Speedometer cable leaking transmission fluid

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MattDoscher
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Speedometer cable leaking transmission fluid

Post by MattDoscher »

On my wife's '65 Comet the speedometer cable will allow transmission fluid to leak out from around the plastic cable housing where it transitions to the metal part going into the C4 transmission.  It's not coming from the O ring it's somehow leaking through the inside of the cable/driven gear and leaking out from where the outside plastic housing of the cable transitions to the metal part of the cable.  It seems to only start leaking when the car has been sitting for a few days.  Is there some sort of seal inside the cable behind the driven gear?  Or do I just need to get a new speedometer cable assembly?  If the O ring was bad the leak would come from further up towards the transmission.

thanks,
Matt
1965 Comet Caliente Convertible
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poboyjo65
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Re: Speedometer cable leaking transmission fluid

Post by poboyjo65 »

A couple things come to mind. Trans has too much fluid in it. or the vent on top of trans clogged up & building up pressure.
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MattDoscher
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Re: Speedometer cable leaking transmission fluid

Post by MattDoscher »

I'll have to check the vent, not sure as to it's condition. I too was thinking of an overfill condition but each time it leaks a good amount of fluid and when I check the dipstick the fluid level is well below the add line so I have to add fluid.
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poboyjo65
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Re: Speedometer cable leaking transmission fluid

Post by poboyjo65 »

Are you checking it with trans hot? also make sure the dipstick tube is all the way in the trans. if it is up this would make the reading on the dipstick wrong & would read low when it isn't low. Make sure it isnt leaking on the cable somewhere else then running down to lowest point to drip off. I have been fooled by a lot of leaks like that. nowdays I always use a mirror with telescoping handle & a good light for my detective work :lol:
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MattDoscher
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Re: Speedometer cable leaking transmission fluid

Post by MattDoscher »

Yes, checking w/ trans at operating temp. I have not verified the tube is all the way inserted into the case/pan, just assumed it was. I'll let you know what I find out.

thanks,
Matt
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Comechero65
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Re: Speedometer cable leaking transmission fluid

Post by Comechero65 »

After I installed the SROD in mine I discovered trans lube likes to run down inside the cable and somehow leaks out the side of the cable at the lowest point. Part of the problem is the cable plugs into the trans below the output shaft whereas most are always above that shaft which reduces the likelyhood of lube getting into the cable.
What I did is install an o-ring inside the cable on the center flex shaft between the sheath and the gear on the end. That seems to have slowed it down some. Not as obvious as before.
Ron
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Re: Speedometer cable leaking transmission fluid

Post by MattDoscher »

Is there a better way to check the vent tube on the tranny short of removing the whole tranny from the car? I have the 3spd auto (C4?) and the metal vent tube is up high on the drivers side and has a few bends to it. I attempted to stick a long zip tie up into it to check for any obvious signs of blockage but it doesn't go past the sharp bend into the fitting on the top of the tranny. The tranny fluid leaks down the outside of my cable.

thanks,
Matt
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poboyjo65
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Re: Speedometer cable leaking transmission fluid

Post by poboyjo65 »

You say it does it after sitting for a while, that makes me think it isnt the vent unless it is coating the trans, then dripping off. I think if you clean the trans really good then coat it in baby powder before a long sit,, then you should be able to track down the leak. If you determine it is indeed coming from the speedo cable then you might try what Ron said, an O ring on the cable. are you parking it an uphill grade? I cant see how fluid could be that high in the trans to come out the cable. here is a video on the different C4s. If yours is original the vent should be like the first one he shows at about 5:44, a short metal tube more on the side. A later 4x4 truck would have a tube on top. Has the fluid been changed lately?

Forgot to put this up
https://www.google.com/url?sa=t&rct=j&q ... 79IPaTPclA
Last edited by poboyjo65 on Sun Feb 19, 2017 10:13 pm, edited 1 time in total.
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Re: Speedometer cable leaking transmission fluid

Post by popscomet »

YEARS ago when my comet still had the c4 in it,the vent was messed up and after it got hot and I killed it ,a few minutes later fluid would come out the filler tube...and I bought a 64 fairlane at an auction that had sat for a very long time,dirt dobbers had built a nest covering the vent,after it got hot,fluid would come from every seal on it,blew back on the exhaust,thought it was on fire at first then I noticed the color of the smoke ,then I knew it was AT fluid,as it was white,,,,after the vents were clear ,it cleared up on both.....POP
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MattDoscher
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Re: Speedometer cable leaking transmission fluid

Post by MattDoscher »

are you parking it an uphill grade?
No. Flat surface in the garage.
an O ring on the cable
It already has the normal o ring on it to seal around the hole on the side of the tranny. If I were to undo the bolt and remove the gear from the tranny fluid will come out. Like I say it doesn't seem to be leaking from around the o ring but rather btwn the cable sheathing and the metal part of the cable end. I do have the C4 as shown in the you tube video w/ the vent tube although I think mine is oriented differently, runs from the top down and to the rear.
Has the fluid been changed lately?
No, not since we've had it in 3yrs. The fluid doesn't look or smell burnt/brown. Maybe it's just a case of being overfilled?

Matt
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bmmaurer
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Re: Speedometer cable leaking transmission fluid

Post by bmmaurer »

Fluid should not come out of the speedo gear hole with gear removed, when the level is correct. The "full level" should fall below that opening.

I suspect you do not have the original dip stick. The 6 cyl and 8 cly tranny sticks are different. (one is longer than the other).

My 2cts...

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poboyjo65
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Re: Speedometer cable leaking transmission fluid

Post by poboyjo65 »

Yea I agree with bmmaurer,,,it should not leak when you take off the cable, & wrong dipstick is first thing that comes to mind. I have a 65 c4 at home,,for a v8. your car is a V8 right??? it is just like the first one in the video,vent on upper side, & a case fil,,dipstick goes into case,,I will measure the dipstick today. If it is that full it is probably coming out the vent when you drive it, if the vent isn't clogged up so you you should still verify it isnt clogged or like Pop said pressure will build & it will push fluid out every seal .
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MattDoscher
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Re: Speedometer cable leaking transmission fluid

Post by MattDoscher »

Thanks BMMaurer, that's probably my issue. JohnO, no I have the 200 6cyl.
1965 Comet Caliente Convertible
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MattDoscher
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Re: Speedometer cable leaking transmission fluid

Post by MattDoscher »

The dipstick that's in it now measures 23 5/8 inches from tip to tip. It does not say FOMOCO on it or have any kind of FOMOCO stamping/part number on it. It only says F L and with engine at idle.
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poboyjo65
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Re: Speedometer cable leaking transmission fluid

Post by poboyjo65 »

My v8 c4 the dipstick is missing. Maybe someone with a 65 6clinder can measure theirs. I dont know if a c4 was available in a 6 before 65.
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