1991Jeep_Man

This bad boy!



Off of a Grand Marquis. The block to the right is a thermostat that either bypasses the cooler until fluid is 175-180* or cools it once it hits that temp. Also incorporates a secondary cooler of choice. I'll be mounting it behind the bumper (vents cut in of course!).

Question: will this thermostat cause the trans to run hot? Last thing I want is to completely do the opposite of my goal, which is keep the AW4 cool. I've been told 175-180* is optimum for an auto trans. I'll be running it in tandem with the stock cooler to get things warmed up (especially in winter) along with a filter after the coolers. Concern: the thermostat obviously prevents flushing. This part was graded 'A' for the listing I bought off of. Should I be concerned as long as I have that filter? My big concern is anything blocking the cooling channels.

Second Question: I've considered using the second cooler (non-thermostat controlled) as a P/S fluid cooler. With stock tires and little towing, would this be harmful? Will the pump have to work harder to move the fluid down and back up?

Thanks!

djb383

What I've read is, 175-180 is the max temp for longest tranny fluid life. Higher temps shorten fluid life. Obviously, if one believes in regular vehicle maintenance of all kinds (including the tranny fluid), tranny fluid life is probably a non-issue. If one checks the tranny dip stick regularly, u can tell when it needs to be changed. Tranny fluid does not go from red/pink to brown/black overnight.

I've got 2 vehicles, besides the XJ, with B&M #70264 auxilary tranny coolers and both vehicles have a ScanGauge to monitor tranny fluid temps. In cold weather, not towing, it'll take forever for the tranny fluid to reach/peak at 120-130. Right now, 3 digit ambient, it still takes an hour or so for tranny fluid temp reach/peak 160-180. Bottom line.....tranny fluid doesn't heat up anywhere near as fast as engine coolant, even when the auxiliary cooler has a thermostat. Will tranny fluid temp go farther north (200+) u bet.....when u latch onto a trailer, pull it 70 mph, in 3 digit ambient.

I'd suggest filling the used cooler with tranny cooler flush (available at the auto parts store), let it sit/soak and blow out with compressed air.....maybe do it 2-3 times.

Anytime fluid has to travel farther (adding a auxiliary cooler) resistance to flow will be increased some.....enough to make a negative difference, I doubt it.

One thing to consider when adding an additional cooler(s), more chances for leaks. We installed the B&M #70264 on the XJ inline with and after the factory rad tranny cooler. Haven't been able to get the ScanGauge in the XJ to display tranny fluid temp but I suspect fluid temps in it are similar to the other 2 vehicles.

If one eliminates the factory rad cooler and runs only an external tranny cooler, I'd strongly recommend installing a tranny fluid temp gauge to be safe/verify fluid temps.

1991Jeep_Man

So given the max safe fluid temp is the same temp that this trans cooler stat opens at, should I just cut it out?

djb383

I would not think so. It probably allows tranny fluid flow thru a few tubes when cold, then when fluid temp reaches stat rating, it opens up allowing fluid flow to all the tubes.

Is that cooler a combo tranny fluid and power steering cooler?

1991Jeep_Man

Yes sir it be!

djb383

That's what I was thinkin'......be sure to get some cooler flush and git after it. Keep us posted on the mount.

1991Jeep_Man

I'll do better than keeping posted! Full write up and results. Before I install it, I want to get a gauge... just decided on the right one. I'm fond the red LED gauge selling.

Quick question: can a generic 'coolant' temperature gauge and sender (standard 12v) be used as a temperature gauge? It seems like they're EXACTLY the same, but one is $25 more than the other.

djb383

It's not critical, but I'd suggest a gauge that displays below 100 and up to say 250. Again, not a big deal but in cool/cold weather a gauge that starts at 100 is not likely to register/display for quite a while.

Fred/N0AZZ

Buy the transmission heat gauge for best results use an analog meter, as far as brand I've always used "Autometer" for all of mine. A good place to mount them is an A-Pillar mount from Summit or Jeg's made for an XJ really good places to buy both.

askingxforxit

I bought the auto meter single gauge pod and it's not a perfect fit...

askingxforxit

See...
Auto meter 15211 gauge pod

1991Jeep_Man

Trying to save a little cash, so unless there is a major difference between a trans temp gauge and a coolant temp gauge, im going to save $30 and get the coolant one. They use the same looking brass sender.

Just gotta hit up Azzy Design Works and see if they can do a gauge face to match my current ones. Only downside is that it reads 100-300 degrees. I'll have to look into this. I wanna say its not a big deal because the stock temperature gauge only starts registering at 100 degrees, but the trans has a lower op temp and slower warm up...

djb383

One of these days I'm going to experiment with one of these units.

http://www.trailtech.net/digital-gau...rature/722-es2

dmill89

I wouldn't worry about it starting at 100F, the AW4 creates quite a bit of heat and will get there pretty quick. I have a 100F-280F gauge (Sunpro ST2) on my XJ and it will get over 100F in just a couple miles, once up to temp it usually runs arround 140-150 arround town, 120-130 on the highway, on long steep grades or grid-lock stop and go traffic on a hot day it will get up arround 180F, however I've never seen it get over 200F (I haven't towed with it though). I have a B&M 70264 cooler on mine.

I used to have a gauge that started at 140F (Stewart Warner 122281) and that was too high though, it barely even registered except on steep grades or on heavy traffic (though it was still usefull for telling if the trans is running too hot).

Granted I have my gauge sender in the "hot" line from the trans, which has fluid comming right from the torque-converter and should be the hottest area of the trans, your gauge may read much lower if you put the sender in the pan.

1991Jeep_Man

Based on running temps I am seeing, I am really wondering if I should cut this thermostat out. Would simple tube and 2 clamps suffice to block the gap? What can I use to cut it clean?