Trans Temp 2012 Silverado

Hi all,

We did some upgrading this summer and early Fall.  In June I found a very nice 2012 Silverado 1500, 2wd, 5.3 liter, auto trans.  It was a Texas truck and it was very clean with 50k miles.  Living in the northeast it was bazaar seeing a seven year old truck without any rust at all.

Last Saturday we traded our Jayco 195RB in on a Coachmen Apex 265RDSS.  We couldn't be happier, lots of room and it's pretty light weight (5545 dry) for a 30' trailer.  As usual there were  a few little things that needed fixed (couple plumbing fittings loose, etc.) that I took care of.

The day we picked it up was a pretty warm day, around 80/85 degrees.  On the three hour trip home through the hills of western PA, the trans temp got up to 208 degrees at one point.  Not sure how accurate the digital gauge is on the truck but guessing somewhat close.  The truck has a heavy duty towing package and it wasn't working to hard pulling the hills on I-79 between Pittsburgh and Erie PA.

My question;
How "Hot", is to "Hot" for the transmission?  Should I look into a better Trans cooler?

Well, the tranny fluid is cooled AND heated by the coolant in the bottom of the radiator. What?s the coolant temp? My 5.3 with 4 speed auto runs about 10-20 degrees cooler than coolant temp ( top of radiator) not towing. Can?t have too much auxiliary tranny cooling though, IMO.

I'd say 208 is somewhat over the acceptable range. Most experts say that tranny (I'm guessing it's the 4L85E) should not be running above 200, even wth a heavy load.  It would be much happier in the 170-190 range.  You should definitely be using a synthetic tranny fluid - it holds up much better at higher temps. Tranny fluid deteriorates quickly at higher temps and the tranny itself suffers heat damage. The effect increases as the temperatures climb, so "too high" is not a clear cut point.  Best I can say is that over 200 ain't good.  I think your tranny will signal a warning to the dashboard if it reaches a temperature that is seriously bad (failure imminent).

This article may be helpful:
http://etereman.com/blog/general-motors-transmission/prepare-the-4l85e-transmission-in-your-suburban-for-towing

Do your tranny a favor and make sure it uses full synthetic fluid,, it will lower the temps. smooth the shifting and extend the life.>>>Dan

jubileee... I have the 5.3 with a six speed auto.  It also has an external cooler for the trans, guessing it still goes threw the radiator first.

Gary RV_Wizard... thanks for the link to the article, good info.  I don't know the model number of the trans, the one I have is a six speed.  I'm going to have it serviced soon and will inquire about the synthetic fluid.  I was thinking the same thing that day I saw it go over the 200 mark.

Utclmjmpr... I am definitely looking into the synthetic fluid.  I've heard good things about a Transmission shop near me, guess I'll give them a try.

The 6-speed would be the 6L80 or 6L90 Hydramatic.  It has an improved internal design (different clutches than the 4L85) and of course 6 gears vs 4.  Newer transmission can still function at higher temperatures, but that's not the same as saying it is healthy for them.  I would not be surprised if it didn't show the over-temperature warning until maybe 230 or even 240.

Your tranny uses Dexron VI fluid which requires at least a synathetic blend for the base oil stock. However, many major brands of Dexron VI are a full synthetic.

At 240F, most fluids will start to degrade.  Coolant should stay close to OEM recommended temps, usually 180-210F (I believe to optimize fuel combustion and fuel economy). But you can run tranny fluid cooler lower, say 170 without compromise. 208F is fine, but if you tow a lot in the heat, it may be worth adding a bigger aftermarket cooler to be safe.

A single instance of getting "hot" isn't a problem. It's repeated hot tranny temps that shorten the service life. What fails is the seals. They start to leak, and then things start to slip, and the more it slips the hotter it gets and the more the seals fail. Its a visous cycle and leads to total failure. Servicing is always a good idea.
Average transmission temps are between 175 and 200 degrees. I wouldn't be worried about 208 degrees. Transmission fluid deterioration begins at 225 degrees. If you breach this temp, do a fluid flush.
The engine and tranny work as a team and the engine computer manages both. Your engine cooling fan controls radiator temps/tranny temps. Make sure it is functioning normally. Do you have a clutch fan or electric fans? Which ever, make sure they are functioning properly.

Now, if tranny temps is a concern for the long haul. Pun intended. You have several options. A larger auxiliary cooler, and/or larger cooling fans by capacity, not physical size. Realize that Chevy has built the transmission and oil cooler into the radiator. They did this for several reasons. The main one is to get the engine up to operating temperature quickly, thus saving fuel and making the engine/tranny team operate at peak performance. IF you add an auxiliary tranny cooler, and/or fans, your engine may never reach operating temperature and your fuel mileage will suffer tremendously!!! 
I highly recommend you take it to a dealer and let them diagnose, service the tranny. There are upgrades they can make to the internals of the tranny that will reduce slippage and thus reduce heat being generated. You will have firmer shifts, but remember this. the softer the tranny shifts, the more slippage occurs. the harder the shift, the less slippage. Less slippage is best. But the side effect is head back in the seat headrest, whiplash.

They didn't built the cooler into the radiator to help the truck warm up quicker.  They built it in there because it's cheaper.
The thermostat on the engine controls the coolant temp.  It stays closed until the coolant in the block reaches about 195*, then it opens to let the coolant flow through the radiator.  The cooling system will reach operating temp well before the transmission does.
When you're towing an external trans cooler is a great idea.  It is typically installed in the return line to the transmission.  Thus the fluid runs through the radiator and is cooled to around the same temp as the engine coolant, from there it goes to the external cooler and is further cooled before returning to the transmission.
Here's a good article in regards to transmission coolers:

https://www.etrailer.com/faq-about-engine-transmission-coolers.aspx

Gotta second what Hanr3 says: 208 once in awhile is no big deal, but if towing your RV always produces temps in that range, you are pushing your luck. 208 in the tranny is also burdening the engine coling system more and maybe it will also come up short on a very hot day.

You can add a secondary tranny cooler in the return line, where it will further cool the fluid as it comes out of the cooler in the radiator.

I have been looking at trans-coolers.  Lots of choices out there, was thinking about a Derale Heat Sink Transmission Cooler.  Has anyone used this or something similar?

Here is a link;  http://derale.com/products/fluid-coolers/transmission/heat-sink/13266-detail

Having had a 1/2 ton truck with a 5.7 and a Yukon with the 5.3, pulling a trailer with the truck and boat with the Yukon, not the best TV's to say the least. Your stepping on some of the same sticks I have stepped on. You say hills, and only 85deg, is there going to be trips with a serious grade and 90 plus temps? What is your axle ratio? Also are your tires stock size, or did the PO go up in size, working against your present ratio for towing? If you plan on keeping the truck for a TV, research your ratio to help the tranny out. Yes It may affect your unloaded mileage somewhat. Buy the biggest aftermarket cooler you can buy,,,gregg

Does a 1/2 ton truck really have a transmission temperature gauge?  Kind of surprising if it does.  Engine coolant temp of 208* isn't bad.

Some thoughts about towing on hills:
--  Don't wait for the transmission computer to downshift on the start of a hill.
--  At the start of a hill, just as the engine starts to feel the load, press a little harder on the accelerator to force a downshift and then back off a bit, but not so much that it upshifts.
--  Or manually downshift one gear as it starts to load up.
--  If the hill is a little steep, manually downshift 2 or more gears.

Bottom line, you want to keep your RPM's up in the 3000-4500 range depending on how steep and long the hill is.  If you are pulling up a hill with RPM's in the 2000-2500 range your transmission will overheat.

Many 1/2 tons do have a transmission gauge. It's generally not in your face on the dash, but can be accessed and displayed using the driver's interface.

kdbgoat said:

Many 1/2 tons do have a transmission gauge. It's generally not in your face on the dash, but can be accessed and displayed using the driver's interface.

Click to expand...

Exactly what I have....

I used the RPO codes in the glove box to determine my axle ratio;

G80 : AXLE POSITRACTION, LIMITED SLIP
GU6 : AXLE REAR, 3.42 RATIO

I also took a good look at the factory installed secondary trans cooler.  IMO it's not very big for a so called Heavy Duty tow package, it's a tube fin type, maybe 3" x 7".  Thinking now it would be easier to replace it with a stacked plate design in the same location.  Maybe something a long the lines of this;  https://www.speedwaymotors.com/AFCO-LL7B-Stacked-Plate-Oil-Cooler-5-3-4-x-11-x-1-1-2-Inch-24-Pass,39664.html

AStravelers said:

Does a 1/2 ton truck really have a transmission temperature gauge?  Kind of surprising if it does.  Engine coolant temp of 208* isn't bad.

Some thoughts about towing on hills:
--  Don't wait for the transmission computer to downshift on the start of a hill.
--  At the start of a hill, just as the engine starts to feel the load, press a little harder on the accelerator to force a downshift and then back off a bit, but not so much that it upshifts.
--  Or manually downshift one gear as it starts to load up.
--  If the hill is a little steep, manually downshift 2 or more gears.

Bottom line, you want to keep your RPM's up in the 3000-4500 range depending on how steep and long the hill is.  If you are pulling up a hill with RPM's in the 2000-2500 range your transmission will overheat.

Click to expand...

That's pretty much how I drive.  I have driven trucks for many years and know the importance of keeping the RPM's up.  That being said, on the day the temp hit 208, I can't honestly say where the RPM's were, guessing around 3K.

UPDATE...

I had the transmission serviced this spring and went with full synthetic oil and filter change.  I installed a Derale 25 row plate fin transmission cooler.  I gave it a good test the last couple of days going through the mountains of WV on I-79, 19, and I-77.  Out of the mountains the tranny temps were in the 140's, they got as high as 192 pulling the first few grades heading south on 19 off of I-79, air temp was in the mid 80's. I'm pretty sure I would have cooked the tranny with the stock tow package cooler that was on it.  Really glad I changed it out.