Here's what I know so far:

First, thanks to everyone who has supplied parts listings and drawings, great ideas and lots of help, especially for the prior year cars.

The 5/8 X 18 fittings from Earls with the GM coupler did not work out. They are not the right size for my 04 and from the responses I have gotten here it looks like the 03 cars are set up the same way as mine.

It appears these fittings are in fact Saginaw (thanks BHP) power steering type fittings. They are however bigger than 16mm. I checked the thread pitch on the fitting and its 1.5mm. I also bought a 16mm x 1.5 nut to see if it would fit, it will not. I think they are likely 18mm and as luck would have it hardware stores all carry metric nuts and bolts no larger than 16mm so I have had to order something in 18mm x 1.5 to verify my suspicions.

I have found a few suppliers of an AN to Metric power steering adapter. Most suppliers only have them up to 16mm. I have ordered two of them in 18mm x 1.5 to 06 AN male. When they get here I will see if they fit the radiator.

As for the fittings from the factory on the hose, I have found no adapter as of yet that might fit. What I have done is to order the complete hose and fittings from my local Chevy dealer. It only cost $31.46 and it includes the pressed on tube fitting as well as the fitting that attached to the radiator. This will give me both parts of the fitting and I plan to use it to find a match somewhere, if it is available.

I have also ordered some Russell hard line adapters. They use a 3/8 tube compression fitting that adapts to a 6 AN male fitting. If the Saginaw power steering adapters will work at a minimum I could use the compression fittings to make up the lines.

When I get this all figured out I will repost here with my results.

I know it all seems obsessive but I have just decided I am not going to give up on this until I figure out a way to do this efficiently, reliably and leak free. If you know of anything that will help in my quest... let me know. In the meantime, thanks to everyone for the help thus far. I could not have discovered as much as I have without everyone else’s help.

 

Charlie, thanks for doing on the "leg-work" on this issue. I discovered this same problem two months ago when I tried to have a B&M 19K GVM transcooler installed on my 04. Same story you told above -- the mounting kit provided did not fit either the 03 or 04 models.

I'm eagerly awaiting the fruits of your labors.

When it all done, I suggest that you post your results, with part nomenclatures and numbers, plus any diagrams or photos to the Tech Tips link above. You'll be providing all of us an invaluable service.

Thanks again and good job, Charlie!

 

We have the adapter fittings you seek for the 2003-'04 automatic transmission fluid cooler lines that adapt to aftermarket aluminum radiator's NPT ports. Give us a call and we can get these to you. (260)407-5455 x11

Regards,
DTE

 

Well folks the plot thickens. I talked to DTE today and they do have a fitting that adapts to the Sagnaw male thread on the hose to 1/4 pipe thread. I can use an adapter to get this over to a 06 AN fitting. Now I must wait for the 06 AN to 18mm x 1.5 Sagnaw power steering fittings to arrive. If these will fit the radiator (we shall see) I will have what is needed to plumb the cooler with Aeroquip lines.

Now More about the DTE fitting. Its a part they have custom made by a local machine shop so its expensive. $39.00 for a single fitting but it beats cutting the line. They use it for customers who install BeCool aftermarket radiators which take 1/4 National Pipe Thread (NPT) at the radiator. That way when they install a BeCool for a customer they don't have to cut the stock lines. By the way they believe GM is going to carry this funny fitting over into the C6.

If I had all of this to do over again I think I would just get the BeCool Radiator. It has enough cooling capacity that you don't need the trans cooler with it. They sell for around $650 and when you consider labor and parts for the trans cooler it may be better to just go with the BeCool. However I have already started down this road and have my parts so I am going for the adapter.

I will be unavailable for a couple of weeks, its vacation time. After that I will catch everyone up on my findings.

 

TTT for ya, Charles! Many of us late model C5 folks are standing by for more of your hard-earned information.

Hope vacation was fun and relaxing....now back to work!

Note that in Charles' last post, the same fitting(s) might be on the C6 as well. The aftermarket folks need to address this mounting hardware issue ASAP!

 

Great info!!

 

Great info, thanks

 

Sorry to keep everyone waiting so long, I just got a little tied up after I got back from vacation.

There is good news and bad news. The power steering fittings from Earl's, part 991956, WILL NOT work in the radiator. However the DTE fittings do work on the tube end. So now I need a way to get a 06 AN fitting on the radiator and I think I have it figured out.

On The Tube:
I am changing my direction a little bit but I still think this can be done. The DTE fitting will work on the hose end. It takes the stock fitting out to a 1/4 male NPT (National Pipe Thread). There are several ways to get this out to a 06 AN male fitting. One way is to use the DTE fitting with a brass 1/4 pipe coupler from any hardware store. This is just a short tube with 1/4 NPT female threads on both ends. To that you can add a Russell fitting that is 06 AN to 1/4 NPT male. If you buy it from Jeg's its part number is 799-660450. This combination of parts will get you a 06 AN connection on the end of your transmission cooler line.

On The Radiator:
Now, getting an AN connection point onto the radiator is a bit more involved and requires some simple fabracation. What you can do is buy the upper transmission cooler line from GM, or from a salvage yard, it's about $34 from the dealer. You will also need the fitting that goes on the end of the pipe and this is around $18 if I remember right. You will also need a "hard tube adapter" from Russell. At Jeg's this is part number 799-639210 and it is a 06 AN male on one end. The other end is a compression fitting that slips over a 3/8 inch tube. Once tightened it crimps down on a small tapered ring inside the fitting that must be slipped over the tube before assembly. This in turn compresses around the tube and seals it off. The catch is that you have to make a short tube by cutting the end off of the new pipe you bought from GM. You put the factory fitting on one end of the tube, this will go into the radiator. On the other end you put the Russell hard tube adapter. Just be sure not to cut the tube to long or to short. This combination of fittings will get you a 06 AN male fitting on the radiator.

Make The Rest Of The Lines Up:
From there you use AN fittings and hose as needed to plumb your cooler. This all sounds pretty involved but the oly alternative I know of is using hose clamps (UGH!) or welding AN fittings on the end of the tube. That requires removing the tube from the car and that's even more complicated. Plus you still have to fabricate a fitting for the radiator.

A New Plan - Doug Dewitt:
I however am going to use a Doug Dewitt radiator. I ordered the early model unit because it comes with 5/8-18 reverse flare connection points. Russell makes a fitting, part number 991947 that goes right in. This combined with the DTE fittings on the tubes will set me up with 06 AN connection points.

The early model C5 Vette's use the 5/8-18 reverse flare fittings. For some reason the late models use this new so called quick connect fittings. I don't know why they call them quick connect because they require a rare and special tool to remove them from the end of the tube. Yea, that means that once you put the factory fitting on the end of the tube it won't come off without this special tool. Doug Dewitt's tells me they have been hearing this fitting will carry over into the C6, we shall see.