Speedometer Cable Replacement

Sunroof · 09-28-2009, 04:21 AM

1973.5T

My speedometer cable failed this past weekend. I removed it from the speedo to see if it was rotating to isolate the problem. It does not rotate! In fact I was able to pull on the inside cable (isn't supposed to be locked onto the housing at the wheel?).

My big concern is how this cable runs through the dash, trunk and down to the front wheel, attachment points and R&R procedures.

Anyone have any experience with removing and replacing speedometer cables?

Can the interior cable just be replaced or do you have to buy the whole unit?

Thanks

Bob

keitho64 · keitho64's Garage

Bob

I did this in my 69 a while ago and wrote this up:
Draft Speedometer Cable Replacement Instructions

Let me know if you have any questions after checking this out.

oldE · 09-28-2009, 07:10 AM

Bob, I'm not familiar with your 73.5, but in the case of my '69, the cable went through the area behind the dash (accessed through the front trunk), then through the central tunnel back to the transmission.

Aside from some retaining clips inside the tunnel (had to take the shifter out to get at these) it was a matter of unfastening the cable housing at both ends, tying a cord to the old one and pulling it out of its resting place, then using the cord to pull the replacement into its new home.

I think there is a procedure in the tech section to give you a better idea, but it is not difficult, if you have a jack and stands (or a lift!) to get the back of the car up to access the transmission.

Good luck.

Les

PS Edit: What Keith said!

ossiblue · 09-28-2009, 07:23 AM

First off, the speedo does not connect to the front wheel hub like in VW's--it connects to the front of the transmission so you have a bit of a hand scratching adventure ahead of you.

Yes, you can buy just the cable without the sheath, but I have had no experience with that type of replacement, so I will advise on a complete cable replacement.

The cable attatches to the transmission, just above the transmission mount--very little clearance but doable. You will need to get under the car and unscrew the nut/collar and the cable will easily release.

You have already removed the cable from the speedo. Now, look in the trunk just in front of the cardboard cover and you will see the cable curving around and down through a rubber grommet in the bulkhead. Inside the car, behind the wooden floor board, you will see the cable coming through and down behind the pedals and going into the tunnel. From there, it passes through to the rear of the tunnel and exits to the transmission.

The PITA, is removing and replacing the cable inside the tunnel. It is held along the way by metal clips that have to be bent to allow the cable to be pulled out. To access the tunnel, you have to remove the read cover (by the rear seats), the carpet over the tunnel, the driver's seat, and the emergency brake--at least remove the brake assembly enough to get your hand inside the tunnel. There is another access hole in the front by the pedals. You will need to unbend all the clips inside the tunnel to slide the cable out, but before you slide the cable out, either secure a cord to one end to pull the new cable back through, or secure the new cable to one end and pull it through while removing the old cable.

It's been a while since I replaced mine, but I believe I pulled the old cable out through the front access hole in the tunnel and pulled the new cable in through the rear of the tunnel (from under the car as the connector to the trans will not fit through the metal hole at the rear of the tunnel.) I recall several snags of the cable as it was passing through the tunnel due to the other cables/tubes/clips inside. That's where the hand scratching came in.

Reconnection is obvious at both ends. Be sure to have as large of sweeping curves as possible from the tunnel up behind the pedals, through the bulkhead grommet, and around to the back of the speedo.

If you can replace just the guts of the cable without the removing the sheath (as described above), then that may be the way to go. Others will describe if that can be done.

Hope this helps.

Gogar · 09-28-2009, 07:23 AM

Bob:

Did your speedo 'wobble' before the cable broke?

My speedo needle 'wobbles' especially at low speeds and I wonder if replacing the cable will eliminate the problem.

jpnovak · 09-28-2009, 07:36 AM

Speedo wobble (most likely) has to do with internal adjustment of the magnetic "ring and cup" inside the speedo. It is not cable related.

It could also be needle friction from being old.

Sunroof · 09-28-2009, 07:46 AM

Thanks...

I was hoping the news would be good!!! That is, without even looking yet, the cable would be connected to the front wheel, like the older VWs. Sounds like replacement takes some time and on your back!

My speedo odometer failed for a short time due to that "pot metal " gear that tends to break. A local speedo repair shop here in Atlanta fixed it and checked all other functions and the speedo appears to be fine.

The cable does not rotate, therefore it cannot be the speedo.

Appreciate the responses.

Bob

Sunroof · 09-28-2009, 08:32 AM

I called a few Porsche shops to get an idea on labor to replace this cable and it averaged 3 hours!

I also called the speedometer repair shop to inquire about cables and they were pretty well versed on the 911 speedometer cable. As they explained the internal "cable" portion has a squared narrow end for the rear of the speedometer and a larger squared end for the transmission.

The cable itself can be pulled from the sheath and replaced. The speedo shop expects that when I pull the cable the part that goes into the tranny will be broken which will require removal.

Here is my big question. Is the gear in the tranny that drives the cable known to fail?
This could afterall become a small fortune when all is said and done.

Thanks

Bob

ossiblue · 09-28-2009, 09:22 AM

Yes, there is a gear in the tranny that can be the cause, but it is far less likely than the cable. My question is, does the sheath have to be removed to replace just the cable inside? My experience with the cable is the break comes along the cable. The "teeth" that fit into the transmission have not been a problem, nor has the gear/fitting in the transmission itself. If you're having a shop do it, see if the labor charge for complete replacement (including sheath) and just internal cable replacement are the same, or close. If they have to remove the entire assembly to replace just the innards, it might be easier to just buy a whole new set up.

Sunroof · 09-28-2009, 09:50 AM

Thanks LJ.
I am going to pull the cable (innerts) out after work and see if the tranny end is missing or damaged. I pulled out about a foot's worth yesterday and it was effortless. The speedo shop can replace it alot cheaper then a new cable unit. They said that the cable itself can be removed without remvong the outer sheath. If it is broken at the tranny end I will take it off under the car and install the new one (cable only). I have to change out my Swepco fluid anyways. My fear is that its feasible the tranny gearing could be a problem.

Bob

kkinzli · 10-09-2009, 12:32 PM

keitho64,

I just did my speedometer cable last night and your instructions were incredibly helpful. It took me about 1.5 hours. Thanks a lot for the great write up

Cheers,
Kristoph

Christien · Christien's Garage

3 hours shop labour? That's nuts! It took me a little over an hour, and I'd never done it before.

If you're lucky, the cable will have been replaced before (likely) and won't be clipped in anywhere. Mine had been, and it was pretty simple. It helps if you know what you're looking for on the tranny, but try looking here for a pic - once you see it you can't miss it.

I used some old clothesline cord I had in the garage - tied it then duct taped it really secure, so that it held, but also so that the connection was smooth and it would catch on anything. It took a lot of jiggling and manouevering, but I didn't have to remove the parking brake or anything like that.

RWebb · RWebb's Garage

post your experiences & deviations from the '69 procedure above

the '73.5 can be a bit of an odd duck - partly early car; partly like a '74; partly unique - I have one too...

one option would be to convert to an elec. setup - prob. too much effort for even a 3 hr R&R tho

PAUL RODELO · 01-27-2010, 10:37 PM

Keitho64,

I'd like to confirm one thing from the procedure you shared.

Did you remove & replace both the speedo cable & cable housing?

If so, then you attached your fishing line to the speedo cable housing...correct?

Thanks,

Paul & Judy

keitho64 · keitho64's Garage

Paul

When I did mine it was the cable and housing. I connected the line to the housing and was able to pull it through with minimal problems.