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Author Topic: Time to do some repairs  (Read 4481 times)
Moes
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« Reply #45 on: June 21, 2020, 08:12:00 pm »

Hi

Today I took the gearbox apart.

I have attached two fotos, one of the new "locking gear" and one of the old one.

I have been measuring the inside of the two locking gears, and they a exactly the same, but the new ones have fabrication groves, as seen on the picture.

I can not feel that much difference when comparing the force it takes too compress one of the new synchromesh rings with either the a new or an old locking gear. But when trying it on an old synchromesh ring the force needed is much smaller!  

It seems the new refabrication synchromesh rings is my main issue.. The dimensions are the same (old vs. new, besides from the worn off friction material on one side of the old ones), It seems the new synchromesh rings needs more force to be compressed  Undecided  

I while ago someone at a scrapyard told me that he had been repairing simca gearbox's a couple of times back in the 70's, a he remembered that it was possible just to turn the synchromesh ring around, because the mostly got worn on one side..

I am not sure what to do right now.. I could try very carefully to polish the fabrication groves away from the inside of my new locking gears, but it seems risky, and it is probably not a good idea, and I do not think I will make much difference, even if I succeed.. It might not even be the groves but the overall shape difference between new and old I can feel. I could also choose to use a set of old synchromesh rings (the other way around)  Huh  But I really would have liked to use the new synchromesh rings...

 - Frederik        
« Last Edit: June 21, 2020, 08:17:22 pm by Moes » Logged
Anders Dinsen
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« Reply #46 on: June 23, 2020, 07:00:20 am »

I've been thinking about your problem, Frederik, and I think there may be something missing. I don't know the Bagheera gearbox, but I suspect the synchromesh also involves som locking mechanism. Could it be that mechanism that's preventing engagement - and not friction, as you seem to assume?

/Anders
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
Moes
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Posts: 166



« Reply #47 on: June 23, 2020, 11:58:14 am »

I've been thinking about your problem, Frederik, and I think there may be something missing. I don't know the Bagheera gearbox, but I suspect the synchromesh also involves som locking mechanism. Could it be that mechanism that's preventing engagement - and not friction, as you seem to assume?

/Anders

Hi Anders

This is the kind of issue where a fresh set of eyes is very much appreciated!

There is a locking mechanism; on the side of the selected gear there are dog-teeth, which will lock with the inside teeth on the "locking-gear" (as seen on the pictures above). Selecting and locking a gear seems to consist of to functions: synchronizing the speed of the selected gear with the low gear axel (the "locking-gear" moves over the synchromesh ring, and compresses it, this is where the friction material does its work), followed by the "locking-gear" dog-teeth locking with the dog-teeth on the side of the selected gear (for power transfer); this should happen in one "smooth" movement   Cheesy

At the moment I think my new synchromesh rings are to hard to compress. But it is of cause difficult to compare new synchromesh rings with old worn out ones..

Hmm mm.. what to do  Huh  

Regards Frederik
« Last Edit: June 23, 2020, 12:25:38 pm by Moes » Logged
Anders Dinsen
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« Reply #48 on: June 24, 2020, 06:40:20 am »

Hi Frederik

It's a frustrating problem, but the solution must be there somewhere.

So the old synchro didn't work well because the speed was only slowly synchronized due to the ring wear, and when you tried to engage the gear too fast, you'd then grind the gears, i.e. wear down dog teeth.

You say the synchro ring is compressed. I think I understand what you mean, but obviously the ring is not compressed. What is compressed, however, is the oil - which of course can't be compressed either, but can at least float away as the compression increases between the two faces.

Are you using the correct fluid? I would imagine that if the viscosity is too high, the oil works, but can't escape and therefore it will resist your attempt to engage the dogs?

/Anders
« Last Edit: June 24, 2020, 06:42:40 am by Anders Dinsen » Logged

'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
Moes
Sr. Member
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Posts: 166



« Reply #49 on: June 29, 2020, 01:30:55 pm »

Hi Frederik

It's a frustrating problem, but the solution must be there somewhere.

So the old synchro didn't work well because the speed was only slowly synchronized due to the ring wear, and when you tried to engage the gear too fast, you'd then grind the gears, i.e. wear down dog teeth.

You say the synchro ring is compressed. I think I understand what you mean, but obviously the ring is not compressed. What is compressed, however, is the oil - which of course can't be compressed either, but can at least float away as the compression increases between the two faces.

Are you using the correct fluid? I would imagine that if the viscosity is too high, the oil works, but can't escape and therefore it will resist your attempt to engage the dogs?

/Anders

Hi Anders

I can see that I have forgot to post a picture of a synchromesh ring, this will probably explain quite a lot  Smiley  The synchromesh ring is en "open" ring made out of some kind of hardened steel or spring steel; with a high friction material on the outer rim. That is why my best explanation is that the ring is being compressed (into a smaller diameter)  Wink

And my explanation of the problem itself might not be bulletproof..   When I mention shifting gear "fast" I should have wrote: "in a normal fashion, but too fast  for a worn synchromesh ring".  Because the ware of the dog teeth can not be avoided over time if the synchromesh ring surface is worn off, of cause double clutching and shifting gear very carefully would help. Since I bought my car (and I got it running) especially 1. and 2. gear has been very bad, and I would normally have to try to get it in gear 2-3 times before succesding..

I have used a classic Castrol EP-90 gear oil, which according to my repair manual was the originally used type of gear oil. It does seem to have a very high viscosity!

Best regards Frederik       
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Moes
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« Reply #50 on: July 27, 2020, 10:58:38 am »

Hello

Yesterday I spend a couple of hours in the garage, after a few weeks of no work on the Bagheera.

I got the spark plugs changed, a new additional air bleed nipple on the coolant system installed, and I eventually got in the mood to have a look at the gearbox.

I tried to gently grind/polish the inside surface of one of the new locking-gears (I have found out that others call them "sliders" or "sliding sleeves"), it did make a noticeable difference, but I donīt feel good about this solution.

I have decided to use my new synchromesh rings, and my old sliders, even though I have read, that the sliders should be changes when the synchromesh rings are being changed. I have decided to go with this solution because it feels much easier to push/slide the old slider onto the a new synchromeshring, that a new slider onto the new synchromesh ring.

Best regards Frederik   
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Anders Dinsen
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« Reply #51 on: August 07, 2020, 04:02:15 pm »

Hello

Yesterday I spend a couple of hours in the garage, after a few weeks of no work on the Bagheera.

I got the spark plugs changed, a new additional air bleed nipple on the coolant system installed, and I eventually got in the mood to have a look at the gearbox.

I tried to gently grind/polish the inside surface of one of the new locking-gears (I have found out that others call them "sliders" or "sliding sleeves"), it did make a noticeable difference, but I donīt feel good about this solution.

I have decided to use my new synchromesh rings, and my old sliders, even though I have read, that the sliders should be changes when the synchromesh rings are being changed. I have decided to go with this solution because it feels much easier to push/slide the old slider onto the a new synchromeshring, that a new slider onto the new synchromesh ring.

Best regards Frederik   

This is interesting. It's always risky to combine different parts, but at the end of the day what matters is how it works. Have you made progress on this job? Sorry for not checking the forum for the past weeks!

/Anders
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
Moes
Sr. Member
****
Posts: 166



« Reply #52 on: August 10, 2020, 09:59:44 am »

Hi Anders

I managed to get the gearbox back together and installed. But sadly my "solution" was not good enough..

2.,3. and 4. gear works..  but it takes to much force to get it in and out of gear, and I am not able to get it in 1. gear..  so I will be removing the gearbox once more  Undecided

Next attempt will be with with the old sliders, and old synchromeshrings; but with the synchromeshrings turned 180 degrees. And then that's it.. I am pretty sure this will result in a working gearbox, and with my expected low yearly milage in the car, it probably will be just fine. But a little bit annoying that I won't be using my new sliders or synchromeshrings..

I plan on doing my "next attempt" the upcoming weekend.

Have a great week!

Best regards Frederik

     
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