6-speed transmission: Do we really need the 5th/6th detent pin/spring?

[sapote]

Driving my 1967 Porsche with the 5-speed dog-leg 901 transmission everyday, it occurred to me that the box only has one detent for the Reverse/1st gear gate, and none for 2/3 and 4/5 gates.
I don't see why the M3 needs the 5/6 gate as it is easily located by feel at the far right on the shifter. I wonder if anyone did the SMG to manual conversion and skip the 5/6 detent pin/spring and how does it shift and feel?

[WestBankM4]

I'd be interested to hear this as well, when my swap was completed, all detents were put in. Thinking of my '89 240SX with the stock 5-speed KA24, I was on the 880 highway in my teens, tried to go from 5th to 4th, well, we know how it ended. It ended with a SR20DET swap of course. Be careful with that P car sapote

[George Hill]

I would say the 5/6 spring doesn't help you find 5/6, it helps you find 3 on the 2-3 shift and slightly 4 on the 3-4 shift.

By that logic you could also say if we don't need the 5/6 because its all the way to the right, then we wouldn't need the 1/2 because its all the way to the left (against the R spring).

[Sharocks]

Bold of you to assume that most people can shift well.

Also bold of you to assume that the 420G isn't a momentous pile of shit.

I think this theory works with lighter and less torquey cars.

And also only works if the person is really good at shifting.

[sapote]

1. I would say the 5/6 spring doesn't help you find 5/6, it helps you find 3 on the 2-3 shift and slightly 4 on the 3-4 shift.
2. By that logic you could also say if we don't need the 5/6 because its all the way to the right, then we wouldn't need the 1/2 because its all the way to the left (against the R spring).

1. Without the 5/6 detent, 3/4 is easily found on the left (stopped by the big coil spring against the anchor pin) and 5/6 is on the right of this free movement section. The movement section from 3/4 to 5/6 is completely free without any spring force against it, but it should be fine for drivers to tell precisely 3/4 at the left most and 5/6 at the right most of this section.

2. Without the 1/2 detent (by the big coil spring and there is no detent pin as R and 5/6 have), we cannot locate where is 3/4 in the middle of a free movement section from 1/2 to 5/6. So we need 1/2 detent. to create a wall for 3/4 gate.

[George Hill]

1. Without the 5/6 detent, 3/4 is easily found on the left (stopped by the big coil spring against the anchor pin) and 5/6 is on the right of this free movement section. The movement section from 3/4 to 5/6 is completely free without any spring force against it, but it should be fine for drivers to tell precisely 3/4 at the left most and 5/6 at the right most of this section.

2. Without the 1/2 detent (by the big coil spring and there is no detent pin as R and 5/6 have), we cannot locate where is 3/4 in the middle of a free movement section from 1/2 to 5/6. So we need 1/2 detent. to create a wall for 3/4 gate.

By that logic why not use the 5/6 and dump the 1/2 detent?

[sapote]

By that logic why not use the 5/6 and dump the 1/2 detent?

To delete 1/2 detent force (1/2 has no detent pin nor its own spring), the big coil spring (wrap around the rotating arm with an attached ball bearing) has to be deleted, but this would create a non-detent section from 1/2 through 3/4, to 5/6, and this would cause ambiguity to find where 3/4 is in the middle of 1/2 on the left and 5/6 on right. Impossible to drive in this case.

[sapote]

Next time if anyone want to renew the R and 5/6 detent pins and springs on the bell housing, just remove the 5/6 detent pin + spring and not use them (no more pin jammed in the sleeve), just install the plastic cap to seal the oil. You will not regret this. Shifting 5/6 would be so easy and light, as there is no detent to compress, and they are easy to locate on the right most against the wall. You cannot have issue to find it. Imagine a car only has 4 forward gears, 1/2 and 3/4 as the H pattern. There is no reason to have any detent for the 1/2 and 3/4 gates. Agree?

[George Hill]

Maybe I am misunderstanding you but I don't think how you are describing the system operation is actually how it is.

The "top" detent pin/spring is for 5/6
The coiled spring is for 1/2
The "bottom" detent pin/spring is for R

The coil spring holds the shift shaft against the 5/6 pin to create the 3/4 gate or center position. If you don't have the 5/6 pin then the shift shaft cold move between the 3/4 gate and the 5/6 gate without resistance. Conversely if you had the 5/6 and didn't have the coil spring the shaft could move between the 1/2 and 3/4 gate without resistance which would be the exact opposite as you proposed but not "impossible to drive."

I've got to assemble a converted BH in the next week, I'll take a video with the options you propose.

Additionally I think you need the pressure of the spring/pin pushing on the back side of the cap otherwise it could "move" around (and leak) as it doesn't bottom out in the bore.

[sapote]

Maybe I am misunderstanding you but I don't think how you are describing the system operation is actually how it is.

1. The coil spring holds the shift shaft against the 5/6 pin to create the 3/4 gate or center position. If you don't have the 5/6 pin then the shift shaft cold move between the 3/4 gate and the 5/6 gate without resistance. Conversely if you had the 5/6 and didn't have the coil spring the shaft could move between the 1/2 and 3/4 gate without resistance which would be the exact opposite as you proposed but not "impossible to drive."

2. I've got to assemble a converted BH in the next week, I'll take a video with the options you propose.

3. Additionally I think you need the pressure of the spring/pin pushing on the back side of the cap otherwise it could "move" around (and leak) as it doesn't bottom out in the bore.

1. You're absolutely right. I forgot that your proposal to keep the 5/6 detent. Yes, with 5/6 detent kept, but remove the big coil spring, then one can find 1/2 and 3/4 gate with no problem, then compress the 5/6 detent to move to the 5/6 gate. I guess it depends on which race track -- more time in 1/2 and 3/4 then keep 5/6 detent and delete big coil spring, or more in 3/4 and 5/6 then delete only the 5/6 detent pin/spring.

2. Yeah, delete the 5/6 detent and save parts and labor for machining the 5/6 hole, sleeve, groove for C-clip or tap threads for diff drain bolt.
3. You're right, the stock plastic cap needs something on the back. I guess I would stuff a wine bottle cork or rubber hose that fits snug in there before the cap.