915 Shifting improvements summary

Vereeken · 05-02-2009, 01:47 AM

Thought I would share.

This is for a 911 SC 1983 (last batch) ROW with a difficult gearbox transmission most certainly when cold. The clutch is new (<5000km).

Symptoms:

1 Slight clutch shudder when moving away when cold.
2 Difficult to select first when coming down from two.

I replaced the following one by one and then drove it:

1.changed transmission oil to SWEPCO. Major improvement in smoothness. Point 1 and 2 not solved.
2. Adjusted bush linking between rear seats following instructions on Pelican. No improvement. Bushing seemed fine and not collapsed.
3. Replaced clutch cable. No improvement on 2 but more feel to the cluctch. Had to readjust several times. 1 improved but not completely solved.
4. Replaced motor mounts with OEM rubber mounts no change at all.
5. Replaced transmission mounts. 1 and 2 gone as if it where a miracle.

Hope this helps someone.

Kr

Michel

runfaster · 05-02-2009, 07:25 AM

Cool...

86911cab · 05-03-2009, 07:47 AM

Changing the Tranny mounts helped that? I have similar problems.

Anyone else changed their mounts and get the same results?

I might have to try that.

JoeyD911 · JoeyD911's Garage

Changed the motor mounts and tranny mounts after I broke the cross mount on the engine. Chased shifting demons for months, adjusted everything I could with no success. Replaced all the shifter bushings and rebuilt the shift coupler, better but still not the fix. Put the new mounts in and it was like I just rebuilt the trans. If you've got the original mounts in the car, it's one of the best things you can do. Simple to do and a cheap project anyone can do in a couple of hours.

GaryR · GaryR's Garage

Makes sense, if the transmission can move on it's mount all kinds of strange things will occur. Mounts and bushings, oil change, and shifter u-joint should be the 1st things tackled on an old 915. At least at that point (after a proper adjustment) you can start looking at internals.

86911cab · 05-03-2009, 08:30 AM

I am on my second tranny oil change (swepco), changed all shifter bushings, and adjusted the linkage. There was a big difference, but I want to get it as smooth as possible.

Great info
Thanks Guys!

Vereeken · 05-03-2009, 09:09 AM

Quote:

Originally Posted by 86911cab

Changing the Tranny mounts helped that? I have similar problems.

Anyone else changed their mounts and get the same results?

I might have to try that.

Yes, this was of each of the items noted above the one with the biggest improvement.

As I said I did every project as a stand-alone, then drove it so I could establish which had the biggest effect. I have the standard engine and transmission mounts inserted (so no Wevo or whatever these things are called.).

Also a prefectly adjusted clutch cable gives a lot for its money. Easy but you need a ramp.

Michel

jvrrdrgz5 · jvrrdrgz5's Garage

I found OEM rubber and solid mounts, which are better to use to fix the shifting concerns?

Vereeken · 05-03-2009, 09:59 AM

Quote:

Originally Posted by jvrrdrgz5

I found OEM rubber and solid mounts, which are better to use to fix the shifting concerns?

Solid. But on a street car I find that unbearable (noise and vibration comes into cabin.. Good on a race car though. Michel

Gunter · Gunter's Garage

Quote:

Originally Posted by 86911cab

Changing the Tranny mounts helped that? I have similar problems.

Anyone else changed their mounts and get the same results?

I might have to try that.

The mounts get compressed over time resulting in a change in the alignment of shift components like the shift-rod vs. the shift-shaft in the transmission.

You can tell how bad the mounts are worn by climbing under the car and observe the space between the rubber insert and the concave washers.

You can also put a floor jack under the transmission and notice how much you can lift the transmission meaning: the play in the mounts that shouldn't be there.

I would go with the mounts first, then the coupler bushings, then the rest of the components like bushings in the tower.

911mnypt · 05-09-2009, 09:07 PM

I just did my trany mounts today and I can't believe what a difference it made. Shifting smoother, noise & vibration total gone.

oregonmon · oregonmon's Garage

This is the post I've been searching for. I suspected my mounts but I am 98 percent sure my shuddering and gear lever popping out of first at launch will be fixed with new ones.
Thanks for the post.

fred cook · fred cook's Garage

When I re-conditioned my tranny I replaced all the engine/transmission mounts with the "sport" mounts. Big improvement. I also (later) installed the factory short shift kit along with a new coupler and shift rod bushing. Now the gearbox feels like it is working thru a shift gate. Very nice feel and the throws are considerablyshorter.

JoeyD911 · JoeyD911's Garage

oregonmon, the popping out of gear is more a symptom of a shift coupler adjustment. Mine still does it occasionally, and I've done all the improvement items short of a tranny internals refresh.

williecoyote · 05-10-2009, 04:43 AM

At this point, I have had everything done in my car except the mounts.
The Swepco, and the coupling have helped a good bit.
The mounts are next on the list.
Thanks for posting this.

ralphnct · 05-10-2009, 05:02 AM

I had similar problems with shifting and clutch shudder. Replaced the motor and transmission mounts with WEVO mounts with the softer black inserts this past winter. So far, the shifting and shudder problems are gone and no noticeable increase in vibration. I only have about 100 miles on the car since the change so may not have seen it under all circumstances.

I also bought a replacement clutch cable with appropriate bushings and springs. I'm starting to think I won't need to install it.

Ralph