Replacing Transmission Oil Cooling Lines

alvocado · January 27, 2008

Does anyone have experience replacing the transmission oil cooling lines which connect to the radiator in a 1500 with towing package? The upper and lower radiator connections look straight forward but I can't see the connections on the transmission itself. Is this a straight forward bolt on? My current lines are leaking where the rubber hose meets the metal tubing so I need to replace both. Thanks.

WFO · January 27, 2008

When I bought a GM tranny cooler I had to hook my lines up to it. I looked and saw that I could not get to the lines with out dropping the tranny on the back side and the transfer case and pulling the drive shaft. So I opted to have my dealer install it. It cost me $150.00 I was afraid of not getting something not lined up right. Money well spent IMO.

C & A s Dad · January 28, 2008

Allen, are they leaking at the front under the radiator? I know these lines have a rubber section in this area.

If so, I would not consider replacing the entire line. I would simply get some good trans cooler line and cut off the ends of the metal lines and replace the rubber portion. Many vehicles come from the factory with screw style clamps on the trans lines. There is not a great deal of pres to worry about and if you are, slide the new hose over the metal line about 2 inches and use 2 clamps. Tighten the clamps until you begin to see rubber protruding through the slots in the clamps and you are done.

The only thing you need to be careful of is make sure you clean off any small metal pieces that would be left over from cutting off the ends of the lines. If you use a tubing cutter, you really have no worry.

I know this sounds like a "shade tree fix" but if this is where your leak is, I would not even think about replacing the entire line.

stss95 · January 28, 2008

When I bought a GM tranny cooler I had to hook my lines up to it. I looked and saw that I could not get to the lines with out dropping the tranny on the back side and the transfer case and pulling the drive shaft. So I opted to have my dealer install it. It cost me $150.00 I was afraid of not getting something not lined up right. Money well spent IMO.

Did you order the GM accessories kit, i just ordered that cooler for my tahoe and figured it would be fairly straight foreward install....

alvocado · January 29, 2008

Allen, are they leaking at the front under the radiator? I know these lines have a rubber section in this area.

If so, I would not consider replacing the entire line. I would simply get some good trans cooler line and cut off the ends of the metal lines and replace the rubber portion. Many vehicles come from the factory with screw style clamps on the trans lines. There is not a great deal of pres to worry about and if you are, slide the new hose over the metal line about 2 inches and use 2 clamps. Tighten the clamps until you begin to see rubber protruding through the slots in the clamps and you are done.

The only thing you need to be careful of is make sure you clean off any small metal pieces that would be left over from cutting off the ends of the lines. If you use a tubing cutter, you really have no worry.

I know this sounds like a "shade tree fix" but if this is where your leak is, I would not even think about replacing the entire line.

This is exactly the location of the leak. It's only very slight and there is no accumulation on the ground so I may leave this for awhile and then try your suggestion. It's certainly not bad enough to drop the transmission for a line swap. Thanks for the suggestion.

az'03Silverado · January 29, 2008

It may be advisable to flare or bead the metal pipe so the hose won't slip off.

WFO · January 29, 2008

When I bought a GM tranny cooler I had to hook my lines up to it. I looked and saw that I could not get to the lines with out dropping the tranny on the back side and the transfer case and pulling the drive shaft. So I opted to have my dealer install it. It cost me $150.00 I was afraid of not getting something not lined up right. Money well spent IMO.

Did you order the GM accessories kit, i just ordered that cooler for my tahoe and figured it would be fairly straight foreward install....

Yes

C & A s Dad · January 29, 2008

It may be advisable to flare or bead the metal pipe so the hose won't slip off.

If you do flare the ends, be very careful not to leave any sharp edges or burrs. Some flare tools will leave a real edge which could cut the hose. These lines are very soft so if there is an edge, simply cut it off with a file. Just be sure and wipe off any small metal shavings or dust.

This would also be a good time and location to install an inline filter if you have ever considered it.

klunkerbus · January 29, 2008

Anyone have insight into how common the cooling line leaks are? In giving my 2004 Z71 Tahoe a once-over after an oil&filter change this weekend, I noticed a wet line that subsequently determined to be going between the cooler in the radiator and the auxillary cooler mounted in front of the radiator. I didn't find many other cases on gm-trucks where people were having this problem, and now today I find one!

My leak appears to also be at the hose-to-pipe crimp. Since I can readily get at both ends of the line, I've got a replacement line on order and will swap it out. For future reference though, is the transmission fluid safe hose readily available?

C & A s Dad · January 29, 2008

There has been a common issue with the engine oil cooler lines on the 2500 and 3500 series trucks but I have never heard of the trans cooler lines leaking before now.

The trans hose is avail at any good parts store. Just be sure you are getting trans cooler hose and not fuel line or other multi purpose hose. There is a difference. Your best bet is to find it at a store that sells Hayden products as it comes prepacked in ready cut rolls.

If you have a CARQUEST Store near by, they either will have it like this or can order it for you. If not, there are many other stores who sell Hayden products or other premium brands.

sagent · January 29, 2008

I just had mine done at the dealer on my 03 Yukon with 106,000 miles on the clock. From what i've read on this site the lines

are a SOB to insert in the tranny side quick connect fittings. Cost me $ 180 in labor and about $ 75 for all three lines. Money well spent considering the alternative of laying on my back in my garage when its -20 outside.

This must be a very common problem with these trucks as my dealer had all three on hand. Usually every part I look for must be special ordered.

If going the route of cutting the bad section out and replacing with bulk hose, would probably be better idea to cut metal tube with a plumbers tube cutter to avoid metal filings.