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What causes a speedo gear to eat itself?

oemoilleaks

oemoilleaks

Member
Joined
Mar 26, 2017
Location
SoCAL
I went for a drive over the weekend and 5 miles in the speedometer cut out.

Upon inspection of the system I found the speedometer drive gear had consumed a few of it's teeth.

What would cause this so suddenly?

I hope I can find the underlying problem before throwing more speedo gears at it.
 
If the metal gear and the plastic gear are compatible and the plastic gear is damaged you may have a binding cable or speedometer.
 
hiperfauto said:
If the metal gear and the plastic gear are compatible and the plastic gear is damaged you may have a binding cable or speedometer.
Click to expand...

Is there a way to test this? According to the green book you simply "spin the cable." Which I did and confirmed the speedometer moves when I do..
 
I drove it around today with the yellow gear... It acts normal, itt doesn't bounce, or waiver... it's just not a correct MPH.

What would be the signs of the cable binding? Of the speedometer itself binding?
 
It sounds like the cable and speedo are okay if it's working with the yellow gear which from what I can tell is what it's supposed to have with 4'10's.

What's the part number on the green gear?
 
YELLOW:

IMG_7916_670.jpg


I'll update with Green tomorrow once I'm back at the garage.
 
Let's not forget plastic being plastic and with all things considered this is a 50 year old soft material, it may have just let go, especially if any contamination made it's way into the gear housing.
 
:nono:

That chart is for 240's. 140's use a speedo with a different number of revolutions per mile.
 
Last edited:
Lol can't blame for trying....ya never did actually specify which vehicle you're talking about

But really just posting for future info. I really like 140s
 
oemoilleaks said:
Is there a chart for the 140?s?
Click to expand...

I wish there was.

According to the greenbook a '67-72 140 with 4.56's used a 380168 blue plastic gear with a 380449 metal gear. With 4.30's they got a 380166 green plastic gear with a 380449 metal gear. With 4.10's they got a 380164 yellow plastic gear with a 380449 metal gear.

A '73-'74 140 with 4.30's used a 380166 green plastic gear with a 380449 metal gear. With 4.10's they got a 380164 yellow plastic gear with a 380449 metal gear. With 3.91's they got a 380861 grey plastic gear with a 381601 metal gear.

Note that all of the plastic gears use the 380449 metal gear except for the grey gear for 3.91's that uses the same metal gear that a 240 with M40 uses.

What's the part number on the metal tag on the transmission?
 
hiperfauto said:
I wish there was.

According to the greenbook a '67-72 140 with 4.56's used a 380168 blue plastic gear with a 380449 metal gear. With 4.30's they got a 380166 green plastic gear with a 380449 metal gear. With 4.10's they got a 380164 yellow plastic gear with a 380449 metal gear.

A '73-'74 140 with 4.30's used a 380166 green plastic gear with a 380449 metal gear. With 4.10's they got a 380164 yellow plastic gear with a 380449 metal gear. With 3.91's they got a 380861 grey plastic gear with a 381601 metal gear.

Note that all of the plastic gears use the 380449 metal gear except for the grey gear for 3.91's that uses the same metal gear that a 240 with M40 uses.

What's the part number on the metal tag on the transmission?
Click to expand...

is there a difference in the number of teeth between the years? Because what you're saying is that the yellow drive gear is the same PN from 67-74, and all but one (the 3.91) have the same 380449 metal gear.

Maybe I'm just confused about what the metal gear is? Do you have a picture? Or a diagram? something that could show where this metal gear lives in the transmission?

I know you already explained how to extract it, but maybe I thought it was something else and that's why I never could extract it.
 
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