinding.

Sorry not trying to compare apples to oranges. I've just owned allot of Fiats with bad gearboxes in my lifetime!

I'm wondering if any of you guys have noticed the same thing or use the same technique when going from 4th to 3rd?

I adjusted the free play on the clutch. Both nuts at the bulkhead were not even tightened up! Before the clutch used to engage about 1" off the floor. Now it engages 1" from rest. So I think I have the clutch adjusted properly.

Just shift gear calm then it usually works fine. What kind of oil is in the gearbox?

Right now I have GL-4 80/90 EP. That was the only weight I could find in GL-4 and even at that I had to order it through Amazon.com.

The oil I drained out of it seemed to have the same pungent smell of GL-5 which scared me.

The Gl-4 smelled more "pure" like GL-1 straight mineral oil.

Once again this type of oil was used by allot of Fiat owners in their gearboxes which ruined the brass syncros because it contains sulfur.

The other gears seem fine. It's just when downshifting from 4th to 3rd "too slow".

I've used some of this stuff in my Fiat Spider's gearbox and differential and it does actually quiet down whining gears. I think it basically makes the current oil "thicker". I thought about adding some of it to my 2CV's gearbox.

http://lucasoil.com/products/engine-oil ... stabilizer

My 2CV is currently on 255,000 miles, and even though the engine had new barrels and pistons in March of this year, the gearbox hasn't had any work done to it yet, so is starting to get a bit weak on second syncro. When I'm down on the British mainland it tends to crunch on the way up the gears, as I'm having to change gear quickly in order to keep up with all the traffic. It's absolutely fine and dandy up here on the very quiet roads of the Shetland Islands though, so I'm not too concerned at the moment. Hopefully get it rebuilt next Spring.

I'm not sure why mine does not grind or make any noise at all when going from 2nd to 3rd.

Or 4th gear syncro is a bit weak and that's not stopping the transmission from spinning when going back to 3rd. And why double clutching does nothing. Years ago I had a different Fiat 124 Spider with a worn 2nd syncro and to prevent it from grinding when going from 1st to 2nd I would double clutch it before going to 2nd. I can't remember if it grinded or not when going from 3rd to 2nd.

It's just when going from 4th to 3rd that it does it and not all that time at that. So I must be shifting at a specific RPM when it doesn't happen.

One thing I have noticed (and may just be a coincidence) is when the gear oil is cold, it doesn't seem to do it at all until I've put some miles on it and heated the oil up.

Like in the case of my Yugo, where 20W50 permitted easier shifting in cold weather caused grinding in 3rd gear when upshifting but going back to GL-1 90 cured (or masked) the problem, I wondered if using a heavier viscosity oil in my 2CV would help things.

Finding GL-4 in any weight is hard enough. Actually I think the 80/90 EP I used is thicker than what is recommended anyway. I believe the recommended weight is 75/80 which is not much different.

I still have enough of the Lucas oil additive to give it a try. You replace 25% of the gear oil with this stuff. But says in heavy duty applications you can add up to 50%. The MSDS says it does not contain sulfur additives. The bottle says it reduces heat which leads me to believe it simply thickens the oil. I do know the bearings in my Fiat Spider's gearbox and differential do not whine like it once did after using it.

With my Trabant, on the flip side, the freewheel device (or sprauge clutch) which kicks the drive train into neutral in 4th gear got to where it would not engage. In this case going from HLP 68 (or 30 weight) down to automatic transmission fluid (20 weight) would allow it to engage for awhile anyway. The manual says you can use SAE30 engine oil.

I tried flushing the gearbox with diesel and then it would engage every time. But using diesel fuel is not a very good lubricant.

I ended up having to have it fixed. But all the snycros in that transmission work fine!

That car is also front wheel drive but uses a mineral oil with zinc additives. It took allot of cross referencing but eventually determined HLP 68 is the German equivalent to American AW 68 which is used in tractors.

That's what baffles me. If my Yugo, 2CV and Trabant all have differentials built into the gearboxes then why does the 2CV require EP? What's so special about 2CV gearboxes?

Where I work we have various synthetic gear oils used in our pumps and equipment.

I think we have some oil that has a higher viscosity than EP 80/90 that might be compatible.

The 2CV gearbox works best with the oil what is mentioned for it. In some gearboxes, what had some odd behavior cured when changed the oil to Total BW (Gear8 now)75W80 oil. Same what I have on my Sm, works a way better than "bulk GL-4" 80W90...

If your gearbox still makes grinding noise, use double-clutch when change higher gear and blip throttle when changing to lower gears. That method works even with gearboxes without any synchromesh...


And, there is some kind of syncromesh in 1st gear, even it have straight teeth on gears. You will find that, when you take a box apart. And on normal operating, you may notice the 1st gear doesn't grind that much what the reverse gear does, there you can feel what that syncro makes at 1st gear. It isn't as good as it is on higher gears...

I will give that a shot. I noticed that if push the clutch in and shift quick enough without letting the RPMs falls when going from 4th to 3rd, it does grind at all. So I'll try blipping the throttle a bit to see what happens.

I'd rather find a technique than removing and tearing the transmission apart. Since I'm the only person who drives this car.

So I drained the oil out of the gearbox today and added 25% Lucas oil treatment and 75% GL-4 80/90 EP.

It maybe too soon to tell but I went on a 10 mile test drive. So far so good! No grinding when downshifting from 4th to 3rd and the gearbox sounds quieter. Typically the grinding from 4th to 3rd occurs after the car has been driven for about 3 miles. My theory the oil is now heated up and the viscosity drops.

The bottle says you can up to 50% for extremely knackered gearboxes and differentials. Mine is not quite there yet so I used 25%. This stuff is thick as honey and very sticky. Every retailed has a demo device on their counter with these plastic gears to show you how it sticks to gears compared to regular oil.

One thing good about it, it does not contain sulfur additives that attack brass.

I don't think it's a "miracle oil", just bumps the viscosity up.

The only downside is, the thicker gear oil may reduce HP or fuel economy a wee bit.

Here is my rig I used to get gear oil into my vehicles. I had to use a hair dryer to speed up the flow.

Looks like a flamin' 2CV Intensive Care Unit, where's the Defib.?

I don't know why I always seem to skip this step but I never heat the oil up in a boiling bucket of water before pouring it in. That would speed things up. I never tried using a microwave! That might be a "recipe" for disaster!

I've used this rig to get oil into the rear differential on a '96 Ford Explorer I once owned.



Last winter I used it to get gear oil into the transmission on my Subaru and the rear differential. Being winter time the oil was quite cold and thick so it took about a couple of hours to fill both! In the meantime I just mucked about doing something else.

I've tried those hand pumps but they are too awkward to use and one wrong move and the nipple seems to pop out of the filler hole! I end up getting more oil on the floor than in the transmission or differential!