Need new syncros. DIY-able?

[bebbetufs]

I can hardly find any gears when the box is cold. This is unfortunate as it is quite often cold over here in Norway. The RS has never been on sale here and there are almost no used or rebuilt parts available. I am the third owner, so no help from Reanault. I can't afford a new box, so I think I need to look to the uk for a rebuilt. Question is can I rebuild it myself. I have all the engine related tools, but I don't have a lot of pullers and other gear box realated stuff. Should I get a rebuilt box, or get the tools and do it over the christmas holidays?

If it is too troublesome to DIY it, could it get a non RS box? What lowish cost options do I have?

 

[shotgunsjay]

Try different gearbox oil maybe?

 

[Paddy_R]

Different oil would be my first port of call. Its the easiest thing to change and the cheapest. As for the actual box somebody posted on here recently somewhere that was selling new boxes for RS Clios for around £400. Might be expensive to ship though.

 

[Mentalpen]

You can't diy a boy as you need a press etc

 

[bebbetufs]

I have changed the oil to RedLine. Could it be that the RedLine is too slippery? I only have trouble when the box is cold. As soon as to oil is hot it the shifts are smooth as they can be.

I have access to several presses, but they are in different locations, and it could be tricky if parts need to be heated to remove and reassemble. I'm more worried about any expensive specialist equipment to set clearances and friction etc.

 

[Foxspeed]

I think its a do-able diy...I stripped one down to its major parts with only a couple of tools...

as for the fault - don't think its the synchros - the gearboxes are like that over here when its cold - might be better going for a "thinner" oil
in the colder weather and then changing it when it gets warmer...

 

[bebbetufs]

Thanks for the heads up. I have it hooked up to an engine heater in the garage so goint to work is not such a pain, but today i had to wait ten minutes for the box to heat up enough to select any gear before I could return from work. Do you have any experience with a thinner oil. After all a thinner oil will cost somewhere like 25% of the price of a new box (ex shipping of course) so it would suck if changing the oil doesn't work.

Which oil would you recommend? I have looked and the recommended oil is pretty thin already, RedLine does not offer any thinner, as far as I know.

 

[Womble]

My findings with the oils, is that despite everyone going on about putting different makes of oil in, mine is better with the Renault stuff in. My tightness was down to a lack of oil in the box and the linkage. I too tried Other makes and blends of oils as mentioned on here. It maybe that the oil just needs changing every year, as it breaks down. For the time it takes to change I would try the Renault stuff back in and check your gear linkage.

 

[bebbetufs]

Thanks. I got a quote of £520 for a new box from the uk. Not too bad considering, but I will take a look at the oil level first, and check the price of the renault oil as well.

Does anyone know the technical explanation for why the syncros will lock when the oil/box is cold?

 

[Womble]

I'm not a 100% but it maybe a case of the oil causing them to stick together! hence why it is better when hot! could be the materials used, clearances, who knows really?

 

[Phil_RS]

I also don't think that the oil is your biggest problem.
The problem comes from the material combination and the matching/clearance/seat of the parts.
Mine needs around 30 minutes of driving if it stood a night outside with -5° before it is starting to work very fine.
I also drove a 265 today and it felt almost the same because it was parked outside for a few days with atleast -1°.
The gearbox oil only takes 10-15 minutes to get warm, but the parts need much longer to get the temperature they need to have their proper clearance/seat.

 

[bebbetufs]

Normally, when the synchros are bad you would expect a grinding noice as the gears are trying to mesh while running different speed. I have no grinding or crunching. Instead the gears are completely locked and there is no way to select them, more like trying to select first at too high speed because the speed mismatch between the input and output shafts is too great.

When my box is locked trying to select a gear causes a noticeable jolt/rocking motion in the car indicating that the input shaft is not completely free/the clutch is dragging. Do you get this rocking motion/jolt in the car as well?

Could the problem be clutch related? Or perhaps the pilot bearing in the end of the crank is bad/dragging when cold causing the input shaft to rotate enough to keep the gears from lining up and with the shaft? I did change brake fluid and bleed the brakes this season, could air have gotten into the clutch line causing it to drag when the air and fluid are cold? Another indicator of a dragging clutch/pilot bearing could be that it is sometimes notchy when pulling it out of a gear as well, a phase of the shifting where the synchros do no work at all, although it could just be me being lazy with the clutch pedal.

I still think you might be on to something, seems strange that this box is machined with such sensitive tolerances though. Today it is +7 and the box shifts from cold without problem. At +1 degree it is impossible to select a gear without rocking the car back and forth or waiting for it to warm up.

I'm considering buying a heating pad for the box to be able to heat it with battery power or grid power. Since it only takes a few degrees it should not need a lot of A/H to make a difference.

For those who want to learn how synchros work take a look at this nice video.
[video]www.youtube.com/watch?v=MXsRfbOiBhE[/video]

 

[Foxspeed]

once the gearbox has been used the internal parts bed-in and will work fine irrespective of the materials used as that is designed in to the gearbox...

there is clearance in the box and various components as I have had one apart!!!

the oil can act or cause drag inside the box when cold/thicker - remember how torque converters work....

in your own post you have just put if its "warmer" it goes in gear but when "colder" is very bad for gears - could this be a clue

 

[bebbetufs]

the oil can act or cause drag inside the box when cold/thicker - remember how torque converters work....

Do you think this drag is enough to make the input shaft spin?

in your own post you have just put if its "warmer" it goes in gear but when "colder" is very bad for gears - could this be a clue

It is a clue, for sure, but I'm not sure I understand what you mean to say. Is the cold oil thick enough to prevent the slider from sliding into place?

Ok, so I watched the video I posted once more and think I found a clue. He says that the worn rings have ridges, almost like threads, on the inner cone surface where the synchros grip the cone of the gear. These are to cut through the oil film on the gear. Could it be that the oil is to thick for the worn ridges of my bad synchros to cut through it and grab the cone of the gear?

 

[Foxspeed]

I used a 75w-90 oil in mine and then when I did the last oil change on the box went 75w-80 and the change was a lot better when cold

 

[bebbetufs]

I used a 75w-90 oil in mine and then when I did the last oil change on the box went 75w-80 and the change was a lot better when cold

This indicates that the syncros don't cut the thicker oil as they need to. Too bad I'm already on 75w-80.