80Avanti Posted January 17, 2022 Report Share Posted January 17, 2022 I recently removed and replaced the th400 tx in my 1980 Avanti to fix numerous tx fluid leaks. Before I took the tx out, I removed the two flexible tx cooling lines that connect to the radiator (both were cracked an not so flexible anymore). The tx is now back in the car and the new flex lines are connected to the steel tx cooling lines from the tx. My problem is I can't remember which flex line goes to the upper tx cooler connection on the radiator and which one goes to the lower tx cooler connection, (both flex lines are the same length). The two steel lines coming from the right side of the tx are one above the other. One line must be for the hot fluid gong to the radiator and the other for the cooler fluid returning to the transmission. I hope someone can advise me on which line goes where. Tim Link to comment Share on other sites More sharing options...
pantera928 Posted January 17, 2022 Report Share Posted January 17, 2022 I would think that it should not matter as they are both going to pass through the radiator and achieve cooling. I can check on my 1980 in a little while to see which is which Link to comment Share on other sites More sharing options...
pantera928 Posted January 17, 2022 Report Share Posted January 17, 2022 Just looked on mine and the upper goes to the upper fitting on the radiator Link to comment Share on other sites More sharing options...
80Avanti Posted January 18, 2022 Author Report Share Posted January 18, 2022 Thanks pantera928, I'll connect mine that way. Tim Link to comment Share on other sites More sharing options...
80Avanti Posted January 19, 2022 Author Report Share Posted January 19, 2022 Just found this info on the corvette forum: I just looked in my "How to work with and modify the Turbo Hydra-Matic 400 Transmission" book. It says that the top line is the return line. and this: On the transmission (TH400) the bottom line is out and the top line is the return. On the radiator the top is in and the bottom out. In other words The bottom transmission line runs to the top of the radiator. The top transmission line runs to the bottom of the radiator. Link to comment Share on other sites More sharing options...
pantera928 Posted January 19, 2022 Report Share Posted January 19, 2022 13 hours ago, 80Avanti said: Just found this info on the corvette forum: I just looked in my "How to work with and modify the Turbo Hydra-Matic 400 Transmission" book. It says that the top line is the return line. and this: On the transmission (TH400) the bottom line is out and the top line is the return. On the radiator the top is in and the bottom out. In other words The bottom transmission line runs to the top of the radiator. The top transmission line runs to the bottom of the radiator. Well, then mine has always been hooked up in reverse. Never any issues. Link to comment Share on other sites More sharing options...
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