Whats up gents
Just out of curiousity,why would someone need to lockout 5th gear?
in other words, 4 speed auto. thanks

5th gear is an O.D. gear. If I remember right the book calls for the down shift when pulling loads in excess of 7000lbs. This I am sure is to save the transmission from ovwerheating etc.

You could also use the 5th gear lockout to run 4th pass redline when dynoing.

5th gear is an O.D. gear. If I remember right the book calls for the down shift when pulling loads in excess of 7000lbs. This I am sure is to save the transmission from ovwerheating etc.

:exactly: Pull a load through Colorado mountains and you'll suddenly realize why you want to lock out 5th. Also, if you try to pull a hill loaded and put your foot in it you run the risk of limping the tranny.

just a way to save the tranny when you have a heavy load so it isnt shifting between 4th and 5th up the bigger hills.

Thanks guyz for your responce
The next time i decide to tow a cat D9 dozer,
Ill keep overdrive locked out:rotflmao:

you should also use tow/haul mode with that load

:grd: :ro)

If you have 10,000 lbs on the hitch, pulling a 5% grade, at 60 MPH or so, you may find that it will pull down the RPM and up the throttle to a point it will shift 5 to 4th. Cruising or manual throttling. Then it'll run the RPM up, and shift back to 5th. Long grades, 5 to 10 miles, or less grade and more head wind will cause a lot of un-necessary wear on the Alley.

If you have a Driver Information Centre.....Watch your miles per gallon. Clear it every 10 seconds or so. For above situation, likely you will see better mileage in fourth. At least until the grade decreases and it will hold 5th on the flat.

If your running serious loads drive it like a truck, not like a car. Look after your mule, it'll look after you.........

Turnpike

'05 Chev, CC, SB, Duramax Allison, SuperChips on tow setting.

5th gear is an O.D. gear. If I remember right the book calls for the down shift when pulling loads in excess of 7000lbs. This I am sure is to save the transmission from ovwerheating etc.

Which book says this?
I thought tow hual was for towing heavy loads? 7K is not much weight to have to lock out OD. This sounds crazy to me.

It has been suggested to me by folks that have learned the expensive way, that if your going to drive it hard, USE tow/haul mode. Keeps the convertor locked, puts the power on the ground - not to heat, and saves the trany. It was even suggested to use tow/haul for all driving except idling out of the parking lot.

Turnpike

'05 Chev, CC, SB, D/A, Superchips on Tow mode.

Which book says this?
I thought tow hual was for towing heavy loads? 7K is not much weight to have to lock out OD. This sounds crazy to me.

I thought everything in florida was down hill.

Tow/haul on, O/D locked out, cruise set. You can get down most interstate grades with a 7k TT and not touch the brakes once...unless traffic gets in the way...:mad:

:exactly: Pull a load through Colorado mountains and you'll suddenly realize why you want to lock out 5th. Also, if you try to pull a hill loaded and put your foot in it you run the risk of limping the tranny.

Add to that, puling a load uphill in 5th will spike your egt's. Dropping to 4th will bring them back down.