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Old 08-24-2017, 07:50 PM   #1
Larryjb
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Default Coquihalla highway

My second trip is to the interior of British Columbia via the Coquihalla. The elevation increases 3-4 thousand feet in 100 km. My wife overpacked and I had a total of 10000 lbs ( Tahoe towing limit is 12000 lbs). The temperature was rising and I had to slow to 30km/h with the AC off and heat on!

This highway is brutal. We made it, but I wouldn't consider that highway with anything less that anything comparable to the Tahoe.
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Old 08-25-2017, 07:55 AM   #2
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Just came back from Vancouver Island after a 5 week stay, destination Calgary. Came across using the Coq as it is know locally. TV being a 2017 Jeep with V-6 engine had no problems at all. Has a 8 speed tranny which would drop back to 4 gear at certain grade with engine speed at 4500 rpm. All gauges, engine temp. transmission temp oil temp and oil pressure all reading in the slightly above normal range but still within safe parameters. Had no problems at all towing the 3462 lbs TM.
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TV 2017 Jeep Grand Cherokee, 6200 lbs tow capacity, 620 lbs tong weight, V6-3.6 liter gas with factory tow package, Prodigie3 Brake Control, Anderson "No-Sway" Weight Distributing Hitch.

TM 2720, 2011, A/C, Awning, Swingtongue, 40 Gal fresh water, Stove and Sink Cupboards, Radio/CD Player, TV ant., Microwave Oven, Electric Tongue Jack, Black Windows and Frame, and Woodgrain Vinyl Flooring
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Old 08-25-2017, 09:04 AM   #3
Bill
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Larry -

30 km/hr is about 20 mph. That is really slow!

Kwantau -

If your rig is 3462 lbs all loaded up, that is pretty light, which would have helped. I bet Larry was well over 4000 pounds.

As you made the crossing, how low did your road speed drop?

The reason I ask is that my own personal experience - far from professional - says that it is better to keep road speed up as much as you can while climbing a steep grade. My "testing ground" was repeated climbs of the Mogollon Rim in Arizona, usually on rte 260 from Payson to Strawberry or Payson to Heber. Many miles of constant 6-8% grade. In our 4.6-L Explorers, heavily loaded, if we slowed down "ease the load on the engine", tranny temp would rise into the danger zone. But if we downshifted and kept road speed to 40-50 mph or more, temp stayed reasonable. Not low, but reasonable. With no further knowledge, I conclude that the higher speed kept more cooling air flowing through the radiators, including the all-important auxiliary tranny cooler. (Larry, do you have one?) At 20 mph, there is virtually no cooling air beyond what the radiator fan can stir up. And since the air is thin at altitude, it cools even less.

I know it is counter-intuitive. Take it for what it is worth.

Bill
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Old 08-26-2017, 07:14 AM   #4
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Bill in answer to your question about speed. Like you said the grades on the Cog are between 6 to 8% also and some of the uphill runs between 2 to 3 miles. Speed would drop off a bit to between 55 to 60 mph, engine speed about 4000+ rpm. I travel no faster than 105 km per hour (65 mph) as recommended by tire manufacturer. Engine temp reached 112C, oil temp about same, transmission 117 C, oil pressure 77 psi. Cruise set at 105 kph. The 2017 GC has a great gauge readout system on the centre screen and can be accessed also on my screen in front of me.

As you probably remember I had a 2013 GC with the same engine as my 2017 has now. The big difference is the transmission, 5 speed compared to a 8 speed. The 2013 would drop speed quickly and drop gears to 3 if I let it. The engine speed getting close to 5000 rpm. The new TV having that 8 speed tranny does shift down but you hardly notice it , to 5th or 6th gear, but it keeps the torque curve right up there giving you that extra get up and go. I even keep it in cruise as the computer seems to handle things better than my foot can and if necessary I drop the cruise setting to 95 kph . They, Chrysler, upgraded to tow capacity from 5000 lbs to 6200 lbs in the new TV. Hope this gives you a good insight Bill.
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TV 2017 Jeep Grand Cherokee, 6200 lbs tow capacity, 620 lbs tong weight, V6-3.6 liter gas with factory tow package, Prodigie3 Brake Control, Anderson "No-Sway" Weight Distributing Hitch.

TM 2720, 2011, A/C, Awning, Swingtongue, 40 Gal fresh water, Stove and Sink Cupboards, Radio/CD Player, TV ant., Microwave Oven, Electric Tongue Jack, Black Windows and Frame, and Woodgrain Vinyl Flooring
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Old 08-28-2017, 09:07 AM   #5
Larryjb
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Quote:
Originally Posted by Kwantau View Post
Bill in answer to your question about speed. Like you said the grades on the Cog are between 6 to 8% also and some of the uphill runs between 2 to 3 miles. Speed would drop off a bit to between 55 to 60 mph, engine speed about 4000+ rpm. I travel no faster than 105 km per hour (65 mph) as recommended by tire manufacturer. Engine temp reached 112C, oil temp about same, transmission 117 C, oil pressure 77 psi. Cruise set at 105 kph. The 2017 GC has a great gauge readout system on the centre screen and can be accessed also on my screen in front of me.

As you probably remember I had a 2013 GC with the same engine as my 2017 has now. The big difference is the transmission, 5 speed compared to a 8 speed. The 2013 would drop speed quickly and drop gears to 3 if I let it. The engine speed getting close to 5000 rpm. The new TV having that 8 speed tranny does shift down but you hardly notice it , to 5th or 6th gear, but it keeps the torque curve right up there giving you that extra get up and go. I even keep it in cruise as the computer seems to handle things better than my foot can and if necessary I drop the cruise setting to 95 kph . They, Chrysler, upgraded to tow capacity from 5000 lbs to 6200 lbs in the new TV. Hope this gives you a good insight Bill.
Bill, our GVCW was 10050 lbs! The GVCW limit for the Tahoe is 12000 lbs or so. That accounts for about 2150 lbs of 5 people + cargo. So, yes, we're going to have to pack lighter for sure. My wife was packing for the trip, so I felt it was better to not say anything. This first experience was important for both my wife and me. My TM axle was 3498 lbs, at the limit. Boy, I'm sure glad I upgraded the tires! My rear axle was 4158 lbs. The weight limit for the rear axle is 3960 lbs, so I was overweight there. The front axle was 2860 lbs. I think I'll get the bathroom scale out today as I unload the trailer and find out exactly what the weight of each of the items were, as best as I can. I did get a WDH while I up in Kamloops, but that may have overloaded the TM axle. I noticed that, with the brakes set up, and the Tekohsha P3 at maximum of 14, I could not lock up the trailer brakes on gravel. I took the downgrades in 2nd gear, which kept my speed stable. I didn't need to use the brakes much, but I could feel the brakes working when I used them. The WDH helped with brake a little, transferring more of the weight load onto the front axle. However, more weight would have transferred to the rear axle as well, probably overloading the trailer axle this time.

As for climbing hills this time, I did take Bills advice and keep the engine revs up. The engine temperature did rise again and I did switch the AC to heat to dump extra heat. It's interesting that Kwantau observes his temperature rising to about 112°C. My temperatures were rising to about the same levels too, but I didn't want to take any chances of boiling over on the Coq., so I found ways to dump the extra heat on the hills.

Bill, we have a 2008 Explorer which doesn't have a temperature guage. For these vehicles, you would probably not notice any temperature problems until it overheats. However, the 4.6L likes to rev high for power, and the 6 speed transmission will likely keep engine revs high on the hills. The Tahoe is an older technology type of engine and like to lug rather than rev, but the Tow/Haul mode does keep the engine revs higher.
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Old 08-28-2017, 10:18 AM   #6
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Bill made some points to me that reminded me that every vehicle is different and requires different strategies for handling difficult roads such as the Coquihalla. I would say that an engine temperature GUAGE is extremely important in avoiding boil-overs because you can prevent heat buildup before it becomes an emergency stop on a freeway that has narrow shoulders.

Also, when I said "anything less that anything comparable to the Tahoe", there are a lot of variables. Some of the newer 6 and 8 speed transmissions make the V6 engines capable of handling such roads. I'm not sure about older V6's with the traditional 3 and 4 speed transmissions.

I wasn't trying to make a plug for Chevy, just that you don't want to be towing at your limit for highways like the Coq.
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Old 09-11-2017, 10:29 PM   #7
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I have to add a note here regarding my towing experience, especially when extended hills are involved.

My Tahoe is 16 years old, and I got it used last year. I suspect there was a fair bit of sludge in the valve train. I switched to synthetic oil this spring which cleaned a lot of the stuff out, and consequently plugged my oil filter. I knew because my oil pressure was dropping. I did an oil change half way through July and put a new filter in. The old filter was totally gummed up with sludge. The oil pressure returned to normal.

Fast forward to our trip to Kamloops. The oil pressure had been normal until our trip to Kamloops. The climb up from Hope, descent to Merritt, another climb out of Merritt and descent into Kamloops, I saw my oil pressure begin to drop a little. It didn't drop nearly as badly as it did before, but it was lower. Upon my return to Vancouver, I changed my oil filter only, and the oil pressure is back to normal. This may have been because there was still some residual sludge that got cleaned out from the harder engine workout, or this could be a normal effect on the oil from towing.

Has anyone else, who has oil pressure gauges, noticed a drop in oil pressure after extended towing? It's probably a good idea to change the oil after such a trip anyway, but at the very least, change the oil filter.
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Various TM images that you may or may not find elsewhere:
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Old 08-07-2020, 12:55 PM   #8
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I wanted to update this thread in case anyone else, especially newbies like I was, come across it.

The following year I discovered that I had a cracked head. It was likely cracked before the Kamloops trip, and the leak was very slow. I have since redone the heads and the machine shop that rebuilt them for me actually couldn't find the crack with pressure testing. They knew it was cracked because I showed them the evidence, but they wanted to make sure they were rebuilding the correct heads, and not the one that was cracked!

Anyway, the coolant slowly seeping into the engine oil was causing the sludge I mentioned. I'm not sure if such a slow leak would have caused the engine temperatures to rise, but I have learned since that it is very common for engine temperatures to rise on the Coquihalla as Kwantau noted. At the time I only had the analogue dash gauge for temperature. I knew it was rising, but I didn't know the exact values as those gauges can be rather inaccurate. I was probably still in "safe" ranges, but if you've ever driven the Coquihalla, there is not much room to pull over if you overheat. Plus, people are doing 120-130 km/h (75 - 80 mph) on that highway. In comparison, the Grapevine which we did a couple of years later, has wider shoulders and trucks/trailers are required by law to stay below 60 mph. I felt much more comfortable on the Grapevine than the Coquihalla. Next time we travel to the BC interior I'll be taking the Trans Canada or another route.

I now also realize just how much transmissions play into all this. Our Tahoe has a 4 speed transmission. Compared to our Explorer, with its smaller engine but 6 speed transmission, it feels much more capable on hills. The 6, 8, and now 10 speed automatics are making a big difference in towing.
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