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4L80 Issue

RI Chevy Silveradoman

RI Chevy Silveradoman

At your service
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I am posting for a new fellow member that needs some help. I am not much of a tranny guy, so I am sure he will get the help he needs.

I've never had a 4L80E. I just need to verify something and get info on the required solution for a problem:
I have my 2500 6.5 TD jacked up in the front with the tires about 5" off the ground to wash out the back before putting Rust Doctor on the diamond plate floor. The transmission fluid (new filter and fluid put in after complete DIY fluid flush and replacement) is dripping quite fast -5' wet circle of fluid in the driveway, from the back of the trans and dripping off the universal yoke.
Whenever I see a seal leaking like this one is, my experience is that the bearing on the other side of the seal needs to be replaced, because that is what usually causes a seal to wear out and leak as fast as this one is. But, I've been all over the internet and can't find a diagram or exploded view that shows an output shaft rear bearing or bushing.
I'd like to know if this leak is a common thing on this trans with 140,000 miles, and what do I need to replace to keep the seal from going bad? The driveshaft on the truck has been replaced, rebuilt, or rebalanced. It is painted with the ID of the last owner - City of Norfolk. I've had a rebalance done on a previous truck and recognize the marking, and I'm pretty sure it's the same place, that specializes in driveshaft repair, that did my driveshaft work.

Is there a bearing or a bushing on the output shaft or that the nose of the front universal yoke goes in? If it's a bushing I guess the rear tail piece of the trans has to come off, maybe for a bearing replacement also.

I went to Rock Auto. They show a bearing, bushing and seal and gasket for the extension housing. I'm guessing I need all of those. It's not a lot of money. If that's what I need to do, that's going to follow the bed painting. While it's up in the air, I'll put the inline filter in the trans fluid line.


Just let me know if I'm on the right track. Thanks

Quentin - QinVB
 
I have some pdf manuals, the site says they are to large to upload. I got them off the internet so a little searching should come up with something.
 
Theres a bushing in the very rear tail cone if it's a 2 wheel drive. With a leak of that size I would check to see if it is dripping from the seal, or if it is dripping out of the yoke itself. If it's a slip yoke(just slides into the trans, doesn't use a bolt to hold the yoke in), then theres a welch plug in the end of the yoke behind the u joint. It's not uncommon for when driveshaft work is done, for somebody to accidentally push the shaft in to far getting everything in, and knock that plug loose. When that happens, you get a sizeable leak like this. Seals that leak from a bad bushing normally leak while driving when the shaft is under a load. And unless the seal is completely cracked, they normally leak bad only when the part its trying to seal is rotating. Check that welch plug and see if its leaking there 1st. If so, you can clean it up good with brake cleaner, and jb weld over it to seal it.
 
Thank you, thank you, thank you. As I noted in the original post the driveshaft has been worked on by a local shop. Fluid level was good before I flushed the tranny, put 20 quarts through it and got some black skanky looking oil out of it at the beginning of the operation, but the pan and magnet were cleaner than many I've serviced. I was happy it didn't smell burned, it was just old, which worried me a little, but the trans worked perfectly on the drive home. When I went to inspect the truck before I bought it, I didn't see any oil under it or on the bottom of the truck, crossmember, etc.

Maybe the plug is gone, cuz it didn't leak until I jacked it up. I'll let you know what I find.
 
I finally have an update on the trans leak situation. It was only 100 degrees today, and no forecast for rain, and I finally attacked the problem. I'm posting this for anyone that has this same problem, although I think it's a rare thing brought on by sloppy work. This is on my 1998 GMC 6.5TD 2500 Sierra Utility body with 4L80E, with the problem as described above.
Unfortunately the yoke on the trans end does not have a plug in it that was knocked out when the driveshaft was replaced. The front joke does not simply slide over the trans output shaft(TOS) and into the trans tail piece like lighter duty vehicles. It is attached to the TOS with a bolt as shown in the pictures below. The slip joint is behind the center support bushing on the front of the rear driveshaft.
The leak: Fluid was leaking past the washer under the bolt that holds the yoke onto the TOS. It's obvious the drive shaft was worked on - new ujoints, center support bushing, and the driveshafts have been rebuilt and rebalanced with new ends all around. However, even though the bolt holding the yoke on the trans output shaft was bottomed out, the washer was loose enough that I could move it around. Don't know if the washer is incorrect - it is smaller than the machined area it is supposed to be tightened against, and it's either not thick enough or there is supposed to be another smaller diameter washer under the bolt head. I'm thinking the washer is wrong, it just covers the hole in the end of the yoke and does not fill the machined area. Looks like the driveshaft shop, or the city garage mechanic, just used what was handy.
So, the leak happened when I jacked up the front of the truck, and the trans fluid ran past the loose washer onto the driveway. I'll look for a factory OEM washer on line, or make one. I feel certain the OEM will be thicker and a larger diameter.

Also, considering the marks on the new front yoke, and the fact that it's more than obvious the trans tail piece has NOT been removed - ever, and the truck has 144K on the odometer, I am going to put a new bushing in as well as a new seal. The seal on there looks original. There is play - I can rock the yoke up and down and side to side all around. I don't know what the acceptable play is, and don't care. The marks on the yoke are all I need to see what has to be done. Fortunately they are just polished and not grooved.
BTW, I wouldn't recommend anyone do this in their driveway. Having the truck on a lift would be so much better - this is a PITA job! Two piece driveshaft, and a heavy duty trans crossmember to remove requires extra jacks and jack stands - makes it harder to move around laying on your back.
The pictures aren't great, but I took them with a cell phone, and I think they get the message across.

I hope this helps the next person with this problem. Thanks to all that weighed in on this and offered their help.

20160820_193231.jpg 20160820_193247.jpg 20160820_193231.jpg 20160820_193247.jpg 20160820_193322.jpg 20160820_193353.jpg
 
I've got more info that may help others:
There are three (3) different transmission extension housing bushings! There is as pre-1994 which is something like 1.9915". Then there is 1994 to 2004 which is 2.015". And the 2004 and up that has a still larger OD. Note that the kit National sells, 5802, which has the seal and bushing and is the one everyone has, includes the correct seal, but the pre-1994 bushing. That is the one that was specified, on a certain "Boys" website, for my 1998 (I got a $10.00 gift card in the mail, so I used it.) That was wrong. The bushing in the Federal Mogul/National bushing and seal kit, #5208, only fits the pre-1994 housing. That bushing fell through my housing, and it did not have the hole or channel for lubrication - it is solid with two very shallow diagonal oil groves. If I had a pre-1994 I would either go to the junkyard, or cough up the $131.00 for the one from the GM dealer, and get the one for 1994 and later. They are far superior and a much, much better design. Yes, the ID of all three bushings is the same, and they all use the same yoke. The OD is the only thing that is different - plus the better oil supply system, which also is only in the 1994 and later extension housings(EH). I can't post pictures showing the difference, but I will post a pic tomorrow of mine which shows the oil supply system that is cast into the later EH and delivers oil to the hole in the bushing.
BTW: I've heard disparaging words directed toward GM for being greedy (wasn't worded that nicely) because they do not sell just the bushing, instead making everyone pay 20 times more for the extension housing complete with bushing and seal. It becomes clear when you find out about the changes. You WANT the later one! THEY want you to have the later one. It directs oil to the center of the bushing. The early one does not - the bushing gets whatever oil happens to run into the oil groove that runs diagonally across the bushing. If you have a 1994 or later 4L80E you don't need the new EH. You just have to spend too much time trying to find the correct bushing, after you mic it so you know which one you really need.
I spent more time than I want to admit researching this matter, and trying to find the correct bushing locally. It is not easy to find out what the heck is going on with these bushings, and few retail store workers know. Everybody has the seal, and most of them have the the Nat'l 5208 kit in their computers. No one should want the 5208 kit.
Last hint: I found three places on the web that have the bushing I needed for 1994 to 2004 although they didn't all list years, just the OD. Two had a good price for the bushing, but the shipping was ridiculous - 13 to 15 dollars. The place to get this bushing, the 2.015" one, is at Oregon Performance Transmission. The bushing and shipping was under $10.00. The order was processed within 2 hours, and I got an email later that it had been shipped. NO WAY to beat that.

Almost forgot. The grooves on the yoke. Someone boogered up the bushing. I'll try to get pictures of that too. Looked like the old one was removed with a wood chisel and it slipped and they didn't fix the cut and bump that was made. The inside of the bushing was all messed up too, along with the edge curled over when they knocked it in the EH. And, THAT'S why I do most (high 90%) of my own repairs.
 
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Here are the pictures of a 1998 EH. It shows the oil passage to the center of the bushing. I also have a picture of the bushing I removed. I did not scar up the bushing taking it out. The defects on it were there before I removed it - wish I took a picture before I removed it. The end of the bushing was rounded over where whoever installed it beat it in and a deep groove in the yoke lined up with that. 20160827_181153.jpg 20160827_181542.jpg I use a bronze driver to remove my bushings and it did not slip and make those marks. Again: this is the reason I do 99% of my own repairs. There is no excuse for this kind of sloppy work. I dressed the yoke to remove any high spots caused by the boogered up bushing, and I will install the new bushing properly.
But, you can see how much better the later EH is and how it supplies oil directly to the center of the bushing. The pre
'94 bushing and EH does NOT do that. I think that is why GM now only sells the EH with the bushing in it. They want the newer design on the trans.
 
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One last thing - a correction. It is now obvious that the trans extension housing on my truck had been removed. It was so dirty and mucked up I thought it had never been removed. Seeing the condition of the bushing, which looks new where it isn't scarred up, it is obvious it had been removed, and the bolts holding the EH on had almost no torque on them.
Below is the picture of the Nat'l kit, and the pre '94 bushing. If you have a pre '94 4L80E you need to consider getting a post '94 or '04 housing.
I'm adding pics of the 5208 kit that seems to be listed on all the retail auto parts websites as the only one req'd for ALL 4L80E transmissions. This thread makes it obvious that that is not correct.20160829_112038.jpg 20160829_112433.jpg 20160829_112512.jpg
I hope this thread will help others and save them the wasted time and money I spent getting the wrong bushing. The year of your 4L80E, along with the different OD determines which bushing you need. The 5208 kit is pretty much obsolete. The key is to mic your bushing. The 5208 kit has the smallest OD - less than 2 full inches, and the pre '94 EH does not supply oil to the bushing. Take your pre '94 EH to the scrap yard and replace it with a post '94 EH.
 
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I didn't even think of that. I have to think back to where I read that. Maybe I got the year wrong.I remember now. It is pre '94 not 91. Darn, I'm sorry. From '91 to '94 the smaller bushing was used. I got mixed up. The 2.015 bushing started after that.
Is there a way to go back and edit the previous posts and correct the info? The misinformation could cause even more confusion about a subject that is already confusing.
 
Okay, last post on this thread - I promise. When I was putting the truck back together yesterday I noticed the O ring that is on the trans output shaft(TOS) that is just behind the splines. It was worn flat around the outside and was too hard. Maybe the original. So, I replaced it - just wanted to mention that so it wouldn't be missed by the next person doing this.
When I put the driveshaft back on I tried to rock the front yoke around like I did when I started this project and it was tight with very little play. I also cut a gasket out of thick paper gasket mat'l for under the washer holding the yoke on the TOS, and added a brass washer between the head of the bolt and the original washer and it tightened down and locked the washer in place - pretty happy about both those things. I used blue thread locker on all the bolts. I've always used red on my 4x4's, but this had blue on it already so I just went with that. Oh yeh, I also turned the washer over, It actually has a raised flat spot where it sits on the yoke. It had been put on upside down. I was going to turn it over anyway, because the edge of the washer had a bevel worn on it from sliding around when it was loose.

Thanks again to RI Chevy Silveradoman and THEFERMANATOR for your help, as well as others who offered help. I hope this helps the next person.
 
I would pull that gasket material back out. It doesn't take long for gasket material to loosen up over time. You're supposed to use RTV under the washer and bolt head to seal them. Thats how the factory does it is a light film of RTV. Works like a charm, will not loosen over time, and squishes out so it won't effect torque.
 
I didn't even think about RTV. There wasn't any RTV on it when I took it apart, there was nothing, which left the washer moving around, and the fluid leaking past. If RTV had been used it probably wouldn't have leaked, but then I wouldn't have found all the other problems. I shellacked the paper gasket in place. It wasn't a thin wimpy paper, it's the actual heavy gasket material made for automotive work. Wish I had thought of RTV, but I'm old school. Been doing this since long before silicon sealers/caulks were around. Did a lot of two stroke engine work as a kid, and paper gaskets, especially those between the carb, reed valves, and block wouldn't last unless they were shellacked in place. I feel it was fortunate that it leaked and I was then able to fix and correct the mess that was in there. Everything is TIGHT and RIGHT now.
You are right though, and I wish I thought of it. I would have if there was RTV on it when I took it apart. But, I'm done laying underneath the truck on an exposed agg. driveway and wrestling with a two piece driveshaft, in humid 90+ degree heat. It's staying the way it is (Place a laughing emoticon here). If I ever have to do it again, which I doubt, I will use RTV, and anyone else doing this will probably also - thanks for adding your post above. After all, who but an old fart mechanic is going to go to the trouble of cutting a paper gasket, and who even has a bottle of Indian Head gasket shellac in their tool box?(add another emoticom). I still have my gasket punches so it's easy for me and I have confidence in using them.
But, thanks again! the info will help the next person.
 
@QinVB I thought I was the only one making gaskets for things anymore. And incase you didnt know, the shellac doesnt hold well up to ethonal, so the carb gasakets will break down overtime now.
And yes the permatex is still the best shellac out there.

To add emoticon, click the smiley face above the box you are typing in- upper left. Then the selection will show up underneath for your selection, just click the one you want. ;)
 
Will L. said:
@QinVB I thought I was the only one making gaskets for things anymore. And incase you didnt know, the shellac doesnt hold well up to ethonal, so the carb gasakets will break down overtime now.
And yes the permatex is still the best shellac out there.

To add emoticon, click the smiley face above the box you are typing in- upper left. Then the selection will show up underneath for your selection, just click the one you want. ;)
Click to expand...

Will L.: Yes, I wouldn't use a shellacked paper gasket that was exposed to our new fuel - I don't think there's much "gas" in it anymore, it doesn't even smell right, and it dissolves fuel lines and fiberglass fuel tanks!!!! I don't do much of that kind of thing anymore except with my lawn mowers, chain saw, etc, and I always buy the gasket that goes with what I'm doing if I need it. Those things are too small and complex to cut out.
Isn't it funny how amazed guys are when you cut a gasket using the round end of a ball peen hammer? Nice to know someone else still makes their own gaskets, and thanks for the emo hint!
 
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