Transmission cooling lines

[Gordie9]

I'm in the process of reinstalling my radiator for a 66', 390 with a C6 trans. and need to know which of the trans cooling lines, the front or back, is the outlet from the trans and which is the inlet back to the trans from the radiator. I've done some searching, but have gotten conflicting answers. I'm guessing that the outlet line from the trans. should go to the lower inlet on the radiator??? Any help would be appreciated. Thanks

[dagelh]

I'm doing a similar project on my '64, but it is a CM transmission. It seems to me that the outlet line on
the transmission should go to the upper line on the radiator but so far have not found where the
hookups are on the transmission; right or left. Also, will the transmission fluid need to be drained
to install these lines?

[Gordie9]

Thanks for the reply,
I'm thinking the transmission outlet lines goes to the bottom radiator inlet based on the following thread/discussion;

viewtopic.php?f=7&t=7009&p=88314&hilit= ... let#p88314

But this thread was discussing a 61', so it may not be correct for a 66'??? When I disconnected the transmission lines from the radiator, I did loose some transmission fluid, but not all of it. I'll top it off when I get this all sorted out.

[ozbird]

Hi,

just replaced all my transmission lines and researched what goes where. Original lines travel down transmission right side, hard 90 degree turns between transmission and engine and then to the radiator lines. I changed so the lines head right the way down the right side then a 90 degree turn to meet up somewhere near where the originals ended up. The reason for this was I put in headers and the old lines were way to close to the pipes.

Anyway, to cut to the chase, the front line from the transmission is the outlet (hot 200+ degrees) and it should go to the TOP of the radiator, the lower outlet will have cooled the fluid down (hot air/fluid rises) and it is then sent to the rear fitting. I know the outlet temp is really hot since I plumbed a filter with temp gauge into it and temp on a run can get to 220+ degrees when simply cruising - wish I knew the temp when it returned to the transmission.

Oh, and I was going to put in an external cooler with fan but A) could not find a place for it and B) radiator was recently rebuilt so should not leak water into transmission!! In fact, from what I have read, the cooling effect from the radiator is excellent and replacing with a stand alone cooler is not much use. Just from what I've read, no first hand experience.

Graeme

[bbogue]

If I may Graeme, I beg to differ. In (hot) at the bottom and out (cooled) at the top is the way my B&M Supercooler transmission cooler is suggested to be installed. For a VENTED system, which transmission fluid is, this makes sense to me. The reverse would introduce air bubbles as the fluid flowed downward through the cooler, never actually filling the cooler. Filling from the bottom ensures the cooler fills completely. My 61 trans runs at least 20 degrees cooler now, with the radiator cooler bypassed. The 61 original trans cooler is on the passenger side of the crossflow radiator and is plumbed in at the bottom and out at the top, like my aftermarket cooler. Unfortunately, the hot engine coolant also enters the radiator on the upper passenger side. Maybe that's why this feature of the 61 is apparently a 1-year design. Would it have cooled better if the connections were reversed? Maybe, even with the bubbles that would have resulted, since the fluid would have exited the radiator from a cooler point.
Just my thoughts and experience.

Bill

[ozbird]

Interesting bill, I only duplicated what was there from factory, also depends on the Web link you believe sometimes.

I have a separate trans cooler with fan, no idea where I am going to fit it!

Graeme

[bbogue]

I have a separate trans cooler with fan, no idea where I am going to fit it!

Graeme

I had room for both an electric (pusher) fan and a trans cooler in front of the radiator of my 61. I think later/other cars had an external trans cooler as well as AC components in this area so it might not work for you.

Bill

[ozbird]

Hi Guys,

check this link ( you don't need to sign in ) - Bill and I are members there and Bill is all over this thread, good work Bill.

Stuart who is the moderator there is the 'go to' man - please make your own decisions based on this mine of information.

http://www.network54.com/Forum/260730/thread/1483384593

regards,

Graeme

[Gordie9]

Thanks to all those who contributed to this thread. I posed the question to my radiator guy, who is a bit "old school" as he actually repairs things rather than just replaces them and also works on many of the classic cars in the area. He told me that the transmission outlet line should go to the lower inlet on the radiator for two reasons; 1) it keeps the radiator reservoir full and 2) minimizes air bubbles resulting in better flow.

[bbogue]

I’m afraid I don’t understand 1) above since trans fluid being cooled by the radiator’s transmission cooler and coolant in radiator and expansion tank are in separate systems which don’t mingle. Are you sure you quoted your radiator guy correctly?

Bill

Added by edit.
Ok. Maybe now I get it. By radiator "reservoir" the mechanic perhaps meant the transmission cooler in the radiator.

[Gordie9]

Yes,...the trans cooling reservoir in the radiator.

[ozbird]

Wow, beating this subject like a dead horse eh!!??

Anyway, my last comment on the subject. I took my original transmission cooling lines and checked them out. If you look at the images the HOT line from the transmission, the one on the front of trans travels to the front of car and ends up 10-12 inches taller than the lower, return COOL line.

So, the HOT line according to my calculations goes to the top line on the radiator.

This is on my 62, other models as Bill pointed out correctly will likely be different.

Cheers and Merry Christmas . . . Graeme

[redstangbob]

I decided to dig around a little, and came up with something that makes some sense as far as cooler flow is concerned. In an old COM manual the flow is described as well as shown in a diagram. According to the book, the front line is pressure with the rear being return. The return is back to the sump (PAN) not to a circuit, so air bubbles don't come into play. I was quoted in an old post, I think I should go back and edit my answer with today's date. For what it's worth the diagram shows the trans cooler in a top/bottom type radiator, but the return to pan remains. JMO, Bob C

[Alan H. Tast]

And to add further to redstangbob's comments, I finally got a chance to look into my library after returning home from an extended weekend trip to find my copy of a service training manual that focused on the C6 circa 1966, and with the help of looking into Master Parts Catalogs' text and illustrations sections was able to finally figure things out. To preface this, the shop manuals and engine assembly manuals do not show how the cooling lines are routed, and MPC illustrations do not show how the C6's transmission lines are run (the Cruise-O-Matic configuration is, though).

In looking at what is listed, the following descriptions are given for the transmission cooler lines:
Basic number - 7A030 - Oil cooler tube - oil inlet
Basic number - 7A031 - oil cooler tube - oil outlet

Sadly, in looking through the MPC's text portions for various years, no year-specific part numbers show up that would give a clue as to how these lines differ, especially for 1966 between the C-O-M and C6. Typically, the parts catalogs would instruct that new lines be bent from bulk tubing. So, between the illustrations in the MPCs showing the basic part numbers, descriptions of how the cooling system works for the C6 and small cut-away illustrations, here's what happens:

Oil flows out of the transmission through a port on the right side of the case toward the front of the transmission. This goes into line 7A030. This line goes from the right-front of the transmission case, crosses over between the transmission oil pan and bellhousing, goes forward along the left/driver's side of the cylinder block, then to the top inlet of the radiator's left/driver's side tank. Not shown in illustrations is a spiral-wound coil of tubing inside the driver's side radiator tank: this has an outlet toward the bottom of the tank. At this bottom outlet, line 7A031 runs back along the driver's side of the engine block, across the lower front of the bellhousing, then back to the rear of the transmission case and into a port that lets the oil back into transmission and into the sump/pan.

If anyone has underside pictures of the C6 application in a '66 that can be added to this post, they would be most helpful.

[bbogue]

I'm enjoying this thread. More learning.
From Alan's comments, I'm beginning to think that for trans cooler-in-radiator systems, having the outlet from the radiator trans cooler at the coolest part of the radiator is more important than whether or not bubbles develop as the fluid flows downward in the cooler. Maybe fewer bubbles form due to flow rate, restrictions, etc. so it's of less consequence. More evidence that the 61 design (passenger side, in at bottom, out at top) was a poor design.
For external trans coolers where the cooling medium is air vs radiator coolant, there is no hot or cold side of the cooler so keeping the cooler "solid" with fluid makes sense. My cooler's connections can be both on top or in at bottom out at top to accomplish this.

Bill
Happy Holidays