411 and 412 speedometer cable nut repair and modification

[raygreenwood]

Speedometer cable nut repair and modification.

This is a repair I did many years ago in my car. I had the parts out in July of 2017 and took these pictures and just got around to posting it.

If you have not already needed this modification/repair before.....you will someday. .... trust me!

For all of those who have ever had the speedometer out of the dash to replace the cable or work on the instruments…there is an inherent risk to taking the cable loose. The nut is easily broken.

The plastic 1/2 turn “cam” nut that clamps the cable to the speedo is crappy plastic. It’s designed to have some spring tension in the slot in the side in the side on some years so it will stay in the notch seen in the picture below. With age…and heat in hot climates….it commonly shatters…leaving you with no speedometer because the cable will not stay on.

There are some early cars that have a similar nut that can work. At one time I found one that fit.... in a parts bucket in a salvage yard. It was yellow gold color and cracked two years later.

I have no idea what model it came from. At that point…I started looking at everything I could find…and realized that most of the other VW’s had a much better nut with real threads…damn.

While I will be the first to admit that trying to unscrew six turns of a speedometer cable nut under the dash of a 411/412 was a great way to cut the crap out of yourself….tear wires loose and learn new curse words…and that the ½ turn cam design of the stock nut was …cool…...it is also not replaceable.

Sorry I have no pictures of a stock one to show you. Somewhere in my collection of small parts buckets I still have the old one and will add it to this thread when I find it.


So let’s get started:

First…since you usually run into this snag when changing the cable…and type 4 cables can be hard to find….here is a list of the 411/412 cable part #’s. You can use a beetle or type 3 cable as long as it’s not too short or grossly too long where it will kink.

411 957 801 – 1100mm/43”-5/16”
From Chassis #: 410 2000 001 Models: 411, 415, 421, 425, 461, 465

411 957 801 B – 1160mm/ 45”-21/32”
To chassis # 419 100 000 Models: 411, 415, 421, 425, 461, and 465

412 957 891 – 1865mm/73”-7/16”
Models: 412, 416, 422, 426, 462, 466

My current cable length is 1390mm/54.72”. This length…and my little black notebook of what I installed years ago… marks it as part # 113 957 801 A…which is listed as fitting type 1 super beetle 1971-79, Type 3 all years and Thing 1973-1974.

Here is a picture of the standard type 4 “cam” nut coupling threads

This picture is stolen from CIP1…and shows the nice threaded coupling that most VW’s have. My first thought was just to find one of these cables in the junkyard and steal the nut and thread my speedometer mounting area.

But…almost all of the cable nuts out there are too small in ID and would need to have too much material removed from the speedometer for strength sake.

So I measured the boss and started looking….in the plumbing department at the hardware store…because the type 4 speedo boss is just about perfect for the starting diameter for a 3/8”-18 thread…which is 3/8” NPT!

So I found this aluminum nut:

I do not remember exactly what this came from….but it was either from a cold water hose for a washing machine, a kitchen sink sprayer coupling, a water connection hose under a bathroom vanity or a toilet water connection. It may have even been a hose coupling nut from an industrial sprayer system.
You can even use a 3/8” NPT brass compression coupling nut….as long as its 3/8” NPT.

The only other items you need are a thread die for a 3/8” NPT and a washer of about .065” thick shown in the picture below.
This was a grade 8 washer that I sanded the ID and OD with a Dremel tool and small sanding drum to use as a spacer. Depending on what type of nut you find..... you may or may not need this spacer or may need one of a different thickness.

You may need to sand the very top edge of the boss on the speedometer to make sure you get a clean flat start for the die.

Work it down by hand…only cutting a little and backing it off. Use WD-40 for a lubricant. DO NOT FORCE IT. Cut a little …maybe 1/5th to 1/8th turn at a time.

Stop frequently to fit the cable and the nut. Bear in mind…that as long as the nut goes on about 3-4 complete threads and tightens up…the nut part is done.
Then you can make your shim to fit to take up the slack.
Do this instead of over working the threading and risking breaking the boss.

Here is some before and after of the threading. The spacer is on top in this picture

Here is how the spacer fits:

And now the nut

The cable assembly and spacer without nut

And the whole assembly put together and ready to install

When I find the original plastic nut I will insert the picture.
Have a Happy New year!
Ray

[anglodeutsch4]

Cool. Solves the problem for sure.

The crummy little plastic nut died not long after I got my 412. In desperation, I figured out a way to hold it on, a bit different than what you did.

I found some screws with the same thread as the two on either side of the cable stem on back of the speedometer (the one with the cam groove in it), long enough to extend up past the end of the stem by an inch or so. I cut their heads off. I threaded them into the screw holes, locked them with nuts, and made a clamp to press on the speedometer cable outer sheath end by cutting a "U" in the side of a chunk of aluminum bar stock. I drilled two holes in that bar stock to match the two headless screws, and then clamped the cable down with the clamp and two big nuts. Fiddly, but worked.

Ditto that inventing new words and pulling wires out bit. I think I ended up describing every VW engineer's family heritage in quite negative terms whilst installing the speedometer last time I did it.
_________________
Lane
MGVWFAN (STF)
anglodeutsch4 (Samba)
73 VW 412 (the Nomad, dropped valve seat land now, argh!)
67 MGB (Built-In Rust from Abingdon)
2002 NB TDI (40 MPG)
2009 JSW 2.5 (love it, love it, love it!)

[WesGhia]

I'm restoring my 1972 Ghia and the cable nut in question broke immediately up on applying pressure to it.

Glad I found your entry here on TheSamba. Now I know how to repair this.

Here are the pictures of the broken nut.

[raygreenwood]

Yep! The late ghia and type 4 cars use the same speedometer part number.

The broken nut issue was an off and on problem. I used to steal the yellowish brittle nuts from ghias in the junkyard. By the time I was getting to them in the 90s....all of them would crack shortly after install. Ray

[WesGhia]

Ok, I did it!! This modification works beautifully... see pics.

Broken plastic nut along with the 3/8" NPT hex die and the 1/2" NPT Brass compression fitting.

Treads cut. Took me about 1 hour of back and forth, going slowly. Die was clamped in a vice and i worked the speedo in my hands.

Assembled the parts, and voila!

[raygreenwood]

Niiiiice work!
Glad this was useful!
Ray