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What causes a speedo gear to eat itself?

Mbeas96 said:
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
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True, I didn't! but I did say what year the engine, trans, and rear axle were.. all of them were before 1975 (the first 240). :lol:
 
oemoilleaks said:
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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I'm not sure if the metal gear in question has a different number of teeth or if it just has a different pitch.

The metal gear is #51 in this diagram. The speedo gear, driveshaft flange and rear seal need to be removed to get to it.

GR-13839.jpg
 
Ahh ok that's what I thought it was, but I don't have the necessary tools to remove the driveshaft flange... What size is that nut?
 
The nut on the late M40's is 1-1/8".

Let me know if you need to borrow the flange tools.

I can probably tell you what metal gear is in the trans if you can provide the part number on the metal tag near the trans mount.
 
The part number appears to be 1208000 and if so that trans came out of a '75 240 and therefore should have a 381601 metal gear. It could have been changed but that's what it would have come with from the factory.
 
hiperfauto said:
The part number appears to be 1208000 and if so that trans came out of a '75 240 and therefore should have a 381601 metal gear. It could have been changed but that's what it would have come with from the factory.
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So I would need a 381603 speedo gear then, right?
 
oemoilleaks said:
Any other way to tell/confirm the year of the trans? There?s an ?m51? casting mark on the side.
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'75 transmissions have a few extra ribs on the outside of the case.

oemoilleaks said:
So I would need a 381603 speedo gear then, right?
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I don't think so because a 240 speedo uses a different number of revolutions per mile.

I really think you have the wrong metal gear. Get the metal gear out of your old trans and use the green plastic gear.
 
hiperfauto said:
'75 transmissions have a few extra ribs on the outside of the case.




I don't think so because a 240 speedo uses a different number of revolutions per mile.

I really think you have the wrong metal gear. Get the metal gear out of your old trans and use the green plastic gear.
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Ok gotcha! Apologies for not understanding what you were saying earlier.. I was told this was a '74 gearbox which threw me for a loop when you said all the metal gears were the same.

The green gear I had is toast now. Any shot you guys have a 308603 (since it's a 240 gearbox) green gear laying around?
 
There is no such thing as a 308603. Did you mean 381603? If so, it's dark red not green.

I never said all metal gears are the same. What I said was:

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.
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Your trans is out of a '75 so it has the wrong metal gear for a 140 with anything but 3.91's.

The metal and plastic gears need to be compatible. If not it will destroy the plastic gear.

You need to swap the metal gear from your old trans and get another green 380166 gear which I have.
 
This is all very relevant and good information. Unfortunately a day late and a dollar short since I just swapped overdrives and found out that now my speedometer is around 80 indicated when GPS says I'm doing reads 65 actual.
 
hiperfauto said:
There is no such thing as a 308603. Did you mean 381603? If so, it's dark red not green.

I never said all metal gears are the same. What I said was:



Your trans is out of a '75 so it has the wrong metal gear for a 140 with anything but 3.91's.

The metal and plastic gears need to be compatible. If not it will destroy the plastic gear.

You need to swap the metal gear from your old trans and get another green 380166 gear which I have.
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Yup! You're right on all accounts. I will probably need a rear gasket as well. On second thought.. do you guys have time this weekend? I'm going to give you a ring.
 
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