Transmission Yoke leak- 88 GMC 1500

[jcain226]

Newbie here- have atf leak from what appears to be the yoke at front ujoint. See pics. From what I have read, the yoke has a permanent seal in the center that can leak.

Con someone experienced with this confirm that is what the leak appears to be?
If so, Is the repair as straight forward as removing the driveshaft and changing out the yoke for a new one? Remove 4 rear bolts to drop shaft and slip yoke out, then replace?

Is there anything I should watch out for? Anything I can damage worse by trying the repair?

Thanks in advance!!

 

[stutaeng]

Rear tailhousing seal leak it looks like. Remove driveshaft, then remove the tailhousing and take it to the bench. Remove the seal by hitting/collapsing it carefully with a flathead screwdriver. Install new seal by tapping it with a block a wood.

Give the yoke shaft a few swipes with a Scotchbrite pad to make sure there's major gouges, scoring or wear marks.

 

[jcain226]

Rear tailhousing seal leak it looks like. Remove driveshaft, then remove the tailhousing and take it to the bench. Remove the seal by hitting/collapsing it carefully with a flathead screwdriver. Install new seal by tapping it with a block a wood.

Give the yoke shaft a few swipes with a Scotchbrite pad to make sure there's major gouges, scoring or wear marks.

Is the tailhousing seal the seal in the picture with the red ring around it?
If so, there doesn’t appear to be any fluid coming from there; the fluid appears to be coming from in between the yoke bracket and the Ujoint. Does that make sense?

 

[stutaeng]

Is the tailhousing seal the seal in the picture with the red ring around it?
If so, there doesn’t appear to be any fluid coming from there; the fluid appears to be coming from in between the yoke bracket and the Ujoint. Does that make sense?

Yes, it the red seal. Maybe it leaks only when driving and the wind pushes the fluid back into the yoke? Does that seal look kinda new to you? You've been having this truck for a while? Or just bought it?

Remove the yoke and see if it has a little hole on the end of the U joint. At least on the 2 piece driveshafts, the center carrier yoke on my truck had a little hole there. Never understood why it had a hole. But the yoke on the transmission end I don't recall it having the little hole.

Edited for clarification.

 

[jcain226]

Yes, it the red seal. Maybe it leaks only when driving and the wind pushes the fluid back into the yoke? Does that seal look kinda new to you? You've been having this truck for a while? Or just bought it?

Remove the yoke and see if it has a little hole on the end of the U joint. At least on the 2 piece driveshafts, the (my) yoke had a little hole there. Never understood why it had a hole. But the yoke on the transmission end I don't recall it having the little hole.

Yes, that seal was replaced recently; I wasn’t sure what it was called, but it was replaced to fix a previous leak.
I parked it on an incline in my driveway last night, so the fluid was pushing that way due to the incline.

 

[Turbo4whl]

Yes, some model's yokes have a sealed plug. Some have a vent, they also have a spring and a vent seal. If it has a vent it would be a small hole dead center on the plug.

Your yoke is most likely not vented. It damaged or rusted if it is leaking.

Is there anything I should watch out for? Anything I can damage worse by trying the repair?

Torque twist will damage a yoke. When you remove the yoke look in at the splines, partway down, do they have a twist? A more powerful engine on a stock driveline can twist a yoke. Large diameter tires on a tall gear set will also push back hard on the trans.

In your picture it looks like the yoke is not in the trans as far as it should be. This also can cause a twist.

 

[jcain226]

Yes, some model's yokes have a sealed plug. Some have a vent, they also have a spring and a vent seal. If it has a vent it would be a small hole dead center on the plug.

Your yoke is most likely not vented. It damaged or rusted if it is leaking.



Torque twist will damage a yoke. When you remove the yoke look in at the splines, partway down, do they have a twist? A more powerful engine on a stock driveline can twist a yoke. Large diameter tires on a tall gear set will also push back hard on the trans.

In your picture it looks like the yoke is not in the trans as far as it should be. This also can cause a twist.

Thanks for the info! I will check it out tomorrow! How would I make it go into the trans more? Doesn’t it slip in and out with normal driving and movement?

 

[stutaeng]

You are supposed to insert the yoke until it bottoms out and then pull it out 3/4" IIRC.

Mark it with a sharpie and check...

 

[jcain226]

You are supposed to insert the yoke until it bottoms out and then pull it out 3/4" IIRC.

Mark it with a sharpie and check...

Gotcha! Thanks!

 

[Turbo4whl]

Thanks for the info! I will check it out tomorrow! How would I make it go into the trans more? Doesn’t it slip in and out with normal driving and movement?

If you have a one piece drive shaft, you can't chance how far the yoke is in the trans. Is the truck lifted? If it is you may need a longer drive shaft.

Did you get a chance to take it apart for look see inspection?