700r4 external cooler lines
Thread Starter
6th Gear
Joined: Mar 2025
Posts: 6
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700r4 external cooler lines
Hi guys, I’m looking at running an external cooler for my 700r4 (2500 stall) and was wondering if -6AN fittings are going to be too restrictive.
the reason I’m asking this is that the stock 5/16 line has an inner diameter of 6.4 mm and the -6 hose ends have an inner diameter of 6mm. Not a big difference but wanted to know what people are running and if this will have any issues
thanks
the reason I’m asking this is that the stock 5/16 line has an inner diameter of 6.4 mm and the -6 hose ends have an inner diameter of 6mm. Not a big difference but wanted to know what people are running and if this will have any issues
thanks
Melting Slicks
Joined: Jul 2003
Posts: 3,482
Likes: 864
From: Saratoga Springs NY
2024 C4 of the Year Finalist - Modified
2022 C4 of the Year Finalist - Modified
I have -6 adapters on the tranny, parker push lock hose, and a b&m stacked plate cooler in front. Works great, never even see 150 degrees. Trans is built, so is the engine, and also have an aluminum pan on tranny which might make a small difference. Either way, yes, -6 is fine.
Melting Slicks
Joined: Mar 2002
Posts: 2,873
Likes: 764
From: Sligo PA
I'm running -6AN lines on my 4L80e in my 84 Vette to an external cooler that sits in front of the radiator. The highest temps I've seen so far were 185. The lines haven't been a problem.
I could be wrong but I always thought that the "-6AN" meant that the smallest diameter that could be in that system would be 6mm. Meaning the tubing could be larger but the fittings would have at least a 6mm opening. I'm willing to bet the a -6AN PTFE braided hose would be less restrictive than 5/16 steel.
Back when I was also debating what size to use I kept reading about people using 3/8" line or -8AN hose. Then a friend reminded me of something. 3/4 ton work vans and trucks have been pulling trailers with 5/16" lines for a very long time. The short -6AN hose will work just fine in my lightweight car that will never see the same load.
I could be wrong but I always thought that the "-6AN" meant that the smallest diameter that could be in that system would be 6mm. Meaning the tubing could be larger but the fittings would have at least a 6mm opening. I'm willing to bet the a -6AN PTFE braided hose would be less restrictive than 5/16 steel.
Back when I was also debating what size to use I kept reading about people using 3/8" line or -8AN hose. Then a friend reminded me of something. 3/4 ton work vans and trucks have been pulling trailers with 5/16" lines for a very long time. The short -6AN hose will work just fine in my lightweight car that will never see the same load.
Last edited by Phobos84; Mar 6, 2025 at 09:20 PM.
Drifting
Joined: Nov 2021
Posts: 1,701
Likes: 375
From: People's Republic of Nueva York
The number refers to 1/16 inch. So number 6 line is 6/16" = 3/8". #8 is 8/16" = 1/2".
It's also a nominal number, so there's a lot of variation in the size of the bores of the fittings. It's not a minimum.
It's also a nominal number, so there's a lot of variation in the size of the bores of the fittings. It's not a minimum.
Melting Slicks
Joined: Mar 2002
Posts: 2,873
Likes: 764
From: Sligo PA
So -6 is 9.5mm ID. It's a lot bigger than 5/16".
Team Owner
Joined: Sep 2003
Posts: 25,330
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I believe that you actually need to consider the ID of the male fittings. A typical -6AN male fitting ID is .30 I believe which is just a bit smaller than 5/16(.3125). And then also consider the spec of the actual hose being used -6 ain't always 3/8ID.
**Phobo - good to see the kid got the D/L
**Phobo - good to see the kid got the D/L
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Thread Starter
6th Gear
Joined: Mar 2025
Posts: 6
Likes: 0
I believe that you actually need to consider the ID of the male fittings. A typical -6AN male fitting ID is .30 I believe which is just a bit smaller than 5/16(.3125). And then also consider the spec of the actual hose being used -6 ain't always 3/8ID.
**Phobo - good to see the kid got the D/L
**Phobo - good to see the kid got the D/L
I thought it was crazy when trying to research AN fittings that nowhere mentioned was the inner diameter of the hose ends. Shouldn’t this be the most crucial piece of information the user needs when building hydraulic circuits?
anyway, also plan on chucking in a few 90 degree fittings, will having such harsh angles effect the way the cooling fluid flows or is it just going to be not enough to notice?
cheers again all
Melting Slicks
Joined: Jul 2003
Posts: 3,482
Likes: 864
From: Saratoga Springs NY
2024 C4 of the Year Finalist - Modified
2022 C4 of the Year Finalist - Modified
yeah you’re correct, that the circuit can only flow as much as the smallest orifice in the whole setup in the case of the AN fittings, this is only 6mm (0.24”). Comparing the stock ID at smallest point is 6.3mm (0.25”), I’ve concluded I’ll run the -6 AN fittings.
I thought it was crazy when trying to research AN fittings that nowhere mentioned was the inner diameter of the hose ends. Shouldn’t this be the most crucial piece of information the user needs when building hydraulic circuits?
anyway, also plan on chucking in a few 90 degree fittings, will having such harsh angles effect the way the cooling fluid flows or is it just going to be not enough to notice?
cheers again all
I thought it was crazy when trying to research AN fittings that nowhere mentioned was the inner diameter of the hose ends. Shouldn’t this be the most crucial piece of information the user needs when building hydraulic circuits?
anyway, also plan on chucking in a few 90 degree fittings, will having such harsh angles effect the way the cooling fluid flows or is it just going to be not enough to notice?
cheers again all
Mine come straight out of tranny, to front of radiator where cooler is, then (2) 90degree fittings into cooler. Its fine.
Drifting
Joined: Nov 2021
Posts: 1,701
Likes: 375
From: People's Republic of Nueva York
yeah you’re correct, that the circuit can only flow as much as the smallest orifice in the whole setup in the case of the AN fittings, this is only 6mm (0.24”). Comparing the stock ID at smallest point is 6.3mm (0.25”), I’ve concluded I’ll run the -6 AN fittings.
I thought it was crazy when trying to research AN fittings that nowhere mentioned was the inner diameter of the hose ends. Shouldn’t this be the most crucial piece of information the user needs when building hydraulic circuits?
anyway, also plan on chucking in a few 90 degree fittings, will having such harsh angles effect the way the cooling fluid flows or is it just going to be not enough to notice?
cheers again all
I thought it was crazy when trying to research AN fittings that nowhere mentioned was the inner diameter of the hose ends. Shouldn’t this be the most crucial piece of information the user needs when building hydraulic circuits?
anyway, also plan on chucking in a few 90 degree fittings, will having such harsh angles effect the way the cooling fluid flows or is it just going to be not enough to notice?
cheers again all