Topic: Downhill and which option to take

[xxSVxx]

So, Cerro Gordo is approx 8000ft above sea level; as we were driving down the hill, I had no idea how long we would be going downhill, and really no idea the steepness of the hill....so I just rode my brakes.  Until they let me know they weren't having it, so I stopped....let them cool for a few minutes, coasted a while and then dropped the tranny into 2nd while in 2wd

I was wondering if the SCCX brain-trust can help me with this...

What is the ideal way to do this?  Drop her into 4lo and let the transmission do the work?  Or just coast and use brakes in 2wd?  I got my brakes done a week before the trip, so I wasn't concerned too much about them going out.....I was doing a bit of work in 4lo earlier in the day going uphill from the campsite, and the day before as well, and wanted to give the tranny some rest.

Anyway....just curious. 

Thanks

[CAWoody]

I ran 4lo the whole trip.  On those steep inclines i shifted between 1 and 2 depending on the angle and the length of the section.  Of course i had 1600 lbs of dead weight pushing me along.

[JFanaselle]

I ended up with pretty bad brake fade going down that hill last year, too, and did some research on the topic when I got home. The short answer is: using the brakes is less safe, but not as hard on your engine/trans/drive train components. Downshifting and using the trans is far safer, but does put a little extra wear and tear on the vehicle (higher RPMs on the motor, strain on the half shafts and gears, etc). In the end, safety should always come first because less wear and tear on my drive train components won't matter if I end up 400 feet down the side of the road on my roof. Truck drivers will tell you, too, that you control your speed down a hill with gears and the engine, not the brakes. My grandpa drove a truck for 50 years and would always laugh at the "rookies" who would burn up their brakes coming down the grapevine and have to hit the runaway truck ramps.

[Celt]

I agree with letting the engine do as much braking as possible. Having a stick shift is best for this kind of thing but there is nothing wrong with going into 4L creeping along. If you are going slow enough it won't drive your RPM's up very high. It will take longer to get down but it's easier on everything in my opinion.

[FrankB]

I'm with the crowd that says use the transmission rather than the brakes, to the extent you can.  I've been downshifting automatic transmissions for as long as I can remember (as in back to the early 1970's), and never had a problem with it. 

When I was coming down from 9,200' back to the town of Independence earlier this month I was pleasantly surprised at how well 2nd on the AT kept the speed down. Granted it's not as steep as Cerro Gordo, but compared to my previous X which was an S-trim and did not have the lower Pro-4X gearing, it was quite manageable.  Braking was still needed of course, but not riding them all the way down the mountain.

If you are off pavement, then you can go into 4L, which is even better.  Don't forget you can run 4L in 2nd or 3rd on the AT if needed.

[pyrofox79]

I was in 4lo for those steep down hills. But I have a stick so it's a little different. It must have been your brakes I was smelling when we got to the bottom of those switchbacks. I agree its better to let your transmission do the work than your brakes especially if you are unsure on how long the down hill will be.

[knightrider]

You definitely want to use the engine to slow you down long grades, if you need to be in 4lo to be effective than so be it.  Not enough people use 4lo enough IMO.  You say you just replaced your brakes but they may be ruined now, age makes no difference.  Overheating them will create a glaze on the pads and rotors and negatively affect your braking performance for the rest of the life of those pads.   Sometimes all you need to do is turn overdrive off, this will put you in 4th gear, if that's not enough go to 3, then 2, then 1.  High RPM's are not to be feared but try to stay under 5k-ish.  Like Frank said, you will not break anything by shifting automatics, the option to do so is there for a reason.  Shifting an auto transmission into lower gears just limits the maximum gear the transmission will go into, limiting your speed.  if you are crawling or expect to be under 30 MPH all day there is no reason to use D, you should put the shifter in 2 or 3.  It's best to keep the RPM above 2k to minimize heat build up in the transmission from overworking the torque converter.

[Riz98]

For almost the whole Cerro Gordo trip I stayed in 4 Low and was utilizing 1 or 2 gear on the steeper descents to control speed and help with braking.  On the long road down after the Ghost Town I was in 2wd but stayed in 1st gear.  The rpms didn't go past 3.5k rpm and at that point I would brake until around 2k rpm and then let the transmission slow me down until speed was picked back up.  It allows enough time in between braking so your brakes don't heat up and start to fade.   

[Sage Bromax]

I was in 4-low the whole time we were on dirt.  But I have a manual transmission.  I can still get up to 50 mph in 6th gear.  Keeping it in low range gives me much better control up and down hill.  I was mostly in 2nd coming down that hill, occasionally in first.   It wasn't until we passed the Sheriff's Off-Road Unit support truck that I got higher than 4th.

[RBduffer]

If you're riding the brake for more than 10 seconds at a time, you're in too high of gear!

Go 4WD and keep the revs between 2 and 4K.  It's better to break firm-ish for short spurts than ride a gentle brake.

Riz ran a great plan.  All the above comments are on the money.

[Ghost65]

Not enough people use 4lo enough IMO.

This.