speedometer cable issue

[CPH]

Hi everyone, my apoligies for my first post being a question rather than assistance. My speedo in my 72 MGB (non-OD) simply stopped working the other day, strangely immediately after a carwash with a manual power wash thingy. I removed the cable from the speedo and it does not rotate when the car is in motion.

What would you recommend be the next step to identify the problem? I understand that the other end of the cable attaches to the tranny, must the car be on a lift to access that? I'm strictly a driveway mechanic.

Thanks for any help. I did a search through all past postings and could not find what I needed, but I apologize if I'm repeating a question.

Best,
Chris

 

[DrEntropy]

No apology necessary, Chris! Welcome to the Forum!!!

There's a couple things to cause what you are experiencing. You ~may~ have a "counter" on that car, a box up on the firewall near the heater box. It'll likely be white-ish with two (speedo) cable ends connected. One from the trans, other to the clock. They get "craminated" (notice we use VERY tech-savvy nomenclature around here :wink: ) and fail. If you do NOT have that gizmo, there's a "right angle drive" unit somewhere which is a gear reduction unit. Most early cars (not sure just where '72 falls in this classification) have it at the tranny where the cable fits into the tailshaft housing. Later cars have one behind the speedo head. You'll have to find which of these (or both) is craminated. Process of elimination. disconnect cables at each device in turn, see if you can spin the cable(s) freely as each one is disconnected on the way UP from the trans connection.

There is a *slight* possibility it can be the drive gear inside the trans, too. They have been known to strip. They're a plastic "worm" gear (nylon, actually) and if that's the case you may be able to spin the cable from the topmost end where it goes into the speedo.

Let us know what happens, or if any of that diatribe gives ya fits, I'll attempt to clarify.

And again: WELCOME aboard!! :thumbsup:

 

[CPH]

Thanks for the great advice DrEntropy, I'll roll up my sleeves and try to ignore the laughter when people see my legs in the air as i work under the dash.