So, after LS swapping the Disco I began to see a need for more effective option for my transmission lines. Flaring the hard-lines did work, however I couldn't get the hose-to-hard-line area to stop leaking completely. Here's a write up of what I did.

First, here are some of the facts I used to base my decisions off of:

A. The transmission tubing is 1/2". I found this to be strange, but after close measurement 1/2" was the closest I could come up with using dial calipers. If I recall correctly all measurements I took in metric ended up around the .5mm range.
B. The threads on the transmission housing that the tube-nut holds in the hard-line are M18x1.5
C. The transmission cooler itself has tubing that comes off of it, that measures 14mm or 9/16".
D. I was not able to find tooling or a flaring tool kit that could exactly replicate the flare on the transmission side of the hard-lines.

The first place of question for me was the transmission side. To spare you of the details off all the research I did, I narrowed the possibilities down to 3 options.

1. I could have custom flaring tooling made from a machine shop to replicate the flare on the transmission side of the hard-line, or have them replicate the flare for a couple of fittings. (This would've been costly)
2. I could use a M18x1.5 to AN -8 fitting adapter with copper crush ring, using Permatex high-temp PTFE thread sealant on the transmission side, to help the seal.
3. I could use a 1/2" tubing, compression style fitting, to AN -8 adapter, mating it to the last 3-6" of the original hard-line, with the tube nut, flare and o-ring.

Transmission housing - where the flare with o-rang and tube nut are inserted.


Option 2

Option 3



Though I wanted my option of choice to be as reproducible as possible, I just wasn't ready to tango with the cost and trouble of the machine shop route. That left me the two latter options. I couldn't decide between option 2 and 3, so I order fittings for both options. The M18x1.5 fitting I ordered from Summit would not work. It was either due to the fact it wasn't full thread, or the metric thread side of the fitting was too long, thus bottoming out on one of the steps for the housing/female/ flare landing. This kept the copper compression washer from sealing on the face of the housing. I feel I could've found a fitting that would've done the job, but I already had fitting for option 3, so I chose this.

Option 2 bottoming out, unable to create the seal with the crush washer.



Lastly, the transmission cooler side.. I could only find one vendor for a 14mm compression fitting on Alibaba, which I didn't want to deal with either. The only other 2 options were to slide a hose over the cooler tube and hose clamp, or somehow incorporate quick disconnect fittings that the vehicle came with originally. I will also mention that I did extensive research trying to find this fitting, but simply couldn't without buying the entire hard-line assembly. 5/8 was the closest I could find, which was for a GM heater hose, if I recall correctly. It leaked,

As you can see, I carefully cut the ferrule and pulled the stock hose off. I brought both of these fittings to a local hydraulic shop.I had them crimp these fittings on one end and a 90 degree JIC8 female to mate with the AN -8. (FYI for those of you that don't know, JIC 37 degree flare fittings are compatible. Though some argue with the differences in the tolerances of both styles, I have never had an issue with the two types of fittings sealing without leak.**Make sure the JIC fittings are not 45 degree flare**). I also gave the shop measurements for how long I wanted the hose to be, and that I needed it to be resistant to ATF, possibly 100psi and 300 degrees Fahrenheit. They had plenty of hose options that would accommodate. I chose a standard black. This hydraulic shop, as well as most others I've been to, does not carry stainless braided line, so if that's what you desire, you may have to bring it in. First I would suggest calling the shop advance and make sure they will crimp on fitting to a hose that bring in.

cut ferrule with quick connect fitting removed

Transmission cooler quick connect fitting

Finished lines from hydraulic shop


Next was the install. Pretty self-explanatory. If you've never installed a compression fitting, there are plenty of YouTube videos that cover this. Also note that if you hard-line is dirty around the area that brass ferrule with be compressed on. This is one of the sealing surfaces, so I chose to use a Scotch Bright "no scratch" type pad and brake clean. This helped to avoid causing further surface imperfections that would promote leaks.

This is the bottom hose installed. I used a short, straight piece of tubing. Making sure to direct the line where accessing the fill plug would still be easily accessible(the tubing I used for this is also in a picture above).

90 degree tubing used for the side.

90 degree, side fitting installed.

90 degree, side fitting installed.


I've now been using these lines for 3 weeks and haven't had an issue out of them.

 

Very nice - thanks for posting

 

Instead of the hard to get quick connects 14mm compression fittings work. I used them on my oil cooler without any problems, absolutely no leaks. Unfortunately the tubing on the cooler is 14.1mm, but it is easily sanded down until the ring fits.

Manufacturer is Swagelok, part numbers are:

SS-14M0-1-8

B-14M0-1-8

They have a 1/2" MNPT thread and hose shops usually have adapters for it.

Stainless steel version:
https://www.ebay.com/itm/1-Swagelok-...8/254044868738

Brass version:
https://www.ebay.com/itm/SWAGELOK-B-...X/233246982778

Brass is absolutely sufficient. I had to use the steel version, since I had no time to wait on the other.

 

Hey all, can someone help me understand why the transmission cooler lines need to be replaced?
Is it simply because they are hard lines and can't be bent easily to clear the larger LS engine?
From what I've gathered so far the bell housing of the Discovery's transmission is being swapped so that the LS can mate up with the original Discovery transmission.
From what it looks like the original cooler lines connect to the transmission just behind the bell housing. Meaning that the hard lines at the transmission aren't affected by the new bell housing.

Any help in understanding why the original hard lines can't remain in place for the swap would be very much appreciated!

Some pics of the transmission cooler lines on my 04 Disco to help show what i'm working with.


The hard lines convert to pliable hoses that connect to the cooler/radiator.


Hard lines coming up from the transmission to the cooler/radiator in the front


Hard lines that insert into the transmission

 

Went ahead and removed the lines from the transmission tonight and pulled the cooler out with the lines attached.

That top hard line was annoying to get out. Luckily I was able to go at it from the top of the transmission while standing in the engine bay. Both were 19mm nuts. The brackets that hold the lines together were a 10mm and an 8mm.

Seems like swapping the bell housing wouldn’t be possible without the hard lines out of the way.

 

Carter, nice work and write up!

Just replaced both oil cooler lines with some nice used ones - but they are getting harder to find in decent shape.

Mods, can we make this a sticky?

 

This is great info.

 

So if the original hard lines that thread into the transmission are slightly larger than 1/2" do you have to sand them down slightly in order to get the Vibrant Performance adapter (1/2" to 8AN) connected?
Those adapters are exactly 1/2" so they're slightly smaller. Just want to make sure you're using the original hard lines and not sourcing new 1/2" line from a hardware store.

 

Would you know where to find replacements for the quick disconnects that attach to the radiator?

 

I used a 14 mm compression fitting with a 1/2 NPT thread. Install an NPT hose end or a barb fitting. I did this for my engine oil cooler (I added the oil cooler they left out beginning with 2003 models). 50psi/240F is no problem even with a barb fitting.