Pop out of 4th gear

[Early911SC]

Vert original SC with 41k mi new clutch a while back. It happens all of a sudden, I could engage into 4th but as I engage the clutch it would pop out of the 4th position into neutral. My driving been around town so I skip 4th and goes the 5th if necessary. I drain the transmission gear oil and found no metal or metallic debris in the magnetic drain plug. I pull the cover and check the bushings in the shift coupling and found no excessive play. Any suggestions before I bring her to local shop?

[rwest]

Since 4th gear doesn’t get much use, I would suspect a linkage, bushing or adjustment problem before I would think its internal.

Besides the tunnel coupler, you have a bushing at the bottom of the shift lever and one in the tunnel that holds the shift rod in place. Bot are pretty easy to replace.

You could also just need to adjust the shift coupler- there are some YouTube videos on doing it.

[Early911SC]

Btw she an early 1978 SC, I had a 76S for many years with close to 200k mi. Upon retirement traded her for this low mileage SC. In the past I modified mine with short shift kit and may be in older now. I like the factory long throw 915 transmission the way it is. It shift positively although a bit long but very pleasant and satisfying. I was going to try out the J West shifter and hardwares but decided to leave it stock then this happens. I noticed J West got shift plate enforcement “ The shift fork inside the 915 transmission has a very common issue of the tiny M6 nuts/studs loosening. This has a direct and large impact on shifting, as it provides a pivot point for the shift linkage moving forward and back inside the gearbox. At worst, there is not enough travel to even get into gear.

There is no way to tell this is happening without draining the gearbox fluid and dropping the fork plate on the bottom of the transmission. About 90% of the plates we drop show some amount of fretting, and many have damage to the fork from contacting the rotating gears.” Is this worth checking for my aforementioned condition?

[Early911SC]

@rwest thanks for the response! I’ll attempt to see the condition of the other bushings … I’ve been searching the site for ideas and noticed Stella spring got good reviews. Probably another topic but would you advise adding this to the shifter if I’m to change the two other bushings?

[rwest]

I haven’t used the spring yet, but have been tempted. Since you need to remove the shifter housing to replace the front bushings, that would be a good time to install one.

I’m not very knowledgeable on the intervals of the 915, although I did refresh a bunch of parts in mine many years ago, but any information retention is gone!

[silverlock]

Check the linkage adjustment: it can slip over time and impact shifting.

A 4th that doesn’t engage could be caused by the rod <> linkage being off in the fore-aft plane, especially given your comment about the throw being long (has that always been the case?).

[tobluforu]

When in any gear and you get on it and let off, how much does the shifter move while in gear. Could be your tranny/engine mounts.

[Winter]

Two very simple and inexpensive upgrades for the 915 are the Kirsten Spring and the Ultimate Shift Rod Bushing. Thread: Ultimate Shift Rod Bushing

Spring - https://stellasautogarage.com/products/915-shifter-spring

Bushing - https://914-6werkshop.com/product/porsche-911-ultimate-shift-rod-bushing-by-jp/

If all of your other bushings are new(er) and you have adjusted your coupler and shifter correctly, these are an easy upgrade.

Of course, other issues as mentioned in this thread could be contributing to your problem. I would probably start with the bushings, adjustments and spring, while also checking mounts. That’s all low hanging fruit.

Best of luck sorting it!

[Early911SC]

Originally Posted by tobluforu

When in any gear and you get on it and let off, how much does the shifter move while in gear. Could be your tranny/engine mounts.

Pay special attention this time no movement when in 1st, 2nd, and 5th. As if the gear if locked in place and 3rd and 4th got an inch side okay with 1/2” for aft play. But no movement so I think mounts are ok. Thanks!

[Early911SC]

Originally Posted by silverlock

Check the linkage adjustment: it can slip over time and impact shifting.

A 4th that doesn’t engage could be caused by the rod <> linkage being off in the fore-aft plane, especially given your comment about the throw being long (has that always been the case?).

So when I back up in reverse, I noticed the position is close to the engaged parking brake level. Like 1 inch max! I remember the 76S was not this close but she had a short shift kit. In 1st and 2nd no play rock solid as if it’s gated. 3rd and 4th got 1” side play and 1/2” for aft play. 5th rock solid. Also in 2nd seems close to the edge of the seat like an inch max from touch. I think you’re right, hope it’s the bushings and adjustments and not the transmission.

[Early911SC]

Originally Posted by Winter

Two very simple and inexpensive upgrades for the 915 are the Kirsten Spring and the Ultimate Shift Rod Bushing. Thread: Ultimate Shift Rod Bushing

Spring - https://stellasautogarage.com/products/915-shifter-spring

Bushing - https://914-6werkshop.com/product/porsche-911-ultimate-shift-rod-bushing-by-jp/

If all of your other bushings are new(er) and you have adjusted your coupler and shifter correctly, these are an easy upgrade.

Of course, other issues as mentioned in this thread could be contributing to your problem. I would probably start with the bushings, adjustments and spring, while also checking mounts. That’s all low hanging fruit.

Best of luck sorting it!

So for less than $100 it’s a no brainer. Ordered both and hope to be a fun and rewarding project. Thank you everyone!

[Early911SC]

Originally Posted by Winter

Two very simple and inexpensive upgrades for the 915 are the Kirsten Spring and the Ultimate Shift Rod Bushing. Thread: Ultimate Shift Rod Bushing

Spring - https://stellasautogarage.com/products/915-shifter-spring

Bushing - https://914-6werkshop.com/product/porsche-911-ultimate-shift-rod-bushing-by-jp/

If all of your other bushings are new(er) and you have adjusted your coupler and shifter correctly, these are an easy upgrade.

Of course, other issues as mentioned in this thread could be contributing to your problem. I would probably start with the bushings, adjustments and spring, while also checking mounts. That’s all low hanging fruit.

Best of luck sorting it!

@Winter one more question on shift coupling. I was going to replace mine with the J West seal bearing type, but I read some of these lime solid brass bushings joints transmit noises to the gear shift. On mine currently had black bushings so probably not original. But no play.

[Winter]

I can’t speak from experience regarding the J West or similar couplings or using brass bushings in the coupler. I have also read that noise is increased, as well as that the “helicopter” style coupler gives a noticeable improvement.

I was having issues with engaging and disengaging from 5th and ended up doing the bushings (including “ultimate bushing”) and the spring (my coupler and associated bushing appeared to have been done recently by the PO) and was stoked enough about the improvements (and bang for the buck) that I didn’t go any farther.