How to replace transmission cooling hard lines on 1993 K2500 with 4L80E

bob850 · Jul 9, 2022

Hey everyone, I have a 1993 K2500 Suburban with the 4L80E transmission. One of the hard cooling lines to the radiator is rusted and leaking. My truck does NOT have the auxilliary cooler. It just has the to hard lines going to the radiator and back. I'm not sure if I can get the old lines out due to the front axle in the way (it's a 4wd model).

Has anyone replaced these and have any advice?

bob850 · Jul 9, 2022

Just to be clear, I'm referring to the transmission fluid hard cooling lines.

alpinecrick · Jul 9, 2022

Does it have the GM quick connects on both ends? Once the wire clips are out it's a matter of wiggling the lines loose. Also there is a bracket retainer that holds the lines on the 7.4's (I think) and 5.7's about midway along the oil pan that the lines clip into. Maneuver the line out from the trans end.

Now is the time to replace the O-Ring in the quick connects also--worn out O-Rings, especially once the line has been removed from the quick connect is often a source of leaks.

bob850 · Jul 9, 2022

It does not have the quick connect fittings. It just has threaded connections at both the trans and at the radiator. Also, I didn't mention before, but it does have the 7.4L engine.

alpinecrick, did you do the job on a 4wd? I'm wondering if they can be wiggled out or not due to the front axle. My lines are hard metal line the entire run (they do not have a middle rubber section like the models that have the aux trans cooler do). So there is not as much flexibility in removing them.

Caman96 · Jul 9, 2022

I guess it’s different for a 4L60E/5.7 cause I replaced those pulling and feeding from front. Have you tried yet?

bob850 · Jul 9, 2022

Caman96, was yours a 4WD? Also were your lines all metal or did they have the middle rubber section? I have not tried to remove mine yet.

Caman96 · Jul 9, 2022

Yes, 4WD, all metal. I’m just thinking if you haven’t attempted, maybe it looks a little daunting but you figure it out as you go along. Just the right twist and pull here and there.
I did add a cooler but the flex parts are near the radiator. I did remove the original non flex tube no problem, so if it was removed it could’ve gone back in. Unless 4L80 is a completely different animal!

bob850 · Jul 9, 2022

Ok, thanks for the reply.

Caman96 · Jul 9, 2022

And like alpinecrick pointed out with the clips that connect the two.

alpinecrick · Jul 10, 2022

I have helped a friend with a 97 k2500 pickup few years ago. The trans side had quick connect, the radiator end had the flare nut. My 96 and 02 vans are the same way.

I’ve never seen a factory trans line with a rubber section on a gmt400.

I’m sure we removed the line by pulling (and twisting) from the trans end. We had the truck up in the air with the passenger front tire off—it makes it easier to see when removing the line. If yours is the return line that exits from the top of the radiator there is that long L shaped portion to deal with. I’m thinking whether pulling from the front or rear jacking the truck up makes it more doable.

How to replace transmission cooling hard lines on 1993 K2500 with 4L80E

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