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06-17-2019, 05:45 PM
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#21
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Multi-Slacker
Join Date: Aug 2017
Location: SoCal
Posts: 2,279
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My Chevy does not have an overdrive button - instead gears 5 & 6 are overdrives. The only choices are whether or not to turn on tow/haul - or when going down hills, to manually downshift.
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06-24-2019, 05:33 AM
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#22
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Junior Member
Join Date: Jun 2019
Posts: 19
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Quote:
Originally Posted by shadows4
I have always towed with overdrive on. I have a scan guage to monitor transmission temperatures, if it starts to get to hot or shifts to much then I will lock out overdrive. JMHO
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Heat kills transmissions. Agree with the scan gauge and monitoring.
From what I heard from a seasoned transmission guy of 40 years is that you should judge how you tow with the particular transmission you have and not a general statement. I had our old Trailblazer transmission rebuilt at 250,000 by him. He asked me all about how and what I was towing and then told me to use O/D in future as that particular transmission was better that way.No issues after that until the Trailblazer rotted around a great performing transmission
Nothing wrong with an additional tranny cooler as well in my opinion.
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06-24-2019, 05:45 AM
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#23
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Senior Member
Join Date: May 2017
Posts: 5,712
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Out on the flats on Hwy or Interstate, I'm running with Cruise ON and OD..(tow/haul mode) not locked....(OFF) Goes into 6th gear and rarely downshifts unless on a longer hill. Lower RPM = Higher MPG.
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06-24-2019, 06:30 PM
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#24
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Member
Join Date: Apr 2019
Location: Richmond, VA
Posts: 44
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I trashed one transmission towing in OD. Not gonna do that again. While I agree that on a level run, stress on the OD would be minimal, those would be the exceptions.
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2015 Wildwood X-Lite 241QBXL
2015 Silverado. 5.3L V8
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06-25-2019, 09:37 AM
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#25
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Senior Member
Join Date: Aug 2016
Posts: 135
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With a 4 speed OD transmission, the transmission will run cooler and be far less prone to slip, if you do not use overdrive. My last TV was a 4 speed chevrolet, I always towed in D3, never had a transmission problem.
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2018 Shadow Cruiser 265RLS
2018 Chevy Silverado 1500 with 5.3 max tow package
Shiawassee County, Michigan
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06-25-2019, 09:42 AM
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#26
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Site Team
Join Date: Mar 2014
Location: Grayson County, Texas
Posts: 21,558
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Quote:
Originally Posted by Tacky
With a 4 speed OD transmission, the transmission will run cooler and be far less prone to slip, if you do not use overdrive. My last TV was a 4 speed chevrolet, I always towed in D3, never had a transmission problem.
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My last TV was a 4-spd GMC. I always towed in Drive (allowed OD) and I never had a transmission problem.
Maybe our experimental data cancels each other out.
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2015 FR Wildcat 295RSX / GMC Sierra
Nights Camped: '13 = 49/'14 = 74/'15 = 74/'16 = 85/'17 = 110/'18 = 111/'19 = 86/'20 =108/'21 = 115/'22 = 135/'23 = 78; Booked for 2024 = 69
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06-25-2019, 09:56 AM
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#27
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Member
Join Date: Apr 2017
Location: Muncy Valley PA
Posts: 96
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The tow/haul button is on there for a reason. If a mechanic tells you you don't need it get it in writing so they can replace the tranny for free. Heat kills and it kills very quickly!
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06-25-2019, 10:00 AM
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#28
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Site Team
Join Date: Mar 2014
Location: Grayson County, Texas
Posts: 21,558
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Quote:
Originally Posted by Tom911
The tow/haul button is on there for a reason. If a mechanic tells you you don't need it get it in writing so they can replace the tranny for free. Heat kills and it kills very quickly!
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You may be speaking to someone's intermediary question but the original post asked about overdrive, not tow/haul. My tow/haul does not lock out overdrive (the top 2 in my 6-spd) although for some trucks, it does.
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2015 FR Wildcat 295RSX / GMC Sierra
Nights Camped: '13 = 49/'14 = 74/'15 = 74/'16 = 85/'17 = 110/'18 = 111/'19 = 86/'20 =108/'21 = 115/'22 = 135/'23 = 78; Booked for 2024 = 69
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06-25-2019, 10:44 AM
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#29
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Senior Member
Join Date: Nov 2017
Location: Dayton Ohio
Posts: 3,591
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In the past the od switch simply looked up the torque converter for better mileage. The torque converter is in a sense a clutch.
By disengaging, it prevented the transmission from hunting. Shifting in and out of overdrive often. Damaging to,the transmission.
Modern transmissions have computers to control that. In the old days it was up to you.
So if pulling a not max load on flat ground, the od is great. If the trans is hunting, then it needs to be locked out.
On a diesel truck pulling a big load the tow haul mode locks out sixth for better operation. Lower temps. Less hunting.
Watch the transmission temp gage. Try it out both ways.
Transmission repair is north of $3000. Improving mileage saves a few bucks.
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06-25-2019, 10:52 AM
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#30
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Pickin', Campin', Mason
Join Date: Aug 2015
Location: South Western PA
Posts: 19,142
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Quote:
Originally Posted by Mr. Dan
You may be speaking to someone's intermediary question but the original post asked about overdrive, not tow/haul. My tow/haul does not lock out overdrive (the top 2 in my 6-spd) although for some trucks, it does.
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Yep... I'll reiterate again for those not following along...
A modern tow/haul button and the older O/D on-off button are two horses of a different color.
You cannot compare apples to oranges and give generic advice about both.
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2022 Cedar Creek 345IK 5th Wheel•Solar & Inverter•2024 Ford F-Series SCREW•7.3L•4x4•Factory Puck•B&W Companion•TST Tire Monitor w/Repeater•Sinemate 3500w Gen.
F&AM Lodge 358 Somerset, PA - JAFFA Shrine - Altoona, PA
Days Camped ☼ '19=118 ☼ '20=116 ☼ '21=123 ☼ '22=134 ☼ '23=118☼ '24=90
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06-25-2019, 11:00 AM
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#31
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Site Team
Join Date: Mar 2014
Location: Grayson County, Texas
Posts: 21,558
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Quote:
Originally Posted by 5picker
Yep... I'll reiterate again for those not following along...
A modern tow/haul button and the older O/D on-off button are two horses of a different color.
You cannot compare apples to oranges and give generic advice about both.
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This is correct!
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2015 FR Wildcat 295RSX / GMC Sierra
Nights Camped: '13 = 49/'14 = 74/'15 = 74/'16 = 85/'17 = 110/'18 = 111/'19 = 86/'20 =108/'21 = 115/'22 = 135/'23 = 78; Booked for 2024 = 69
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06-25-2019, 12:01 PM
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#32
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Junior Member
Join Date: Apr 2018
Posts: 8
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I have an 08 F150 and pull a 4000lb loaded camper. I always pull with OD off. RPM are a bit higher but it is still reasonable at 2500 RPM at 60-65 mph. I'm not an expert, but the shifting and OD slippage can not be good with a load. We have towed at least 15,000 miles and through the Rockies OK. 150K on truck as of today.
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06-25-2019, 12:15 PM
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#33
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Senior Member
Join Date: Aug 2016
Posts: 135
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Quote:
Originally Posted by Mr. Dan
My last TV was a 4-spd GMC. I always towed in Drive (allowed OD) and I never had a transmission problem.
Maybe our experimental data cancels each other out.
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Hi, Mr Dan.
I'm certainly glad that you never had a problem, but I've got more than experimental data. I was a transmission technician at a GM dealer for many years, after which I provided technical assistance to GM dealer mechanics, as a GM contract employee. While I was in the dealership, we advised, on the recommendation of GM engineers, that customers did not tow heavy loads in OD. I repaired or replaced some number of them due to towing in OD.
Any time power flow goes through a gearset, heat is generated. In third, D3, power flow in is power flow out. There are no working gears. In overdrive, the overdrive ratio is generated by using one of the planetary gear sets, so operating in overdrive inherently creates more heat. Additionally, every time there is a shift, there is a certain amount of slip. The overdrive band releases, some slip there, and the one way roller has to take the power, again, slight slip. Anything slipping creates heat. The real issue is that torque capacity in 4th (OD) is not as great as in D3. When in D3, there are 2 clutches applied, the 3-4 clutch and the overrunning clutch, both holding the same parts. In OD, the 3-4 holds one part, the 2-4 band holds a different part, torque capacity is reduced. If there is slight slip under load, it is not likely to be noticed until you see the fluid and the smoke coming out the back. At that point the transmission needs major repair.
OK, enough technical babble, but it does inherently have higher torque capacity, and runs cooler, in D3.
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2018 Shadow Cruiser 265RLS
2018 Chevy Silverado 1500 with 5.3 max tow package
Shiawassee County, Michigan
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06-29-2019, 04:44 PM
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#34
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Moderator Emeritus
Join Date: Sep 2008
Location: Shenandoah Valley of Virginia
Posts: 9,280
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I towed a 5500 lb camper with a 2006 F150 5.4L with 3.73 gears. I found the 5.4L was a very capable towing engine. I never saw over 3500 rpms (a couple of "surprise" downshifts), with about 3000 rpms the norm in 2nd gear pulling bigger hills at 55 mph. I could have gone faster, but I saw no need to rev the engine just to get to the top a bit faster. I just sat back and enjoyed the scenery with the big trucks. I read where so many people make their engine scream just to go fast.
On level road, the 5.4L did a great job of pulling in OD (4th gear) unless there was a heck of head wind. In rolling hills, if the tranny downshifted, I turned off OD.
Concerning the comment that torque converter locks up just in OD, I saw the torque converter lock up in 2nd, 3rd, and 4th monitoring a ScanGauge II. Usually the 1st downshift felt was actually the torque converter unlocking.
I think the 2006 F150 owners manual stated something like: "Tow in OD unless the is transmission is downshifting frequently"........or something like that.
1 thing I did not do is engage cruise control in OD after a few pulls trying that. The cruise control would call for too much gas, causing the tranny to downshift, where I could feather the right peddle so that would not happen. If I wanted to use cruise, then I would lock out OD.
Hope this helps.
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2017 F350 Lariat CCSB, SRW, 4x4, 6.7 PS
2017 Grand Design Reflection 337RLS
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06-29-2019, 05:02 PM
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#35
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Multi-Slacker
Join Date: Aug 2017
Location: SoCal
Posts: 2,279
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Not sure if this is responsive or relevant, but with our 2018 Chevy 6.0 w/4:10 I believe the upper 2 gears of the 6 spd transmission are OD ratios. Except for downhills or >= 6% grades, we just engage tow/haul and let the computer figure it out. For the exceptions, we do things manually.
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