Gearbox selection issues....

[roadiesean]

Hi all ! Me again !!!

Okay so when I bought my car the gearbox was seriously Mr Floppy, seriously ! So I changed all the bushings from front to back. It's now much better than before.

But......

When I'm driving some times the shift is perfect, other times it's just like the gate is in the wrong place and every shift hits the horrible noisy thing that sounds like the gates of hell have arrived.

When I did the bushing at the back under the little peep hole in between the two back seats I set the position as per the book because it initially it was slightly off.

I was out today and it was literally like every shift was 5mm out and you hit the gears every time. When I got home with the engine idling every gear went in like a knife through butter absolutely perfectly.

What it feels like is when you are accelerating and then jumping off the accelerator onto the clutch in the usual gearchange fashion, the engine rocking from side to side is causing the gears to not select properly. Could it be the problem is with the gearbox or engine bushings ? Every piece of rubber or hard plastic that I've taken off the car is completely knackered so I'm sure they are too.

Any help/thoughts/suggestions etc guys, as usual, gratefully received !!!!

[SeanP]

I would change the engine and gearbox mounts as you suggest

Made a huge improvement when I did mine

Sean

[Timo]

Yep, I had a beetle that used to do a similar thing, changed the knackered gearbox mounts and it fixed the problem.

[roadiesean]

So any idea where to get new mount bushings from ? I'll do the engine and gearbox at the same time, I know they'll both be knackered. I keep reading that the aftermarket ones are too stiff and transmit a lot of noise and vibrations. Mine are so bad that they need doing regardless of this, but I would prefer them not to be too bad !!!

Any ideas ???

Oh and are the ones for our cars different to the 911 ones of the same vintage ?? I thought they shared the 5 speed gearbox that mine has !

[Timo]

912 gearboxes used a different mount to 911s for some reason. The big rubber cubes used on the engine mounts are also used on the gearbox mount so you will need 2 for the gearbox and either 2, 4, or 6 for your engine depending what year car you have. You should be able to source them from Porsche or any of the 912 parts suppliers such as roger bray or revival cars.

[roadiesean]

Fantastic Timo, thanks very much.

[neilbardsley]

912 gearboxes used a different mount to 911s for some reason.

That doesn't make any sense? Same gearbox, same body but different mounts! I believe you but why?

[Timo]

I know it sounds weird Neil but it is true. The only thing I can think of is that maybe a 911 needs a bit more support due to increased acceleration forces, maybe more force travels through to the mounts?

[Nine One One]

I fitted a 911 gearbox mount to my 912 Targa, with no issues at all, the only issue I had was sourcing the correct bolts with the right taper on them for the mount to body.

It certainly makes it more sturdy, and there is no difference in road noise or vibration that I can tell

Ian

[Bruce M]

I thought the 912 mounts were different because (1) the is less torque twisting the mounts & (2) the 4 bang engine is inherently less smooth than the six and the 912 mount provided more noise isolation.


But I'm probably wrong

[SeanP]

It depends on the year of the car my 66 has the same mounts as a 911 from the factory. I think the change over year was 68

[roadiesean]

I've got underneath the car this morning and I have to say the mountings look perfect, they are still "squishy" so they haven't gone all hard. I'm wondering whether the position I have set for the rear UJ in the gear linkages is absolutely spot on, I've had a fiddle and we'll see how she goes........

[camperco]

Possibly too squishy your gearbox might be moving upwards under load. When you lift to change gear it moves in the opposite direction moving the shift rod with it.

[Nick Moss]

Make sure that the clamp at the back of the gear change shaft is nipped up tightly, it's very common, if this is slightly loose, for the gear change pattern to move around.

[roadiesean]

Thanks Nick and Angus, yes the clamp is good and tight and I think maybe part of the problem is that its very slightly out of alignment (you know getting the gearrod and the UJ and the spigot into the gearbox just right) I had a fettle the other day and it is better, but still not right and yes Angus, they are squishy, this could be a problem ???? Not knowing what "normal" feels like I just don't know. Max at Revival thought not mounting bushings.....

Driving me nuts.