Transmission cooler

[Jansen]

I've read a lot of posts on this forum where it has been recommended to get an auxilary transmission cooler. Is the transmission cooler that comes with the towing package not enough for these trucks? I know weights and distances can vary, just looking ballpark.

 

Jansen

[ken1mod]

The factory cooler is good but not real big. If you are towing anything big in hot weather, I would install another in series with the factory teeny cooler.

 

It is perhaps more important to drive with the torque converter locked up. this means moderate (less than 25%) throttle. trans heat comes exclusively from unlocked converter. Technique is important. My motor home was previously owned by an old-timer who installed a vacuum gauge to monitor engine load. He said he never went below 8"Hg continuously. seems like a good idea to me. I drove by it too.

 

Ken

[mmmikkke]

Hey, maybe I should try that.

[01z71]

Alright, this may sound stupid but how do you know if your converter is locked up?

[ken1mod]

I'm sure there is a fancier way but you have to be sensitive to each shift. trans normally shift 1 to 2 to 3 to 4 then 4 lock-up. each of these is "feelable" or noticeable by the tach. in lock up, the tach and speedo are in lockstep, like a manual. under heavy load, the sequence reverses and below about 35 in high the converter is open.

 

Chevy computers are pretty good about keeping things locked up. you mainly need to be careful climbing long hills. Shift manually into third at any long hill. converter will lock in third for sure. I try to stay around 2500 or so climbing hills in third. personally I don't exceed 3000 continuously but 4000 is ok. big truck governors with small block used to be set never to exceed 4000 rpm, ever.

 

I have no trouble keeping my 5.3, 3.73 silvy cucumber cool towing my 4000 lb boat up evil hills. just because it will do it at 80 (and it will), that is how you cook 'em. Ease up on the big hills and go like hell on the flats. think of yourself as an 18 wheeler driver.

 

Ken

[Bish]

I tow around 5000lbs pretty regularly. I bet I have towed for 50K of my 170K miles. I have the factory tow option cooler. I also put an Escalade cluster in so I had a trans temp guage. When I first towed on OD (in tow/haul mode), seemed fine on flats but tranny temp would shoot up if pulling up hills as the trans unlocked the torque converter and started hunting for a gear. Since that one time, I tow in 3 and temp never gets above 200 except for very rare occassions when I am pulling a heavier load or it is VERY hot outside.

 

IMO, stock cooler is fine unless pulling heavy loads, or pulling in the mountains a lot, or pulling in the desert heat. Then again, you bigger is generally better so no harm in going bigger on the cooler.

[asilverblazer]

Last time I had a rental, a Pontiac, we were cruising through a mountain road, not up and down but curvy, lots of slowing down to 20mph speeding up to 35mph. After about 1 hour of this the transmission temperature was up to 235 degrees, in a car, at night, ambient temperature around low 80's. SOOOOO, just because you aren't climbing hills doesn't mean not to watch the temperature. The normal for that car all the other times was around 180 degrees. In alot of ways those conditions were much worse than towing out on the highway. That being said I have 140K on the ticker of the truck and it does it's fair share of work all with the factory tranny cooler. Which is literally so small I didn't see it the first few times I looked for it.

[bigdogxx]

Really if i towed a bunch especially in the summer months why would you not buy something that is cheaper then a tank of gas practically and is known to prolong the tranny since heat is the number 1 factor when it comes to destroying trannys.

[ken1mod]

This is all really important info. Cooler is always better. I, too, couldn't find the extra factory cooler for quite a while.

 

I would say that an occasional jaunt to 235 is no big deal, but I wouldn't want to see it regularly.

 

I would argue that even with the largest cooler available, maybe even two, I can overheat any trans with louzy technique and tow a big load with factory equipment and stay cool. it really has a great deal to do with how you operate your right foot.

 

The old-timer 18 wheel drivers call it "soft-pedaling". Do that and most machinery will last forever, thrash it with a heavy load and you will be picking pieces of it out of your teeth.

 

Ken

[Jansen]

Ok, I had 6500lbs behind my truck, I never exceeded 45mph and had tow/haul operational in 3rd I did not use OD on this trip. It isn't mountainous by any means in Chillicothe Oh. My trans is fine by this, but I wish I had a temp gauage for it.

 

Jansen

[dewfpo]

T/H mode will definintely keep temps down, even if you aren't towing but driving in the mountains or high heat situations.

 

DEWFPO

[the blur]

I tow 6000lbs regually, and my guage never goes above 200F. This is an all stock 03 Denali. maybe once I hit 210 going up a steep hill.

you think I am going through the effort of chopping into my tranny lines to add another cooler, I think not.

 

GM designed this one pretty well.

[Jansen]

My truck never had a problem with the 6500lbs considering I have 4.10's but then again I kept it at 45pm, 3rd gear, and T/H mode. Does T/H mode keep it locked together until 2500rpm or longer?

 

 

The Blur:

 

Good to know on the temp though, I'm sure mine was about the same. Thanks for giving me a ballpark temp.

 

I just had the trans fluid and filter changed at 30,000 miles. Fluid is a nice deep red and looks great. 6qts of fluid went out.

 

Jansen

[ken1mod]

I'm with the Blur on this one, My trans stays so cool in Phoenix that I can't even get a reliable hot reading on my dipstick. I can always let a drop fall on my wrist, only warm.

 

Ken

[toneman]

I dunno how you fellas manage it, but even w/ the factory external tranny oil cooler on my DXL, my tranny temps read anywhere between roughly 175-185 on average...and this is while cruising in 4th/OD, outside temps in the high-70's/low-80's, no towing or heavy load of any kind, and no matter if A/C is on or off (w/ A/C on, tranny temp usually more towards the 185-190+ range). I'm not running low on tranny fluid, it doesn't appear to be burnt, and tranny seems to operate fine otherwise. This is especially frustrating for me--especially after reading the post from the one guy who says his tranny temp never goes over 200 even when towing 6000 lbs....yet there have been more than a few times where the gauge would hit close to (as in, one tick below)--if not right at--200 even if I'm just towing a toy boat...and as mentioned earlier, I have the factory tranny oil cooler on my ride! What gives???????