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On the 2007 LBZs, 5th and 6th are both Overdrive gears, and a relatively small ratio difference between them. The transmission tows well in 6th, and quite frankly, if the transmission thinks otherwise, it just goes ahead and downshifts.

Regardless, it beats the heck out of my Tahoe's 4L60E for towing, which uses engine revs to make up the difference and immediately downshifts when towing to 3rd, then slams into 2nd. (I live in the mountains). I'll take the 6th to 5th downshift and 2100 rpm to the 4-3-2 abrupt downshifts and running 4,500 rpm with far less weight.
 

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I'm getting ready to tow a 34' Jayco 5'er thats 17k+ loaded thru New Mexico and all thru Colorado next month and I'm not a bit worried. For the most part the truck will pull most hills in 5th without downshifting, but on some very steep grades I may drop to 4th and lower the speed some. All my mods have been for towing and lowering EGT's. The best I can figure, the LLY with good bolt on parts and with me using the level 1 tune the motor should be cranking out 390ish crank HP and 780ish crank TQ. Thats a little better than any new diesel you can buy, and in this low Economy tune my MPG is better and even towing heavy on long grades or WOT runs the EGT never excedes 1,100*. I could turn it up more but down really need insane power to tow. Just enough to keep it in gear without downshifting and get the loads moving faster. Too high of EGT's for too long puts alot of strain on the engine and cooling system, which on the LLY is under engineered. So after getting my EGT's to max at just 1,100* the highest coolant temp recorded on the edge towing 12k, even at WOT at times because of stupid houston drivers, was 199*. I have yet to break 200* since getting the EGT down. With the trucks stock everything and the Edge on stock (yes I hear it still adds a little timing) the EGT's could easily top 1,350* at WOT, the coolant would hit 208* pretty quick and stay fairly steady there on flat ground. Now it gets better mpg, tows and drives with more power, and best of all runs alot cooler!

I dont tow with the tow tune because I was seeing just over 1,200* and really dont need that little more power.

I just prefer the older trucks because of price and how much simpler they are. If I ever have a load the Dmax cant move, the old 12 valve will surely get it done. LOL
 

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I have had both the 5 and six speed allisons. One in an 05 lly, one in an 06 LBZ. The 06 was damn salty, just seemed to have more cahones pulling my 650 JD dozer. The 05 will pull it fine but it works a whole lot harder to do it. Both trucks have the superchips tow program on them.
I would take the 360 hp 6 speed over the 300 hp 5 speed all day long. A little better tow mileage also. 7.5 -8 on the 05, 8-8.7 on the 06.
For reference a 650 JD dozer weighs about 18,500 lbs plus the trailer which was 4400 lbs.
 

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I have had both the 5 and six speed allisons. One in an 05 lly, one in an 06 LBZ. The 06 was damn salty, just seemed to have more cahones pulling my 650 JD dozer. The 05 will pull it fine but it works a whole lot harder to do it. Both trucks have the superchips tow program on them.
I would take the 360 hp 6 speed over the 300 hp 5 speed all day long. A little better tow mileage also. 7.5 -8 on the 05, 8-8.7 on the 06.
For reference a 650 JD dozer weighs about 18,500 lbs plus the trailer which was 4400 lbs.
My personal truck is the 05' with the 5 speed, but my company truck up untill our "spin-off" was an 07' classic GMC LBZ with the 6 speed. I put the bully dog tripple dog on it, but other than that it was stock. To be honest having driven both of them I do prefer the 6 speed and the LBZ. It was a really fast truck stock. It also idled and ran quieter then the LLY. IMO the best Dmax to date is the LBZ trucks. The LLY is still an very good truck, but I wished it had the 6 speed trans.
 

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Discussion Starter #25
Just pulled my car in an enclosed trailor. My guess is I pulled around 8klbs.. The truck did not know it was back there with the Edge set on 2 and fuel 5. Never went over 200F cruising at 65mph... Now I just need to put something double the weight behind her and see how she responds...
 
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