I am brand new to the auto tranny world. I have a few questions about towing a 8-9000 lb. fiver. '03 SO 250 hp auto. It only has a OD lockout switch. Should I tow in OD or lock it out (mountain driving) and in what gears will the tc lock-up? This may sound silly but how do you know when the tc locks? I need help understanding this.
Andy

 

When towing leave OD on when flat ground, I'd lock OD out when in mountain driving. As far as the TC locking factory will 1st lock in 3rd at a super light throttle about 33mph just cruising , Normally in 4th around 45mph cruising the Rpms drop; ie. (1900rpm> dropping to about 1500rpm) the truck feels sort a boggy and the exhaust sound will drone then your locked.

 

Lock it out only when you can't maintain 1800rpm or higher. usually 6% grades lock out. 3rd gear tc lock is obtained about 43mph(80Kmh), but for slower hills, like radium hot springs heading east 50Kmh(30mph) manually drop to 2nd and the TC will lock. Do you have the 47re or the 48re tranny, both still should react the same.

 

I was unaware the T/C would lock in 2nd on either 47 or 48re.

 

I found out not to long ago, and tried it and yes it locks in 2nd only if you manually put in second and are above 25mph. Tach drops about 100-200rpms and you can feel the truck pull. i thought i read it on here somewhere. Will see if I can find it.

 

I would check on that for sure. Tony Garcin @ Dunrite told me they will not lock in 2nd. I know my '01 won't even with Tony's VB. He says you need a lock up switch to do that. I have a buddy that has an '05 and asked me how to put in a switch because his doesn't lock. I'll have to ask him if he has tried it in manual 2nd.

 

2nd will not lock if you are in D.

 

My 05 locks when in 2nd gear manually.

 

Good find! Never knew the T/C could lock in 2nd if you manually shift it.

 

I dont have an exhaust brake and Ive found that on a steep downgrade 6% or so, I can manually select 2nd gear, rev the rpms to lock the TC (over 25mph) and use it to help slow the truck down.

 

I added a LED light that comes on when the TC is locked. It tells me what Mr Grey already knows that 1800 is the magic number. There are times in the mountains on long grades that I will increase rpm to 2000 or a little higher to lower EGT's.

 

I'll have to let my bud know that.

 

Thanks to all. It is clearer to me now.
Andy