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Part 119: Speedometer Cable Replacement

A brand new speedometer cable and housing fresh from overseas awaits installation.

All the way back in 1993, I remember the Fairlane's speedometer making the dreaded vibration noise any time the car was in motion. If you have been around old cars any length of time you know what I mean. While the speedometer may work fine, when the cable needs to be replaced or lubricated the needle will bounce a little and this awful racket will emanate from the instrument cluster. Four or five years ago, I had settled on just removing the whole thing, cleaning out the housing and the cable, and generously lubricating it with graphite. That worked extremely well - until now. I just believe the cable is worn out.

These days, restoration companies sell replacement cables/housing assemblies. Except for NOS units, you really do not see much in the way of exact replacement readily available anywhere. I decided to purchase a new cable and housing assembly to replace the whole works. All of the speedometer cables I was able to find were made overseas, but I was willing to take a chance knowing that many other parts in the aftermarket world are made in China and used in multiplied thousands of classic cars. Since this is not a critical part for stop and go, nor for safety, I made the purchase.

The shop manual does not have much to say about the process of replacing the cable.

Call me what you will, but I am one of those guys that enjoys looking up various aspects of the car in the shop manual. When I was a teenager, I could be found on a Saturday night lounging around, flipping through page after page, reading up on procedures, parts lists, and diagrams. Long time subscribers to the blog will recall that I have an article here on the website that emphasizes the use of several of Ford's manuals from the 50's. However, If you consult the shop manual to read up on how to replace the speedometer cable in your 1955 Ford, you are not going to find too much. Back in the day, it seems that replacement only included removing the cable from the housing and replacing it with a new, lubed cable. The housing is never really discussed in the speedometer section.

Access to the rear of the speedometer assembly is easy with my setup.

The first order of business, after disconnecting the battery, was to unscrew the cable housing from the rear of the speedometer. If you have the factory dash still intact, then access to the back of the instrument cluster will include lying on your back and reaching up underneath the dash to remove the cable. Warning: this can be very tight. A few years back when I put the dash back together, I decided to set the housing in position without using the brackets and small hold-down hardware the factory had used when these things rolled off the assembly line. The front lip of these clusters fits so tightly to the dash that I have not had any problems at all, even over rough roads.

Pulling the cable housing through the hole in the two-piece sheet metal plate for the steering column can be quite a feat, especially if you have a set of headers like I do. The carpet will have to pulled back a bit to see the hole in the firewall plate. No matter if you have a Fordomatic or a manual transmission, the firewall plate for the steering column is in two pieces and has both a large, flat sheet of rubber for a seal and a small hole at the bottom for the speedometer cable housing to run up to the dash.

The original housing was insulated from the factory and routed close to the steering column.

You will have to peel back the carpet and jute insulation to access the hole in the firewall.

Once you have cleared the interior, it's time to get under the car and remove the housing and cable from the tail shaft of your transmission. For the most part, this is going to be a pretty simple affair. A bolt with a 7/16 head needs to be back out of the tail shaft to remove the retainer clip. The large end does have an O ring, so expect the housing to be nestled in the tail shift tightly. One you remove the large end, be sure to keep track of the speedometer driven gear. While that piece was out in the open, I did inspect it for any signs of wear. All appeared normal.

Popping the speedometer cable housing out of the tail shaft is quite simple.

Once the cable and housing were out in the open it was time to make comparisons between the factory cable and the reproduction version. The factory version is certainly better in quality, but it also has more serviceable parts. The picture below shows a small bakelite barrel and a "needle" that actually slides in the barrel and engages the speedometer unit. Overall, the length of the new housing and cable is roughly 12" longer than the OEM part and is 70.25" long overall. As the video at the end of the blog post shows, this gave me more cable to deal with underneath the car. It made routing much easier, will give the dash unit more room to be tilted forward should I need to service, and kept the tail shaft end from taking so tight a turn to engage.

The reproduction cable was certainly different in design from the original version.

Once I was satisfied that each end of the reproduction cable would work, the size of the collar was correct, the tail shaft end was on the money, etc, it was time to lubricate the cable. Let me say, this is an important step. Graphite has been the historical favorite lubrication of many mechanics. However, I chose something a little more modern that I believe will give years of trouble free service - Motorcraft PTFE lubricant. You can get a tube at your Ford dealer or most any online retailer who sells serviceable auto parts.

Motorcraft's PTFE lubricant is an excellent choice for speedometer cables.

To "grease" the cable, I complete removed it from the housing. From tip to tip, I rubbed the PTFE material all over the cable as I re-inserted several inches at a time back into the housing. Once the whole cable was back in the housing, I spun the cable around quite a few times to get the lubricant to spread; then I removed the cable completely and repeated the process. Just to double check the depth of engagement for the speedometer gear, I put the cable on the workbench and inserted the gear to spin the cable.

Double check the gear and the lubrication by testing rotation on the workbench.

The most difficult part in the process came next - routing the cable housing and collar back up through the firewall. I suggest you tape the collar to the end of the cable housing so as not to be frustrated with fiddling with the collar sliding down. The access hole is a part of the two-piece sheet metal assembly that surrounds the steering column.

The collar was held in position by masking tape when it was fed through the firewall.

As you fish the cable up to the speedometer assembly at the top of the dash you will want to double check the routing of the cable so as not to interfere with the brake pedal. If you have to reach up under the dash to connect the collar it will be a difficult feat, but if you connect the dash end first you will have plenty of play to work with. The slack can be taken up, if needed, by pulling the cable housing back down a bit when you get back underneath the car. In times like these I am glad I have re-installed the dash instrument cluster this way. One of these days I may use a pair of springs to "hold it down" but to this day I have not had a rattle or anything loose.

The reproduction cable length provided plenty of play to attach the collar to the speedo.

Once the cluster was back in position, I reattached the aftermarket tachometer to the steering column. Next, I looked below the dash where the cable assembly went through the firewall and pulled down the slack just a little. I took some 3M strip caulk and ensured that the access hole was sealed; then I put the carpet and rubber steering column grommet back into place.

With the interior ready to go it was time to crawl back under the car and route the cable assembly back to the tail shaft of the transmission. Since I have headers and 3" down pipes there is not as much room under the floor pan in that area like the car had when it left the factory. However, this was quite a simple task and without much delay the tail shaft end of the speedometer cable was ready to go back into the transmission.

Remember to put the cable back into the clip under the floorpan.

Ford had various tooth counts available for the speedometer gear to match ratios.

Before I put the cable back into the tail shaft, I inserted the speedometer gear (which is in good shape by the way) into the housing and spun the gear by hand. This was just a simple check to ensure that the cable was engaging the speedometer at the cluster. You should feel a little bit of resistance but not much. If you are off on your speedometer needle reading, you can purchase different tooth count speedometer gears to try to match your reading to true speed. A free GPS speedometer app on your smartphone will help you get as close as possible.

Make sure the cable housing is fully seated in the tail shaft.

The last step in the process before a road test is to simply reinsert the speedometer gear and cable end together into the tail shaft. Ensure that the O ring is lubricated before putting it all back in, and of course keep your cable housing from kinking up. The video below shows where the "extra" cable ended up. To be frank, I think this is a better setup than what I had originally - the OEM setup seemed to be very tight with little to no room for give. The end of the video also includes the road test - noise gone and speedometer working correctly!

Speedometer Cable Replacement Video

The Hot Rod Reverend


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