Crazy transmissionn temps

[wyomingcowboy]

My 2011 5.3L has experienced some CRAZY temp issues lately. On a trip to the 4 corners area i decided to check the trans temps just out of curiosity because I was bored on the long drives and 100 degree outside temps. Anyway, I saw elevated temps over 200 so I monitored for the rest of the trip. Twice I got the message that the trans was overheating and I needed to idle the engine. I did for about 20 minutes the first time and then 35 minutes the 2nd time and temps came down and I slowed down and made it home. I flushed and refilled and changed the filter and am still having the temp issues. It seems to want to climb to over 200 and then steadily climb right on up to 250+ until I shut down and let everything cool down. The kicker here is that the engine coolant temps never climbed over halfway even with AC on and climbing mountains. (The radiator is pretty new and coolant is too.) Also, the transmission never acted funny. No slipping and no loss of gears, etc. Is there a chance that my Trans temp sensor is bad or what the heck? I flushed several gallons through the whole thing so I'm pretty confident I got most of the bad old fluid replaced. There is no transmission shop close to me so I'm relying on you all!
TIA

 

[Fairweatherider]

You might check for what amounts to a thermostat that sometimes fails to open, meaning that fluid from the transmission can't make it to the cooler. There is a bypass kit that you can buy for this, which eliminates the thermostat. This is apparently easy to install yourself. If I come across the brand and info, I'll post it here.
This is a known issue on some models. I don't know if the 2011 is one of them.

 

[swathdiver]

My 2011 5.3L has experienced some CRAZY temp issues lately. On a trip to the 4 corners area i decided to check the trans temps just out of curiosity because I was bored on the long drives and 100 degree outside temps. Anyway, I saw elevated temps over 200 so I monitored for the rest of the trip. Twice I got the message that the trans was overheating and I needed to idle the engine. I did for about 20 minutes the first time and then 35 minutes the 2nd time and temps came down and I slowed down and made it home. I flushed and refilled and changed the filter and am still having the temp issues. It seems to want to climb to over 200 and then steadily climb right on up to 250+ until I shut down and let everything cool down. The kicker here is that the engine coolant temps never climbed over halfway even with AC on and climbing mountains. (The radiator is pretty new and coolant is too.) Also, the transmission never acted funny. No slipping and no loss of gears, etc. Is there a chance that my Trans temp sensor is bad or what the heck? I flushed several gallons through the whole thing so I'm pretty confident I got most of the bad old fluid replaced. There is no transmission shop close to me so I'm relying on you all!
TIA

You don't have a thermostat on this generation truck for the transmission oil.

You might have a clogged transmission oil cooler(s) and or lines. You said that you recently changed the radiator, the first transmission cooler is in the tank on the passenger side. If you have the enhanced cooling package, you'll have an external transmission oil cooler in front of the condenser as well.

Let's summon our resident expert:

@NickTransmissions

 

[NickTransmissions]

What @swathdiver said; check for restrictions in the system. Perhaps flush the cooler(s) and cooler lines to clear any crud or build up to ensure your system is performing at it's optimal cooling efficency.

 

[rdezs]

You indicated the radiator is fairly new.... Is that a genuine GM AC Delco, or one of the inexpensive aftermarket? I question the aftermarket radiators, as you have no idea what sort of heat exchanger setup is in there in the side tank. My suspicion is that if it's one of the cheap made in China radiators, there's nothing more than a tube connecting the two fittings inside the side tank, instead of a plate style cooler. I haven't disassembled one of the Chinese ones yet, so it's just my assumption, and your symptoms would make me seriously consider that's a possible problem.

Nick, any input on the subject? I'm assuming you have had more to do with what sort of cooler is inside the side tank of the radiator?

 

[Charlie207]

You indicated the radiator is fairly new.... Is that a genuine GM AC Delco, or one of the inexpensive aftermarket? I question the aftermarket radiators, as you have no idea what sort of heat exchanger setup is in there in the side tank. My suspicion is that if it's one of the cheap made in China radiators, there's nothing more than a tube connecting the two fittings inside the side tank, instead of a plate style cooler. I haven't disassembled one of the Chinese ones yet, so it's just my assumption, and your symptoms would make me seriously consider that's a possible problem.

Nick, any input on the subject? I'm assuming you have had more to do with what sort of cooler is inside the side tank of the radiator?

I have the cheapest radiator Amazon sells, and it works fine... great, even. I've been too lazy to get my all-aluminum radiator welded up, because this one just works.

 

[wyomingcowboy]

I have an inexpensive one from car parts.com if I remember correctly. No idea what sort of heat exchanger is in there but I know I don't have a clog as I was able to flush most all the fluid out through the top side fitting. Is there an external cooler I can install similar to bullet proof diesels oil to air oil cooler they make for the 6.0 powerstroke?

 

[wyomingcowboy]

A quick search just showed me that there are in fact a ton of options available for an aftermarket cooler, many less than $100. Who here has had experience with them? Good, bad, no change?

 

[Doubeleive]

A quick search just showed me that there are in fact a ton of options available for an aftermarket cooler, many less than $100. Who here has had experience with them? Good, bad, no change?

the general recommendation is the tru-cool 40k, but there are more pricey options.
the tru-cool is a quality unit, I think they typically run just over a $100 depending on where you shop, amazon is usually a go-to
if you go that route there are some braided an lines and adapters that will never leak versus the screw clamps and hose the tru-cool comes with.

 

[DaveO9]

I'd consider going with the OEM-style external trans cooler. My 2013 Tahoe did not come with enhanced cooling, but I've since brought it up to that standard by adding an OEM external cooler AND replacing the radiator with the OEM-style one that has built in engine oil cooler. The benefit of OEM-style: 1) everything fits up nicely 2) you can order the correct, pre-fitted hoses on RockAuto or similar 3) you get the benefit of GM engineering - the entire cooling system was designed integrally 4) the OEM trans cooler is not huge, smaller than most after-market. It's probably not a problem, but I was worried about the tru-cool units covering up too much of the main radiator and negatively affecting engine cooling.

After the cooling upgrades, we purchased a 20', 4000 lbs travel trailer. I pulled it on a 1500 mile trip from Portland, OR area to just north of the bay area just a few weeks ago. The siskiyou mountain passes in southern OR/northern CA are brutal (like 6-7% grade for as many miles). It was 90ish degree heat and the worst trans temp I ever saw was 217 and that was for just a minute or two. I'm pretty happy with the GM stock enhanced cooling setup. I got this advice from @Geotrash before I did my upgrades - passing it along!

 

[wyomingcowboy]

I just talked to a transmission shop and got some advice/bad news. I just realized that I have never listed the mileage for this vehicle - it's at 239k. Anyway, after going through the story with the shop owner he thought it sounded like a torque convertor failing. He said that if it drives and shifts like normal but the TC never locks up then it gets real hot real fast and that 230k miles is a long life for this transmission. What do you think? I know the motor has been acting tired but actually did pretty well in with a compression check last winter so I didn't think too much more about a rebuild. If I need a new trans I might as well get a new motor as well. The rest of the vehicle is in pretty good shape and the whole family does better on trips in this than they do with my F350.
I thought I read somewhere that a 6.2L will just drop right in with no other changes. Is that true? Maybe I could find a wrecked one somewhere and do a swap? I know we cannot afford a rebuilt trans right now much less a new trans AND motor or, heaven forbid a new vehicle.

 

[wyomingcowboy]

I just talked to a transmission shop and got some advice/bad news. I just realized that I have never listed the mileage for this vehicle - it's at 239k. Anyway, after going through the story with the shop owner he thought it sounded like a torque convertor failing. He said that if it drives and shifts like normal but the TC never locks up then it gets real hot real fast and that 230k miles is a long life for this transmission. What do you think? I know the motor has been acting tired but actually did pretty well in with a compression check last winter so I didn't think too much more about a rebuild. If I need a new trans I might as well get a new motor as well. The rest of the vehicle is in pretty good shape and the whole family does better on trips in this than they do with my F350.
I thought I read somewhere that a 6.2L will just drop right in with no other changes. Is that true? Maybe I could find a wrecked one somewhere and do a swap? I know we cannot afford a rebuilt trans right now much less a new trans AND motor or, heaven forbid a new vehicle. We bought it with about 118k miles and his been my wife's daily driver for years as well as the family car as long as we don't need to pull a gooseneck trailer.

 

[rdezs]

That's basically correct. A used 6.2 with the matching 6L80 transmission..... And make sure you get the ECM out of the vehicle.... Will in fact bolt right in. Even with the ECM, there will be some minimal tuning to do. (Changing the VIN number in the ECM for example)

Sounds like you're have a bit of a budget.... The 6.2's are quite popular with the hot rod crowd, so there's a lot of demand for them, which has pushed the prices up. A used 5.3 is probably the least expensive option. Bolt it in and go.

Whichever way you go with the transmission, rebuilt or used, it will need to be programmed before you start it up and take off driving. It's pretty common to just have it towed to a dealer or the transmission shop, for a nominal fee they will program it.

 

[rdezs]

If you don't mind getting into some tuning, and iron block 6.0 is an excellent affordable option. An easy upgrade with a cam can you bring you right up to the horsepower of the 6.2 reliably. (And much more even)

 

[rdezs]

If I was on a super tight budget, I would find the lowest mileage 5.3, freshen it up with new front and rear seals, oil pickup tube o-ring, maybe a new oil pump and timing chain set.

Transmission, I would splurge for a rebuild. Buying a 6L80 used is expensive, considering you really don't know what you're getting.

 

[wyomingcowboy]

I found a trans and 6.2 out of an escalade with 157k miles. Any reason why the escalade setup wouldn't work the same way?

 

[rdezs]

Out of what model year?

Keep in mind that transmission is approaching the upper end of its average lifespan. Which really depends on how well it was maintained, and how it was driven. The big failure item is the torque converter which usually takes out the transmission when it goes.

I'm assuming the 6.2 probably has AFM/DOD. You'll definitely want to physically delete that and get it turned off in the ECM.

If it's a 2010 to a 2014 model, the harness will be identical. Get the ECM with it, have it programmed with your VIN number, and if you delete the AFM have it turned off in the ECM as well.

We have some members here well versed in the programming side of things.... They could fill you in for sure on more specifics. I'm fairly sure that if it's a matched set out of one vehicle, the transmission probably won't need to be programmed.... But wait and see what one of the transmission guys here says.

My advice if you go with it, at a minimum, would be:

New aftermarket torque converter
Full AFM delete with L92 or L9H OEM camshaft
New Delphi LS7 lifters with new genuine GM lifter trays.
New Melling 10296 oil pump and timing chain set, VVT solenoid and actuator, front and rear seals. Felpro oil pan, head, front and rear cover gaskets. Upgrade to the aluminum dog bone behind the rear cover.
And plug the oil pressure relief valve in the oil pan. Trunnion bearing kit for the rocker arms and some quality push rods. (Which you will need to measure for)

That should get you at least 100,000 more miles down the road on the engine. The transmission is a roll of the dice....

 

[wyomingcowboy]

I'm sorry but I don't know what AFM or DOD mean

 

[rdezs]

It's the hardware GM added to switch back and forth between 4 cylinders and 8 cylinders. Active fuel management, and displacement on demand. It's a very trouble-prone technology, worth deleting if you expect the engine to last. It has a nasty habit of eating lifters.

 

[wyomingcowboy]

Are there threads on here detailing how to do that?