Help Porsche 911 Sportomatic

[Chopsey]

Hi, new to the forum, I need some advice from someone who knows the Sportomatic functions please. I have 6 Porsche's right now and one is a 1977 Sporto. Well the issue i am having is a shifting issue. If I sit in my garage with the car running I can shift it into all gears no problem. Out driving it when I try to shift into 4th, it will not go in. All the other gears work. If I am at dead stop I can put it into 4th. I tested the vacuum actuator on top of transmission and it is holding good vacuum. I adjusted the servo, correctly and still no luck. Could it be a clutch issue. Vacuum issue etc. Your help is appreciated. The car drives fantastic, Sportomatic is super fun to drive people get really confused with these cars thinking they are automatics, the shift with an actual clutch and they have a very good power band, the clutch moves when you touch the shift instead of pushing with the foot clutch, the torque converter keeps it in gear so you can do automatic shifting interesting cars for sure and very rare. It is strange that I can shift while sitting still, the clutch doesn't know what gear your are in neither does the servo or vacuum actuater. Could there be issue with the shifter micro pins. Thank you!!!

[Discseven]

Chops... welcome to forum. Sportmatic is complete mystery to me so no help here. Did look around for info and for others like myself who are curious about Porsche trans-systems... a link to short article covering history of Sportmatic, Tip and PDK (double clutch racing trans.)

A History of Porsche

[Matt Monson]

You sure you aren't shifting into reverse? Starting in 1976 the Sporto became a 3 speed.

[93nav]

What Matt said. Though reverse is down and left, so I would think you would be getting into 2nd, but I am not the best on mechanicals.

Also, people have swapped in 4 speeds in later cars, or the original 3 speed can be converted to a 4 speed.

Chopsey, do you have any paper work showing work done to the tran?

[93nav]

Thinking about it, if you get a look at the top of the shift tower (or whatever it is called), parts 49 and 50 in the diagram below are unique to the 3 speed. The area that would allow going into 4th, down and to the right, are blocked off. It will be obvious when you look at, especially if you have another 4 or 5 speed to compare it to.

[Matt Monson]

Here's the shift pattern on the 3spd. Not really sure what he's engaging. But originally this would have been a 3spd vehicle.

[DanPez]

I had some info for when I worked on my 73 RoW 905/21 transmission. (Sporto)

925/15; ’77 RoW 911 3-speed; 15:36(C,2), 21:30(K,3), 27:25(V,4-5); 8:27; 1900±200 rpm; 1.8:1; 3200±200 rpm.

925/16; ’77 RoW Carrera 3.0 3-speed (used through ’80 911SC worldwide); 15:36(C,2), 21:30(K,3), 27:25(V,4-5); 8:27; 1900±200 rpm; 1.8:1; 3200±200 rpm.

925/17; ’77-‘80 911S USA, 911SC 3-speed; 15:36(C,2), 21:30(K,3), 27:25(V,4-5); 8:27; 1900±200 rpm; 1.8:1; 3200±200 rpm.

All 3 speeds


The links below may help .... it is a general alignment for centering the shift.
Bushings maybe worn, cup may need to be replaced.

Thoughts on shifter couplers W/ photos

Pelican Technical Article: 911 Shifting Improvements

[Discseven]

Matt, must have been different versions. Article indicates 4th...



A History of Porsche

[javadog]

Originally Posted by Discseven

Matt, must have been different versions. Article indicates 4th...

Matt knows this...

They were originally offered as a 4 speed, then they were changed to a three speed.

The first thing I'd do is crawl under the car and get the gearbox type and serial numbers. That should sort out which version he has. If he has a US car, it should be a 925.17, with a serial number starting with 767.

JR

[Matt Monson]

This has me wondering if maybe this car has the proper 3spd gearbox in place but a 4spd shifter assembly?

[DanPez]

Originally Posted by Chopsey

If I sit in my garage with the car running I can shift it into all gears no problem. Out driving it when I try to shift into 4th, it will not go in.

Just speculating but if its been changed to a 4 speed then:
While the car is running and stopped ....... engaging into 4th gear ..... letting go the shifter should make the car move.

[djpateman]

We really need the serial & type # from the trans case. You have to look for it on the rib under the diff section.

[Okla Marshal]

Just looking for shifting knob for 3 speed sportomatic