Speedo Sensor Leaking Trans Fluid in Cab?

[Rembrant]

Gents,

I just discovered that I'm having this problem with my newly installed M5OD. I was getting a drip on the floor every now and then...happened maybe 3 times, a single drip off the bottom of the clutch pedal. I reached up there today, and the back of the hood latch handle bracket is covered in oil, and when I look further up, I can see the red trans fluid drips hanging off the dash end of the speedo cable...lol.

What a bugger.

Any suggestions on what to do with this? It didn't seem to happen with my old 3-speed...but it had gear oil in it, I assume.

 

[Gary Lewis]

Yipes! I'll bet your speedo runs smoothly.

Check to see if your tranny has too much fluid in it?

[Rembrant]

Check to see if your tranny has too much fluid in it?

I'll check it, but I didn't think there was any way to overfill it? The truck was on level concrete floor, and I put the fluid in the hole until it leaked out. Interesting.

I found a thread on FTE where this happened to another guy that swapped an M5OD into an 85 Bullnose. He said he installed some kind of speed sensor adapter "in front of" the cable...whatever that means.

I replaced every seal in the trans...it's tighter than a frog's butt and doesn't leak a single drip otherwise, so I was sure it was a venting problem, but the guy on FTE said he added a vent and it didn't fix it.

What a stupid problem...lol.

 

[Gary Lewis]

Check to see if your tranny has too much fluid in it?

I'll check it, but I didn't think there was any way to overfill it? The truck was on level concrete floor, and I put the fluid in the hole until it leaked out. Interesting.

I found a thread on FTE where this happened to another guy that swapped an M5OD into an 85 Bullnose. He said he installed some kind of speed sensor adapter "in front of" the cable...whatever that means.

I replaced every seal in the trans...it's tighter than a frog's butt and doesn't leak a single drip otherwise, so I was sure it was a venting problem, but the guy on FTE said he added a vent and it didn't fix it.

What a stupid problem...lol.

If you filled it through the filler hole on level ground then it is at the correct height. I've never heard of that problem, but then I've not been around an M5OD either.

The adapter is probably the later one that goes into a regular speedo gear hole and provides both the mechanical speedo drive as well as the electrical one that the computers want.

[Rembrant]

The adapter is probably the later one that goes into a regular speedo gear hole and provides both the mechanical speedo drive as well as the electrical one that the computers want.

Yessir...that sounds like it. So it would go in the trans, but I could still attach my original speedo cable to it, am I understanding that correctly?

 

[Gary Lewis]

The adapter is probably the later one that goes into a regular speedo gear hole and provides both the mechanical speedo drive as well as the electrical one that the computers want.

Yessir...that sounds like it. So it would go in the trans, but I could still attach my original speedo cable to it, am I understanding that correctly?

Yes. But, that begs the question of if the oil continues to come out, and if not why not? And if it does, where does it go?

[Rembrant]

Yes. But, that begs the question of if the oil continues to come out, and if not why not? And if it does, where does it go?

Well, I dunno. All I know is in the thread on FTE, the guy said he installed the sensor/adapter that was from the 1988 donor vehicle, and that cured the leak. I guess that adapter must have a seal in it?

I'm just trying to find out what they're called so I can find one (Ebay or aftermarket, etc).

[Rembrant]

Yes. But, that begs the question of if the oil continues to come out, and if not why not? And if it does, where does it go?

I guess this is it?

https://www.rockauto.com/en/moreinfo.php?pk=40876&cc=1121971&jsn=8

So, I'd pop the driven gear off of my cable, then install on the this adapter, and then stick my cable in the back of it?

I guess that is the question...will my original 1984 cable work in this VSS/Adapter? Or would I have to buy a cable specific to this adapter (IE:. from a factory 5spd truck).

[Gary Lewis]

I guess this is it?

https://www.rockauto.com/en/moreinfo.php?pk=40876&cc=1121971&jsn=8

So, I'd pop the driven gear off of my cable, then install on the this adapter, and then stick my cable in the back of it?

I guess that is the question...will my original 1984 cable work in this VSS/Adapter? Or would I have to buy a cable specific to this adapter (IE:. from a factory 5spd truck).

Yes, that's the guy. And your cable should plug right into it just like into the transmission. But you do have to move the driven gear as you said.

Here's what I've found.

First, the catalog says it looks like this:

Second, here's a snippet from the calibration parts list for '87 and '88 trucks. Note that the part numbers match the Rock Auto listing.

[Rembrant]

Yes, that's the guy. And your cable should plug right into it just like into the transmission. But you do have to move the driven gear as you said.

Here's what I've found.

Second, here's a snippet from the calibration parts list for '87 and '88 trucks. Note that the part numbers match the Rock Auto listing.

Gary, thank you very much kind sir! You are awesome...it is so nice to so quickly remove all doubt on buying a part;). Thank you for the details.

Having found a thread where this cured the problem, I think it's a cheap solution to try.

Must have something to do with the design of the M5OD combined with the watery thin Trans Fluid;).