International Lancia Forums

Some weeks ago I overhauled the gearbox of a 1975 Fulvia Monte Carlo. Input shaft was bent. As a consequence the needle bearing and the seal were destroyed resulting in massive oil leakage.
I followed normal procedure and also replaced all other seals and checked the synchro rings. Synchro 3 had 0,8 mm which is near the minimum of 0,6 mm. I replaced synchro ring 3. The other 4 synchro rings had more than 1,1 mm which means "like new". One possible conclusion is that #3 wears quicker than the others.

After 200 km the customer complained that he could not put it in 3rd gear without severe teeth brushing. It often happens that a synchro has to be driven in so we decided to try another 200 km. It did not get any better. I test drove the car and deed indeed find the 3 to be too bad to be solved by running in, all others fine.

Today I opened the gearbox and found that syncro ring three actually had a negative clearance meaning the flanges touched while the sharp circles did not touch at all. All other synchro's were also worn to below the minimum of 0,6. #5 even as low as 0,2. The mileage is now 700 km.

The gearbox was filled with Millers CRX 75W90 fully synthetic gearbox oil which I have been using for a number of years on my own cars as well as customer's cars. No problems. Elena has done 200.000 km with it and still shifts like a new car. Tina has done 32.000 km after synchro replacement. No problem.

I have absolutely no idea what could cause all synchro's to totally wear within 700 km. #3 most probably even within 200 km. Many years ago synthetic gearbox oil could dissolve yellow metals. This is a long long time ago and Millers guarantees their oil does not do that. This is proven by the fact there is no problem on other gearboxes.

I can understand a problem with one synchro ring. Bad repro part (parts were assured to be original Lancia) or assembly error (hardly possible but nevertheless).
I cannot understand why 5 rings went bad practically before the car turned a corner.

The only possible reasons I can see are:
1) clutch did not fully release. When I test drove the car I was expecting a problem on 3 only and did not fully test the clutch. On the other hand I would have noticed if it was not working properly.
2) a problem with the oil. I spoke to one of the technical persons of Millers today. He assured me it is not possible the oil could be the cause. Nevertheless I am sending a sample of virgin oil from my stock and a sample of the oil drained from the gearbox to Millers for analysis.

Can anybody think of any other possible cause?

Huib

Is there metal debris in the gearbox?

If the oil "dissolved" the rings, then would there be any metal debris in the gearbox or does the oil absorb the metal?

If the rings are worn by mechanical means ( bad clutch or whatever) then there should be metal debris in the gearbox.

It is surprising that all 5 rings have worn, so there has to be a common fault. So they all have to be not installed properly or the oil which is common to all, must be a factor.


Regards

Michael

Michael

There was very little steel on the magnets of the drain plugs. Probably came from the teeth of #3 gear wheel.
The synchro rings are bronze. There is a strange substance in the oil remaining in the right hand gearbox half after opening. This could be the bronze from the rings. Tomorrow (wednesday) morning the dutch agent for Millers will pick up the samples and send them off to the factory in the UK for analysis. We will probably know monday or tuesday.

If the oil attacked the bronze there should also be damage on the outside of the rings. There isn't.

Installing even one ring the wrong way is impossible as it won't be possible to put the tightly fitting shaft in place. Not installing 5 rings properly is 500% impossible mechanically as well as very unlikely statistically

Another thing is that I grind the bronze rings against the steel cones on the gear wheels using valve lapping paste. I did change the brand of lapping paste earlier in the year and used it on several gear boxes among which this one. The parts go into the cleaning tank after the grinding but minute amounts of lapping paste may have been left. After lapping the braking action is a lot better but the rings have a tendency to stick to the steel cone is you rub them against each other with your hands. I have been doing this grinding for a number of years and never had a problem like this.

There is a story of another gearbox. We restored a very early1200 coupe this year. During test driving two weeks ago the gear shift was exceptionally smooth and precise. However the gearbox leaked along one side at the very rear part. Initially I thought it to be one of the long bolts going though the gearbox. In fact the rear most one also holding the mounting bracket. The O ring under the washer under the head was indeed damaged. Replacing it did not solve the problem. Friday Claire diagnosed it to come from the shaft of the fork operating 1st and 2nd gear. The shaft sticks out of the rear of the gearbox. She then took the gearbox off and replaced the O ring. I keep all the gearbox seals, O rings etc in stock. We found that the bag with the particular O rings contained two sizes. One the right size and the other slightly thinner. The thinner one was in there.This morning I started putting the gearbox back onto the 1200 coupe but stopped working on it when some one else had opened the 5 speed Monte Carlo gearbox. I just talked it over with Claire and we decided to drop the 1200 gearbox again and open it for inspection. It is now easy to do as it is only attached to the engine with only a few bolts. The reason is that it may be filled with oil from the same 5 liter can and the same lapping paste was used. It has driven some 400 km's. If it has the same problem the rings should have worn a lot.

I will let everybody know.

this is a sherlock holmes crime-solving adventure..with lots of mysterious characters appearing:
Clair with greasy hands (which impresses me), Elena, Huib , Millers Beer, Michael, at least 1 mystified
Fulvia-Walker or is it now 2 (who can't be fulvia-drivers with no gearboxs in their Fulvia's) & now "me"
(standin on the sidelines) & every 1 else in the Fulvia-world who wants to know " Who Dunnit" ! .

I haven't had time yet to open the 1200 gearbox. The 5 speed gearbox was occupying the bench and had to be assembled first. I did drain the oil. Does not look good.

The 1200 gearbox was taken apart today. All 4 synchromesh rings had worn 50 to 70% (50 to 30% useful life remaining). This happened over 436 km. It corresponds with the wear pattern of the Coupe Monte Carlo.
The cause is still a mystery.

Huib,
That amount of wear after only 436 km must be caused by an abrasive contaminant; either a bad batch of gear oil or (more likely) that new lapping paste you're using.

When it comes to mechanics, I don't believe in coincidences; if this problem only started to occur after you changed to a different lapping paste, then that is very likely your answer.

Sounds indeed logical, Ed, except that it is washed off from the parts before they are put on the main shaft..

Another change I made is the type of cleaning liquid in the cleaning tank. This was done over a year ago.

Both gearboxes have been assembled with new synchro rings. What I plan to do is to fill them with low cost EP90 oil, run them for 15 minutes, drain the oil and fill with the 75W90 synthetic oil. Just to make sure any remains of the old oil, remaining lapping paste and cleaner are flushed out

Huib, if the change in cleaning fluid was made a year ago and you're just now having this problem, then it probably isn't the cleaning fluid. Problems don't cause themselves spontaneously, but neither does something this serious wait a year to show up.

You have undue wear, and if we rule out assembly problems, then very few possibilities remain. If the synchros rings are good, then the lubrication must be itself bad or there must be contamination from a third substance. If the lubrication is good and not contaminated, then the syncho rings must be wearing too quickly from bad metallurgy (are they all from the same batch?).

Theoretically, it's possible that you have a bad batch of synchro rings *and* contaminated lubrication, but that's one of those improbable coincidences, and I'm just not a big believer in coincidences. Of course, the only other variable is assembly.

Unfortunately I did not keep a record when changing the cleaning fluid nor the lapping paste nor how many gear boxes I did when. I have done quite a few over the last few years. All other gearboxes I have done including the one on Tina, the 67 coupe which I use daily have done considerable mileage in the meantime. For the moment I assume they do not have the problem.

There is at least one other gearbox done early spring which was done using the same lapping paste and cleaning fluid and also filled with the Millers CRX. As far as I know, no problem.

On the 1975 S3 gearbox only one ring was replaced. The others were the original ones. This eliminates the possibility they were all from the same batch. This was done say 6 weeks ago

On the 1965 1200 gearbox all synchro's were replaced. This was done in spring. They may all have been from the same batch.

I lap the rings on the cone using lapping paste untill the braking force is all right. I even do that on original rings good enough to go back. This was recommended by the factory in the 60's and standard practice with Lancia dealers for Flavia and Fulvia gearboxes. The workshop manual also says the rings have to be lapped. It does not noticeably change the clearance which is measured again anyway before cone and ring go back onto the shaft. If it is under 1 mm for used ones or 1,1 mm for new ones, they don't go onto the shaft. The parts are washed in the cleaning tank. Some paste may be left.

I stock the oil in 5 liter cans. I have one can left which has 1,5 liter in it. The used 3,5 liters are most probably used as follows:
2,5 liter in the S3 gearbox
1 liter in the 1200 gearbox
If this is the case, 1,5 liter for the 1200 gearbox must have come from another can. If I had two cans from a bad batch of oil, there must be 3,5 liter around in other gearboxes unless a gearbox was drained soon after assembly and testing and the oil was thrown away which does occasionally happen. BTW, I did not test run these gearboxes on the bench.

Assembly error is hardly possible, unlikely to be the same error on a total of 9 gears and no evidence found when diagnosing the gear boxes.

Another possibility is electricity which sort of tries to weld the parts together. Unlikely on a Fulvia gearbox, very unlikely on two Fulvia gearboxes of different models and I checked for brown spots. Found none.

When examining the S3 gearbox a bad clutch was a possibility. It is unlikely two Fulvia's had a bad clutch.

I agree with you that either the oil was bad or it was contaminated. If the latter, most likely by remaining particles of the lapping paste.