When to downshift

[NCMODELA]

Hi, I tow a approx. 6000lb trailer with a 03 Yukon xl 5.3, 3.73 gear. I took it for a drive today (middle NC) and it was in third, hit a small to medium hill (bump in the road to western people) at 2800rpm doing about 65 to 70 and it started slowing down, hit the gas some rpm went to 3000 and kept speed around 62 or so. hit the gas harder just to see what would happen and how it would react, it downshifted into 2nd, 4500 rpm and it pulled and gained speed up the rest of the hill. I was just wondering from people who have towed with similar vehicles do you let it downshift or let it lose a little speed then gain it again after the hill? It seemed really excessive to downshift into 2nd for that hill because I would have maintained 60-62 going up the hill.

When do people decide to floor it to downshift excepet on mountain grades? do you have to slow down a lot before you do it?

[APT]

NCMODELA wrote:
When do people decide to floor it to downshift excepet on mountain grades?

Everyone has his own mental limit on speed before downshifting.

On my last truck which was similar to yours, I cruise in 3rd gear at 2600-2800rpm (62-68mph), let speed drop to about 55mph before I kick down to 2nd gear. My current TV I cruise in 5th gear at 2200-2400rpm (65-70mph) and kick down to 4th gear at 60mph.

Be careful of that 3000rpm. That's running in 3rd gear with the torque converter unlocked which generates a lot of heat. 2nd gear with torque converter locked up would be better for trans life.

[Gale_Hawkins]

Hybridhunter wrote:

NCMODELA wrote:
Thanks, I do not normally run at 70, I run at 62, and I don't expect to run in the hills as fast as in the flats. I was running it a little higher to get a good feeling of how the TV would react, just for my knowledge. How do I know if the Torque Convertor is locked or not? Is there a light on the dash?

Experience or a Scangauge II. You can tell a converter is locked partially by feel. When it is UN-locked, you can see the rpm vary at the same speed, because there is slip.

As for the shifting, GM's really try to hold a gear, and are a little more reluctant to downshift. I personally like to set my cruise at a certain speed, and leave it on when climbing. I don't like being a nuisance to other drivers when it's as simple as, well, doing nothing but maybe downshifting, but that's just me.

Once you familiarize yourself with how your truck behaves, you may want to manually drop a gear when it starts struggling. 4500 rpm is about perfect on a smaller V8, it's where the engine makes most of it's "torque" (or highest horsepower at the lowest rpm). 4500 certainly shouldn't do any harm.

I agree about experience. I had my thoughts but driving out west for a few weeks my experiences changed some of my thoughts. 🙂

It did not take long to learn RPM's were my friend. It just took the temp gauges in our case. We did get into one case where when in 1st gear we could not gain RPM's at WOT but that was our mistake on pulling the Old Priest Run into Yosemite.

Soon we were down shifting early going up and down in the big hills of the west.

[Hybridhunter]

Similar posts lol.
But the OP has a 4 speed auto.

[TomG2]

Truck drivers (and fuel mileage competitors) have known for years that the most efficient way to deal with hills is to gain a little speed going down and lose a little going up. However, other drivers may not appreciate that on a two lane road and it does not work with the cruise on. The newer six speeds make the whole process a lot easier as a quick tap will put you right where you want to be in the power band.

[Hybridhunter]

NCMODELA wrote:
Thanks, I do not normally run at 70, I run at 62, and I don't expect to run in the hills as fast as in the flats. I was running it a little higher to get a good feeling of how the TV would react, just for my knowledge. How do I know if the Torque Convertor is locked or not? Is there a light on the dash?

Experience or a Scangauge II. You can tell a converter is locked partially by feel. When it is UN-locked, you can see the rpm vary at the same speed, because there is slip.

As for the shifting, GM's really try to hold a gear, and are a little more reluctant to downshift. I personally like to set my cruise at a certain speed, and leave it on when climbing. I don't like being a nuisance to other drivers when it's as simple as, well, doing nothing but maybe downshifting, but that's just me.

Once you familiarize yourself with how your truck behaves, you may want to manually drop a gear when it starts struggling. 4500 rpm is about perfect on a smaller V8, it's where the engine makes most of it's "torque" (or highest horsepower at the lowest rpm). 4500 certainly shouldn't do any harm.

[Gale_Hawkins]

Hannibal wrote:
I set cruise with tow/haul on at 65mph on interstates and 60mph on backroads where that's the speed limit. On rolling hills where speed can be maintained, I've become familiar enough with my truck that if a hill is going to slow us down 5mph and downshift anyhow to regain that lost 5mph, I'll give the loud peddle a momentary push to the floor to cause an earlier downshift to maintain rather than regain speed. My 5.4L F250 with 3.73 runs 3800-4200rpm in those instances. Won't hurt a thing.
I did the same thing with my Cummins Rams with autos except instead of downshifting from direct to 3rd, they downshifted from O/D to direct. Didn't hurt them either.
Lugging to preserve a false sense of perception isn't good for either engine. Engines don't get tired like people do if you have to pedal your bike a little faster in a lower gear to get up a hill. Just the same, we don't walk very slowly for fear we're going to wear out our hearts if we walk at our normal gait. Same applies to our engines. Let them run in their normal rpm ranges. 4k rpm is just getting into the sb gas V8's power band.

True statements but hard for many non gear heads to get their minds around.

[Terryallan]

64thunderbolt wrote:

old guy wrote:
why do people have to think they need to go up hill at fast as they go on the flats????? so you slowed down , big deal. it is easier on the tow vehicle if you just let it have it's own way. I pulled cabbage hill in eastern Oregon today and went up doing 40 to 45 mph. a little faster than the semi's and a nice easy ascent. another thing you need to know, and that is TT tires are rated at 65 mph tops, not 70

not all trailer tires are rated for 65

True. Not all are. Some are rated to 100mph. But they don't come on a new TT. You have to buy them after market, and they are really pricy. Prolly 99% of the trailer you see on the road have 65 mph tires

[Fixed_Sight_Tra]

old guy wrote:

why do people have to think they need to go up hill at fast as they go on the flats????? so you slowed down , big deal. it is easier on the tow vehicle if you just let it have it's own way. I pulled cabbage hill in eastern Oregon today and went up doing 40 to 45 mph. a little faster than the semi's and a nice easy ascent. another thing you need to know, and that is TT tires are rated at 65 mph tops, not 70

If the speed falls below about 50 then you are out of the power band and with only a 4 speed I am forced down to 1st and 30-35. Taking it easy on the hills is fine but 30 sucks.

[Hannibal]

I set cruise with tow/haul on at 65mph on interstates and 60mph on backroads where that's the speed limit. On rolling hills where speed can be maintained, I've become familiar enough with my truck that if a hill is going to slow us down 5mph and downshift anyhow to regain that lost 5mph, I'll give the loud peddle a momentary push to the floor to cause an earlier downshift to maintain rather than regain speed. My 5.4L F250 with 3.73 runs 3800-4200rpm in those instances. Won't hurt a thing.
I did the same thing with my Cummins Rams with autos except instead of downshifting from direct to 3rd, they downshifted from O/D to direct. Didn't hurt them either.
Lugging to preserve a false sense of perception isn't good for either engine. Engines don't get tired like people do if you have to pedal your bike a little faster in a lower gear to get up a hill. Just the same, we don't walk very slowly for fear we're going to wear out our hearts if we walk at our normal gait. Same applies to our engines. Let them run in their normal rpm ranges. 4k rpm is just getting into the sb gas V8's power band.

[NCMODELA]

Thanks, I do not normally run at 70, I run at 62, and I don't expect to run in the hills as fast as in the flats. I was running it a little higher to get a good feeling of how the TV would react, just for my knowledge. How do I know if the Torque Convertor is locked or not? Is there a light on the dash?

[Executive45]

64thunderbolt wrote:

old guy wrote:
why do people have to think they need to go up hill at fast as they go on the flats????? so you slowed down , big deal. it is easier on the tow vehicle if you just let it have it's own way. I pulled cabbage hill in eastern Oregon today and went up doing 40 to 45 mph. a little faster than the semi's and a nice easy ascent. another thing you need to know, and that is TT tires are rated at 65 mph tops, not 70

not all trailer tires are rated for 65

True statement...most U-Haul tires are rated at 45....:W....Dennis

[Turtle_n_Peeps]

I go as fast or as slow as I want up hills. I let the puter figure out what gear I need to be in. I paid big bucks for an Allie tranny so I will let it make the choice of gear I need to be in.

[64thunderbolt]

old guy wrote:
why do people have to think they need to go up hill at fast as they go on the flats????? so you slowed down , big deal. it is easier on the tow vehicle if you just let it have it's own way. I pulled cabbage hill in eastern Oregon today and went up doing 40 to 45 mph. a little faster than the semi's and a nice easy ascent. another thing you need to know, and that is TT tires are rated at 65 mph tops, not 70

not all trailer tires are rated for 65

[old_guy]

why do people have to think they need to go up hill at fast as they go on the flats????? so you slowed down , big deal. it is easier on the tow vehicle if you just let it have it's own way. I pulled cabbage hill in eastern Oregon today and went up doing 40 to 45 mph. a little faster than the semi's and a nice easy ascent. another thing you need to know, and that is TT tires are rated at 65 mph tops, not 70