TV Transmission Cooler Fan

[austinado16]

Today I added a pusher fan to the big transmission oil cooler. (photo taken prior to painting)


Scored the fan for $2 at the local swapmeet it's an OEM pusher off something like a 3/4 or 1 ton GM truck.

There have been a few instances of transmission oil temps spiking to 230*F while climbing steep grades at lower speeds.  Not really that dangerous, since it only lasts a few minutes and comes right back down to the 160-180*F range (depending on air temps), but I'd like to keep the temps closer to 200*F if possible.  

After having this 4L60(700R4) trans rebuilt and upgraded internally for towing about 3 years ago, I added the huge cooler, a big B&M cast aluminum pan that holds 4 extra quarts, and a mechanical temp gauge bunged into the pan.

I'll report back once I do some towing in the heat.  We're heading back to the Grand Canyon on July 31st, so that'll be 1,320mi across the Mojave Desert and Arizona in 100teen temps.

[wavery]

Do you use synthetic oil in your engine and trans? They make a huge difference in cooling.

The fan is a good idea. You are getting very little air flow to your radiator with all that crap in front of it and any air that it does get is pre-heated. Do you have room to mount the trans cooler somewhere else under the hood? (heck.....I think you could build a house under that hood :p). As long as you have that fan on it, it doesn't need to be in front of the radiator.

[austinado16]

Yes, 5w/30 synthetic in the engine, which just rolled 260,000mi on our last camping trip.  But still using regular ATF.  I may dump the ATF before we go to the Grand Canyon and replace it with Valvoline Synthetic Dexron VI.

The layout in front of the radiator is exactly how GM built them.  That's the original oil cooler on the passenger side.  (It's also how oil cooler manufacturer's like B&M and Hayden, etc. recommend their coolers be installed.)  Of course being a 1/2 ton model Suburban, it didn't come with an external trans cooler.  But if it was the 3/4 ton version, it would have come exactly like I've got it set up.....huge trans cooler, and that same pusher fan.  Behind both of those is the huge a/c condensor.

The radiator is huge, and built to handle exactly how the truck is set up.

[austinado16]

Just back from a 3 dayer in Kings Canyon Nat'l Park.  Man, what a test of the cooling system for both the engine and transmission.

Drove into the Sequoia Nat'l Park side from Hwy 198 east of Visialia, CA and up over the steep mountain pass that's labeled "Vehicles over 22 feet not advised."  I'm guessing it's a 5,000' climb via 10mph switchbacks, many of which are more than 180 degree turns.  Outside air temps were in the mid 90's and I was locked down in 2nd gear doing 10-30mph for about 45min.  With the trans cooler fan running and the radiator fan clutch engaged, I saw trans temps steady at 205*F with a brief spike to 210*F.  Not bad I guess, considering the the load and lack of speed induced airflow over the trans cooler and radiator.

The climb out of Kings Canyon was equally taxing as air temps were in the mid 90's and we ran into traffic.  This is about a 4,500' climb and trans temps spiked at about 225*F and held there for about 15min.  Wasn't happy to see them so high, but considering we saw 230*F a month ago in 70*F outside air temps with no traffic, I guess that's an improvement.

I think there's still more I can do to improve cooling and the first thing will be a switch to synthetic ATF.

[wavery]

Sounds like a good time was had by all (including the TV).

225 temps are not that extreme for the trans. It's best to keep it below that but the oil won't start to burn until about 250-275. If you get the slightest hint of a burnt smell in the fluid, get rid of it (I'm posting this for others also, I know that you know this). My experience has been that synthetic trans fluid will drop the extremes by 15-25 degrees. This also takes a load off of the radiator cooling as well, if the the factory trans cooler (inside the radiator) is still being used.

The beauty of synthetic oil is that is acts as a coolant (petrol based oils will retain heat much longer) and it won't burn, even in temps exceeding 300 degrees.

[austinado16]

I appreciate the input on the temps and the synthetic.  I'm a German car guy, so playing with big American stuff is sort of new to me....although I've had the 'burb for 4 or 5 years now and have done quite a bit of work to it.

I was going to switch to synthetic ATF before we left, but the current fluid is still clear and pink, and that's after 2 hauls to the Grand Canyon, and maybe 4 or 5 to Kings Canyon.  I do other towing/hauling with it year round for car and camper projects, ski trips up in the mountains, etc. but during those, the trans temps always hover in the 160-180 range, so they aren't even a challenge (temp wise).  I'm glad I didn't switch, because now I know what the temps do with the current system, in high heat, high load, low airflow, and when I switch to synthetc, I'll have a better apples-to-apples comparison.  Had I switched along with the cooler fan, I wouldn't know which was providing benefit.

Spoke to a couple of GM techs (the guy who built my trans and another guy whom I used to work with) and like you, both said 230 isn't bad for the short periods that I see it.  I did have a concern that the new GM radiator fan clutch wasn't working, but they told me it won't even start to come on until it "sees" about 230*F coming through the radiator.  These throttle body injected trucks run at 200*F to begin with, so that's starting make sense.  And sure enough, once I got into that first slow hot pull coming out of Potwisha CG, the rad-fan began to roar like a diesel locomotive and it continued like that until the coolant temp gauge was down at 200.

I am still using the radiator heat exchanger and I need to decide to either by-pass it, install some mechanical valves that I can switch for summer or winter, or do something with oil thermostats.  I'm leaning more toward valves, but I'm undecided.  Need to do more thinking, and research.  I'm after a simple and dependable solution.

Coming home yesterday across the Central CA Valley, a guy hauling a HUGE 5er with a Chevy 2500HD pickup passed me going up hill, like we were standing still.  I was proud of the steady 55 I was holding and watching the trans temps hover at 200 or so, and he went blasting by without a care in the world hauling 5 times the weight and 100 times the frontal surface area.  What the hell??  I was impressed!

[PattieAM]

Me and my 2000 Durango just hauled the Niagara to Orlando - all was fine until I hit rush hour outside Orlando....got to the campground and gate person told me he smelled t-fluid.....Durango is currently in a local shop - front differential leak, transfer case leak, rear differential leak.  but, the durango has 219,000 miles on it...time for something to go.  Just replaced the engine about 5,000 miles ago!

[austinado16]

Did the synthetic ATF change and a new filter yesterday, so we'll see what happens.  It holds just over 7qts w/ the big B&M cast aluminum pan, so that's a pretty good dump of oil.  Probably only 3-4qts didn't get changed.

PattyAM, sounds like you're getting your money's worth out of the Durango.  Nice!