Hey guys,

I have 98 xj 4x4 with 3.5" lift on 33" tires i use as a daily driver. I just moved out here in the desert. Point is, its hot, the engine gets stressed with headwinds; not to mention theres occasional mountains that add stress to it. I go extended periods at 3k-4k rpms during these times. The engine seems to barely manage staying cool at 205°-210°F at times. It Does well on flat surface 195-200°F during summer 115°F with AC going on. My quad core radiator does well at that.
Is it frowned upon to get an oil cooler? I can't seem to find ANY youtube videos of anyone owning one on their xj's. So I dont know if there's a notion against it. I fear extreme oil heat is wear my gaskets and O'rings. It didn't use to leak oil this often back home when it was better weather.
I am thinking of getting a transmission cooler for the trails.

**Side question**
Is it possible to break off (remove) the oil adapter pin and rotate the oil filter so that it orients vertically? Much easier to pull off without spilling oil everwhere.

 

Good question. Any idea what sort of oil temps you're running during those long drives on the uphill stretches? I've measured my oil filter with an IR gun (assuming that's accurate), and the highest I've seen is 240 °F, and that was after driving 10 miles straight through soft sand in the summer. 240 °F with 5w-40 full synthetic Rotella T6 doesn't concern me. What oil are you using?

Also, what's your diff ratio? Did you regear with those 33" tires?

My only experience with an aftermarket oil-to-air cooler is on my VW track car. That brought my oil temps down by around 30 degrees, and the highest I'll see now is 245 °F on a hot summer day on a fast track like VIR or Watkins Glen when I'm at full throttle most of the time. IIRC, you'll need to use one of those sandwich plate setups that mounts between the oil filter and the adapter and mount your cooler somewhere with good airflow that won't get crunched by road debris or whatnot. Since this would primary be for highway use and not off-roading, you wouldn't need a fan for the cooler.

I'm not sure about rotating the filter adapter so it points down, but perhaps the bottom of the block where it meets the oil pan would interfere with the filter. Just a guess.

 

I'm not sure what the temps are. But say it were to be 240°F, would it hurt the engine (that always runs hot anyhow) if i dropped it 30°F as in your scenario? Im using 5W30 fully synthetic mobile oil.

I didnt regear. Its stock. I thought 4.10s.

The oil filter would be pointing up so that the filter is closer to the valve cover.

 

If you've got a 4.10 diff ratio, you're good to go with 33s. Without some data on temps, installing an oil cooler is probably unnecessary, particularly with synthetic oil. Those coolant temps you mentioned in your first post seem pretty normal to me, so I wouldn't be concerned.

You mentioned running 3-4k RPM at times. Is that with the transmission in D and the torque converter unlocked, or are you in 3 with the TC locked up? If it's the former, that'll heat your transmission fluid right up and then promptly dump that heat into your radiator.

 

I dont have 4.10s yet.. Thats 3-4K with the tranny D. I'm not familiar with locked/unlocked torque converter. All I know is that its between the engine and tranny. My TC stays in 2H.

 

The torque converter (TC) allow slip between motor and tranny, however it can be locked, i.e. no slip. When the TC slips extremely high heat is generated, the fluid (Tranny fluid) gets hot, so hot it maybe broken down, burnt and your tranny destroyed. You only want slip in limited circumstances, for short periods.

If left in drive with huge tires without changing the axle diff. ratio the tranny will want to stay in 4th gear, but do to the the now messed up overall ratio do to huge tires, the engine will need to spin very fast, but axles will spin slow compare to stock tired jeep. this means the TC will be in slip mode, unlocked. Great heat will be generated in the TC, and since the TC f,uid is the atf fluid that circulates in the tranny, the tranny will be harmed. The atf goes thru the radiator also, in a seperate circuit from the engine coolant, but it will dump its heat into the engine coolant, making your engine run hotter also. But the main concern is over heating the atf and thus your tranny, the atf will be burnt, turn from red to brown, lubrication will break down, your tranny will be damaged.
To avoid slip, to get the TC to lock, put her in 3rd gear and she will lock at speed.
if you run a tranny temp gage, you can see huge temp increases almost instantaneously when the TC is slipping!

So down shift to 3rd, when ever the tranny is slipping, say on an upgrade at highway speeds. you want her locked.

once you regear to you wont have as much a problem
I recommend you get a tranny temp gage so you can see the heating, over heating when slipping. if she is getting hot, then DOWN SHIFT.
there are kits that allow you to select 1st gear and stay in it when the 1/2 position is selected. Jeep made a mistake when combining the 1 and 2 lever position. this becomes a big deal when trail crawling as without that kit, she will tend to stay in 2nd, at low trail speeds, again causing slipping of the TC.

dont just put her drive with huge tires and stock axle ratios! Add a tranny temp gage, add a tranny cooler, add a tranny inline filter when you add the cooler. Magnafine makes a very nice tranny filter, install before cooler, you want to filter before the atf is cooled.

 

Pretty much what Rob said. When you're on those long hills in the mountains and the transmission downshifts and stays there while in D, you'll want to put it in 3 instead. That way you'll keep the torque converter locked, which will keep the transmission and engine cooler and give you a bit more power up the hills. Your effective gearing is different than mine, but I can keep the throttle wide open in 3 at about 70 and above, and it'll keep the torque converter locked without downshifting.

If anything, I'd look at an auxiliary transmission cooler before I thought about an oil cooler.