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83Blzr62
08-09-2006, 06:00
Does any one know which line coming out of the radiator is the return line? I would check myself but I already have my transmission out and did not think of doing it before hand. I want to put in an external cooler inline with the radiatorand have the fluid go through the extrernal cooler last. It seems like it would get cooler this way, because the radiator is warm because of the coolant.
Thanks,
Kyle
JeepSJ
08-09-2006, 10:27
I have always routed it the other way - external cooler first, then through the stock cooler. That takes some of the load off the radiator (the trans fluid is cooler when it passes through the radiator) and it helps keep the trans fluid at a more stable temp in colder weather. It is possible to overcool the trans.
83Blzr62
08-09-2006, 14:01
Which line is the return and which is the feed though?
ZZ
08-09-2006, 18:31
I went through this last year. The bottom line on the radiator is the outlet line from the tranny. The fluid runs up through the cooler.
83Blzr62
08-09-2006, 21:48
Ok, thanks.
Bnave95
08-12-2006, 03:30
I went through this last year. The bottom line on the radiator is the outlet line from the tranny. The fluid runs up through the cooler.
ZZ
I remember this being talked about because I needed to know if I had my inline filter going the right way. Dr Lee brought this up and the older trucks differ than the newer ones,being that the newer trucks have trans inlet on rad.(outlet from trans) at top of rad. flowing down, than to ext. cooler. Why the older truck have inlet at bottom flowing up has always been a question as to why.
ZZ
08-12-2006, 04:49
The only thing I can figure is that flowing up would take more time; thus giving the fluid more cooling time in the radiator. I have factory service truck shop mnual for my '90 GMC and it shows the direction of the fluid flow into the bottom of the radiator.
DmaxMaverick
08-12-2006, 08:16
The only thing I can figure is that flowing up would take more time; thus giving the fluid more cooling time in the radiator. I have factory service truck shop mnual for my '90 GMC and it shows the direction of the fluid flow into the bottom of the radiator.

Up. Down. Sideways. The fluid doesn't care, and it makes no difference. An advantage to having the fluid exit the top is to prevent as much sediment/contaminants from returning to the tranny as possible. Part of GM's tranny service procedure is a cooler flush. Any low point in the system will collect sediment. The cooling system is closed, pressurized and airfree, so direction plays no part of cooling characteristics. The time the fluid spends in the cooler is the same, in any direction.