On the hunt for Speedometer parts for a 72


Aug 18, 2015
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Westminster MD
My 1972 Custom Suburban's speedo gave up. It is a 360ci wagon with Speed-Control. I am on the hunt for preferably a NOS cable from the Speed-Control to the Transmission. And, I also need the gear which goes inside the transmission. Anyone have any wisdom of a good place to source these from?

Westminster MD
Tom, if you can provide us with part numbers that may help quite a bit. I know that I have an NOS speed control cable for a 72 small block C Body but I don't recall if it is the upper or lower. Part #3620703 - it is referred to as the adapter package. I think it is the upper cable.
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Did the cable break internally or the gear wear become too much for it to contact the drive gear on the trans output shaft? The existing gear would be identified by color and number of teeth. The tooth count might be stamped into the gear near the shaft, sometimes. Might also be available through the aftermarket or a trans shop rather than having to come from Chrysler specifically.

When you remove the driven gear from the trans, look to make sure the drive gear (on the trans output shaft) is still anchored to the shaft with its metallic clip or similar.

The cable will be specific as to length, BUT due to the architecture of the engine/trans, those lengths might well be pretty common with C-bodies up to '78 or so. Reason I say that is that in the earlier '70s, when the national speed limit was decreased to 55mph and cruise controls were being installed where they didn't come from the factory, I went to the Chrysler store where I was in college and asked about installation on my '66 Newport Town Sedan. The dealership tech knew what I was wanting to do and said the then-current ('75) factory cruise kit would work just fine. Only thing was that a little more clearance would be needed behind the current turn signal switch so the wiring from the stalk could clear it. I later looked at a new Chrysler and the dimensions for the whole factory installation looked like they were the same dimensions as my '66 Newport had (383). The dimension from the cruise transducer on the fender apron to the cowl and head might have been very close. The dimension from the transducer to the trans would have been similar. Don't know that engine size would matter in this deal, as it's more body architecture than engine architecture. Where the engine would matter might be on the actuator cable from the transducer to the carb, I suspect.

Let us know how it turns out,
I found the cable on RockAuto. Two different manufacturers offering it up. It is the lower cable from the speed control to the transmission that went up. My mechanic buddy looked into what was wrong and came back wanting these two parts. I did find the Pinion Gear for the transmission end of the cable on a Transmission Specialist site. Lots of used ones out there for cheap, but I think I would rather go new. What was interesting was that I also found on these transmission parts supplier sites, tables for figuring out which Pinion Gear tooth count one needs to switch to in order to keep their speedo accurate when changing tire/wheel sizes or rear end gearings. For now I drive with a SpeedoMeter app running on my iPhone so I know how fast I am going (when the traffic around me does not dictate the speed). The parts were easy to find as MOPAR (for good or bad) did not change core items very often. TF 727/904 were in service for a long time!
Update... All the websites say the lower cable is 63". Well, my factory cable was more like 57". My mechanic buddy ended up using a universal core kit to get everything working. That lasted a moment or two before the Speed Control shredded the new cable. Apparently that is the point of failure.

Not having a lot of luck finding a new Speed Control Module (part mounted to the LF fender). :-( Seems like I will end up with cable going from speedo to trans.
That speed control "head" was pretty common from '68 - mid-80s. Might be some good ones in a salvage yard or some remans from an auto supply source.

Final result, tried a straight through cable from dash to trans but the attachment to the trans was different. Ended up cleaning out the debris from the disintegration of the speed control guts, getting another cut-to fit core cable and redoing from the speed control down to the transmission. To a show judge, I still have speed control. :) Amazed at how much quieter it all works now.