Thanks once again. I’ll see if I can get the bushing to suck in a little Kroil tomorrow. That stuff will go anywhere.
Studying the speedo heads a little closer reveals an interesting drivetrain from the spinning shaft to the odometer cylinders. A worm gear on the spinning shaft engages vertical splines on a horizontal nylon (?) shaft. The nylon (?) shaft has a worm gear at the far end of it that engages a circular gear on a black plastic horizontal shaft. That black plastic shaft has a worm gear on the far end of it that engages a circular gear on another horizontal shaft that has another circular gear on the other end of it. This second gear engages a much smaller idler/reversing gear on another horizontal shaft and that idler gear drives a white plastic circular gear on the end of the main odometer spool. On the other end of the last shaft is an identical idler/reversing gear that drives the trip odometer gear which appears to be brown plastic or phenolic. I would expect 1,000 revolutions of the input shaft to advance the odometers by one mile. I see that the zero setting of the needle can be adjusted by bending a steel ear on the mounting bracket. This should not affect speedo calibration.
I’m quite sure that the ‘50’s and ‘60’s cars were calibrated to read 60 MPH at 1,000 RPM cable speed. The equation involving tire size, differential gear ratio and speedo cable drive pinion tooth count was beat to death previously. Mfrs are said to have built in a little positive bias (+ 2-4 MPH) in choosing speedo drive pinion tooth count to protect ourselves from ourselves and the local constabulary.
While I have the clusters apart, may I ask if anyone has a spare 300-J speedo head with the 150 MPH dial and if there is any reason it would not bolt in and perform accurately? The ’63 parts book lists two different 150 MPH heads-one for a Newport (cop-car?) 2290394 and 300’s: 2290674. Lacking that, I can use the stub-end of the needle and add 90 MPH to it. It would be interesting to hear true confessions of any brave 300K pilotos that have seen the sunny side of 120 MPH—or of 300J pilotos with similar experience. I hear tales of 140 MPH + and that the J & K coupes, properly geared, were the fastest letter cars. Just curious—not trying to stir up y’all. Maybe the stick cars were fastest?
Finally, I note some differences between the two speedo heads I have out and in front of me. The MPH figures on the unit that came out of my 1964 300K are all horizontal with 60 MPH at high noon. The MPH figures on the ‘63 face area all aligned radially with the pointer—making the 120 MPH value a little harder to read (and how much time does one have to glance at the speedo as one buries the needle?). The needles are also different with the ’64 300K pointer having a penny-sized+ polished aluminum center and a mostly polished aluminum needle with a ¾” dayglow orange tip. The ’63 needle is tapered to a small point and is all dayglow orange. Mechanicals seem to be identical.
Brentwood CA (Rainy!)
Yes Rich .. There is a spinning brass bushing/ bearing in there that receives the square end on the drive cable . It spins in the die cast housing . In earlier ones there is a cap --looks like the drain on side of water valve but male . It is to oil that bush , via a small felt . It was greased at assembly but grease always gets dry and hard . It is often all that is wrong with speedo ( learned that the hard way -- after pulling apart whole thing and wrecking it the first time ) . That and atf into cable . Has to spin totally free at speedo head as if nothing is connected to it . I think if you have speedo out you can get oil into the space around spinning bushing by putting face down and putting oil around it into space while turning it . ( without getting the plug out ) WD 40 or penetrating oil might help , then like 10 weight . Or atf . I think you are right .. Later ones they greased or oiled and then put in plug like a core plug by denting center . Save .05$ . Any messing with inside of speedo head rarely turns out well . Very touchy to calibration .. Not just at one point , across whole dial can be ok one end off other end non linearly. I think but am not sure 1000 rpm there is 60 mph on all cars . ( actual number can be checked ) . I Used drill and whittled wood square like large toothpick to check ( approx) it worked ok after freeing it up . If friction there cable winds up a little against friction then snaps forward causing ~ 5-10 jump in mph number . Repeat !! Especially cold weather . Sometimes odometer is stuck or broken ( plastic !) much older ones are metal , mopar replacement parts , 50's -- at least once i used a metal one , nos off ebay to fix / replace that plastic one, but forget years that crossed . When odometer jams it usually breaks free from input drive by stripping a plastic gear in there , but sometimes can go snap , snap snap as teeth jump . .. Makes speedo jump very regularly , you can tell this one as Odometer does not move , eventually teeth wear off . Speedo works again after a while but no odo . Sometimes better to just accept that . If you get into the spinning magnet scraping etc , very hard to fix. That scraping shows as huge 30+ mph jumps off zero even when going slow . Can stop the scraping by careful bending but then calibration all off . At that point goes to pro if you have not by then wrecked it .. I think scraping is caused by wear in input bushing lets the part sag and hit . Half the magnet device is supported only by that same bushing . Has to stay square and centered . That sort if means it is worn out ?
Been there on these! Good luck !
Posted by: "Rich Barber" <c300@xxxxxxx>
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