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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Thornton93 on March 27, 2016, 11:20:11 pm
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Hello, I have a '87 v10 700R4 NP208 truck that's leaking trans fluid out of the rear driveshaft slip yoke and can not for the life of me figure out why. First I thought it was the rear output seal so I replaced that. Then noticed it still leaking but now I can see plain as day it's coming out of the yoke and I'm stumped. Do I need to replace the slip yoke? Any help would be much appreciated. Thank you for your time.
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Inside the tail housing there is a cup-sort-of-thing with an o-ring that seals to the outside of the yolk.
When this seal is gone, fluid will get inside the splines of the yolk, and weep out a hole conveniently drilled in the back of the yolk right by the u-joint.
There are many ways of dealing with this. I JB-Welded the weep hole closed on mine, and it's been fine since.
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Welcome. Remove the slip yoke. Clean both outside and inside so they are dry and clean. Put RTV silicone on both sides of the middle. I.e in the middle behind the u joint on both the outside and inside. When the RTV is dry, reinstall and top off trans fluid as necessary. Never worry about it again.
Some slip yokes have a weep hole and sometimes they leak. You can weld it closed also if you want or replace it with a yoke that has no weep hole. RTV is just as good tho. This topic was just covered not to long ago for another member. Use the search tool and you should be able to find the thread.
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I have a 700R4 in my 75 that was doing the same thing. Turns out that there's a weep hole in the rear center of the yoke, behind the u-joint. I talked to a few tranny guys and they told me to just weld up the hole. Worked perfectly and I didn't have to rebalance anything. You might check if yours has the same type of weep hole.
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LTZ didnt you already answer this..?
http://forum.73-87chevytrucks.com/smforum/index.php?topic=32788.msg278327#msg278327
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Well I check the yoke and mine does NOT have a hole in the mind of the yoke. So I'm assuming it's my yoke that is bad. Correct or no?
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Post pics.
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LTZ didnt you already answer this..?
http://forum.73-87chevytrucks.com/smforum/index.php?topic=32788.msg278327#msg278327
Yes that's the topic I was referring to for the original poster to search for.
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If it is for sure leaking around the outside of the yolk, and a new seal does not fix it, it is likely the tailhousing bushing is worn. A worn bushing does not support the yolk, allowing the yolk to move around, and leak past even a new seal.
Often, a leaky seal is a result of a worn bushing.
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I have a 700R4 in my 75 that was doing the same thing. Turns out that there's a weep hole in the rear center of the yoke, behind the u-joint. I talked to a few tranny guys and they told me to just weld up the hole. Worked perfectly and I didn't have to rebalance anything. You might check if yours has the same type of weep hole.
Yup, that's what I was told by about 50 people, except RTV did the trick for me, and only on the one side facing the shaft I applied it. Dry as dust ever since.