This may have been answered before ,& believe me I did a search,but can't find a definate ,just a consensus.Which trans cooler line on my '03 A4 is the return from the radiator trans cooler BACK to the trans?I'm going to put a B&M 70264 & they recomend to put the cooler after it goes through the radiator cooler back to the trans.On the B&M instructions they list a 700R4 ,but not a 4L60E, (the 700R4 is the non-electronic version of the 4L60E?),& they state the cooler line on the top of the radiator is the one that goes back to the trans,but on this forum I read others who disagree.On the "Grid" website they call the line going into the radiator cooler the "pressure" side & they state that is the bottom cooler line.Thus, like the B&M instuctions, they recomend to put the aux cooler in the top radiator cooler line.
To further add to this confusion ,on pages 7-247 to 7-249,of the factory shop manual,pertaining to flushing the A4 , it appears the show an aux trans cooler hooked into the bottom cooler line?

Who can clear this up?Is there anyone out there who actually took the lines off & saw which way the fluid flows?Thanx, geocor

 

The return line is the top line

 

Bottom line IS the pump/pressure side at radiator cooler on the C5. Typically an aux cooler goes in series with the top return line.

 

Yes , I thought it was the upper cooler line that goes back to the trans.I'm going to stick with that & splice the aux cooler into those lines ,since I will probably get a 3:42 w/ a Vigilante TC @ about 2600 ss.I'm pretty sure the top cooler line mount will give you a better reduction in trans cooler temps, opposed to the lower line mount that some do?

 

FWIW my Hayden transmission cooler is installed into my lower radiator line.

With 3.42s and a Pro Torque 2600 stall, installed in early May of '04 I am usually around 169* and have never seen over 185*. I drive the car normally and get on it on occasion, so we don't baby it. It has also been to the track after the gears, TC and cooler and still see the 165-169*.

I was told that it didn't matter as much as some make it out to, as the fluid is still being cooled twice anyway before it makes it back to the transmission. Been running this way for over 2k miles and not a problem.

My installer gave me this information about the top vs the bottom line and he got it from one of the highly regarded transmission shops in this area. This was after I argued with him armed with the information I had recieved right here regarding the top vs bottom line dilemma. He insisted that it was the bottom line to splice into, I insisted on the top and planned to take the car somewhere else to have it done "right". He also referenced the shop manuals.

It would seem that he was right. Can't argue with success.

 

I wonder still if anyone out there actually witnessed which way the fluid flows?Guess I could try the top & if that does'nt cool as good as you're getting EB ,it wont be that hard to go to the bottom line.With the new style F.Injetion type clamps & barbed conections that could handle 80psi,& flaring the stock lines there hopefully will be no problems.Just have to worry about warranty issues,don't know on that one?

 

Good luck with the gears and TC. I love my setup. The 2600 stall and 3.42s are a fantastic combination.

I recall reading somewhere another technique of determining which line is the return line. It involved starting the car while it was cold, letting it warm up, and then touching to feel which line was coolest. I believe the cooler of the two is supposed to be the return line.

Each time I have tried this, and I did try it a couple times after my gear, TC and transmission cooler install, both lines were warm to my touch in part due to engine compartment heat, so I gave up. That plus with nearly consistent 169* temps, at this point I really don't care.

If I go up a long steep hill after driving for say 1.5- 2 hours, I'll see 183-185 momentarily. Especially if there is a traffic light at the top of the hill and the car is not moving, ie air is not moving over the transmission case. But once I get moving, its soon back to the mid 170s and when I reach cruising its at 169*.

On the trip home from the track, the first night I ran it after the gears and TC had been done, granted it was a cool night, in the 60s around midnite, she was in the low 160s for the transmission temps, for the trip home, and I live about 30 miles away.

It could be that the auxilary cooler is cooling the fluid first, and then it goes through the transmission cooler in the car's radiator and is cooled further and this is what gets me the good temperatures. I don't know.

Or it could be going through the transmission cooler in the radiator first and then through the auxillary cooler second and being cooled further, I don't know.

But my tranny temps are always lower than my coolant temps. And sometimes not by a little amount either. Sometimes by as much as 15 20 degrees or so. I run a 170* thermostat.

Thats why I said before, you can't argue with success. I have no intentions of moving to the top line now, whereas at one time, immediately after the install, I did.

 

The trans cooler flow on all C5's is most definately in at the bottom and out at the top. I have faced this same issue and did extensive research on it. My tuner mistakenly installed my cooler on the bottom line and moved it to the upper line when the mistake was discovered free of charge. My trans temps dropped by 20 degrees across the board after this was done.

From my research it looked like people who live and drive in cold climates do attach their cooler on the bottom line. This was due to concerns that when cold weather hits the trans might never get warm. However it seems to me that you could just block the flow to the aftermarket cooler to get the same results. This is a method that over the road truckers have been using for decades I suppose because they drive in so many different climates.

On the late model Vettes GM uses a fitting at the trans called a quick connect fitting such as the one on my 2004. This is going to cause you problems because trying to find fittings that will adapt to the GM fitting is problematic. DTE has one side of the problem solved, the line side, but I could find nothing that fits the radiator which will adapt to a cooler line.

If it helps here is a thread where I discussed what to do about it with several other very helpful people including some help from DTE.

http://forums.corvetteforum.com/showthread.php?t=853972

 

That could explain it. I am in the northeast. I certainly would not want to have my temps drop from 169* to 149* in the summer months. They might be even lower during the winter. But on a hot day, its good to see that 169* while cruising. I drive around with my tranny temp displayed at all times.

 

Appreciate all who gave input here.Since I do not drive my Cor in the winter months, I think w/the mods I will make, max cooling will be needed,& that appears to be hooking up the cooler to the top line.I live in the Chicagoland-NW Indiana area & low temps 0f -25*F or bellow are possible,so with this set-up I'd be crazy to drive the car in winter.

I have a '98 Camaro as my daily driver with a 14K LB. trans cooler set up w/ the top line install & never had a problem, & I do drive it year round.Since I don't have a trans temp guage on it , don't know the trans temps.I was told by a trans shop not to worry about overcooling ,even in winter ,because getting out of snowdrifts can raise trans temps to the roof too! Again thanx to all!