4L60E smoking when towing

[upper_tanker]

First off, I thought I posted this issue here before but if I did, I can't find it.

97 2 door Tahoe, 4x4, info is in my sig. I had the trans built by a reputable builder near me. My rebuild receipt says:
5 pinion R. Planet
street shift kit
Corvette servo
Kevlar band
Beast sunshell
HD Z pack 8 clu. 3-4 upgrade
2000 stall

I didn't do any towing with this vehicle before the rebuild, so I don't know if it did it before.

It doesn't matter if I'm towing an empty open 12'x6.5' trailer, or a 3500 lb camper. After towing it any speed, in 3rd or OD, I am getting smoking coming from the trans. I look under it, and there is fluid all over the rear half of the trans. I'm assuming fluid is blowing out from somewhere. The vehicle doesn't lack any power when I'm towing. Trans temps stays between 135-165 all of the time, no matter what I'm towing, how hot the outside temp is, or what gear I'm in. This is viewed using BAFX OBD2 bluetooth device and dashcommand.

I have checked the fluid numerous times before and after towing, and it's always full or near it. I've also pulled the vent hose off the top of the trans and blew it out.

Any idea what my issue is or what to check next? One of these days if/when I have time, I'd like to spray the trans down and clean it so there's no fluid on it, then go for a drive towing something and check it right after to see if I can pinpoint where it's leaking at.

 

[TheAutumnWind]

take it back to your local reputable builder

 

[upper_tanker]

The rebuild was done in March of 2018. I pulled the trans and took it to him. It's actually a shop that mainly supplies parts to a lot of other local trans shops, but he has a few people who rebuild transmissions out of the vehicle on the side. I just got off the phone with him literally a few minutes ago and he said he's going to call the builder and give me a call back. Let's hope for the best. Ha!

 

[evilunclegrimace]

It sounds like it is over full and pushing ATF out of the vent. Remember that these need to be checked hot, running in park/neutral. Make sure that you have the correct dipstick

 

[upper_tanker]

I agree that it sounds like it's over full, but it's not. I've checked this thing every time that I drive it, which is maybe a few times per month.

It's not leaking out of the vent tube. When I removed it to inspect/clean it, the vent tube was dry as a bone. The entire rear half of the trans was and is wet, though, which is wierd.

Truthfully, as much as I hate leaks, I really could deal with this one as long as there was no risk of it catching on fire, which is not possible with where the trans fluid lands.


Anyways, the guy called me back and suggested I take it to one of his "customers," which is a trans shop about 15 minutes away. I called the guy, and he said he will look at it for free, drive it to get it hot, and look at it again to see if he can identify the leak. As usual, I'm sure it's not going to leak unless he hooks a trailer up to it.

I sure would be a happy camper if this could be resolved for $300 or under. LOL. I'm almost hoping that the rebuilder made a mistake and the trans shop pays for it, although it's doubtful.

Wish me luck. I'm taking it to him on Friday morning, he said I may not get it back until Monday.

 

[evilunclegrimace]

There is a UV dye that you can put in the tranny and then hit it with a black light and it will glow just like the fun house at the Amusement park. It can be helpful to locate the exact spot that the leak occurs.

 

[alpinecrick]

Given you've covered most of the stuff I can think of, what about the transfer case? It's got a vent too.

Also, here in Colorado, most trans rebuilders I consider good, have gotten away from 8 clutch packs--they are fine for running the streets, but don't seem to like pulling the mountain passes--much less with a trailer.

 

[upper_tanker]

The trans blows fluid whether I'm towing on the expressway or just towing an empty trailer doing 45-55 mph. There are no mountains by me, or at least where I travel. I do understand how obviously that would put more stress on the drivetrain, specifically the transmission though.

I didn't know that about the clutch packs. I don't even know what the added benefits would be. I just gave him the trans and said, "Here, can you try to make it be able to take some abuse?"

 

[upper_tanker]

Ok, got an update. I took it to said trans shop today. They called me and said they got it up to temp and put it on the hoist and fluid was seeping out of a hairline crack in the case. Unfortunately for me, this trans is not under warranty anymore because even though it only has 5k miles on it, it was done March 2018.

I called the original builder to see if he had reused my original case or gave me another one, just so I knew. The original rebuilder only rebuilds transmissions that are brought to him out of the car, since he's technically a trans parts supply shop and not a rebuild shop. He said that unfortunately due to them not being able to run the transmission, it's possible that they may have missed it.

Regardless, I'm now paying $1k to have the recommended shop swap all of my parts over to a new good case. I'm not too mad at this because I'm more than happy to have my last leak in the vehicle fixed, and I don't have to worry about catching on fire from that anymore. I also told him to obviously check for all of the **** as he's pulling them out, and he said he would anyways.

I just KNEW I was procrastinating on doing the -6an line swap for a reason!

 

[Schurkey]

I just KNEW I was procrastinating on doing the -6an line swap for a reason!

It would be a mistake to install hose where double-wall seamless steel tubing works just fine.