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09-23-2020, 09:30 AM
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#1
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Junior Member
Brand: Thor Motor Coach
Model: Fourwinds 23U
State: Missouri
Posts: 20
THOR #17298
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Mountain Driving Issue
Driving from St. Louis to San Diego had no problemS until I was going down the mountain from Flagstaff to Phoenix. 8% slope. I had it in drive with tow-haul button engaged. I was trying to keep a steady speed Downhill when transmission seemed to disengage and accelerator was making engine rev a lot. Pulled over and tried to change gears and it just bucked and continued to rev. Ended up having it towed to a Ford/RV dealer in Dewey AZ. They say there is nothing wrong with it. What did I do wrong? Afraid to try to drive it down to a Phoenix.
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09-23-2020, 10:11 AM
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#2
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Senior Member
Brand: Thor Motor Coach
Model: Tuscany 42GX
State: Missouri
Posts: 1,158
THOR #9178
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Tow Haul switch will shift to a lower gear increasing engine RPM
At the same time feather or pump brakes as needed to control your speed keeping the RPM in houtarget range
It didn't disengage or your RPM wouldn't have went up
Test it on flat land, sounds like it is working
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09-23-2020, 10:17 AM
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#3
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Junior Member
Brand: Thor Motor Coach
Model: Fourwinds 23U
State: Missouri
Posts: 20
THOR #17298
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Mountain Driving
Thanks. It got very hot and something smelled like it was burning. I had not been driving downhill that long and had not rode my breaks for them to be hot. Every time I hit the breaks after it started bucking it would rev up.
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09-23-2020, 10:24 AM
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#4
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Senior Member
Brand: Thor Motor Coach
Model: Tuscany 42GX
State: Missouri
Posts: 1,158
THOR #9178
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Use the brakes harder and slow down until the engine RPM is in your target range
Smell is probably brake pads
Start the decent at a slower speed
I start down a pass at the same speed and gear I came up it in
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09-23-2020, 10:26 AM
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#5
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Senior Member
Brand: Thor Motor Coach
Model: 2020 Magnitude SV34
State: Florida
Posts: 4,164
THOR #12751
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Quote:
Originally Posted by eenie34@hotmail.com
Thanks. It got very hot and something smelled like it was burning. I had not been driving downhill that long and had not rode my breaks for them to be hot. Every time I hit the breaks after it started bucking it would rev up.
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When you hit your breaks going down hill, that is a signal you are trying to slow down and / or maintain speed. As a result the transmission will downshift. When it does, engine RPM's go up. The ECM (the onboard computer) should prevent it from over-revving and hitting a redline condition on the tachometer.
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09-23-2020, 12:08 PM
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#6
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I Think We're Lost!
Brand: Still Looking
Model: Tiffin Wayfarer 24 BW
State: New York
Posts: 22,195
THOR #8860
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Judge is right: Tap the brakes to downshift.
But...
You can sometimes find yourself feeling as if the engine is revving too high.
The computers won't let it commit 'Overrev Suicide".
But I could never resist dropping out ot Tow/Haul mode every once in a while, and letting the transmission regain it's composure.
And I'd start the process all over again.
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"What: me worry?"
Good Sam Member 843599689
Current coach: Tiffin Wayfarer 24 BW
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09-23-2020, 12:28 PM
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#7
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Senior Member
Brand: Thor Motor Coach
Model: Hurricane 34R
State: Indiana
Posts: 616
THOR #19887
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The computer will use the full RPM range of the engine when in tow mode to hold the vehicle and that is normal.
My previous rig was a V8 F150 with 10 spd towing a 9000lbs camper and when going downhill the transmission would downshift and if you let it it would go all the way to 6000rpm.
I didn't like that so I would use the breaks to keep the revs. at 4500rpm.
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09-25-2020, 11:18 PM
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#8
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Junior Member
Brand: Thor Motor Coach
Model: Fourwinds 23U
State: Missouri
Posts: 20
THOR #17298
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I want to thank everyone who gave me advice about driving in the mountains with my Fourwinds Class C 23U it was very helpful and it backed up what the dealer told me. He actually took me for a drive to help me understand how to use the transmission on my trip. I actually ended up just leaving it in drive and topping each ascent at the speed I wanted to go down the mountain and that worked well. We are continuing the trip to San Diego with a lot less stress. You all are the best!
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09-28-2020, 08:00 PM
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#9
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Member
Brand: Still Looking
State: Alberta
Posts: 59
THOR #2791
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Personally I would have maintained the same speed downhill as I could maintain uphill on the same hill. At 8% that would be about 35-40 mph in 2nd Gear. JMO.
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10-03-2020, 07:11 PM
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#10
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Senior Member
Brand: Thor Motor Coach
Model: Axis 24.1 KC's Big Box
State: Kansas
Posts: 2,171
THOR #3510
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Quote:
Originally Posted by eenie34@hotmail.com
I want to thank everyone who gave me advice about driving in the mountains...... We are continuing the trip to San Diego with a lot less stress. You all are the best!
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If that is a scary drive for you.we have made that trip....
then you don't want to do I-70 west into Denver...that will get your attention quickly...and you must trust your transmission to do the job for you..if you ride your brakes too much you will burn them up ! As Bob and Judge said...if you must scrub off speed...tap the brakes
have fun ..
Ron
__________________
Ron & Kay n KC too !
2001 Scamp 13'
'KC's Little Box'
Jeep Wrangler TJ
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10-03-2020, 08:55 PM
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#11
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Senior Member
Brand: Cruiser
Model: Georgetown 30x3
State: Idaho
Posts: 223
THOR #17441
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Two other things you can try:
1. Manually downshift to 4. Tow/haul and brake jabbing work in 4, but not in 2.
2. Set cruise at a relatively low speed (40ish). With tow/haul in D it sometimes works fine.
The V10 will go up to about 4,200. It is happy there.
The trans control is adaptive. It will improve after a few downgrades.
Works fine for me on many mountain passes I need to traverse to go anywhere...pulling Cherokee behind Georgetown 30x3 I load to full 18K.
From manual:
“ Automatic Transmission AdaptiveLearningThis feature may increase durability andprovide consistent shift feel over the lifeof your vehicle. A new vehicle ortransmission may have firm shifts, softshifts or both. This operation is considerednormal and will not affect function ordurability of the transmission. Over time,the adaptive learning process will fullyupdate transmission operation.Forced Downshifts•Allowed in drive (D) with the tow/haulfeature on or off.•Press the accelerator pedal to the floor.•Allows transmission to select anappropriate gear.” (PS: I don’t find pressing accelerator causes downshift. But jabbing brake does.)
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10-03-2020, 08:59 PM
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#12
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Senior Member
Brand: Cruiser
Model: Georgetown 30x3
State: Idaho
Posts: 223
THOR #17441
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Quote:
Originally Posted by Judge
When you hit your breaks going down hill, that is a signal you are trying to slow down and / or maintain speed. As a result the transmission will downshift. When it does, engine RPM's go up. The ECM (the onboard computer) should prevent it from over-revving and hitting a redline condition on the tachometer.
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Tach on F53 doesn’t have a redline.
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10-04-2020, 12:13 AM
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#13
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I Think We're Lost!
Brand: Still Looking
Model: Tiffin Wayfarer 24 BW
State: New York
Posts: 22,195
THOR #8860
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...But the engine does.
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10-04-2020, 12:21 AM
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#14
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Senior Member
Brand: Thor Motor Coach
Model: 2020 Magnitude SV34
State: Florida
Posts: 4,164
THOR #12751
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Quote:
Originally Posted by IDguy
Tach on F53 doesn’t have a redline.
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Bob is correct..... the tach may not have a visible redline but there is a rev limiter in the ECM to protect the motor.
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10-04-2020, 12:38 AM
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#15
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I Think We're Lost!
Brand: Still Looking
Model: Tiffin Wayfarer 24 BW
State: New York
Posts: 22,195
THOR #8860
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The V-10 won't blow up... but sometimes it's easy to forget that fact!
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10-04-2020, 01:32 AM
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#16
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Senior Member
Brand: Thor Motor Coach
Model: Chateau 31L
State: Florida
Posts: 2,063
THOR #12189
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Quote:
Originally Posted by IDguy
Two other things you can try:
1. Manually downshift to 4. Tow/haul and brake jabbing work in 4, but not in 2.
2. Set cruise at a relatively low speed (40ish). With tow/haul in D it sometimes works fine.
The V10 will go up to about 4,200. It is happy there.
The trans control is adaptive. It will improve after a few downgrades.
cut...
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I've actually noticed this; particularly crossing the state of TX. I used my foot almost all the way from San Antoine to Ft Stockton. Somewhere along the way, I put the cruise back on. There were still grades but the transmission didn't downshift. I thought to myself, 'Holy crap, this thing is learning'.
After 4mths in AZ will the battery disconnected, that learning was lost for good.
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10-04-2020, 01:41 AM
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#17
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Senior Member
Brand: DRV
State: Texas
Posts: 678
THOR #3109
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It will re-learn, give it a chance.
__________________
2016 Tiffin 40QBH
2015 38RSSA--traded
2005 36TK3--retired, but it was a good one
2017 F450 KR
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10-04-2020, 02:12 AM
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#18
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Senior Member
Brand: Thor Motor Coach
Model: Thor four winds SF 35
State: Texas
Posts: 179
THOR #13025
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It is working like it should. When you tap your brakes, it downshifts to a lower gear like it should. Start down the hill much slower in a gear that will keep you near that speed using your brakes very little.
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10-04-2020, 04:49 AM
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#19
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Senior Member
Brand: Cruiser
Model: Georgetown 30x3
State: Idaho
Posts: 223
THOR #17441
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Quote:
Originally Posted by Bob Denman
...But the engine does.
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No idea what you are posting about. Please use “ quote reply”.
But if it was about the fact the tach does not have a redline it is for two reasons: the engine is designed for high rpm and the engine computer won’t let it overspeed.
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10-04-2020, 11:50 AM
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#20
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Senior Member
Brand: Thor Motor Coach
Model: Freedom Traveller A27
State: North Carolina
Posts: 2,447
THOR #17765
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Quote:
Originally Posted by Bob Denman
Judge is right: Tap the brakes to downshift.
But...
You can sometimes find yourself feeling as if the engine is revving too high.
The computers won't let it commit 'Overrev Suicide".
But I could never resist dropping out ot Tow/Haul mode every once in a while, and letting the transmission regain it's composure.
And I'd start the process all over again.
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I do this same thing as we have done most of our travels through the mountains of western NC , Va, and WV. Just disengage the tow/button and start over again. I’m only pulling 3500 it’s so on flat hiways I don’t even engage the tow/ haul button.
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