1BOSS83

I've been chasing down some issues with my speedometer and I'm out of ideas at this point. For context- lower cable has been replaced, upper cable has been replaced, speedometer gear in transmission has been replaced and a functioning factory speedo head was installed yesterday (Thank you again, Troy).

Timeline:

- When I put the car back on the road some years back the speedo was not working. The shop that did the inspection put on a new lower cable and all was well.

-The first long trip with the H/O the speedo fell flat 10 miles in. I took it a local trans shop and he put in a new transmission gear as the original had "cored." The speedo worked fine again (for a short time). After some driving (20 miles) the speedo head started to click and bounce around very erratically and then, yup, flat line.

-I replaced the upper cable at this point, nothing. I put in the new head yesterday, clamped a drill onto the cable and the head was spinning free and fine. I buttoned everything back up. The speedo head bounced around a bit from 5-20mph and then laid flat.

-For diagnostic context- at a low speed coast (10-15 mph, estimated ) I can hear a click (think baseball card in a bike spoke). I pulled over and disconnected the cables at the transducer. No more noise.

- The upper cable spins freely and registers on the head. The bottom cable does NOT spin free with the car at rest (a sign to me that the gear in the transmission has not been damaged).

-My theory is that the transducer is providing too much resistance in the trans->lower cable->transducer->Upper cable->head.

I'm ok replacing the transducer, they are around 100 dollars. I'd rather get a used piece and am putting up an add in the parts wanted forum. What I don't want is to replace the transducer and still have the same problem.

As always, any insight would be great.

Thank you,

1BOSS83

I picked up a used transducer from the local bone yard and installed today. Went out for a ride and 2 miles in everything is working great. After accelerating past 55mph the needle went straight to zero on the head. After that the needle would loop between 25 and 45 while shaking back and forth 1/16" in each direction like a leaf on a tree.

Came home, pulled upper cable and spin it with my fingers, Itspun free/consistent on the head. The bottom cable still has a bit of white lithium grease on it. Is it possible that the cable is TOO lubricated? It sounds counterintelligence but i'm running out of ideas.

Octania

Maybe it is the speedo itself dying?

1BOSS83

Are you referring to the piece in the transmission?

joe_padavano

How about what trans are we talking about for starters?

Which speedometer gear in the trans was replaced? The drive gear or only the driven gear? I'm guessing only the driven gear was replaced, and if it was excessively worn, a plastic drive gear (the one on the output shaft) would be similarly worn. Unless you are talking about a 200-4R, the tailhousing needs to come off to replace the drive gear. Drive gears come in plastic as well as metal. Inspect this before losing more sleep.

1BOSS83

-200-4R transmission (Not original, replaced in 03, 20k miles).
- The driven gear was replaced. It was excessively worn when replaced.

I believe I have eliminated everything else but the drive gear. Let's assume the drive gear (driven gear= plastic gear that creates the force on the lower cable and is removed w/o removing the tail housing, correct?) needs to be replaced. Do I go plastic or metal, and, supposing I do; Will a metal drive gear working with a plastic driven gear cause me an issue in the long term?

Thank you,

joe_padavano

The 200-4R has the funky speedo drive gear that's part of the governor. You need to pull the governor to inspect it, which means you need to drop the pan.

1BOSS83

Thank you for the clarity, I'll be back with more news. Stay Tuned! :-)

Octania

No I meant the part in the dash that has the needle that shows speed.

It appears that, as usual, Joe P has the lowdown on the trans end pieces to inspect for flaws.

1968_Post

I'm curious if when you're replacing the lower cable, are you replacing the cable only or the cable and casing?

1BOSS83

The lower cable/casing was replaced by the shop that did the inspection to put it back on the road in 2012.