Got some kind of leak

[Skunksmash]

I think that the part in the pic is... has something to do with the speedometer cable. There is a cable coming out of it and running towards the front of the truck. I had the transmission rebuilt 3 years ago when I bought the truck by a trusted specialist so I don't think it would be the tranny itself. Is this part that the speedo cable connects to, capable of leaking? I think it was different on my 81 than on this 87. I think on my 81 the cable just went straight on into the tailshaft without having to go into this part. Anyone know what that part is called?

I have the truck jacked up from under the front in these pics, so that may account for the driveshaft sticking out a little too far. Maybe. Not sure. But I also wanted to ask if this seal leaks. The one in the pic where I point to the seal in the tailshaft. Does that seal ever leak? If so, is it hard to replace? It really looks like its just that one little speedo part that is leaking but I thought I'd ask anyway.

[Skunksmash]

I think it may be possible that the fluid on that seal, came from the speedometer part that is leaking. Not real sure though.

Oh, forgot to say its a 1987 TBI 5.7L 2wD with 700R4 automatic.

[firefighter]

The piece that the speedometer cable is screwing into looks like one of the pieces that I just learned about in one of the other threads. It looks like a speedometer compensator. It's kind of a gear reduction/increaser to help correct the speedometer for tires size other than stock.
I don't know if the speedometer port is capable of leaking or not. I don't believer there is any kind of seal in the part that screws on to the transmission.
I'm sure you'll get more responses.

The rear seal where the driveshaft goes into rear of the transmission is replaceable externally. You just have to remove the driveshaft and pop the seal out, put a little sealer on the new seal lip, and tap it back in. That one if fairly easy to replace and I've had one leak before.

Hope you get it figured out.

[Skunksmash]

Ok good. Maybe they're both leaking heh. Looking at it though, there doesn't seem to be any fluid in between the two suspected leak points. So its hard to imagine that fluid leaked out of the seal, and then somehow made its way all the way up to that speedometer correction thing. I think it may be more likely that the fluid was dripping out of the speedo thing, and its somehow gotten back to that seal area.

[Skunksmash]

Anyone know if those speedometer compensator units were there from the factory? I don't remember that thing being there on my 81. I had to change the cable on that truck. Maybe its an aftermarket part or something?

[zieg85]

Anyone know if those speedometer compensator units were there from the factory? I don't remember that thing being there on my 81. I had to change the cable on that truck. Maybe its an aftermarket part or something?

Usually seen on trucks with oversize tire options.  I personally have only had them on 2 trucks over the years that I know of.  One was on my 72 K20 and the other was a heavy half ton C10

[bake74]

     Both of those are capable of leaking.  Though as firefighter said, the tail shaft seal will be easier to replace.  If memory serves me right, the  speedometer compensator screws into your transmission in a dry area, the seal is inside in the next step of the transmission which means you would have to take 2 part off transmission to get to the seal.

[bd]

Anyone know if those speedometer compensator units were there from the factory? I don't remember that thing being there on my 81. I had to change the cable on that truck. Maybe its an aftermarket part or something?

They are standard from the factory on 1987 TBI trucks.

[Skunksmash]

     Both of those are capable of leaking.  Though as firefighter said, the tail shaft seal will be easier to replace.  If memory serves me right, the  speedometer compensator screws into your transmission in a dry area, the seal is inside in the next step of the transmission which means you would have to take 2 part off transmission to get to the seal.

So I need to remove the tailshaft? Do you think this can be done without removing the whole transmission? Never done this before.

[bd]

     Both of those are capable of leaking.  Though as firefighter said, the tail shaft seal will be easier to replace.  If memory serves me right, the  speedometer compensator screws into your transmission in a dry area, the seal is inside in the next step of the transmission which means you would have to take 2 part off transmission to get to the seal.

So I need to remove the tailshaft? Do you think this can be done without removing the whole transmission? Never done this before.

The output shaft seal can be replaced by pulling the driveline and changing it, just as "firefighter" posted, above.

For the speedo adaptor (compensator) leak:
1 )  unscrew the cable and remove the speedo adaptor along with its steel drive key,
2 )  remove the single 6mm bolt (10mm head) and "Y" shaped flat steel retainer,
3 )  remove the aluminum speedo gear sleeve with the plastic gear,
4 )  push the plastic gear out of the sleeve and inspect the outer (speedo adaptor) end of the gear shaft,
5 )  the leaking "seal" is the small (~1/2" diameter) soft rubber lip seal at the outer end of the sleeve - it should be installed with the lip pointing toward the "toothed" end of the gear,
6 )  inspect the plastic gear - if the gear has a concentric groove worn all the way around the speedo adaptor end of the gear shaft, then the gear is worn out (you'll need to count the number of teeth and note the color of the gear to get the proper replacement),
7 )  slip the gear all the way back into the sleeve and wiggle it side-to-side at the inner (toothed) end - if the gear has any appreciable side-to-side movement (greater than ~0.015"), the aluminum speedo sleeve is worn out (you'll need to count the number of teeth on the plastic gear to get the correct replacement sleeve),
8 )  if the gear and sleeve are in good shape, reassemble with a new rubber lip seal for the gear and a new o-ring for the outside diameter of the aluminum sleeve.

[Skunksmash]

Thank you sir. I will definitely use that when I repair.

[beastie_3]

remember to have your wheels chocked when disconnecting the driveshaft, as well as e brake set.

[Skunksmash]

Yeah I will do that. Glad you reminded me.

[Skunksmash]

The rear seal where the driveshaft goes into rear of the transmission is replaceable externally. You just have to remove the driveshaft and pop the seal out, put a little sealer on the new seal lip, and tap it back in. That one if fairly easy to replace and I've had one leak before.

Hope you get it figured out.

What type of sealer would you use? Just that black high temp RTV automotive silicone like they have on the shelf at any auto parts store?

[Skunksmash]

Also I found this weird spring-ring in there. Its real springy and stretchy. Not sure how to put it back cause I found it laying on the ground under the tail shaft lol