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Transmission Cooler Line thread?


NAXJA Forum User
Ellensburg, WA
Is it just a universal thread size? I might have accidently some how fubared up the threads and cross threaded it a little bit so now I need to go buy a tap to fix things up. Anyone know off hand what size I need? I tried to measure and the closest I could come up with was 1/2"-16 I believe it was, either that or 18
What did you mess up? Did you mess up the threads in the radiator, the threads on the nipple screwed into the radiator? I am not sure what you need but it may be 1/2-NPT. NPT stands for National Pipe Thread, different from bolt thread. Will you need a "tap" or do you need a "die"?

If you are close to a Harbor Fright then go in and buy their tap & die set and it should have the ones you need.

If it not the threads in the radiator then flard fittings are used, that a totally different thing. You can buy a new nipple at the hardware store if that the piece you messed up. Now if you messed up the flare fitting on the end of the hard line that connects to the upper fitting on the radiator.
Unfortunetly I wasn't that lucky,I managed to screw up the threads where it screws into the transmission some how. I was thinking the easiest way would be to find a tap with the same threading and clean it up or would I be mistaken?
Good question! I measured and got close to 1.50 X 14 metric, my 1.50 metric thread gauge, actually fit a little better than the 18 american gauge. I tried a 9/16" X 18 die and got about four threads before the tranny adaptor I have, started to bind a little in the die.
I don´t have a metric 1.50 X 14 MM die, my set jumps from 1.25 to 2.00 (in many diameters). My best advice would be to get a 9/16" X 18 nut and a 14 MM X 1.50 metric nut and see what fits best. At a guess and allowing for my poor eyes, I´d guess the metric. I don´t have either a 1.50 X 14 or 9/16" X 18 nut handy to try.
If you buy a tap, remember the hole ends just about where the threads end. Your probably gonna need a blind hole or a tap without the tapper on the end.
In summary, it seems the production variance (the plus or minus variance allowed during production) in my AW4 tranny oil cooler line adaptor, is about the same as the difference in the 9/16" X 18 and the 1.50 X 14 MM thread sizes.
M14x1.5. It's an Asian transmission, so don't go thinking that it's going to be a regular "inch" thread.

You could probably take it up to a pipe thread - but it would be at least 1/2"NPT. For that, you'll have to drill out the hole a little larger (I don't think there's a pipe thread that will work from a 9/16" or 14m/m hole.) I think 1/2"NPT will astart with a 5/8" hole - but that's something that would have to be checked. You might want to at least remove the valve body and set it aside before drilling those holes out - you can remove it without taking it to bits, tho.

If you go that route, you shouldn't have too much trouble finding a 1/2"NPT to -6AN adapter, and you can find hose barb fittings in -6AN for 3/8" hose all day long (check for a local Parker-Hannifin Fluid Power Systems dealer, or similar.) The -AN adapters would be permanently installed, and anytime you'd need to remove the hoses you'd just pull the -AN fittings off the adapters. Keep a couple of -6 plugs around, and if you're quick you won't drain the lines if/when you disconnect them (that's how I do it.)

Failing that, you're in for a larger job that you're probably ready to tackle. Consider yourself edified...

On my 88 XJ the cooler lines are attached to the transmission using the plastic retainers. The same retainers which were used on the radiator end. When I replaced my lines in 2000 the parts guys told me to keep using the plastic retainers at the transmission even though the radiator end had been redisigned with the metal retainers.

I did not they had changed the attachement method for the cooler line at the transmission. That a case case and takes a lot to change a casting.

Since it is the transmission end you may want to go to the dealer and see what they show for the fitting which threads into the trans case. You may end up installing a helicoil into the threaded hole to repair the damage.
After some closer looking the damage doesn't look like it will be too bad, a thread and a half or so so hopefully it'll be enough. The only bad part no where in a 70 mile radius had a M14x1.5 tap so I had to order it and it'll be here tuesday. Thanks for the info and wish me luck :D