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Old 01-12-2017, 06:46 AM   #15
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Originally Posted by WyoFree View Post
My primary consideration is regarding the diesel exhaust brake as that is what my coach has.

Some of these posts seem to indicate that the transmission is of limited importance in the exhaust/engine brake function. Both of these supplemental braking systems provide more retarding power at high RPM. When the brake activates, the transmission will select a lower gear. Typically 2nd or 3rd.
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Old 01-12-2017, 06:52 AM   #16
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When I was young, yes just before the earths crust cooled and I thank you for pointing that out. All transmissions in all vehicles were manual. The first vehicle I drove was a big old John Deer tractor.

With the manual transmission in cars and trucks you were trained to downshift which was a brake, slow down, unto itself. When I'm going down hill in my car with auto transmission I downshift to keep from using the brake. Not long ago I was reading a thread where someone said "it's a lot more expensive to replace the transmission than the brakes". That's a true statement and one I hadn't considered.

You don't see cars in the emergency turn out, you see trucks! It's a place I don't want to be and know the exhaust brake will help me from being there. I want to use the brakes, transmission and exhaust brake to slow me down and do it all as intended. That is actually the information I'm after and apologies for saying it so poorly!
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Old 01-12-2017, 06:55 AM   #17
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While I agree on the intermittent use of brakes while descending "stabbing" the brakes? That brings to mind a quick, hard push followed by a quick release. If I used that technique on my bus my elderly clients would certainly call me out as would my wife when driving with her.

I use a very "caressing" method increasing brake pedal pressure very slowly to the needed pressure to produce appropriate speed adjustment and then slowly decreasing the pressure.

Just my pet peeve as my Dad "stabbed" the brakes in quick succession while we uncomfortably rocked back and forth.
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Old 01-12-2017, 07:29 AM   #18
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One thing to keep in mind on the Ford transmissions. If you have "tow/haul" on the shifter you can use it to slow you down. If you have "OD off/on" do not use that or manually down shift to slow you down. Why...The transmission with the OD cancel button engages all of its internal clutch's (forward ones anyway) depending on the year it could be in the teens (amount of clutches internally) on deceleration most disengage and only a couple engage, if you down shift it to slow you down you will wipe them out quickly and the torque convertor is not locked on deceleration so the fluid in that will be come over heated fast, as they are not designed to slow you down, just provide light engine braking, mostly to keep the rpms up on the engine to match the transmission speeds.
On an Allison all clutches stay engaged as well as the torque converter stays locked on deceleration, it is designed to work in conjunction with engine braking no matter which system you have (exhaust or compression brakes).
I tried to keep that not to technical for those without an automotive or truck technical career.
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Old 01-12-2017, 07:34 AM   #19
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There is a 3rd type of brake, and my old BlueBird had it (and it was great!).. the electric retarder (often used on trash trucks). Mine was a "Telma" brand and was a 4 stage (4 different braking "powers"):

Electromagnetic Braking Systems - Telma S.A.
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Old 01-12-2017, 07:39 AM   #20
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One must be careful with a subject like this, it is often interpretated as who's wife is prettier.
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Old 01-12-2017, 11:38 AM   #21
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One thing I will add is when you first drive your coach in the hills get used to how it works. When going up a steep grade it will shift itself down as needed. The trick is to watch your engine temp. and if it starts to climb higher than you think it should be manually shift down another gear. This normally does not happen unless you are on a really steep grade and in really hot temps.

Going down the other side people say use the gear that you came up in. That does not always apply as it can bee steeper on the downside.
A good rule of thumb is to select the gear you came up the hill and set your exhaust brake and then go for a ways and see how it is holding you back. If you have to be on the air brakes to keep slowing it down it is time to slow it down and shift down another gear. The object is to be in a gear that the exhaust brake is holding you back with the occasional stab of the air brakes to bring the rpm's down.
Doing it this way you can always shift up a gear if you are going to slow and it is holding back too much. If you let it go too fast in a higher gear you can heat your brakes very quickly and wind up in one of those runaway lanes. Don't feel you are going to slow and worry about traffic behind you, worry about getting down the hill in safe manner. As you drive it a few times you will get used to it and it will be second nature.
In the gasser yes it would be harder on the trans. in tow haul mode because the trans. is doing all the work. On the diesel the exhaust brake is doing the lions share.
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Old 01-12-2017, 11:48 AM   #22
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There is a 3rd type of brake, and my old BlueBird had it (and it was great!).. the electric retarder (often used on trash trucks). Mine was a "Telma" brand and was a 4 stage (4 different braking "powers"):

Electromagnetic Braking Systems - Telma S.A.
The Telma is a system very seldom seen now due to the other excellent, cheaper systems out there now. But, yes, it is out there too.
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Old 01-12-2017, 12:18 PM   #23
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One thing to keep in mind on the Ford transmissions. If you have "tow/haul" on the shifter you can use it to slow you down. If you have "OD off/on" do not use that or manually down shift to slow you down. Why...The transmission with the OD cancel button engages all of its internal clutch's (forward ones anyway) depending on the year it could be in the teens (amount of clutches internally) on deceleration most disengage and only a couple engage, if you down shift it to slow you down you will wipe them out quickly and the torque convertor is not locked on deceleration so the fluid in that will be come over heated fast, as they are not designed to slow you down, just provide light engine braking, mostly to keep the rpms up on the engine to match the transmission speeds.
On an Allison all clutches stay engaged as well as the torque converter stays locked on deceleration, it is designed to work in conjunction with engine braking no matter which system you have (exhaust or compression brakes).
I tried to keep that not to technical for those without an automotive or truck technical career.
My 2000 E450 V10 has the " OD Off " button.
Pushing the button takes the transmission out of 4th gear ( overdrive ), making it a 3 speed automatic.
I use the " OD Off " button any time I am on secondary highways where the speeds are less than 55 mph. I also use it while descending long hills. When I use the shifter, it will drop to 2nd gear, and hold my speed for the steep hills.

45,000 miles with no overheated trans oil or any other problems.

I can't imagine Ford installing a feature that quickly burns out your trans clutchs. You need to be more specific on what models and years your refering to.
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Old 01-12-2017, 01:55 PM   #24
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On my 2012 F250 and 2013 F350,
I used the tow haul just about every time I wanted to stop...

I had 100k warranty on the tranny and ZERO on the brakes

And that tranny worked perfectly - really miss my trucks !

Now in the motorhome the 'engine brake' is on all the time...
helps bring down 36k lbs of coach and toad in a 'hurried' stop!
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Old 01-12-2017, 03:09 PM   #25
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Quote by jleamo1

Why...The transmission with the OD cancel button engages all of its internal clutch's (forward ones anyway) depending on the year it could be in the teens (amount of clutches internally)


I think if jleamo1 rethinks his statement here, he'll realize he didn't write what he was thinking. I'm not the sharpest tack on the block but have had a automatic apart and know that there is NO automatic transmission that "engages all of its internal clutches (forward ones anyway)" all at the same time. That would absolutely lock up the transmission and no automatic is valved in such a manner to allow this to happen.
If all the internal forward clutches were engaged at the same time, it would be in "first", "second", "third", "fourth", etc. all at the same time, and that just doesn't happen.

I think twinboat, with a few thousand miles experience, has it's operation down pretty well.
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Old 01-12-2017, 03:21 PM   #26
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The only production MH that has the Allison retarded is Foretravel, Bounder has never used them.
Don't know what you mean by an Allison retarded, but my 2006 Monaco Safari will automatically downshift with the exhaust brake all the way from 6th to 2nd as speed allows, keeping the Cat C7 under 2500rpm.
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Old 01-12-2017, 03:37 PM   #27
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Don't know what you mean by an Allison retarded, but my 2006 Monaco Safari will automatically downshift with the exhaust brake all the way from 6th to 2nd as speed allows, keeping the Cat C7 under 2500rpm.
The Allison retarder adds another unit to the transmission that acts to use the fluid in the transmission as a brake. Totally different than downshifting the transmission. It is usually controlled by a joystick on the drivers console and is infinitely variable using that joystick.
Here's a like to a site that explains it: Transmission Retarder Operation - How Does It Work
Here's another one: http://www.mcicoach.com/service-supp...serinfo13B.htm
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Old 01-12-2017, 03:37 PM   #28
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One thing I will add is when you first drive your coach in the hills get used to how it works. When going up a steep grade it will shift itself down as needed. The trick is to watch your engine temp. and if it starts to climb higher than you think it should be manually shift down another gear. This normally does not happen unless you are on a really steep grade and in really hot temps.

Going down the other side people say use the gear that you came up in. That does not always apply as it can bee steeper on the downside.
A good rule of thumb is to select the gear you came up the hill and set your exhaust brake and then go for a ways and see how it is holding you back. If you have to be on the air brakes to keep slowing it down it is time to slow it down and shift down another gear. The object is to be in a gear that the exhaust brake is holding you back with the occasional stab of the air brakes to bring the rpm's down.
Doing it this way you can always shift up a gear if you are going to slow and it is holding back too much. If you let it go too fast in a higher gear you can heat your brakes very quickly and wind up in one of those runaway lanes. Don't feel you are going to slow and worry about traffic behind you, worry about getting down the hill in safe manner. As you drive it a few times you will get used to it and it will be second nature.
In the gasser yes it would be harder on the trans. in tow haul mode because the trans. is doing all the work. On the diesel the exhaust brake is doing the lions share.
Well stated plan for brake use and safely transitioning a hill, but the gasser and the diesel are both providing braking by the engine thru the tranny. The tranny itself does nothing to provide braking power, it just transmits that power built up in the engine. A gasser has the throttle plate. Using engine braking, this throttle plate builds vacuum in the engine. There is little air available for the intake stroke because the throttle plate is closed. This vacuum is present in the combustion chamber thru the intake and unpowered power strokes, causing the engine to try to stop rotation.

A diesel has no throttle plate. When you release the throttle, the engine coasts, filling the cylinder with air on the intake stroke (no fuel) building pressure on the compression stroke that 'bounces' the piston down on the unpowered power stroke, and actually exhausts that unburnt air on the exhaust stroke. The braking physics of the throttle plate are performed by the exhaust plate in the exhaust brake, but here, pressure is built up in the exhaust stroke against that closed exhaust plate. The pressure during the exhaust stroke is the engine brake, the downshifting transmission only amplifies the engine forces in both the gas and diesel.
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