I have read all the posts on this topic but am left with questions. I use my tow haul mode for city driving while towing, but when do i put on the OD lockout? and can it be put on while in motion or do I have to stop to engage it? Please help, chevy's online help was of no help. Also should i use the t/h mode when towing on a long straight open highway?

Thanks

I have read all the posts on this topic but am left with questions. I use my tow haul mode for city driving while towing, but when do i put on the OD lockout? and can it be put on while in motion or do I have to stop to engage it? Please help, chevy's online help was of no help. Also should i use the t/h mode when towing on a long straight open highway?

Thanks

Do a "Search" on Tow Haul. You will have more to read than I could write tonite.

Idahofox

You can switch the OD on and off at any time.

Generally I will switch off the OD when pulling up a grade towing, if it gets to the point where the tranny wants to hunt between 4th and 5th. I have also turned the OD off going down hill, for the compression braking. This way if I need to give it a little gas, it won't shift into OD, just so I have to tap the brake to force a down shift again.

I think I'm confused??? Tow/Haul and OD lock out? Aren't they one in the same? If not, where's the OD lock out button???

Thanks

Dave...

End of Shift lever.

Tap for Tow/Haul: Tap On/Tap Off

Hold in for 1 - 2 sec for OD lock out: Hold in On/Hold in Off

It's in the owners manual.

Idahofox

Thanks, I didn't know that. Owners manuals are like directions "who needs 'em"...
Guess I should do a little reading...

Thanks again...

Dave

Just make sure you read the Diesel supplement in addition to the regular owners manual. Remember, the owners manual was written assuming that you did not have a Diesel so, some information will contradict the info in the supplement. When in doubt, go by the diesel supplement.

I use the OD lockout with my predator as it will lug down at 1500RPM in OD. Above 70 mph, it will redline and then the governor will back you to below redline.

Just to be sure ...no od lockout on the 01,02 d/a trucks, correct?

I believe they added the switch sometime in the 01-02 timeframe. You can add one if you didn't get one from factory.

Just to be sure ...no od lockout on the 01,02 d/a trucks, correct?

Correct. The OD lockout switch was standard on the 03's and up. You can add to the 01's and 02's via a kit or take to the dealer IIRC.

ADD the switch.

It is the best thing you can do if you do any towing, in my experience.

My .02

The O/D lockout is very handy if you do a lot of towing. Most of the time the Allison is smart enough to know what gear to be in and when. But, it is blind and can’t anticipate changes in terrain. That’s when I take over. On a stepped climb, for example, where steep grades that would force a downshift are followed by short, less steep grades where the trans would upshift only to be followed by another steep section, and so on, I’ll hit the O/D lockout and just hold the gear for the duration. As for T/H, I use that whenever there is something attached to the hitch. I learned a long time ago that in hill country even a light load of around 3k lbs can be enough under certain conditions to cause the trans to withhold a T/C lockup on a long pull, which adds heat. With the T/H engaged the trans will downshift, lock the T/C and run cooler at about the same rpm as it would with the T/C unlocked in a higher gear.

TC

When I'm towing (8,000#), I use T/H for acceleration and deceleration (red lights, mostly) around town, because it locks the torque converter. When I get over 45 or so, I tap the button to put it in OD where the TC again locks in. I haven't used the OD lockout at all so far. I'm thinking it would be good for going down a mountain.

Ed

Tow haul works very well with grade braking. I've read other posts saying these are unrelated but on my tow last weekend through the rockies I was going downhill tapping the brake and wasn't getting any downshifts, realized I wasn't in tow haul, put t/h on and the ally downshifted as soon as I touched the brakes. So they are related, and work great together. Can't say I missed the od lockout feature, possibly because my 5th is only 6500lbs, didn't feel any hunting . The ally never missed a beat and seemed to grab the right gear in t/h.

I do not know what the big fuss is over this. When I tow I used tow haul all the time. I am in Alaska right now and pulled a 16,000+ 5th and it handled like a dream.


Tony

When you tow just use your tow haul switch. Tony's got it right. That's why it is there.

OK. Got the T/H thing down. What is OD lockout and does it help with highway towing? Owners manual sayd put it on to prevent truck from going into 5th gear over 50 mph. Is that a precaution or just ignore it?

I use the tow/haul anytime my added weight is over about 4000 pounds. I also use T/H if the tranny temp is up. The only time I lock out OD is when I am in a lot of rolling hills and the tranny keeps downshifting going up and up shifting going down. Does that make sense?