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Hittenstiehl · 02-17-2016, 02:24 PM

Question: When towing up and down grades what is the appropriate usage of the 3/2/1 gears.

I have the PRND figured out.

Yes I've read the manual but I want to know how you do it.

For those who need to know it's a 1500 pick up.

No arguing, name calling, brand bashing please. Educated explanations, experience and hands on welcome.

r carl · 02-17-2016, 02:41 PM

Do you have a tachometer?

Hittenstiehl · 02-17-2016, 03:10 PM

Yes

A W Warn · 02-17-2016, 03:11 PM

All 1/2 ton trucks are not the same. Each downhill grade is different. There is no one correct answer.

Going down:
With my present truck I can press the tow haul button, the computer will apply the grade brake (shift the transmission), with me braking as needed.

With my prior trucks with 6 speed I had to manually shift down to an appropriate gear for the grade. If I started coming down a mountain grade 5% to 8% for miles, I would slow down at the top of the hill to shift to 2 or 3 depending on the grade and apply brakes as needed.

With the prior trucks with a 4 speed, I would shift down to 2 and manually apply brakes as needed.

Again, to clarify, I'm talking about steep grades in the mountains where I drive regularly.

Going up:
I try to select a gear that keeps the RPM's in the 3000-4000 range, where the gas engine has higher torque.

Hittenstiehl · 02-17-2016, 03:33 PM

OK thanks for your input.
Yes on all trucks are different.

So do you shift when going uphill also to keep the engine from whining/winding up.

I've been reading about going up and down in the same gears.

jcl · 02-17-2016, 03:48 PM

Going uphill the transmission will generally select the correct gear. Leave it in drive. If the engine is running at too high a speed then slow down some.

The exception to this is if you are climbing a hill, and the transmission is hunting between two gears, going back and forth repeatedly. If you encounter that, then manually select the lower of the two gears to prevent the hunting, as the shifting is what causes heat and wear. Shift back to drive when appropriate, or keep in in the lower gear to descent the hill.

Jeff

HowieE · 02-17-2016, 04:07 PM

The rule of thumb is. What ever gear you climb the hill in is the gear you use to go down the hill.

All too many people just leave the trans in high gear when the start down a long hill. They lose all engine retard and run the risk of losing their brakes.

If you crest a hill and see a grade sign that sign was put there for a reason.

xrvr · 02-17-2016, 04:15 PM

That's the best advice anyone can give to a newby.

Hittenstiehl · 02-17-2016, 04:17 PM

So climbing RPM's and a high crescendoing whining noise is an indication to step off the gas slightly, thereby losing a little bit of speed, and downshift to 3.

xrvr · 02-17-2016, 04:22 PM

Yes, trying to maintain a set speed is counter productive. Getting to the top is what you want to do, not set a speed record.

Hittenstiehl · 02-17-2016, 04:27 PM

Okay, start up the grade in D, if RPM's climb high and engine whines shift to 3, if it persists shift to 2.

Once up top or going over if there is a steep descent start in??

xrvr · 02-17-2016, 04:31 PM

The tranny should down shift itself to third then second. If the engine is revving too high, slow down to lower rpms. Anyone, is this correct?

NWGetaways · 02-17-2016, 04:35 PM

Jeff got this right. Going up you want to stay in the torque peak range of your engine. If it keeps hunting between two gears either slow down so it will be happy in one of the gears, or manually select a lower gear that will keep you in the happy RPM range.

Quote:

Originally Posted by jcl

Going uphill the transmission will generally select the correct gear. Leave it in drive. If the engine is running at too high a speed then slow down some.

The exception to this is if you are climbing a hill, and the transmission is hunting between two gears, going back and forth repeatedly. If you encounter that, then manually select the lower of the two gears to prevent the hunting, as the shifting is what causes heat and wear. Shift back to drive when appropriate, or keep in in the lower gear to descent the hill.

Jeff

Hittenstiehl · 02-17-2016, 04:38 PM

Okay thanks everyone.

If the transmission shifts itself then what is the 3 the 2 and the 1 for.

The original question is how to properly drive up or down steep grades and how to properly use the 3,2,1.

jcl · 02-17-2016, 04:42 PM

Quote:

Originally Posted by Hittenstiehl

Okay thanks everyone.

If the transmission shifts itself then what is the 3 the 2 and the 1 for.

The original question is how to properly drive up or down steep grades and how to properly use the 3,2,1.

321 is for going down hills, when you don't want the transmission to shift to a higher gear and you want some more engine braking. When you go up a hill, the transmission will automatically downshift, so you don't need to use 321 unless it is hunting (shifting repeatedly). If the engine is running too fast and making too much noise back off the throttle.

Jeff

jcl · 02-17-2016, 04:43 PM

Quote:

Originally Posted by avionstream

The tranny should down shift itself to third then second. If the engine is revving too high, slow down to lower rpms. Anyone, is this correct?

Exactly right.

Hittenstiehl · 02-17-2016, 04:53 PM

OK Jeff that was a good explanation in a way I was able to understand. Thanks.

It hasn't been a major problem but occasionally when that engine whines I get a bit worried about transmission. And of course you always want to protect those brakes on the way down.

Tuco · 02-17-2016, 04:58 PM

The reason for 3,2,1 is to give you positive control of what gear the transmission is in. Just like a manual transmission. Everyone has given you great advice, but as stated above no two trucks, hills, loads or drivers are the same. You need to learn your vehicle and come up with a procedure you are comfortable with (IE pucker factor).

Phoenix · 02-18-2016, 03:35 AM

This is how we handle long steep grades (e.g., I-70 Eisenhower Tunnel west of Denver, CO):

Uphill

Make sure tow/haul switch is ON. Let transmission select the appropriate gear. If transmission hunts, manually select the gear the transmission has chosen, to stop hunting. If engine rpm is excessive, slow down.

Downhill

Pick a target speed appropriate for the grade, which is slower than the speed limit; for example, 45 mph in a 55-65 mph speed zone. Manually, downshift from DRIVE or highest gear until target speed can be maintained WITHOUT BRAKES being applied. To maintain this speed, it's preferable to use the accelerator pedal, rather than ride the brakes.

If 45 mph (or other target speed) cannot be maintained without brakes, downshift one-gear-at-a-time until this equilibrium can be achieved. On extreme grades, this may be 25 mph in first gear.

If first gear will not hold speed, as engine approaches higher rpms, brake moderately for a few seconds to slow speed by 5-10 mph. Then, release brakes and allow speed to slowly gather. Do NOT allow transmission to shift to a higher gear. Repeat intermittent braking, as necessary. If grade continues, after several brake applications (and before brakes overheat), stop in pullout and allow brakes to cool for 20-30 minutes before continuing.

If target speed CAN be maintained, and a faster speed (still slower than the speed limit) is desirable, slowly increase speed and shift up a gear, as necessary. If the new target speed safely can be maintained WITHOUT BRAKES, continue your descent.

Important Notes

Never coast with transmission in NEUTRAL.
Do NOT use brake controller manual actuator, except in an emergency (e.g., to stop trailer sway). Specifically, DO NOT RIDE TRAILER BRAKES. Trailer drum brakes fade faster than TV disc brakes; and in an emergency, you may need full braking power on your Airstream.
Do not block (or park in the approach to) a runaway truck ramp. Besides getting stuck in deep gravel, you risk a collision by a runaway vehicle.

paiceman · 02-18-2016, 04:36 AM

Phoenix is correct and it's the way Class A CDL drivers are trained as well as School Bus Class B CDL drivers are trained. The vehicle should select the proper gear while going up a hill. Upon reaching the top of the hill pick the speed you want, as mentioned slightly lower than posted speed and manually select the gear the computer selected while going up the hill, and when you vehicle reaches 5 MPH over your selected speed, bring it back by using the brakes then brake until speed is reached you decided on and then off the brakes and let the engine and tranny do the work. Process works. good luck and enjoy

Bud