915 Tranmission Question

[Targa3.0+]

1975 911S, 4 speed. Car has 330,000 miles on it, 3.0 has 130,000 on it. I've always been careful shifting and it has always shifted well. The last 6 months or so, I've noticed that in 4th gear (top gear), the shift knob will move back and forth about half an inch when I accelerate or lift off the gas. I just changed the fluid with the usual Swepco, no change. Took the bottom plate off and looked at that little plate holding what looks like shift rods, it was tight. What could be causing this? Is something serious wrong in there? The car is my daily driver if it's not raining, and I put 30-40k on it a year. I like the 4 speed, as the range matches the 3.0 with p66+ cams and PMOs. The 5 speed on my '86 911 doesn't do this. Any wisdom?

Bob
Louisiana
'75 911S Targa 3.0
'86 Carrera Cab

[rowingone]

Shifter bushings or coupler

[gled49]

If I recall correctly, 75’s had an unusual motor mount, I would check engine and transmission mounts.

[AG81]

If the mounts have 330,000 or 130,000 miles it's time for motor and transmission mounts.

[john walker's workshop]

Could be shaft end play due to a worn bearing retainer.

[stownsen914]

All good things to check. Shift linkage (possibly including John suggestion, though technically not shift linkage) is pretty easy to check in the garage. Look for play as the move the shifter around, and you can observe which parts have the play.

If it were me, at that age/mileage I'd replace the mounts and drive it again to see if the problem is still there.

[Targa3.0+]

thanks to everybody! Engine and tranny mounts are relatively new from the engine rebuild 4 years ago. Coupler is 6 months old, shift bushing are prob 10 years old.....years go by, so I'll replace those and see what happens. Strange it only happens in top gear, case pends with new bushings!

[Targa3.0+]

To recap, 4 speed 915 shifts great on 330k mile 1975 911S with a 3.0, gear ratios line up nicely with torque curve on the P66+ cams and the PMOs. My concern is that in forth gear, the gear shift knob moves about an inch back and forth when I accelerate or let off the gas. Hit the gas it moves forward and let off the gas it moves back, about an inch each way. It only happens in forth, and forth is top gear since it's a four speed.

I installed new engine and tranny mounts yesterday. The old ones were only 5 years and 120k miles old from when I rebuilt the engine and seemed ok, but I put new ones in to see if that was it. it wasn't. I put in new shift bushings last week, new shift linkage connector under the back plate two weeks ago. Again, nothing changed.

I think it must be something in the transmission? If so, how hard would it be to fix or replace whatever needs replacing? Thoughts or advice?

many thanks!