1970 911T Sportomatic

[RenC]

Im new to the forum and looking for help. I recently finished my project and it looks great. It wasnt but 1 week after I was done that the transmissions is slipping out of gear on the road. Its never done this and I have read it may be as simple as adjusting the valves. If you have insight, I would appreciate it.

[Grady Clay]

RenC,
Welcome to the Forum
You will find a lot of help here.

Nice looking Targa. You will have a lot of fun.
It looks like you will be a great caretaker.
Please post more pictures.

When you say “…the transmissions is slipping out of gear on the road.”, do you mean that the shifter ends up in the neutral position or the clutch disengages? In either case the engine is disconnected from the road wheels.

Does this happen in all gears?

Best,
Grady

[kidrock]

what a great looking ride, welcome to the forum. Mr. Clay can definitely point you in the right direction.

[LakeCleElum]

Welcome to the forum. Great looking Targa, my fav. color.

I have the same parking brake for my JD garden tractor....

[RenC]

Gentleman,
Thanks for the warm welcome! It seems to me like the clutch is disengaging...in fact today I could not get the clutch to stay in gear...unless I held the stick in position. When I did this, the car runs fine.

[aminter0]

Beautiful looking car

[Grady Clay]

OK, this is easy.

Something is amiss with the electric switch at the base of the shift handle. This switch senses
if the handle is pushed forward or rearward and disengages the clutch. Yours is operating the
switch without moving the handle.

Lift the shift boot and carpet piece and inspect the switch. Be very careful with the switch.
It is white plastic and may be broken. It is a NLA part so you may have to ‘make do’ repairing
this one.

The part number for the switch is:
905.613.039.00

There are two pair of contacts. Specification clearance when open is 0.3 – 0.4 mm (0.012” to 0.016”)
and should be the same fore & aft. The gap can be changed by bending the terminal
but BE CAREFUL.

You should also clean the contacts with some 800 grit paper.

The slot in the switch goes to the front.

Here are some images and exploded diagrams.


© 1969 Dr. Ing. h.c. F. Porsche K.G.


© 1969 Dr. Ing. h.c. F. Porsche K.G.


© 1969 Dr. Ing. h.c. F. Porsche K.G.


© 1969 Dr. Ing. h.c. F. Porsche K.G.


© 1971 Dr. Ing. h.c. F. Porsche A.G.
(I tried to erase the big grease fingerprints.)

Best,
Grady

[crater64]

Originally Posted by Grady Clay

OK, this is easy.

Something is amiss with the electric switch at the base of the shift handle. This switch senses if the handle is pushed forward or rearward and disengages the clutch. Yours is operating the switch without moving the handle.

Lift the shift boot and carpet piece and inspect the switch. Be very careful with the switch. It is white plastic and may be broken. It is a NLA part so you may have to ‘make do’ repairing this one.

The part number for the switch is:
905.613.039.00

Our host lists that part as a "Cable Harness" and available as a Genuine Porsche item at $97.00.

Pelican Parts - Product Information: OEM-90561303900

I hope that's right because I think I'll be needing one of these soon myself.

Thanks, Grady and welcome, fellow 70T Sporto owner.

Ed

[RenC]

Thanks so much for the info....I owe you a beer sometime!!

[Grady Clay]

Good news.

Pelican Parts comes through again.
Thank you Wayne & Scott.


The difficult part of replacing the switch is getting the shift knob off and back on.

Img 6

© 1969 Dr. Ing. h.c. F. Porsche K.G.

img 7

© 1969 Dr. Ing. h.c. F. Porsche K.G.


The Factory illustration shows holding the shank of the shifter in a ‘soft’ brass-jaw vice.
That will damage the chrome plating.
Best is to make a wood piece, split with a hole larger than
the shaft diameter.
A leather interface is best.
You then use the vice to clamp the wood & leather.

The removal tool is “of local manufacture”

Img 9

© 1969 Dr. Ing. h.c. F. Porsche K.G.

Porsche recommends 6 mm thick stock. I have 3/8” and is better.
I also have a 2-piece clamp-style collar with clearance to the shaft.
I use this between the homemade tool and the knob.

Img 10

© W.W. Grainger

I have a soft Nylon washer glued to the knob side of the collar (and then split).
This gives full-circle force on the underside of the knob.


The knob is on with a spring-ish interface piece. It was on tight when new.
I suspect it is on tighter after 40 years.
The part number is 999.532.001.00 “Tolerance ring”.
This is common to many Porsche models.


The P299 installation tool is of ‘soft’ white plastic.
You might ask a long-time Porsche Dealer if they still have one.

Building one is not difficult. This hardness plastic is easily worked on any lathe. Keep in mind
some knobs have a separate piece for the shift pattern. There should be clearance to
the pattern piece.

Be sure to clean and wax both the tool and the knob. This prevents any marking.
Wax paper works well as an interface.

Remember to align the shift pattern properly.

If you radius the contact surface, be sure and make the radius a few mm larger than the knob.
Ask me how I know.

Best,
Grady

[RenC]

Grady
I cant see that the electric switch or anything is broken, however I can see that the contacts have no gap between them...they are touching. I will gap to the right size
I pulled apart the stick and took a look at everything. After foing this, I noticed that the stop ring is deteriorated. Are these that big of a deal. Should I look at anything else.