Old Man Minimalist

Did a fairly thorough search and found some older threads on the subject but decided to start a new one. In my "de-bubba fying" my '99 Cherokee Sport I keep finding stuff that needs repaired. I noticed yesterday that the transmission lines just above the control arms have pretty good dents in them. Probably choking off 50% of the flow, so I am going to replace them with factory lines.

That said, this might be a good time to add and auxiliary cooler but is it necessary? I am mostly bringing this back to factory original with some updates but no lift, no extreme "wheeling" and stock size tires (maybe one size up). I won't haul heavy loads but may tow a utility trailer on occasion.

The previous owner claimed that at times it ran hot and the overdrive wouldn't kick in.(not sure that those two correlate). I assume choking off the flow couldn't help in keeping it cool.

What do you think?

And if the general consensus is to add a cooler, I'd like it to mimic OEM as much as is reasonably possible. I like that it has a lower profile and leaves more of the AC condenser/radiator exposed to the wind. But factory may be hard to find and maybe the aftermarket has better technology so I am open to that.

00t444e

Yes add one, mine had the factory small axillary cooler and trans temp would still get above 220 on a hot day just driving in stop and go traffic. I added a Hayden 405 cooler and trans temp has never got above 200 even off road.

Old Man Minimalist

The 405 looks to be much taller than the factory. Will a 401 supply adequate cooling?

I also found a couple of B&M coolers that are sized a little smaller.

IJM

IIRC, those B&M coolers are stacked-plate design, so they're a bit more efficient for their size than the Hayden tube-and-fin style.

robsjeep

Cooler atf will give you MUCH longer tranny life. Trannies generate high peak loads of heat into the atf very quickly, if you run a gage you can see that temp rise fast. A nice big cooler helps smooth these out and keep over all temperature lower. This is critical in an autotranny do tl the various rubber and plastic bits in the fluid circuit. High heat is very bad for their life. ATF itself will also breakdown at higher temperatures.
It is a win win win to add a cooler even for stock around town street use. It is a must in my opinion for off road, mountain driving, heavy loads, desert heat etc...

Remember, cooler always goes in front of radiator.

Consider adding one of them Magnafine brand atf inline filters in the steel can. they have a magnet and a paper filter element, plus a by pass valve so they wont plug up the flow ever. I mlunted mine just below my cooler, kn the front cross member, back side. Used a steel band hose clamp and some holes in that cross member panel to pass the hose clamp band through, then around the filter, nice and snug.. Run the filter on the hot side of the cooler(s) oils filter best when hot as hot oil is less restrictive through the filter, thus less bypass valve operation, and less pressure drop.

Also run the new cooler after the stock radiator side tank cooler, NOT before, as the radiator cooler can only at best get the aft down to 180 or 200F lowest, (i.e. the engine coolant temperature). After the radiator cooler, then the new cooler will lower the temlerature more as it is cooled with cooler outside air. If you do it wrong, air cooler first then radiator cooler, you find the atf is too cool for the radiator cooler running at maybe 200 F to do much good, hence you end up with hotter atf than if you reversed the plan and do it correctly, which is... first radiator cooler, then new cooler. With optional inline filter before the radiator cooler.
Also the new cooler I think should go in the path of the fan. You may find high atf temps at low vehicle speeds, which means little air moving over the new cooler, UNLESS that cooler is in front of the fan(s).

There are some nice graphs and charts showing huge increases in autotranny life verses lower atf temps. If you can keep it below 160F verses 200F, the lifetime difference is a multiple of times. Of course I did see it on the internet.
But understanding that some of the little valves, seals, check valves, etc.. and such in the autotranny are polymers, rubbers, plastics, yes it sure makes sense that the lifetime can drastically drop over just a few tens of degrees F in atf temperature for these components.

IJM

Just one minor clarification that the coolant temperature on the cool end of the radiator where the transmission heat exchanger is located is significantly cooler than the coolant temperature exiting the thermostat (where the sensor is), particularly at higher speeds.

00t444e

Yes the cold side where the transmission cooler is runs 75-100 degrees colder than the coolant coming out of the engine, if it is 180-200 degrees on the cold side then you would be overheating big time.

Old Man Minimalist

I really don't want to add Tees to lines in order to add a temp gauge and having a temp gauge is not a definite requirement. However, it would be nice to have one for S&G's. Has anyone used one of the drain plug adaptors in the pan with good success? Like this one:

IJM

I wonder how the fluid temp in the pan compares to the fluid temp in the transmission outlet line. Probably a bit cooler, but I'm not sure how fluid flows internally.

Old Man Minimalist

I have read that it reads about 10 degrees cooler. I haven't confirmed it yet but I'm not sure it would matter since the gauge would be mostly for kicks and to spot an overheating issue.

Saudade

Mine came with the factory tow package that included a class 1 hitch, aux trans cooler and LSD.

The Mopar part number is 52028516AF. There are a bunch on ebay and other sites if you search by the part number if you choose to go OEM.

lawsoncl

If by overdrive, they really meant torque converter lockup, then fix that first. The t/c nor locking up will add lots of heat to the radiator.

Old Man Minimalist

Yes, that is probably what he meant. I'll look into it. He said it only happened when it got hot. He is in Texas.

I don't know much about lock up converters. AT's are the last hurdle for me to tackle on an automobile. Seem complex to me...

I haven't driven it other than home when the guy met me a couple hours away from my house. I didn't notice that it didn't lock up. I'll have to drive it some and see what it is really doing before I start tearing into the items that effect lock up. Thanks.

So, I'll replace the fluid lines since I know they are bad and while the vehicle is on jack stands.

peligro113

I used one of those but I drilled a hole in the transmission pan so that the drain plug could still be used to drain the pan. I have two temp sensors on my transmission one in the pan and one on the transmission test port. The fluid in the pan will generally stay at 180F if I let the vehicle ide 10 or so minutes after traveling a while on the highway the temps in the pan will reach 200F. The temp in the transmission test port normally reaches 260-280F. I check the transmission fluid condition every time I add fuel and it has remained in good condition. I change the fluid every 30k miles.

https://www.cherokeeforum.com/f46/pe...9/#post3604227

Old Man Minimalist

I was thinking I'd drill a hole in the side of the pan and install it there.