Speedo cable leak?

[Skunksmash]

I'm still having trouble with my 700R4 leaking. In my 87 silverado 2WD 5.7L. It has that speedometer compensator thing that the speedometer cable plugs into. Its there to sort of adjust for larger tire sizes than stock. Then that thing, the compensator unit, goes right into the side of the trans.

Well something is leaking trans fluid. And I think that it may actually be the cable itself. I went to take the whole assembly apart and look for the bad seal, but when I unscrewed the speedometer cable, a thin black plastic thing fell out. It looks like it sort of went up inside the speedo cable end somewhere.

Can a bad speedo cable seal cause a leak in some vehicles? Cause I'm starting to think that's what's causing mine. I couldn't even get the little black plastic thing to go back on so I just left it off and screwed the speedo cable back in. Now my speedometer gauge doesn't work. Could it be possible that all I need is just a new speedometer cable? I'm used to my old truck's turbo 350 where the speedo cable seal against any fluid and when you took it off, it was dry other than maybe a little grease.

[hatzie]

Scroll down this page for the gear housing seals.
http://www.transmissioncenter.net/sp...n_______va.htm

As you discovered the black plastic piece is needed. I don't remember how that sleeve fits. Maybe someone will pipe up that's done it more recently.

[Skunksmash]

I just never thought that tranny fluid made it all the way to the speedo cable itself.

[hatzie]

Originally Posted by Skunksmash

I just never thought that tranny fluid made it all the way to the speedo cable itself.

There's always some fluid in the tail. The speedo gear will pick it up. If that seal isn't in good shape it'll seep out wherever it can.

[Skunksmash]

Yeah that's kind of what I'm afraid of. I went to take off that whole assembly. And then the fluid starting pouring out. It poured out like all of the fluid in the trans was going to come out. I really don't want that. The hole in the side is like 2.5" so you can imagine how it started pouring out of there.

I guess I could always just catch all the fluid in something clean, then pour it all back in when I was done working on the trans. Ugh. Don't really want to buy 5 quarts of fluid just cause I had a tiny little seal leaking somewhere. Oh well. Guess I'll have to deal with it one way or another.

[darush01]

My 83 th350 didnt have the compenstor thing the cable went into the trans but it leaked the whole time i had it i finally gave up and just added fluid once a week
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[hatzie]

There are a couple seals in the speedometer gear housing. They all need to be in good shape and the gear shaft needs to not have a groove.

[Skunksmash]

Is it difficult to rebuild all that and replace all the seals? It seems some seal in mine is leaking somewhere, and its coming out through the speedometer cable.

[hatzie]

It's pretty straightforward.
As I recall there's an O-ring around the large diameter of the housing. The seal that's leaking on your rig looks kinda like a brake caliper seal. It's inside the housing near the outer threaded end of the gear housing.

I'd replace both cause they cost around $3 for the set.