MTcherokee

Hey cherokeeforum folks
I'm a long time lurker on the site (mostly because my cherokee knowledge is way lower than the average joe here) and its helped me learn a ton and save ridiculous amounts of money (- replaced the header, rear main, oil filter O-rings, leaf springs, and installed cruise from the threads on this site).

So, current problem: I have stock (no lift, 30in tires) 99 cherokee 4.0, 4wd, 150K with what appears to be a stock auxiliary/transmission cooler sitting in front of the radiator (hopefully the photo was attached). On several occasions (~4-5), however, my transmission has overheated, sizzled fluid on the exhaust and blew smoke out the back like I was rolling with Cheech and Chong. Since overheating has been fairly infrequent and only when particularly hot or under stress (I was in the southwest for a few years and towed a uhaul once) I just monitored the fluid and did the drain and refill route (didn't want to flush - too scared of tranny seizing). It has not occurred lately but I'm in the pac NW and its just not that hot. However, I am about to move across the country to North Carolina where it is quite hot and during the hottest time of the year (August) and I'm trying to prep my Jeep for the immediate trip and the long term, I love this Cherokee and I want to drive it a long long time. I won't be towing, but the cab will be plum full of my stuff and probably a couple things on the roof.

I'm thinking a B&M transmission cooler will be a nice addition for my XJ but I don't know if this is possible with the current aux cooler affixed to the rad. Can anyone lend me some advice? Can I just remove the current cooler and use the inlet/outlet tubes for a new cooler? Should I place the aux cooler after the rad or bypass the heat I'm expecting? Is it necessary to have a temp gauge as well (I'm pretty inexperienced with wiring) If I have an overheating tranny with a stock cooler, is the problem deeper than a new cooler can fix?

I plan to do a coolant flush/fill this weekend and I'm in the process of draining and refilling the tranny - but I haven't replaced the filter, yet. Coolant color looks healthy and as far as I know the rad and cooling system is original.

Sorry for the long post and thanks for the help!

Bustedback

You can ditch the original and use the stock plumbing, but you should look for the leak that is spraying ATF on the exhaust.

MTcherokee

Thanks bustedback

i was under the impression that when overheated, the transmission fluid boiled over through the filler tube and dripped onto the cross tube of the exhaust (that's what it looked like when I popped the hood after a smoke event). never thought about a leak. my fluid stays steady otherwise but I'll look at the lines in case.

md21722

Transmissions work best with fresh, clean fluid. I drain the pan and refill every 20,000 miles. When towing use 3rd gear instead of "D". Never had a problem towing even double axle enclosed trailers on the interstate for hours in the summer into a Kansas headwind. I don't even have an auxiliary cooler.

BlueRidgeMark

Can't hurt anything to replace the existing cooler, and maybe even upgrade it. But I think you have more things to worry about. I have towed some heavy loads in the summer here in Virginia and haven't overheated the trans anywhere near what you have described. Might be slipping too much. Slipping = heating.

Before you make the trip, I suggest you do a flush yourself. NOT by taking it to a shop, where they might do a power flush. The power flushes can knock crud loose and plug passages, resulting in a trashed trans.

You just want to replace the fluid, but ALL the fluid. Since you are replacing the cooler, this is a good time.

1. Get a couple of gallons of new trans fluid.
2. Recruit an assistant, better yet, two.
3. Find out which one comes from the trans to the cooler. (IIRC, it's the rear line, but check on that.)
4. Disconnect that line from the cooler.
5. Attach a rubber hose and direct it into a bucket or drain pan. (Your old fluid will dump out here.)
6. Stick a funnel into your dipstick/fill tube.
7. Get your new trans fluid ready to go. (Opened and close, ready to pour.)
8. Put one person behind the wheel, one ready to pour in fresh trans fluid, and one watching the old dump out.
9. Start the engine and start pouring in fresh fluid. The goal is to pour it in as fast as it pumps out.
10. When fresh, clean trans fluid is coming out of the rubber hose, stop. Stop the engine, stop pouring fresh fluid.
11. Button everything up, check your fluid level, and adjust as needed.
12. Enjoy greatly improved transmission life.

I have personally seen this take my slipping, doomed transmission back to life and I've got maybe 20,000 miles on it since doing it. My fluid was black and burnt smelling, and the trans would start slipping badly after about an hour of driving. Now it runs like new.

MTcherokee

Ok, I hear you blueridge. I'm also a little concerned that there is a deeper issue at hand but as far as I know the PO did regular fluid changes. That said, I have only drained and filled the transmission once. The last time I overheated was in AZ last summer at about 100-110 degrees outside going up a hill with a small uhaul trailer. It never did it again but the fluid definitely got dark and needed changed.

Do you guys think it was just bad fluid? Will a new cooler do anything that the current one doesn't? I don't want to waste money obviously.

I've always assumed this issue (blowing smoke, etc) was my transmission based on searches I've done on this site and others. My engine never seems to be much off of 210 operating temp and has only gone above when it was really hot outside. but after it happens its really hard to tell where the fluid is coming from, but i don't think it was coolant.

As far as doing a flush as you prescribe - how much fluid does the transmission hold? I have a gallon on hand currently so I'll need to purchase more but wondering how much.

Thanks

MTcherokee

Also, on the stock trans oil cooler, which is the inlet/outlet? I assume the bottom is coming in and the top is going out to the tranny, correct? Would there be any downside to mounting it in the exact same place? I have read elsewhere that a new cooler can block airflow to the radiator, making engine temps go higher. Sorry if these are stupid questions!

BlueRidgeMark

Only if:

1. The existing cooler is gunked up.
2. It's too small for the conditions.

If it's working fine, I wouldn't replace it, but I'd add another cooler. I'd also add an inline filter. I plan to do that on all my vehicles this year.

I need to replace the trans on my family vehicle, and found that Ford sells a reman which comes with a 3 year guarantee if you install an additional cooler and an external trans filter. Otherwise, it's a one year guarantee.

All the new big Fords and Chevys come with external trans filters. Sounds like the industry is finally catching on to what I've been saying for a couple of decades - not having an external filter is just stupid.


Yeah, it's tough to sort out after the fact. It does sound like it was an overheated trans pushing fluid out the dipstick.


IIRC it's 5 or 6 quarts. Definitely under two gallons.

Dumajones

Install a B&M cooler 70264 inline with the OEM, thats what I did on my 2000.

Here is a vid on what I did.

BlueRidgeMark

Nice!

20 degrees is nothing to sneeze at.

I think you'd see a bigger difference if you were hauling a load up a long grade, really working that transmission.

Dumajones

Yeah,, I havent tested it wheeling or hauling yet. I have my E-fan on a switch so when I hit the switch it pulls air through the Trans cooler and helps cooling if im not going fast enough to draw air through it.

I would do this mod if I was the OP..

My fluid was change two months ago also.

MTcherokee

Duma and blueridge - your info is much appreciated. I won't have time to do this mod until the weekend but I'll try to take photos and update for anyone else interested in the process. Thanks a bunch ya'll!