Can an aftermarket bumper cause excessive transmission temps?
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Hello, I'm wondering if anyone with an aftermarket bumper has experienced high transmission temps due to the bumper blocking airflow?
I recently had a steel bumper installed on my 4Runner and subsequently noticed my cupholders in the center console getting hot after long drives. I took it in to a shop and they couldn't find anything wrong mechanically but suggested that it might be due to the new bumper blocking airflow to the lower section of the radiator. (I'm guessing the transmission cooling section is isolated to that region of the radiator?) I bought a bluetooth OBDII scanner to monitor the transmission temps for myself and finally had a chance to try it out yesterday via a 1.5 hour drive into the mountains. It was mostly freeway driving with speeds around 60-65 mph with outside temps in the mid 80's. I left OD on since I was staying in 4th gear most of the time. It was only my wife and I in the vehicle with no additional weight or towing load. I do have 33" tires, roof rack, aftermarket bumper and a 4.88 re-gear. Temps got up to 190 fairly quickly and remained there for a while until we started traveling at an incline where temps started increasing again. From there it was in the 220-240 range most of the time with one downshift spike going to 260. I plan to install an additional cooler in series with the radiator but I hear those only take off around 20 degrees so I suspect I'll also need to modify the bumper to add some airflow to the lower radiator section as well. Before I go too far down that road though, I was wondering if anyone else with an aftermarket bumper had experienced anything similar and if so, did adding some airflow down low help? |
That entire lower half of the bumper is blocking the lower half of the radiator. I would think that could cause some issues. How is your coolant temp? The needle gauge can be way off from the OBD temp. I bet you are over 190 on your coolant temp. I sit right at 189 degrees all day long with my stock bumper.
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The stock trans cooler will keep the temps under 200*F much of the time (though it can't keep up if you are putting down some power with the torque converter unlocked). I'd suspect a cooling issue - and seeing as how the whole front is blocked off, I'd suspect the bumper is part of it. Once you have those coolant temps, that will be the information needed - it could also now be showing your fan clutch is weak or some other similar issue too.
My trans cooler is up behind the upper grill for this exact reason though (best airflow given that I have a plate bumper on there). That said, there are still large holes down lower to allow airflow to the bottom half of the radiator. -Charlie |
The answer is yes. Aftermarket steel bumpers cover some of the air flow getting to the radiator.
To keep my trans temp in check on my heavilly modified 3rd Gen, I installed a Hayden 699 cooler and decided to bypass the stock cooler in the radiator. <iframe width="560" height="315" src="https://www.youtube.com/embed/34wnfq85_qk?si=b6s4405kqhKjFD34" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" allowfullscreen></iframe> This is another video covering how to run a trans cooler in-series. <iframe width="560" height="315" src="https://www.youtube.com/embed/2nVbwe2t2T8?si=JJzgTzf6_o2TKC8q" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" allowfullscreen></iframe> |
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Oh, and YES, I monitor my trans temp. Everybody with an auto trans should. Ignorance isn't bliss. If you wait for the "Idiot Light" to illuminate on the dash, you've done damage to your trans. That light comes on at around 300 degrees, which means your trans fluid is torched and you've no doubt done some damage. Here's some more videos on this subject: <iframe width="560" height="315" src="https://www.youtube.com/embed/BEZfDOkGVno?si=wGh1oXdvnfIcoEf9" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" allowfullscreen></iframe> <iframe width="560" height="315" src="https://www.youtube.com/embed/fT_2szdKXRM?si=AvyHWdSEK0CXXipj" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" allowfullscreen></iframe> |
The CFM is what does the work for heat rejection.
I never noticed it before, but since Tim's thread about temps recently, I've been paying more attention to the various steel bumper brands and how the airflow is addressed. They all seem to have less open area than factory visually. I'd be interesting to what the open areas actually measure out to on some of these bumpers. |
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With the AOR plate bumper triple digit temps slow rolling auto trans I've seen 190* at times, like Tim said choose your gears.
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Do you also have an extra transmission cooler or are you staying below 190 with the stock transmission cooling? |
My biggest gripe with Coastal Offroad's bumper design is that it blocks half the radiator. It does a great job of keeping a good approach angle and it's an attractive design, but it's a big compromise in engine cooling. I struggle to keep mine at normal temps, and I cut some holes in the back of the bumper to try to get some more air through the bottom half of the radiator, and added a B&M aux trans cooler.
My engine coolant stays around 190, and the trans is usually around 163-176, but on long grades it'll spike to 210. |
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I solved my engine coolant issues (set the jiggle valve on a new TStat to 6 O'Clock along with a new radiator and cap) and my high transmission temps issue ( trans cooler, drain-n-fills, magnefine) while I still had a fatlip bumper.
After installing a TNF plate bumper, I saw no changes at all. I use an ultragauge to keep track of temps. Edit - Prior to the work I was seeing up to 212 engine and (shudder) a max trans temp of 249. Only once (that I know of). Work to fix that began immediately. Now I see engine temps of 188.6 all day on the freeway and 194ish under max offroad strain in hot ambient temp (4Lo OD off) The trans temps now are at 155 freeway to 190/200 in the max off road conditions above. |
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