2012 GMC 1500 trans hitting 250 towing Jeep up mountain pass

[401 YJ]

Here is the full story. I had a 2008 GMC Sierra Crew cab 1500 and now have a 2012 identical to the 2008 but the new truck does have the 6 speed. My Dad has a 2009 silverado 1500 with the 4 spd. All 3 are 5.3 and 3.42 gears. We are from Illinois and tow Jeeps to play in the Colorado Mountains. The trucks tow fine and stay cool until we start up mountain passes. Thats when both trannys get to 250 degrees and above. My 2008 was exactly the same. The motors also get hot. Dad replaced his stock trans cooler with a much larger one and this made now difference. The Jeeps on Car haulers weigh less then the trucks stated towing capacity. We tried both manualy holding the trucks in lower gears and letting the transmissions choose their own gears. It made now difference either way.

 

Here is the kicker, before we upgraded trucks I towed my Jeep with 2003 Tahoe and Dad with a 2003 Avalanch. Both older trucks never got hot, even on the hardest pulls. My thought is the new truck have electric fans and the older trucks had engine driven clutch fans that just pulled more air.

 

My question is what can we do to the new trucks to keep them cool. Aside from stopping every 5 minutes and letting them cool down. I can't imagine 250 is a good thing on the transmissions.

[Jsdirt]

Get the biggest aftermarket cooler you can find - and if that doesn't work, hook 2 up in series. They also sell ones with their own cooling fan & thermostat, so they can be mounted pretty much anywhere.

 

I notice this too. My '72 El Camino tranny never even came close to 200°, let alone 250° ... but my '07 routinely hits 200° on steep grades in hot weather, even 100% full of Amsoil ATF.

 

The conspiracy theorist in me says this is so your not driving these trucks in 10 years. They want you buying new ones every 5 ... like we can all afford that ...

 

I suppose time will tell, but I've read a few posts on here of serious mechanical tranny & engine problems on these trucks around 150k miles. If you tow often, I'd be installing as many coolers as necessary. You can't hurt a tranny by keeping it "too cool" ... and coolers are cheaper than rebuilds.

[kstruckcountry]

^ ditto, bigger cooler may help.

 

I'm curious too as to how long they'll last in the 900s, but I know plenty of people over 300k in 800s so I'm not worried about mine too much. Looking to get an aux readout though, towing with ambient temp 112 can't be good on it.

[401 YJ]

I guess I am going to try putting another cooler in line with the stock cooler. Some guys have been using the style i am planning to use on their offroad riggs around here. It basically looks like a large cylinder with fins. It should give me another quart capacity of tranny fluid. Its just frustrating to have a brand new truck (my first new vehicle ever) and not be able to tow as well as my 03 Tahoe with well over 100,000 miles on it.

[Jsdirt]

I feel your pain brother.

 

My lower ball joints were junk at 38k miles, struts junk at 50k miles, more squeaks and rattles than my old '94 K1500 with 266k miles on it, and I noticed my front diff leaking out the CV axle output (probably due to a smoked bearing, judging from the play there) at around 50k miles. Not to mention body panels and bumpers that fold like a lead sheet at minimal impacts.

 

But she sure does LOOK pretty!

 

Can't wait until I start getting check engine lights! That should be fun ... and right around the corner ...

[401 YJ]

Don't get me wrong I love the truck 98% of the time. Its just that once a year we make a trip to the Mountains and I wish it would just stay cool. Can't justify the extra expense for a heavy duty truck for that one trip a year. Dad thinks a 6.2 would be better but I say it would have the same problem, possibly worse just because the motor is bigger and makes more heat.

[Jsdirt]

Then you've got to factor in worse gas mileage to that.

 

You'll be fine. An extra cooler or 2 will keep those temps down where they belong.

 

As for me, when this truck is done, I'll build the next one myself.

[00Silverado4x4]

To the OP:

What speeds were you driving? Were you running AC? It's been pretty warm across the country and if you were running AC up those hills you're going to run hot and quick. I've never seen my engine temp gauge move until I was pulling my trailer through the "Grapevine" in California. When it did, I kept the trans in 3rd, tow/haul, slowed down and turned off the AC and then I was able to keep my temps in a more acceptable range.

 

I know, I'm comparing apples to oranges on our vehicles but the principles are the same.

[crankman]

Are you using a car hauler trailer or just pulling them directly? Just curious not sure if there would be any difference in the the rolling resistence.

[401 YJ]

Air was off and the temp was in the low seventies at the top of the mountain. The only other thing I could have done was have the heater on but the motor wasn't even close to as hot as the transmission so the motor wasn't as much of a concern.

 

We were pulling car haulers. I would guess flat towing the Jeeps would make a difference but i have managed to break axles and even broke a frame once out there on my Jeep so its nice to have all 4 wheels off of the ground. Not to mention how much 37 and 40 inch tires cost to have just rolling on the pavement.

 

Hey Crankman does your 6.2 have a motor driven clutch fan or an electric fan? I am curious if the bigger motors have different cooling systems.

[kstruckcountry]

I think all new vehicles have e fans?

[yukon_denali_05]

I towed an airstream 25ft that weighs 7300 lbs on steep uphill grade for over 3 miles with outside temps of 97 degrees and full A/C on and my tranny temp never went above 180. Stock trans cooler. I do have a vette servo for firmer shifts and amsoil full synthetic. Your truck should never hit 250.

[crankman]

Air was off and the temp was in the low seventies at the top of the mountain. The only other thing I could have done was have the heater on but the motor wasn't even close to as hot as the transmission so the motor wasn't as much of a concern.

 

We were pulling car haulers. I would guess flat towing the Jeeps would make a difference but i have managed to break axles and even broke a frame once out there on my Jeep so its nice to have all 4 wheels off of the ground. Not to mention how much 37 and 40 inch tires cost to have just rolling on the pavement.

 

Hey Crankman does your 6.2 have a motor driven clutch fan or an electric fan? I am curious if the bigger motors have different cooling systems.

 

It has two electric fans YJ I think you better off with using the car haulers. What was your motor temp you said it was (hot)?

[Coolmaker]

I pulled my toyhauler to the beach for my son last Thursday. Toyhauler weighs 5800 stripped, had it loaded with bicycles, food, chairs, grill, and a golf cart in it. My 6.2 did not know it was back there, and the trans temp never went over 180 with the outside temp at 96 degrees.

[aflesch]

Keep in mind that the thinner air at high altitude significantly reduces the effectiveness of the cooler. The 4L60E tranny will go into constant TCC lockup at 265 to help reduce temps so while 250 is not optimal it is still within the limits that GM has set for it. I was in Colorado last week with my 09 Silverado Z71 and climbing some of the mountains at 60 mph at 10000+ ft my tranny hit 200 while not towing anything.