I just installed 33” tires on my 98 XJ with 4.0 and AW4 tranny. Someone I know recommended installing an auxiliary tranny cooler due to bigger tires. Is this really necessary? Or am I risking damaging transmission? It’s a daily driver that does mild/moderate wheeling a few times a year.
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Do I need an auxiliary tranny cooler
- Thread starter JeffDB
- Start date
RCP Phx
NAXJA Forum User
- Location
- Phoenix,Az
It would be in your best interest if you plan on any wheeling/travel. More important would be to change the gears.
Unclewolverine
NAXJA Forum User
- Location
- Kansas
Partly depends on your gears, but pretty much most xjs will benefit from a tranny cooler.
RCP Phx
NAXJA Forum User
- Location
- Phoenix,Az
Look for a axle tag but most likely 3.55's.
- Location
- annapolis, md
aux. tranny coolers are always a good idea.
denverd1
NAXJA Forum User
- Location
- Dallas, TX
Bigger cooler IS cooler BRO!!
Sent from my SM-G975U using Tapatalk
Sent from my SM-G975U using Tapatalk
FatSlobBob
NAXJA Forum User
- Location
- OR
May as well pick one up. They're cheap and easy to install.
Do I need a tranny cooler, well how hit is it getting?
I'd assume if used offroad a good cooler with a fan on it would help alot. Temps are likely 300plus coming out of the tourqe converter. This is same for all auto.
My pickup use a heat exchanger were it cools fluid to coolantvtemp then goes to cooler
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I'd assume if used offroad a good cooler with a fan on it would help alot. Temps are likely 300plus coming out of the tourqe converter. This is same for all auto.
My pickup use a heat exchanger were it cools fluid to coolantvtemp then goes to cooler
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smokeyyank
NAXJA Forum User
- Location
- Littleton, Crawlarado
I personally bypass the rad cooler entirely and just run an auxiliary cooler. I think the design is dumb af to run the cooler off the rad. Engine operates at 210 but the tranny likes to stay below 180. Not to mention the possibility of having a strawberry milkshake of death. I know it's brought up that if you live in a cold area that bypassing the rad doesn't work. I've never had issues running these systems for years on both my XJ and my WJ and I live in CO.
Jim Malcolm
NAXJA Forum User
- Location
- PA
I'm running a B&M 70268 with a high-end Autometer gauge w/ 2 °F graduations on the face and the sensor installed in the temp port on the side of the AW4 case. The hottest it got this past winter was ~180°F while romping on it but during normal light-to-light driving, it very rarely got above 160-165°F. No stop-and-go around here to test. On the flip side, I have a 12 mile drive to work; a few lights, then a long stretch, a few lights and I'm there... When it's down around 40°F, the gauge rarely breaks 120°F and when it's down around 20°F, I've made it all the way to work without the gauge breaking 100°F or a number of occasions. I bypassed the radiator last winter when it sprung a leak and made me fiend a strawberry milkshake. Ran it with just the cooler this past summer while abusing it with numerous 20 mph jaunts while in 1st gear pulling 2,500 lbs. Added the temp gauge this past fall so I really only have 1 winter worth of numbers; for what they're worth...
Another observation that's relevant to the conversation but for which I don't really have any data is the fact that the aux fan doesn't kick on nearly as early as it used to during those sustained 20 mph jaunts in 1st gear, indicating to me that even when the radiator is good and hot, it's still pulling heat out of the transmission fluid when you're abusing it...
Another observation that's relevant to the conversation but for which I don't really have any data is the fact that the aux fan doesn't kick on nearly as early as it used to during those sustained 20 mph jaunts in 1st gear, indicating to me that even when the radiator is good and hot, it's still pulling heat out of the transmission fluid when you're abusing it...
maxbraketorque
NAXJA Forum User
- Location
- PDX
Interesting stuff. Is the temp sensor port associated in outlet or inlet fluid flow at the tranny?
Jim Malcolm
NAXJA Forum User
- Location
- PA
Prior to 98, the AW4 has a port right next to the "hot" outlet to the cooler that is used in the Toyota applications of the transmission. Being that it's literally right next to the "hot" outlet, I presume it is the temperature of the fluid leaving the transmission, but I don't know that for sure and haven't yet seen it discussed.
I believe the B&M 70268, Bypasses the oil if not up to temp. The B&M's with the integrated barbs are suppose to have this feature. Also, the Plate types are more efficient than the tube types. The stock liquid to liquid is suppose to be more efficient that liquid to air. Still, you are pumping heat into a marginal cooling system. I do run a Tube fin though on one of my XJs. I did plumb it before the radiator.
I did pick up two trans coolers from a ZJ. I plan to run one before the radiator and one after. I'd run one even if a stock XJ.
I did pick up two trans coolers from a ZJ. I plan to run one before the radiator and one after. I'd run one even if a stock XJ.
maxbraketorque
NAXJA Forum User
- Location
- PDX
Interesting data. Sounds like my 2000 XJ will not have this port.
I think you're the first person I've seen who said that they run the tranny cooler before the radiator. I'm thinking of putting mine in this location. I like the idea of precooling the fluid before it gets to the radiator, and then letting the radiator set the base temperature for the tranny fluid. I plan to use a tranny fluid temperature triggered fan on the cooler so that I get some benefit at slow speed on trails and perhaps in slow traffic.
I don't think I am the only one. I am going toward two aux coolers. One before the Radiator and one after. I have two from ZJs. They are attached to a 'V' hoop. I need to extend the 'V', so it will place and attach in the XJs front. I know some others have done it this way. There is the issue of plumbing the lines. In my next build, I will be looking into a Davis radiator. I am wonder if they could flip the Radiator Trans fitting to the front. It would help.
- Location
- West Sacramento, CA
My buggy has the Derale DER-13900 cooler with fan as the only cooler. Not a ton of run time on it but it sometimes turns off after a wile so I think that means it is cooling adequately. I don’t have a temperature gauge on it.
RCP Phx
NAXJA Forum User
- Location
- Phoenix,Az
Just realized you started a thread which directly relates to this. Besides investigating the cooling system, the proper gears will go a long way!
