What's going wrong here?

[Skunksmash]

For some reason I can't seem to fix this leak. My 700-R4 in my 87 Silverado 2WD 5.7L is leaking out of the speedometer cable port. I ordered a new seal for the inside, and put it in to the best of my ability. I couldn't tell any difference between the way the old seal was in, and the way that I put the new one in. Yet it still leaks. Its the last rubber seal right before you get to the speedometer cable itself.

I don't understand why its still leaking. Its extremely irritating to have done the proper fix for something and still have it be screwing up. Does anyone know if fluid getting in the speedometer cable, can somehow harm the cable? Or perhaps, the speedometer itself?

[RT Big Block]

Is your vent tube on the trans. plug up ? I have seen that happen a lot .

[Skunksmash]

I was not aware that such a vent tube existed. Where exactly is it located?

[zach33]

How did the inside of the bore look where the seal goes. It could have been damaged from installation or removal from a previous seal.

[geezer#99]

Originally Posted by Skunksmash

I was not aware that such a vent tube existed. Where exactly is it located?

http://www.justanswer.com/chevy/71oh...c-diagram.html

[Skunksmash]

Originally Posted by zach33

How did the inside of the bore look where the seal goes. It could have been damaged from installation or removal from a previous seal.

I didn't really notice anything. I just had a thought though. Can a person just buy a brand new cover with a new seal already installed? For some reason I was thinking that you'd have to buy a whole new trans to get a new speedometer cable port. But its really just a little piece of metal that bolts to the tranny. Does anyone know if you can just buy another one somewhere? I'll go check rockauto.

Originally Posted by geezer#99

http://www.justanswer.com/chevy/71oh...c-diagram.html

The vent tube is all the way on the top? Can you verify that? Hope I can reach all the way up there and get to it somehow. I assume I don't just rip it off of there. LOL

If its all the way up there, what method is best of... I don't know... checking it for being clogged? Or cleaning it out?

[Skunksmash]

Found this. There is a seal inside where the speedo cable screws on. This is the thing that keeps leaking. I see the fluid coming out right where the speedo cable screws on. And its driving me freakin crazy. Only thing is I don't know which one to buy. There is one for "USE WITH 34 THRU 39 TEETH GEAR". And another one for "USE WITH 40 THRU 45 TEETH GEAR".

I have the 2:73 rear end gear ratio. Can anyone tell from that, which one I need?

[pwradder]

if you clean off the housing, there should be some visable numbers stamped on it- 40-45 or 34-39. although, i dont think you need a replacement, i'd try removing it and running a light bead of silicone around the o-ring first.

[Skunksmash]

Does anyone know if you can do any kind of cleaning on the vent tube without removing the transmission from the truck? And where does stuff get trapped? In the tube itself, or down inside where the tube connects to the transmission?

[Tx Firefighter]

Before you throw any more parts at it, look closely at the speedometer gear. Those plastic gears get grooves worn into them over time from the seal. A new seal won't stop the leak if the gear is too far gone.
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[Mr.Chevy4x4]

Originally Posted by Skunksmash

Found this. There is a seal inside where the speedo cable screws on. This is the thing that keeps leaking. I see the fluid coming out right where the speedo cable screws on. And its driving me freakin crazy. Only thing is I don't know which one to buy. There is one for "USE WITH 34 THRU 39 TEETH GEAR". And another one for "USE WITH 40 THRU 45 TEETH GEAR".

I have the 2:73 rear end gear ratio. Can anyone tell from that, which one I need?

Believe it or not the plastic gear will wear the aluminum housing into an oblong shape and a new seal will never keep it from leaking. Here is a link that will show you what your speedometer gear ratio currently is.

http://www.73-87.com/7387garage/drivetrain/speedo.htm

"The speedo gear combination for a 2.73 rear (assuming 29-inch diameter tires) is a 18-tooth drive gear and 35-tooth driven gear."

Hope this helps.

Mike

[mMad Dawg]

If you go to a GM dealer and tell them the color of the gear you should be able to get the right one. Each gear ratio is a different color . Hope this helps.

[Skunksmash]

Originally Posted by Tx Firefighter

Before you throw any more parts at it, look closely at the speedometer gear. Those plastic gears get grooves worn into them over time from the seal. A new seal won't stop the leak if the gear is too far gone.
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Originally Posted by Mr.Chevy4x4

Believe it or not the plastic gear will wear the aluminum housing into an oblong shape and a new seal will never keep it from leaking. Here is a link that will show you what your speedometer gear ratio currently is.

http://www.73-87.com/7387garage/drivetrain/speedo.htm

"The speedo gear combination for a 2.73 rear (assuming 29-inch diameter tires) is a 18-tooth drive gear and 35-tooth driven gear."

Hope this helps.

Mike

From what yall are saying, it sounds like I need to just rebuild the whole system. If the aluminum can be wore by the plastic gear, than I need an new aluminum piece like the one in the pic I posted earlier. And if the gear itself can age and get worn down and also cause a leak, then I need a new gear. I'm generally not one to just throw parts at a vehicle but in this case it seems as though I've no way of knowing if its ever going to be fixed, unless I replace both.

It would get on my nerves to replace one and have it be the other, so since both parts are fairly inexpensive I'll just do both. I will be using factory tire sizes for an 87 half ton 2WD truck. IIRC, those are 28 inch tall tires.

[Tx Firefighter]

You're on the right track. Replacing the housing and gear both aren't very expensive and should give you another 30 years of good service. I seem to remember that new OEM GM housings even come with a new internal seal already installed in them when you take them out of the package. Be sure an get a new o ring for the outside of the housing if it doesn't come with one of those too. After that, you've covered all the bases thoroughly.
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[Skunksmash]

EDIT:

Found this site:


http://www.transmissioncenter.org/GM...eter_Gears.htm

Guess all I need is a 35 tooth speedometer gear and a new housing off that site.