Tow haul and overdrive

[falconbrother]

Does tow haul lock out overdrive? Mine doesn't seem to or, I haven't observed correctly.

[JIMNLIN]

The Op is talking apples and most are talking oranges.
Shifting parameters/clutch locking and unlocking parameters/OD or no OD/the whole tow/haul event depends on the trucks transmission size/year model.

The 6L80e in the wifes 2016 1500 chevy 5.3 (and her old same chevy truck in a '06 5.3 4L60e) has a completely different tow haul operation than my sons 2016 2500 chevy Dmax/A crew cab.

All the tow/haul does in the 1500 '06 and '16 truck is hold the TC clutch unlocked to a higher rpm while accelerating. In fact the TC clutch is still unlocked while going downhill at that rpm/speed. At certain speeds/rpm there is no engine braking simply because the TC clutch is unlocked. Thats why I stopped using T/H mode in both trucks. Neither truck T/H mode locked out OD.

My sons '16 Dmax/A tow/haul works completely different and does a really good job all around.

[Hannibal]

No way to lock out O/D with my 2010 5.4L F250. 5spd Torqshift.

[Bedlam]

SoundGuy wrote:

gmc6000 wrote:
No, tow/haul does not lock out overdrive on any GM or Ram truck, at least. Tow/haul only changes your shift points on the transmission.

I guess it depends on what one means by "overdrive" but I recently bought a 6-spd 2012 Silverado 1500 to replace our 2005 4-spd Avalanche for towing and in Drive when I engage Tow/Haul it absolutely does lock out 6th gear. If I disengage Tow/Haul while towing at highway speed and happen across a relatively flat section of road only then will the transmission upshift to 6th, otherwise with Tow/Haul engaged the highest it will go is 5th, which as it turns out is right where it needs to be - 2000 rpm in 5th, downshifting occasionally to 4th as road conditions may require.

You may want to try this unloaded: Get the vehicle over 100 kph and then engage tow/haul. If it does not downshift, your top gear is not locked out. If it does not go into top gear while towing, your vehicle may not be developing sufficient power at that speed to sustain 6th gear.

[transamz9]

Cummins12V98 wrote:

Bedlam wrote:
You were told wrong.

I should have added when towing at let's say 60.

My 68RFE would tow at 60 in 6th all day with 3.42's on flat ground with tH and EB engaged.

MeAgain???

My Aisin with 3.42's will not shift into 6th until 65mph but once it's there I can back down to 60 in 6th. If it downshifts to pull a grade then it will not go back to 6th until 65. I'm sure it's rpm and load related but 65 is the magic number to get 6th with TH on. 5th is 55mph. It will run in 4th until 55 with TH on. This relates to 2000 RPM.

Unless I'm running interstate I always lock 6th out towing my rig. There are times I will lock 5th out in the rolling backroads.

[Cummins12V98]

Bedlam wrote:
You were told wrong.

I should have added when towing at let's say 60.

My 68RFE would tow at 60 in 6th all day with 3.42's on flat ground with tH and EB engaged.

MeAgain???

[tinner12002]

Cummins12V98 wrote:
From what I have been told tow haul will not allow use of 6th with the AISIN trans.

MeAgain what say you???

Mine does, it uses all gears as in normal mode but just changes shift points, probably does more too but RPM is same towing or not the best I can tell with factory tach.

[SoundGuy]

gmc6000 wrote:
No, tow/haul does not lock out overdrive on any GM or Ram truck, at least. Tow/haul only changes your shift points on the transmission.

I guess it depends on what one means by "overdrive" but I recently bought a 6-spd 2012 Silverado 1500 to replace our 2005 4-spd Avalanche for towing and in Drive when I engage Tow/Haul it absolutely does lock out 6th gear. If I disengage Tow/Haul while towing at highway speed and happen across a relatively flat section of road only then will the transmission upshift to 6th, otherwise with Tow/Haul engaged the highest it will go is 5th, which as it turns out is right where it needs to be - 2000 rpm in 5th, downshifting occasionally to 4th as road conditions may require.

[Bedlam]

You were told wrong.

[Cummins12V98]

From what I have been told tow haul will not allow use of 6th with the AISIN trans.

MeAgain what say you???

[LIKE2BUILD]

Bedlam wrote:
Tow/haul changes shift points for upshifts and downshifts. It also tries to keep the torque convertor locked to keep transmission temperatures down. You can still lock out higher gears with the shift selector if the transmission is hunting between gears due to your load, speed and terrain combination.

Yup, this is it.

[ktmrfs]

BB_TX wrote:

gmc6000 wrote:
No, tow/haul does not lock out overdrive on any GM or Ram truck, at least. Tow/haul only changes your shift points on the transmission.

If your truck normally shifts into overdrive at, lets say 55 MPH, in tow/haul mode you may need to hit 60-65 before it shifts into overdrive.

Same for Ford. At least for the last 10 yrs or more.

yup, same on my duramax's. you CAN lock out overdrive, but not by selecting tow haul. have to select OD lockout seperately.

and in tow haul the 6 speed shifts into 6th around 62mph. out of tow haul low to mid 50's.

and on my 2015 tow haul also locks up the torque converter clutch for 2nd through 6th gear.

[BB_TX]

gmc6000 wrote:
No, tow/haul does not lock out overdrive on any GM or Ram truck, at least. Tow/haul only changes your shift points on the transmission.

If your truck normally shifts into overdrive at, lets say 55 MPH, in tow/haul mode you may need to hit 60-65 before it shifts into overdrive.

Same for Ford. At least for the last 10 yrs or more.

[Bedlam]

Tow/haul changes shift points for upshifts and downshifts. It also tries to keep the torque convertor locked to keep transmission temperatures down. You can still lock out higher gears with the shift selector if the transmission is hunting between gears due to your load, speed and terrain combination.

[gmc6000]

No, tow/haul does not lock out overdrive on any GM or Ram truck, at least. Tow/haul only changes your shift points on the transmission.

If your truck normally shifts into overdrive at, lets say 55 MPH, in tow/haul mode you may need to hit 60-65 before it shifts into overdrive.

[gmcsmoke]

does a 2000 1500 even have tow/haul?