1979 930 Turbo shifting issues

[Scott_Tucker]

Hi,

I have a 1979 930 Turbo that is having some shifting problem.

When you step on the clutch pedal and put into into reverse when you are stopped, it grinds going into gear like the input shaft is still spinning.

In addition, when you do quick upshifts (not bang shifting, but spirited shifting) it grinds going into second and third. It also grinds on downshifts into those gears.

We have replaced all clutch components including the flywheel, pressure plate, disk, pilot bearing, and throwout bearing. I suspect it is in the clutch because the input shaft needs to still be spinning in order for it to grind going into reverse. It seems like the clutch is not releasing all the way.

If it did not grind in reverse, I would have suspected it had bad synchros. It did not grind before we replaced the clutch.

We have tried swepco 201 85w/90, swepco 203 90 weight, and Redline lightweight shockproof oil. What oil is normally used in these gearboxes for best shifting?

Is this a common problem on these vehicles?

Any direction would be great.

Thank you.

[ELZ's930]

I'm sure you have, but did you double check the clutch travel? There should be no grinding. If you can find all gears then it most likely isn't a coupler alignment issue.

Also when engaging reverse, give the shaft time to stop spinning before selecting reverse.

[willtel]

I always had to double clutch reverse on mine to keep it from grinding.

[Scott_Tucker]

I've called some different Porsche shops and they say don't worry about the reverse issue, it is completely normal. And honestly, as long as you delay shifting into reverse after depressing the clutch, it shifts OK.

Its the 2nd and 3rd grinding that is bugging me. I read a lot of places on the internet that say the synchros on these transmissions is a weak point and that you basically have to baby it when shifting. I am OK with that as long as I am hearing from people who are experienced.

I don't want to have to tear down the transmission if this is a normal characteristic since there sounds like there would be a slim chance it would fix it.

Can anyone give me a recommendation on gear oil? What number Swepco? Do you think putting a thicker tranmission fluid such as redline heavy shockproof gear oil in it will help?

[ELZ's930]

If the clutch travel checks out then you may be dealing with the previous owners poor shifting habits. There should be no grinding. It sounds like you have figured out how to minimize the grinding but with proper shifting it should shift well.

The syncros are a weak point ( especially 2nd and 3rd as those are often "rushed" ) but some folks have managed to make them last for 100K miles.

I don't think the oil will make a difference but would be cheap enough to check.

Good Luck,
Leonard

[OldSpool87]

Reverse for me requires a 3 Mississippi count prior to selection and engagement. Deliberate shifts with a split second pause in the neutral part of the gate and no grind. If I shift too quick from 2nd to 3rd I'll get a reminder. I read somewhere that you can actually have gear oil that's too slippery for the 930 box synchros. I'm certainly no expert in any if this.

[DSPTurtle]

Mobil 1 75/90 works well in both my boxes. But I did rebuild both when they first came into the family.
Shift into 2nd and then reverse and you'll have no grinding.
Slow up shifts are reality. Replacing synchros will make it a little better but under no circumstances will you ever be able to speed shift these boxes. The synchro design won't allow for it. It's not hard to do, but the synchro parts are dang expensive.

[gsxrken]

Originally Posted by Scott_Tucker

It did not grind before we replaced the clutch.

If that's true, you need to look at the clutch and the true travel you are getting.

Sometimes a bent or cracked fork can not be applying the travel you think you are getting.
Are you going by the shop manual for adjustment procedure?
Are the parts reputable and confirmed to be matching the old ones?

[zcoker]

I had grinding problems like you described and tried everything with no results. Once I rebuilt the transmission, I've had no grinding no matter how fast I shift. The worn parts inside the transmission were very apparent and I could see that no masking would've done anything to stop it. You have to take a few deep breaths, though, before you venture into a transmission rebuild, that is, if you are going to do it yourself. It's a bit different from a motor rebuild. Sure does save on money doing it yourself and it's fun, too. There's a few threads on here that walk you through the process. A couple of horror stories, too. So be careful.

[proffighter]

Just before you disassemble the tranny

I had grinding issues as well and it would be a big chance but check the rollpin at the clutch pedal, mine was sheared... started with a little scratching and went to impossible to shift