I was over in the LLY section reading about the fact that the fan seems to come on quite a bit pulling a load. When pulling my 8k trailer, the fan comes on a lot, especially going up a hill. Even driving through a windy road doing 35-40 it cycles on and off. I am only pulling about 1/2 of what this truck is rated for. I was always curious as to what would happen if I was pulling a 13 or 14k load up a hill. Well I was talking to a buddy of mine who has a 4.5 or a 05. He has had it for about 6 months. He pulls a keystone raptor that weighs 13-14k loaded. For those of you on the west coast, there are a couple of areas that have pretty decent grades, the grapevine and the cahon pass, maybe 6 or 7%. He was telling me that he climbs those hills about 65, sometimes 70. I asked him if his fan comes on a lot and he said "oh yea it is screaming". He also said that he is full throttle when he is climbing those hills. I take it east on the throttle and can climb those hills in 4th doing 55 or 60. How hard are you guys on these trucks when climbing hills? Are you full throttle or partial? And what gear are you in? Also, is it bad for the motor to get on it when the fan is on? Maybe I am not driving this truck to its full potential and it really is stronger than I think it is. Kind of on a side note, if these new trucks didn't have overheating issues, maybe the fan wouldn't come on as much? Any thoughts? Jerry.

I just got a new 05 and have only towed with it twice. As with yourself, both times the fan was on and off. As for the power there was plenty of it. I was not even close to full throttle and was in the left lane going up large hills at 65-70 pulling a 36ft loaded race car trailer.
Fans are normal and no big deal - just drive on :ro) .

Jerry and Mike,

I can provide a non-technical response on this subject. If you recall, there are several radiator components in front of that fan. The radiator, the transmission fluid cooler, a brake fluid cooler, the intercooler, and the power steering fluid cooler. Any of which may be heating up during your pulls and will trigger the fan clutch to engage, as they are temperature monitored.

Hope this helps.

RF

I"ll give it that, but how much throttle do you give it going up a pretty decent grade? Can you do 65 up a 6% grade pulling a decent load?

J.

Can I? This is where some decisions have to be made. If the sign indicates 6%+ for 10 or more miles, I'd never try to race up at 65 mph at or near GCWR, since heat build up is cumulative. I watch the temp. guages and choose a gear and speed appropriate to keep within the normal range. Air temperature and altitude have a lot to do with this as well (again, removing heat is also cumulative).... warmer air and low air density limits heat dissipation. Another factor is the coolant temperature at which point I start the uphill pull. Often, I have to do some low speed maneuvering with the load before starting off on the highway, which can really heat up the engine compartment and all vital component fluids which can cause premature chemical breakdown, so I start out at a speed that allows temps to come down, usually 40-45 MPH at GCWR, then gradually build up speed until is see the temps start to rise. A 30K+ GCWR will usually only allow 55-60 MPH on long uphill pulls, any faster, and the coolant temp will get real close to the "RED". These are MY guidelines, as I intend to keep this truck/engine running for many years/miles. You decide which "rule of thumb" you want/need to follow, according to your own needs.

RF

RF, so are you ok with the engine temp gauge at around 235 on a hill? Or is that too much? The reason I ask is on our last trip, the temp got to the line just below 235 on
a decent grade. About a mile before we crested the grade, the temp fell back to 210. The tranny never got above 200. Jerry.

Why do you seem to be in a hurry when towing?

Climbing hills at full tilt boogie will only make you have to stop for fuel a bit faster. So in reality, you are not gaining time, and you are definetly losing money. Not to mention the excessive wear and tear on your trucks.

And then we get into safety........

Sounds like we have some self control issues...........

I have no self control... :D

It is actually safer to go 75mph uphill, than 55mph downhill on a 6% grade. This is based on braking distance.

Normally, I set the cruise control to 75mph in states that it's legal. Watch out for Texas as the limit is lower at night. And California is just plain backwards. I guess the lower limit in CA is due to our crappy roads that we pay the highest per capita taxes to not maintain. Why you can drive 50,000lb bus at 70 legally, but not a tow a 500lb jet ski at 56mph is beyond me.

I can guarantee you that it is not safer to go 75 uphill in CA. The majority of the time you are in traffic anyway.

Not to mention that you and your big ass trailer is in the way of my TDI that likes to climb the hills at 90............;)

But really, the CA trailer law is absurd. They should segregate it by weight. These trucks can tow at least 3000 lbs (braked weight) just the same as anyone else can drive a car. Pry better for truck and trailer anyway.

Where is everyone racing to?

Where is everyone racing to?

Avocado stand :D

I wish!!!

I'm towing around 8,000 to 10,000 lbs from San Diego to the Imperial Dunes area. I'd have to say that I push my truck as far as I'm comfortable. I constantly monitor my tranny, engine and EGT's. As soon as I start heating up, I back off or down shift depending on whats heating up. With these weights and ideal conditions I'd have to say I do 55 - 75mph on the flats and 50 - 65 mph up grades.

Hopes this helps!

I'm with McRat on those stupid California speed limit towing laws!

Jery01,

Sorry for the slow reply. Just got my Comcast HSI back on after relocating to Albuquerque NM.

Which brings up a point about your coolant temp question.... LT's and MDT's are different animals, when it comes to towing. We left Baltimore MD towing doubles (a 29' fiver and a 20' car hauler loaded with a 2004 Chev. Impala Indy SS). The RF tipped the cat scales at 13,280, the fiver at 8080, and the wiggle wagon at 5130, for a gross combined weight of 26,490 lbs. Keeping your query in mind, we kept an extra vigilant eye on the guage and noted that anytime the temps reached 210, the large fan would come to life, creating a loud vortex sound (Cessna prop spinning up), until the temps droped 15-20 degrees. On the long hill pulls, the fan would stay on (maybe getting a bit louder), but the temps never rose above 210 at any time, even at posted speed limits of 70 or 75 MPH (OK and NM). We arrived in Albuquerque 5 days later (a working vacation) having only to stop to change another fiver tire in OK (seems everytime we go through OK we blow a Good Year Marathon?!).

Overall fuel mileage was 9.8 MPG, and roughly 1/2 qt. of Rotella. The rented car hauler required tire inflation every 200-250 miles (U-Haul....of course), and the above mentioned fiver tire blow-out.

The performance of the GM MDT may not be equal to that of OTR HDT's with 450+ HP and 1500+ TQ, but it was quite satisfactory. The only emergency stop I had to do throughout the trip was when the co-pilot indicated that the campgroud we were to put in for the night (Amarillo TX KOA) was 250' in front of the truck, while travelling at 65 MPH....I made the turn at 15 MPH...but the kitchen in the fiver had to be put back together (BTW, excellent KOA).

I guess I am bragging a bit about the RF... but after owning 3/4-1 tons for towing larger trailers for over 30 years, it is difficult to explain how much different these apparently oversized and relatively slow MDT's are from the LT's, when it comes to doing grunt work safely and economically.

RF

I honestly have never to this day put the accelerator to the floor,never towed nothin-btw 11000 miles on the truck as of today.

Never put it to the floor? LOL...man you gotta live a little! You haven't lived till you've mashed the go-pedal of a turbo diesel on 'roids and rolled some black smoke.

I've towed the grapevine many times and I live near Cajon. It seems reasonable to pull those hills at a moderate throttle rather than trying to race up the hill. I'm usually more concerned with tranny and turbo temps on hills than coolant temps. That's were I see the most increase on long tough hills. Part of the reason I got a diesel is so I didn't have to "Beat" a gasser up 7% hills at 108º. When you push vehicles hard not all parts take the beating evenly like turbos and transmissions.

I ask myself, "What world changing thing am I going to do with 3 minutes I save by pushing so hard in traffic?" Then I slow down and relax!