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09-07-2017, 09:33 AM
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#1
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Senior Member
Workhorse Chassis Owner
Join Date: May 2003
Location: Lakewood Ohio
Posts: 568
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8.1 rpms varying
Occasionally the rpms on my rig will vary by 200 or so rpms. There is no misses or stutters.its as if I am depressing and letting up the gas pedal but Im not. Happens on or off cruise control. Flat or level terrain and not a hard pull. Looking for suggestions I don't believe the tranny is downshifting as I had my cluster indicating the gear I was in
Thanks
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WIT# 34347
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09-07-2017, 12:12 PM
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#2
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Senior Member
Winnebago Owners Club Workhorse Chassis Owner
Join Date: May 2016
Location: Kamloops, BC, 60 miles from the Center of the Universe according to the Rinpoche, of the SF monks.
Posts: 7,305
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What speed and rpm's is it happening at? Could be just dropping down to 5th from 6th on a slight incline? Do you have the 6 speed Allison? May be something else like electrical signal interference if it's not shifting, you did say you were watching the display.
Happy Glamping.
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Happy Glamping, Norman & Elna. 2008 Winnebago Adventurer 38J, W24, dozens of small thirsty ponies. Retired after 40 years wrenching on trucks! 2010 Ford Ranger toad with bicycles or KLR 650 in the back. Easy to spot an RVer, they always walk around with a screwdriver or wrench in one hand!
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09-07-2017, 08:50 PM
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#3
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Senior Member
Workhorse Chassis Owner Rexhall Owners Group
Join Date: Feb 2003
Location: Everywhere,USA
Posts: 1,518
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It would be interesting to see if it does it with overdrive off.
What is the year of your chassis? Is it the 8.1L engine with Allison Transmission?
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Full-Timers
in a
2003 Rexhall Aerbus 3550BSL
W22 Workhorse
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09-07-2017, 09:14 PM
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#4
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Senior Member
Join Date: Apr 2011
Location: Powell River, B.C.
Posts: 31,269
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Only 200 RPM , I doubt if this is a gear down shift ; BUT ; the possibility of the torque converter going in/out of lock-up is there.
If this is happening when operating in cruise ;
Are you always using the cruise control at the same speed ?
If you increase the speed ; say by 5 MPH ; on the same road , do you see the same change in RPM, at the slightly higher speed ?
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99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.
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09-07-2017, 10:43 PM
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#5
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Senior Member
Monaco Owners Club Workhorse Chassis Owner
Join Date: Aug 2002
Location: Clovis, CA, USA
Posts: 13,090
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Quote:
Originally Posted by Skip426
Only 200 RPM , I doubt if this is a gear down shift ; BUT ; the possibility of the torque converter going in/out of lock-up is there.
If this is happening when operating in cruise ;
Are you always using the cruise control at the same speed ?
If you increase the speed ; say by 5 MPH ; on the same road , do you see the same change in RPM, at the slightly higher speed ?
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I think Skip is right about the torque converter going in and out of lockup. Transmission shop told me of this variance and said not to worry about it.
Mine does the same thing.
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2004 Monaco La Palma 36DBD, W22, 8.1, 7.1 MPG
2000 LEXUS RX300 FWD 22MPG 4020 LBS
Criticism is easier than Craftsmanship
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09-08-2017, 10:39 PM
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#6
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Senior Member
Winnebago Owners Club Workhorse Chassis Owner
Join Date: May 2016
Location: Kamloops, BC, 60 miles from the Center of the Universe according to the Rinpoche, of the SF monks.
Posts: 7,305
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At 60 mph, when my 6 speed Allison kickes down from 6thh to 5th it drops 500 rpm.
Just a thought.
Happy Glamping.
__________________
Happy Glamping, Norman & Elna. 2008 Winnebago Adventurer 38J, W24, dozens of small thirsty ponies. Retired after 40 years wrenching on trucks! 2010 Ford Ranger toad with bicycles or KLR 650 in the back. Easy to spot an RVer, they always walk around with a screwdriver or wrench in one hand!
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09-18-2017, 06:10 PM
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#7
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Junior Member
Join Date: May 2016
Posts: 21
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Hi
I noticed my rpms fluctuating about 200 on my last trip. Usually between 60 and 65. overdrive on and off. I also noticed it seemed to be bump related. It seemed to happen during or right after a good bump. How concerned should I be? Another trip to a race in Texas next month.
Racecork9
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09-20-2017, 06:38 PM
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#8
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Senior Member
Workhorse Chassis Owner
Join Date: May 2003
Location: Lakewood Ohio
Posts: 568
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Quote:
Originally Posted by Skip426
Only 200 RPM , I doubt if this is a gear down shift ; BUT ; the possibility of the torque converter going in/out of lock-up is there.
If this is happening when operating in cruise ;
Are you always using the cruise control at the same speed ?
If you increase the speed ; say by 5 MPH ; on the same road , do you see the same change in RPM, at the slightly higher speed ?
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it is NOT a downshift it is in 6th gear when I notice it and it doesn't make a difference when I change speed. I don't understand the torque converter idea. Please explain.
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WIT# 34347
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09-21-2017, 08:55 AM
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#9
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Senior Member
Join Date: Apr 2011
Location: Powell River, B.C.
Posts: 31,269
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Torque converter " lock up " is a function of modern automatic transmissions .
Internal in the torque converter is a plate that resembles a manual transmission clutch plate . As the transmission controller senses the correct conditions the lock up plate in the torque converter is applied , to provide a solid link between the engine and the transmission , for best fuel economy, and allowing the transmission to run cooler.
This function; lock up ; allows the solid link to be accomplished at a lower engine RPM than a standard torque converters , hydraulic lock up ( the point when the converters drive and driven vanes are turning at the same speed, sometimes referred to as the torque converters " stall rpm " .
The controller will dis-engage lock up to prevent drive line " shudder " similar to operating a car with a manual transmission in to high a gear for the vehicle speed .
On transmissions without the torque converter lock up plate ; hydraulic lock wouldn't occur until 2,400 rpm and higher, and below that rpm the torque converter would continually be heating the fluid in the converter.
I'll see if I can find any online files with diagrams and maybe a better description.
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99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.
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09-24-2017, 01:29 PM
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#10
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Senior Member
Workhorse Chassis Owner
Join Date: May 2003
Location: Lakewood Ohio
Posts: 568
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Quote:
Originally Posted by Skip426
Torque converter " lock up " is a function of modern automatic transmissions .
Internal in the torque converter is a plate that resembles a manual transmission clutch plate . As the transmission controller senses the correct conditions the lock up plate in the torque converter is applied , to provide a solid link between the engine and the transmission , for best fuel economy, and allowing the transmission to run cooler.
This function; lock up ; allows the solid link to be accomplished at a lower engine RPM than a standard torque converters , hydraulic lock up ( the point when the converters drive and driven vanes are turning at the same speed, sometimes referred to as the torque converters " stall rpm " .
The controller will dis-engage lock up to prevent drive line " shudder " similar to operating a car with a manual transmission in to high a gear for the vehicle speed .
On transmissions without the torque converter lock up plate ; hydraulic lock wouldn't occur until 2,400 rpm and higher, and below that rpm the torque converter would continually be heating the fluid in the converter.
I'll see if I can find any online files with diagrams and maybe a better description.
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Thank You.
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WIT# 34347
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09-25-2017, 05:43 PM
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#11
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Senior Member
Join Date: Apr 2011
Location: Powell River, B.C.
Posts: 31,269
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Brief description on page 14 .
Still looking .
U tube video ( 0.46 sec ) available too ; If you do an " Allison 1000 series torque converter lock up " search on Google.
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99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.
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