I am guessing it just takes it out of overdrive but does it do anything else?

Anything?

 

The OD OFF prevents the trans from shifting to 4th gear, which is overdrive. If it is in 4th gear when you press the button it will downshift to 3rd gear.

It also applies the coast clutch so that there is engine braking in 1st, 2nd, and 3rd gears. When the OD OFF light is not lit there is no engine braking in the lower gears.

 

Thanks, thats about what I figured

 

It will also warn you of impending transmission failure with a blinking, that cause's a shrinking of the wallet.

 

It will also cause ******* shrinkage. When that sucker starts blinking it could mean anyone or more of a 1/2 dozen problems.

 

I knew that your screwed if it's bliking but I didn't know that it applied an engine brake. Thanks, learn something new everyday.

 

You sound like a good person to field auto trans questions. Any harm in pushing button (disengage od) and downshift with the gear selection lever? Will the computer prevent the downshift if speed is too high? thanks.

 

Anyone know why this button wouldnt work at all?? Mine doesnt seem to work and I really have no idea where to start.

 

I think I know the answer, but I'll just subscribe to this thread and wait for Mark to reply.

 

Just a quick question about this statement...This coast clutch you mentioned, does this also keep the T/C locked as well? I wondered if you DO have an EBPV wired up as a brake, will pushing this button in before you start down the hill and close the valve keep the T/C locked down the hill? Just wondering. I have a DP tuner and the T/C locks up about 35 mph anyway...

 

Your button could be bad, or atleast the wire through the shift lever may be chaffed. It is replaceable. I would start there, pull steering column cover, find the wire, and check with a multi meter.

 

No, it doesn't apply an engine brake. I wasn't clear enough.

It applies the coast clutch in the transmission so that when you are coasting the transmission will drive the engine, which causes braking. If the OD light is not on and the transmission is in 1st, 2nd, or 3rd gear the trans will freewheel and the engine will go to idle speed.

Pressing the OD button will not lock the torque converter, but you don't need the torque converter locked to provide engine braking.

You can push the OD button or downshift with the shifter at ANY speed. If you are going to fast for the shift to happen the computer will delay it until the truck slows down. I've put the shifter in 1 at 80 MPH. It immediately downshifts to 3rd gear, then when the truck slows enough it shifts to 2nd gear, and when it slows more it shifts to 1st gear.

 

You're a braver man than I. Of course with your background you have a higher comfort level with these things than I do, but I'd still be scared to try something like that. Of course I have some trust issues when it comes to dealing with computers.