• If you currently own, previously owned or want to own an Avalanche, we welcome you to become a member today. Membership is FREE, register now!

Big transmission leak, just replace what was lost?

acedown13

Full Member
Joined
May 27, 2013
Messages
54
2002 Avy z71 with around 234k
While looking for an what i thought was an oil leak from where i thought was around my radiator, up around the right side of the engine compartment , i found that my top transmission fitting that goes into the radiator was loose, I tightened it down and thought that maybe what i thought was the oil leak around that area was just a really really slow leak from that. Well, i thought i fixed it. Next day the wife and i were driving and about 20 miles away from home,  felt the transmission slip a few times as the engine rev but no extra power, then code 1870 popped up, and the transmission really started to slip or just rev up while giving it power. I popped the hood and there was no transmission fluid, luckily i had some and put some in , while idling it went back up to the notches of being full. Started to drive a few hundred feet and it was slipping really bad, pulled over again and i realized tranny fluid was just pouring from where the cooler line the metal tip plugs into the the transmission fitting that goes into the radiator. I took the metal clip off that locks it in place and put it all back, started it up again and continued to come out, it seems to be coming out where the metal clip locks in, i noticed when i pulled on the cooler line it seemed to slow down the flow a lot, like the cooler line wasn't properly seated firmly in the fitting which was causing the leak . I'm guessing for whatever reason me tightening the fitting yesterday somehow messed it up. I am HOPING by just replacing the fitting that goes into the radiator it will solve the issue and i hoping i wont have to replace the entire cooler line.
Anyways, not knowing how much tranny fluid leaked out, can i just put more in and mix it with the old tranny fluid? How will i know how much to put in? I'm hoping i didn't damage  the transmission and once replacing and refilling it will work again.
 
If I were to hazard a guess (since I can't see what's going on), I'd say that an O-ring got nicked or torn when you tightened the fitting.
Clean off the area with brake cleaner and allow it to dry (or blow it off if you have shop air), and after topping off the transmission, have someone start the vehicle while you watch at the fitting to see exactly where the fluid starts to come out from. It could be coming out from between the line and the fitting, or the fitting and the radiator. Hopefully this helps you narrow it down enough to take corrective action, whether it be a new O-ring or gasket or the fitting or whatever else.

CarMech1969
 
i had my wife start it when i was watching, it seems do be a steady stream coming from the connection of where the cooler line , the metal tip, connects into the fitting as if it wasn't sealed anymore, it's coming out from where the little metal clip goes in the notches to lock in the tip
 
does that mean i most likely need to replace the entire cooler line? i followed it back , it looks like an awful place to have to get my hands up into
 
If the line is not damaged at the tip where it goes into the radiator fitting, there is no need to replace the line. Just a new O-ring should be sufficient.

CarMech1969
 
Well after all the fluid loss I'd be very happy if all I had to do was replace a line and not the tranny.
How is it doing now?
Before you refill or fill the transmission look up the capacity; most books will show 2 capacities, one with fluid change (refers to only what's in the oil pan; this is the one I would start with) and a capacity when you have a dry converter and pan. If I were installing a dry converter follow the MFR's instructions to the letter or I'd ask a trans guy how much to put in the converter before I install it. That way I wouldn't start the engine with a dry converter. So anyway, find out what the capacity is for changing the filter\ refill the pan only and if your pan is low add fluid slowly.... You'll find that you have to wait for the fluid to get out of the dip stick tube before you can recheck the level, check the dip stick with the motor running. If the dip stick still indicates a low level you can add more fluid again SLOWLY.
This would be a great time to replace the filter. problem is you'll need a seal puller (avail for rent at many auto parts stores) to get the filter seal out of it's home where the filter neck goes. Once you get it out just follow the included instructions to install the new seal. WARNING: do not rely on reusing the old seal. I had to rebuild my 700R4 (nearly a clone of the 4L60E) because I counted on the old seal being ok.
 
A couple of years ago, out of the blue, while sailing down the Interstate, one of the cooling lines popped off of the transmission of my EXT.

I was able to drive across all lanes of traffic and make it to the outside shoulder before it quit pulling.

I had the truck towed to my mechanic's shop and was I fearing the worst.

I figured the transmission was toast and a rebuild was in order.

My mechanic addressed the popped off line and refilled the transmission fluid.

And off I went.

It has worked fine ever since.
 
Back
Top