U-Joint Leaking?

Sounds weird, I know, but my U-Joint between the transmission output shaft and the propellor shaft is soaking wet with red fluid. At this time it is dripping fluid at the rate of about 1 drop per minute or more.

I had just fixed the last leak in my transmission, the speed sensor housing, just a couple of weeks ago. Its been doing great, no fluid loss from anywhere on the tranny.

I ride a MC for my daily commute to work, so the truck has been sitting for the last 4 days, since last Monday when I drove it last (Scout meeting). Today, Friday, driving up the road I noticed a larg puddle of fluid under the truck, I checked and the U-Joint is covered in fluid. The checked the output shaft all the way around and totally clean, except for road dirt and grime, no fluid coming from the rear tranny seal.

Is it possible for tranny fluid to come though the middle of the output shaft from inside the tranny and come out where the U-Joint is?

Any input greatly appreciated...

Hoping to get this fixed asap since we have Hurrican Gustave coming to visit early next week.

well, ain't no transmission fluid inside the yoke and cardan joint, so it can come only from trannie.
sounds like the output shaft seal is busted. yoke is solid piece, does not have holes in it, splines on solid rod.
change the seal.
btw, make sure you do not overfill trannie, as it blows gaskets and seals.
also, your yoke might have crack in it that serves as a channel for fluid to drip out.

What year and transmission?
Does the yoke have a small vent hole in the center yoke plug?

Thanks for the input, kinda figured I was going crazy. I'm gonna pull the u-joint today and the output shaft out to see what I can see, obviously tranny fluid comming from somewhere. Thought I had this thing sealed up, oh well.

Sorry, 92 regular cab stepside truck with 350 and 700R4 (4L60) combo. All original, no rebuilds yet, just fixing leaks as they come. I'm close to pulling the tranny to have a seal job done but I'm one of those who likes to wait till it falls out of the truck before I fix it. The tranny is working beautifully, for a 225,000 miles of wear, just a little leaky.

If the yoke with the small vent hole in the center it will need the tin tube/shield seal inside tail shaft replace or fixed.
If not check rear transmission seal and bushing and for wear on yoke.

when you'll be replacing transmission seal, please, inspect the slip yoke. as far as i know, it's hollow inside, with splines that engage the output shaft in transmission. though they say that leaking seal will cause THE FRONT of the driveshaft be soaked with the fluid, and SOMETIMES the transmission rear end, i'd still look for crack in the yoke. seal might be ok, but it might be leaking through the crack. might be a hair crack.
what is that they use to spot haircracks? UV light?

Sorry, 92 regular cab stepside truck with 350 and 700R4 (4L60) combo. All original, no rebuilds yet, just fixing leaks as they come. I'm close to pulling the tranny to have a seal job done but I'm one of those who likes to wait till it falls out of the truck before I fix it. The tranny is working beautifully, for a 225,000 miles of wear, just a little leaky.

I've replaced the tail shaft bushing,O rings and seals before...this is not difficult....the use of OEM seals is recommended aftermaket seals are inferior...just compare quality...


On your leaks,,,I have used transmedic seal conditioner , this product works great to stop non synthetic transmission fluid leaks..


Since I now only use synthetic,, none of my vehicles have any leaks...

Pulled the shaft and sliding yoke today. The rear u-joint feels very smooth in all of its directions. The front u-joint feels very rough, like the pin bearings are not seated or worn. I greased the u-joints, they have the zirk fitting at the center of the tee, and re-installed the shaft and sliding yoke. I greased the sliding yoke splines liberally. I think the front u-joint broke a seal and lost its lube oil/grease and that was what was leaking. As of the last two days there has been no more fluid loss from the u-joint area. Another reason why I believe the u-joint itself is bad.

The sliding yoke did not have a vent hole through it, or it didn't appear to have hole through it with all of the road grime. I believe something is wrong with the front u-joint, since it didn't feel smooth at all when it was off the truck. I didn't take it out of the yoke or shaft, don't have the tools for that.

As far as the tranny is concerned, no apparent leak path anywhere from the tail assembly or the slip yoke. I didn't inspect the yoke for cracks, again no equipment for that. In the next couple of weeks I'll have to pull the shaft and yoke again to replace the front u-joint and I'll get the slip yoke inspected at that time for cracks.

Pulled the shaft and sliding yoke today. The rear u-joint feels very smooth in all of its directions. The front u-joint feels very rough, like the pin bearings are not seated or worn. I greased the u-joints, they have the zirk fitting at the center of the tee, and re-installed the shaft and sliding yoke. I greased the sliding yoke splines liberally. I think the front u-joint broke a seal and lost its lube oil/grease and that was what was leaking. As of the last two days there has been no more fluid loss from the u-joint area. Another reason why I believe the u-joint itself is bad.

The sliding yoke did not have a vent hole through it, or it didn't appear to have hole through it with all of the road grime. I believe something is wrong with the front u-joint, since it didn't feel smooth at all when it was off the truck. I didn't take it out of the yoke or shaft, don't have the tools for that.

As far as the tranny is concerned, no apparent leak path anywhere from the tail assembly or the slip yoke. I didn't inspect the yoke for cracks, again no equipment for that. In the next couple of weeks I'll have to pull the shaft and yoke again to replace the front u-joint and I'll get the slip yoke inspected at that time for cracks.


replace the forward U joint,, replace the transmission tail shaft seal and you should be good...