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MIKEGOUGH1

Transmission cooler connection

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MIKEGOUGH1

Is this the correct hook up, line on bottom of 71C Velvet drive connects to the water input end of the cooler and the water output end of the cooler attaches to the top(high pressure) of the transmission?

Edited by MIKEGOUGH1

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NorCaliBu

Mike,

Your question isn't very clear (at least to me, but I'm not very smart Crazy.gif ). The tranny cooler has four ports on it. Two large ports at the ends (water in & out) and two smaller (threaded) ports on the side of the cooler (tranny fluid ports). Unless they have changed something and made the coolers simpler than they used to be (not likely) all the cooler is is a large tube that water flows through to cooler the fluid that is flowing through smaller tubes within the large tube. There are no check valves or anything so you really can't connect it wrong. The length of the hoses should determine which go where. On my sporty the water intake hose coming from the pump goes into the bottom of the cooler, the hose on the top goes up to the "manifold" at the top of the engine. The two fluid lines on the side (one high, one low) one of the lines is probably longer than the other...the way mine mounts the top port is further away and therefore requires the longer fluid hose. Hope that helps. If not, post pic's so we can see. Good luck.

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SunriseH2OSkier

You are confusing me a little too, but the bottom line is it doesn't matter which line goes to which fitting. The oil cooler is not directional in nature. I posted this description of a trans oil cooler on the old MBO, and maybe it will help you here:

Envision a pop can with several holes in each end of it. Now envision the holes on each end of the can connected by straws (the straws run parallel inside the can). Next, envision a couple fittings on the side of the can. These fittings provide access to the air space inside the can but between the straws.

The space inside the straws is for cold (raw) water to pass through, which makes the surface of the straws cold. Space inside the can (between the straws) is where the hot trans oil goes. The trans oil enters the can through one fitting, cools as it passes over the straws, and exits the can through the other fitting.

Edited by SunriseH2OSkier

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HRemington

quotes like that from the old MBO make me misty eyed everytime...especially something as beautiful as Jerry's metaphor of a transmission cooler as a pop can with straws...please, just give me a minute... Cry.gif

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MIKEGOUGH1

Sorry guys, I should have been more specific. I am referring to the transmission lines, not the water lines. From my understanding, it is directional, the high pressure goes in the fitting on the water intake end, and connects to the bottom, or high pressure fitting on the tranny. The fitting at the output end should go to the return, or top fitting on the tranny.

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SunriseH2OSkier

Mike,

The difference in pressure between the lines is what forces the oil flow. Oil will flow from the high pressure line through the cooler to the low pressure line, no matter how you connect them to the cooler. The cooler itself doesn't influence that flow.

Edited by SunriseH2OSkier

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SunriseH2OSkier

Boy, that there is the proverbial brick poop house, but yes, it is the same thing I described above. Don't know what that unit costs, but it looks like it would be more robust to freezing than the typical unit used on boats (which isn't much more than a pop can).

Edited by SunriseH2OSkier

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MIKEGOUGH1

Found out the hard way that the transmission fluid lines hooked up to the transmission cooler are required to go a certain way. I had mine hooked up backwards and overheated my tranny, fortunately shut it down before I did any major damage. The transmission fluid shoud run opposite the water flow. The high pressure output from the tranny, the top fitting should go to the farthest, or output end of the cooler, then the fitting on the input end of the cooler goes to the return fitting, or bottom fitting on the tranny. I discussed this with an engineer at

velvet drive and he says it will run the other way, but you do risk the overheating problem. Vince and Richard at Skidim say they have seen many occasions when tranny's overheat due to inproper cooler connections. FYI

By the way, my tranny temp sensor alarm never sounded. Anyone know how to trouble shoot this.

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Waterbuggy

Mike,

I don't think you have a temp sensor alarm on the Velvet Drive 71C. The electric part you see is a neutral safety switch. And how do you know it overheated? I would be suspicious of the tranny rebuild if you are having slippage problems and your fluid levels are ok and not frothing and the linkage is properly adjusted. Did you replace the hoses? The tranny cooler outboard water jacket holes are sometimes hard to see and clear.

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MIKEGOUGH1

I just had it rebuilt, all it needed was a clutch pack, had it pressure tested, everything else was fine. After the install, I ran it for about 3 hours and noticed a leak, which turned out to be caused by a bad damper plate, but when I pulled it to check on the leak, that is when I detected the burnt fluid. Sent the tranny back to the rebuilder(skidim) and the pump everything still looks ok, I did not get any slipping, must not have gotten too hot, but I was concerned enough to have it inspected.

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SunriseH2OSkier
I discussed this with an engineer at velvet drive and he says it will run the other way, but you do risk the overheating problem.  Vince and Richard at Skidim say they have seen many occasions when tranny's overheat due to inproper cooler connections.  FYI

Oops.gif

Well, I'll take a page from the lesson plan that a former contributor to the site (intials 'TR') never paid attention to (Whistling.gif): Defer to the experts and admit I was wrong. My appologies for misleading you Mike, and I'm glad you got the problem taken care of.

I'm not a heat transfer guru, but being the engineer that I am (Crazy.gif) I like to understand why things are the way they are. I'll offer up this line of thinking as a possible explanation of why it makes a difference which way the trans oil lines are connected...

It seems to make sense that the heat transfer is more efficient if the flow of water is opposite the flow of the trans oil:

-------------------------------------------------------------------------------

Cold Water ------> warms as it passes by Trans Oil ------>Hot Water

-------------------------------------------------------------------------------

Cold Oil <------------ cools as it passes by Water <----------- Hot Oil

-------------------------------------------------------------------------------

In this arrangement, a given drop of hot oil (flowing right to left above) will be cooled a little by each of many drops of cold water (flowing from left to right above).

If the connections were to be reversed as such:

-------------------------------------------------------------------------------

Cold Water ------> warms as it passes by Trans Oil ------>Hot Water

-------------------------------------------------------------------------------

Hot Oil ------------> cools as it passes by Water -----------> Cold Oil

-------------------------------------------------------------------------------

then each drop of the hot oil flow would effectively have to be cooled entirely by a single drop of the cold water flow (assuming oil flow rate and water flow rate are approximately equal).

Any thoughts? (Insert pocket protector references here... :) )

Edited by SunriseH2OSkier

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kbtheboz

You're right Sunrise,

It's been several years since my Heat Transfer classes but a "counterflow' heat exchanger is more efficient than parallel flow. I remember there something about Log Mean Temperature Difference LMTD but I purged all of that!!

Fancy software makes idiots out of all of us.

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MIKEGOUGH1

That makes my brain hurt. Takes individuals much smarter than I to figure this stuff out. Sometimes just knowing it works and not necessarily how and why is good enough for me.

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Waterbuggy

I'd bet that with the short length of these tranny coolers and the water flows of a normal cooling system, you could not get more than a 5º F temp differential reversing the oil flow direction, hardly enough to effect fluid properties. On a longer exchange unit maybe 24" - 36", you will see the effect of reverse flow cooling. Not to knock the Velvet Drive engineers or SKIDIM, but it sounds like someone's blowing smoke up your ----. Still suspect something else if you keep finding degraded fluid.

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