Driving downhill: Pump or riding

[Mollysdad]

Back in the day when I drove a MH over the rockies and towed a trailer too. I worried on the long climb up about overheating, and then worried more on the way down about overheating the brakes.
So I'd slow down to 50'ish, shift down so the RPM stayed under 2500 (diesel) and pumped the brakes if the speed got up to 60.
Eventually, I was back on flat'ish land and thought, "Phew!"

[kendrick.l.j]

The OP is asking the break question regarding an older motor home not a TV. I wish people would read the question and reply appropriately, giving advice about a pickup or car isn’t helpful.
On the other hand, the OP has gotten some good advice about manually changing from drive down to second gear and will hopefully heed the advice. All those emergency “runaway” vehicle stops are inplace because too many people simply don’t know how to drive in the mountains. Rule #1, slow down. Don’t let your mode of transportation get out of control. Make sure your equipment is in good shape and well maintained and you’ll be ok.

[xrvr]

Common problem here....people answering a question that was not asked!.

[Boom Sounds]

I would look at the hydroboost or partially collapsed brake lines.
I have driven over the rockies, alps and Pyrenees using standard braking and 2nd on steep inclines. I pump where necessary and I am careful not to overheat the brakes. I’ve not had issues, aside from mild anxiety on the hairpin bends.

[Boxster1971]

Originally Posted by xrvr

Common problem here....people answering a question that was not asked!.

More then that there are comments in this thread that I would consider dangerous. Like suggesting that riding the brakes is better. Another suggesting it is OK to tow your trailer faster than you would drive your motorhome.

Thankfully the majority of the comments are constructive. Down shift and slow down.

[WayneG]

I am still looking for comment on how well the TH handles 2nd gear for extended periods, uphill or down? I hope that is not out of line to ask here.

[Protagonist]

Originally Posted by HowieE

When it come to braking on a long hill it is better to ride the brakes than to periodically stab them. less heat build up.

That completely contradicts my experience. Friction causes heat. Brake pads in contact with brake drums or disks cause friction. More friction for more time equals more heat.

I can't state unequivocally which technique is best for the motorhome downhill slalom. But I personally would downshift, keep my foot OFF the accelerator, keep an eye on both the tachometer and speedometer, and brake HARD only when the speed gets too high OR the rpms approach redline, and let off the brakes as soon as practical.

I'll be the first to admit my Interstate, with its 5-speed automatic transmission, is a completely different case than a larger motorhome with only three gears. But I have come down long steep grades in 3rd gear, foot completely off the accelerator, at 3300 rpms (well below the 4000rpm redline on my Interstate), and only had to brake for about 5 second each time to kept my speed under the limit. Minimal braking, minimal shifting.

[Bruce B]

I am still wondering why the brakes are locking up when hot...
Typical overheated brake failure is a loss of braking not locking up.
Boiling brake fluid can lead to a loss of “brake pedal” or pressure and overheated linings simply do not stop well even if fluid is not boiling and there is plenty of pressure or pedal.
I’d be looking hard at anything that might be able to prevent the release of brake fluid back into the master cylinder when the brakes are released. I’d be curious to see the condition of all of the actual mechanical brake parts too.
Does this chassis use a proportioning valve?
I’ve seen these symptoms caused by faulty master cylinders and even brake hoses in autos.
Bruce

[mrdfred]

I have had a 1987 GMC 454 engine with a turbo 400 3 speed tranny pulling a 38' trailer. By all means DOWNSHIFT to slow down. Anticipate the hill and slow down as you approach the hill. I have slowed enough to shift into 1st gear on one hill. Do you notice that trucks USE THEIR 4 WAY FLASHERS? Use them when you slow down well below the speed limit. I never had the engine or transmission have any problems due to using lower gears on long downhills. I have also never had any problems with my brakes when doing this. Best of all, I have never scared my wife or myself because I was going slow.

[Boom Sounds]

I’ve had two experiences of brakes locking up. One caused by intermittent collapse of a weak brake hose and the other being faulty hydroboost.
In terms of pumping the brakes on downhills. My approach has always been to keep your speed down, which means less extended braking and less heat. When braking, i have always considered some short pumping of the brakes to be a more effective means of maintaining a slow speed on downhills than continued application of the brake. Happy to be corrected on that though. I think all about speed control. For me, it’s been inconceivable to not run downshifted to at least 2nd on the steep hairpins in the Alps. I’m certain the Chevy Motorhome guide instructs you to downshift.

[GCinSC2]

Originally Posted by Bruce B

I am still wondering why the brakes are locking up when hot...
Typical overheated brake failure is a loss of braking not locking up.
Boiling brake fluid can lead to a loss of “brake pedal” or pressure and overheated linings simply do not stop well even if fluid is not boiling and there is plenty of pressure or pedal.
I’d be looking hard at anything that might be able to prevent the release of brake fluid back into the master cylinder when the brakes are released. I’d be curious to see the condition of all of the actual mechanical brake parts too.
Does this chassis use a proportioning valve?
I’ve seen these symptoms caused by faulty master cylinders and even brake hoses in autos.
Bruce

Ah an attempt to find if there is any brake system problem, I like it.

No need to point out I don't have a MH. Its a good review of the entire brake system.

[GinaParmesan]

Originally Posted by WayneG

I am curious on how well the Turbo hydramatic handles 2nd gear going down hill for long periods?
Somewhat related, I also wondered what source if hill grade maps everyone uses for plotting routes?
I was trying to find the grade of the Mass Pike just west of I91.
I can do that hill in 3rd both ways with only touching the breaks occasionally.

I have the same question about maps for freeway mountain passes. Maybe Google Earth has an overlay?

Tried downshifting today. Slowed to 35 or 40 mph, then manually shifted to 2nd....and it was the same as being in neutral. So I guess the next hill I’ll slow to *25* before downshifting. Yeesh! Uphill I can go to 2nd at around 45 mph...

Thanks for the tips about RPM, I’ll keep it max 3,500-4,000 up or down.

PS for other responders, 290 is the smallest length of classic moho for this chassis so I’m not all that heavy. I went to a weigh station and I’m under GVWR even loaded up for full-timing. And lastly, this Chevy 454 purrs like a (tiger) kitten at 65 mph. :

[tevake]

Yes, good on point post Bruce!

My only brake problem was on a trip down from Lake Tahoe, Long sustained not terribly steep downhill I thought third would be ok. But the brakes got hot and I had bad fade, the peddle going nearly to the floor. After pulling over for a cool down period they came back, but did fade a bit before making it to the bottom.

Since then I switched to fresh dot 4 fluid, and downshift earlier to take it easy on the down hills. I also let the engine do as much of the braking as possible only using the brakes to bring the speed down more when needed, letting them cool as much as possible between use.

The locking brakes is a different matter, and would have me looking at the parts of the system that could be causing this. The master cylinder , flex brake lines at the wheels etc.

Changing fluid every couple of years is a good practice, as it can absorb water from the atmosphere making it more prone to boiling. Dot 4 is better with high temps too.

Cheers Richard

[Isuzusweet]

Originally Posted by kendrick.l.j

The OP is asking the break question regarding an older motor home not a TV. I wish people would read the question and reply appropriately, giving advice about a pickup or car isn’t helpful.
On the other hand, the OP has gotten some good advice about manually changing from drive down to second gear and will hopefully heed the advice. All those emergency “runaway” vehicle stops are inplace because too many people simply don’t know how to drive in the mountains. Rule #1, slow down. Don’t let your mode of transportation get out of control. Make sure your equipment is in good shape and well maintained and you’ll be ok.

I wish people would know how to spell, "brake" not break problem.

Cheers
Sidekick Tony

[HowieE]

Originally Posted by Protagonist

That completely contradicts my experience. Friction causes heat. Brake pads in contact with brake drums or disks cause friction. More friction for more time equals more heat.
.

They may have changed things since I got my CDL, but then the teaching was down shift and steady light pressure rather than stabbing the brakes. Maintain a given speed and when you can't and start to exceed that it is time for a complete stop because you won't get a second chance once the brakes overheat. Both will build heat but stabbing builds much higher temperature and that is what causes failure.

[Isuzusweet]

I and others with Classic motorhomes have looked at possibly mounting one of these. Certain Sprinter van applications have these as well.

https://www.youtube.com/watch?v=hsJ5Z7zwZ1M

Cheers
Sidekick Tony

[Waipio Rim]

Originally Posted by GinaParmesan

Tried downshifting today. Slowed to 35 or 40 mph, then manually shifted to 2nd....and it was the same as being in neutral. So I guess the next hill I’ll slow to *25* before downshifting. Yeesh! Uphill I can go to 2nd at around 45 mph...

My transmission doesn’t like to downshift as early as I think it should when going uphill, so I am always shifting in and out of second by hand when the roads get steep. Whenever I go from “D” to “2”, uphill or down, I give it a little gas to bring the rpm’s closer to where the trans wants them to be right when I am making the shift. Kind of the same thing that you would do with a manual transmission, to ease the shock to the clutch and the rest of the drivetrain. That might encourage yours to downshift when you want it to. I’’be been driving mine this way for the last nine years or so, and the trans works just like it did when I got the coach.

[Bruce B]

Originally Posted by Isuzusweet

I and others with Classic motorhomes have looked at possibly mounting one of these. Certain Sprinter van applications have these as well.

Cheers
Sidekick Tony

Interesting... I’d still suggest that the original poster find the problem with the factory supplied brake system first but, this is kind of like a diesel exhaust brake without the diesel! I did go to their website and find another video that better explains how it works.
Bruce

https://youtu.be/5FMoUEmSsdE

[Smartstream]

Originally Posted by GinaParmesan

I have the same question about maps for freeway mountain passes. Maybe Google Earth has an overlay?

Tried downshifting today. Slowed to 35 or 40 mph, then manually shifted to 2nd....and it was the same as being in neutral. So I guess the next hill I’ll slow to *25* before downshifting. Yeesh! Uphill I can go to 2nd at around 45 mph...

Thanks for the tips about RPM, I’ll keep it max 3,500-4,000 up or down.

PS for other responders, 290 is the smallest length of classic moho for this chassis so I’m not all that heavy. I went to a weigh station and I’m under GVWR even loaded up for full-timing. And lastly, this Chevy 454 purrs like a (tiger) kitten at 65 mph. :

This is a great reference for info on grades. http://www.mountaindirectory.com/shop/ It is available as books or apps.

The TH400 has a 2nd gear band that is only used when the gear lever is moved to "2". It has nothing to do with normal shifting or trans operation. If you do a lot of towing or use in a moho the band gets hot and the metal will fail, break. The effect is neutral when you pull the lever into "2". The replacement bands are a much thicker metal and eliminate the problem. Unfortunately you have to disassemble the trans to change the band. If you can live with it wait until the trans needs work. Again it has no affect on the normal operation of the trans. I had the problem with an old Chevy pick-up and drove it for several years. With your moho this may be more of a problem. With my diesel I can come down a 6% grade in top gear and barely touch the brake. I can't say for sure how your 454 will handle it. 6% is the max allowed on federal interstates with few exceptions. I have done 13% down grades in first gear and lived to tell about it.

Your disc brakes don't react quite the same to heat as drum brakes, they are much better. However the brake fluid also gets hot and if you have marginal brake hoses or a weak return valve in the master cylinder or incorrect push rod length to the hydroboost you can experience lock-up.

My CDL training was use the correct gear and if speed increases, brake with authority to bring speed down and then get off the brake and allow speed to increase slowly and brake again. If you need to brake frequently you need to drop another gear. Good luck.

[WayneG]

Originally Posted by GinaParmesan

PS for other responders, 290 is the smallest length of classic moho for this chassis so I’m not all that heavy. I went to a weigh station and I’m under GVWR even loaded up for full-timing. And lastly, this Chevy 454 purrs like a (tiger) kitten at 65 mph. :

You are almost the shortest Airstream Labeled MH, Mine is a 270, The argosy's go all the way down to 20'.
That said I tend to overload mine (with spare parts & beer) and tow a Trailer with a full size Polaris UTV.
So far I do well on the hills on the Mass Pike, I can go up in high gear but I am under 60MPH
Going downhill, I do like others mentioned, keep it in drive gear, keep off the gas and only brake when the speed gets higher than 60, then brake hard enough to get down to 55 in a reasonable time, and repeat as needed. If the speed creeps back up to quickly then set the top speed 5MPH slower and so on.
There are sure to be worse hills than the Mass Pike, I have not tried my method elsewhere.
It sounds like staying in 2nd for too long may cause problems with the TH trany, sure dont want that to fail going down hill!