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I had to replace the transmission in my 93 Dakota. To get it to drop I had to cut the metal coolant lines that lead to/from the radiator. The stock lines are .315 ID. My question is, can I use a rubber hose instead? I know they make ATF strength hoses. I've even heard that upping the size to .5 ID would actually help.

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  • It's kind of ancillary to your question, but why cut the lines? Why not remove the fasteners? Were they rusting in place never to move again? It is a '93 after all... I dread having to move some of the fasteners on my 2000 Toytoa Camry. – cdunn May 25 '16 at 17:28
  • I didn't know much about how they worked at the time. There were 3 pieces to each and I though there was only 2. I could only reach one of them. Plus I bent the pipe in the process. – White Development Studios May 25 '16 at 17:47
  • Cutting was last-resort. – White Development Studios May 25 '16 at 17:48
  • The ID of the rubber hose would need to match the OD of the metal pipe right? So it sounds like 0.5" wouldn't really be a choice? Of course I don't even know if any of this is possible. – JPhi1618 May 25 '16 at 17:53
  • Yes rubber lines will work just fine. – Moab May 25 '16 at 21:19
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The best way to fix this is to use flared butt ended fittings, or to replace the line whole. The rubber, while it will hold, is still the weak link in the chain. Over time it will weaken and wear, and ultimately fail. Using the dual ended but joint like I have pictured below (or something like this), if installed correctly, will not fail any sooner than the metal line itself will. On the ends of this will be brass nuts which will slip over the line, then you'll need to flare the ends. This is called a Brass Flare Fitting. They make all different sizes, but you'll need it to be a butt connector type to work properly and have the least amount of resistance to transmission fluid flow.

enter image description here

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  • This is how it was, I even have the connectors. What if I used a hose to jump the gap between the two instead – White Development Studios May 25 '16 at 23:17
  • @WhiteDevelopmentStudios - You can do whatever you want, obviously, but it isn't the way I'd get it done. Get it done right the first time and don't worry about it. You can be assured at some point in the future, if you use hose to jump the gap, you'll blow tranny fluid all over the road. When that happens, it will be the most inopportune time for you and your passengers. Since Murphy said it, it must be the law. – Pᴀᴜʟsᴛᴇʀ2 May 26 '16 at 1:06
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You can use proper hose without a problem. Just make sure it's SAE J1532 or J1019 hose - it should be stenciled on the sides - most auto parts stores sell this "transmission cooler line hose" by the foot. You'll likely need 3/8 or .325 ID.

Make sure there's 2-3 inches of overlap on each end of the cut metal. Double clamp each end with quality clamps spaced about a half inch apart.

This, done properly, will not "blow tranny fluid all over the road". It's far more likely the original pipes will rust out, and THAT will be the weak link fail. In fact, Dorman makes replacements because this is a very common problem on that age of Dakotas. And the parts are cheap, too - probably less than $75 for the pair. Installation is not a breeze, however. But it avoids the rust problem that might be headed your way as well.

While I agree a perfectly proper job should be complete replacement, the cost-effective and "just fine" approach for that age of vehicle suggests patching using quality rated hose and clamps. Note that the OEM arrangement has a rubber section (with crimps that often fail), since hard-mounted lines between the moving elastomer-mounted transmission to the chassis-fixed radiator would fatigue and fail metal lines in no time.

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