Can anyone help me with a 1971 240Z gearbox problem?

240z, 260z, 280z

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Can anyone help me with a 1971 240Z gearbox problem?

Post by toycollector10 » Fri Mar 01, 2019 8:01 pm

Hi Guys,
After restoring my car from radiator to differential including the engine I am still having problems. My NZ new car has a 5 speed gearbox and it started to make a bad noise on overrun in 2nd gear. I took it to a gearbox specialist who diagnosed too much lash. The box was reassembled with a bearing and gasket kit. When it was handed over to me the box was very stiff. I had to literally push and pull the lever to change gears. That is, it wasn't "buttery" like it should have been. I took it back under warranty and they diagnosed that it had Porsche type synchromesh. The owner of the business told me that they had reversed the synchro's on re-assembly, i.e. flipped them, as they are reversible. He claims that by doing this I now have in effect new synchros and stiffness is normal. Apparently this is a normal procedure. I don't doubt his honesty but I would just like to know if anyone has had experience with this issue.

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Post by bernjean » Tue Mar 05, 2019 2:29 pm

Never heard of it, sounds suspect to me. Call up some other gearbox guys and ask them the question?
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Post by Baker93 » Wed Mar 06, 2019 6:58 am

The term Porsche style synchro just refers to the type of synchro band in your particular box. Simplistically some cars had metal style bands and others had brass/bronze bands ( or some such material. ) They didn't diagnose this. It just has them.

Reversing synchro bands can be done to eek a little more life out of them as one side of a band will wear more than the other under normal driving conditions.
I don't know if this is normal procedure for them it obviously is. I guess it depends on the brief that you gave them and what you have been charged for.
I have done this myself many years ago but I personally would not do this on a customer car. As i said it can be done but i don't recommend it, especially on the intermediate gears as the synchro gets used in both directions ie as you change up and down through the gears. It is sort of ok to do on 1st and 5th. If you think about it you never change up into first or down into 5th this leaves one side of those bands in good condition. Obviously there is a little more to it as there are quite a few other parts to a synchro arrangement that wear.

With regard to it being stiff hard to change and it being normal.
Umm... no !
Was it like this when the car was new ? I think not.

You don,t in effect have new synchros. You have reversed old synchros that are running on a face they haven't run on before.

It is not assembled correctly. Or something is wrong.
Personally i would be finding someone who knows what they are doing and stops telling you porkies.

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