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looking for a way to lockout 6th gear when towing a medium load.
OD off spins too many rpms for the load I pull.
chris
 

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Put it in manual and select 5th gear.
 

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SNOWBLIND;1585315; said:
looking for a way to lockout 6th gear when towing a medium load.
OD off spins too many rpms for the load I pull.
chris
IIRC, 6th gear is double overdrive. 'Could be wrong, I thought both 5th and 6th were below 1.

As was said, put it in manual and pick what you want.
 

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Is this on a factory 6 speed or a suncoast 6 speed? My truck doesn't have an OD lockout. I just have the M mode. If it is a suncoast 6 speed, I was under the impression that putting the truck in T/H mode locked out 6th gear, but still allowed 5th to function as normal. What is wrong with running 6th anyway?
 

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SNOWBLIND;1585315; said:
looking for a way to lockout 6th gear when towing a medium load.
OD off spins too many rpms for the load I pull.
chris
:iamlost:
 

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SNOWBLIND;1585315; said:
looking for a way to lockout 6th gear when towing a medium load.
OD off spins too many rpms for the load I pull.
chris
I thought the difference between 5th and 6th was about 250 rpm at highway speeds.....:confused:

DEWFPO
 

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I thought on most trucks holding in TH button locked out 5th and 6th?
 

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LTChip;1588154; said:
I thought on most trucks holding in TH button locked out 5th and 6th?
My 06 doesn't do that. If I want to lock out a gear I have to use manual mode.
 

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Tow/Haul mode on my truck prevents it from going in to 5th or 6th, if you want to run in 5th you need to go manual. Good luck.
 

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truckie481;1588240; said:
Tow/Haul mode on my truck prevents it from going in to 5th or 6th, if you want to run in 5th you need to go manual. Good luck.
Something is very different because my 06, in tow haul mode, will go to 6th. You use the M and select what gear you want to be the highest gear to go to. Maybe you aren't going fast enough to get into 5th.
 

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I have no problem with 5/6th in TH -> it goes in no problem. If I want to lock out 6th, then I just use manual mode.
 

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5 & 6 no problem with tow haul mode.
 

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floriduramax1;1588253; said:
Something is very different because my 06, in tow haul mode, will go to 6th. You use the M and select what gear you want to be the highest gear to go to. Maybe you aren't going fast enough to get into 5th.
I don't know about on the 6 spds but on my buddies 5sp (2005 DA) the TH button serves two purposes. First you can toggle TH mode. Regular TH mode has all gears available - it just changes the lock up, shift points, and downshifting characteristics. Second, when you hold it in for a few seconds the ODLO light comes on and the truck won't shift past 4th: it is still in TH but has overdrive locked out. I would have thought that the 6 spds would have kept this feature and locked out 6th or possibly 5th and 6th.

This feature is not on my 01 (although they made a kit to add it). It may be that they dropped it in favor of the 6 spd manual mode. I don't have a 6sp Allison to look at though.
 

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LTChip;1588459; said:
I don't know about on the 6 spds but on my buddies 5sp (2005 DA) the TH button serves two purposes. First you can toggle TH mode. Regular TH mode has all gears available - it just changes the lock up, shift points, and downshifting characteristics. Second, when you hold it in for a few seconds the ODLO light comes on and the truck won't shift past 4th: it is still in TH but has overdrive locked out. I would have thought that the 6 spds would have kept this feature and locked out 6th or possibly 5th and 6th.

This feature is not on my 01 (although they made a kit to add it). It may be that they dropped it in favor of the 6 spd manual mode. I don't have a 6sp Allison to look at though.
I can tell you my truck does not do that. I tried it the other day. The only way I can lock out a gear is to use manual mode. I think the only reason they had that feature before is because there weren't enough positions on the column shifter to have a detent for 4th gear. Now they have the "M" position on the 6 speeds so they don't need the ODLO switch anymore.
 

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Got it. I think it would have been nice to have the odlo switch as well.

I know I towed with my buddies 05 and I really liked having it.

I might reprogram my TH to lock out 5th whenever TH is engaged. Then if I need 5th I can turn TH off. As I approach a grade I can put it back on and command 4th.
 

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Or does the truck still downshift when in manual mode?
 

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Yeah, the transmission shifts normally. Manual mode is the same as your 3 2 1 postions on the column. They just put all the positions in digital format on the DIC. You can't actually command a gear; you just limit the highest gear it shifts into. I believe you lose the grade braking feature when you are in manual mode, but it isn't hard to click the "-" button to cause a downshift.
 
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