5-speed Or 6-speed?

Midwestcruiser · July 22, 2008

Looking seriously at finally getting a 2500HD Dmax diesel, '04 '06. I've heard nothing but good things about the Allison tranny. Other than the obvious, which is better...the 5-speed or 6-speed? Advantages/disadvantages, pros/cons, etc. Thanks.

98silvz71 · July 22, 2008

I have the 5-speed, but I wanted the 6-speed. Either way you can have a 6-speed. There is a kit from Suncoast that converts the 5 into a 6-speed. The tap-shifting on the gear selector I don't think helps anything on the 6-speed. It just lets you keep in from up shifting any higher than the gear selected. What you are basically want to look at is the engine and not worry about the trans.

In 04 there were 2 Dmax's, the LB7 (Gen I) and the LLY (Gen II). I have the LB7 and am pretty happy with it. One nice thing about the LB7 is that there is a free replacement warranty on the injectors up to 200,000 miles or 7 yrs. It has pretty good power and mine does not go over the 210 degree mark.

The LLY is a revised LB7 engine with a different, more powerful turbo and I'm sure a few other parts inside the engine. One downfall is that it can run hotter than the LB7s in times of towing and what not. My FIL has an LLY and it frequently goes above the 210 degree mark while towing. I have heard chips, exhaust, intake, etc, etc can cure it but not a surefire way.

If it were my choice I would go with an 06 LBZ and 6-speed Ally. The LBZ is a total redesign with stronger parts and more power. It's the quietest of the three and the easiest starting in my experience. I do not have very much experience with this engine but have heard good things.

Hope this helps.

Shaners · July 22, 2008

My '05 has never gone above about 210*. I have towed pretty aggressively (only 4k lbs) on days with temps in the mid 90's the A/C on and 5 people in the truck on hilly 2-lane roads with sharp turns and alot of shifting. My truck has the Edge EZ chip in it otherwise it's stock. I am very happy with my LLY and 5-speed Ally tranny.

98silvz71 · July 23, 2008

I'm not saying that every LLY runs hot. It just so happens that my FIL's stock LLY towing about 8500 lbs runs hot. We are looking into an EDGE-EZ for it too. How do you like it Shaners?

Shaners · July 23, 2008

I'm not saying that every LLY runs hot. It just so happens that my FIL's stock LLY towing about 8500 lbs runs hot. We are looking into an EDGE-EZ for it too. How do you like it Shaners?

The Edge EZ is simple to install and doesn't require any exhaust work. I left the toggle switch under the hood so it wouldn't be as tempting for me to switch between the three levels all the time.

It works great! I am currently leaving it in level 1 and the power difference over stock is still very noticeble. Fuel milage is also beter than stock although you have a tendancy to use that extra power more often because it is fun which probably doesn't help the MPG's!

98silvz71 · July 23, 2008

It comes with a toggle or you added one to it? What would you say your gas mileage is for it before and after? Hwy for him we get about 16 and about 13-14 city.

Shaners · July 23, 2008

It comes with a toggle or you added one to it? What would you say your gas mileage is for it before and after? Hwy for him we get about 16 and about 13-14 city.

The Edge EZ that I have is a three stage chip. It comes with a toggle that you can mount in the cab so you change it on the fly. I left mine under the hood.

I towed my 3500-4000 boat to Erie and back a couple of weeks ago and at 65-70 MPH with no a/c on the way up and a/c on the way home with 5 people in the truck plus gear I averaged 15.4 mpg's according to the DIC. Total round trip was about 160 miles. I had the Edge set on "1" which is the lowest stage and is supposed to deliver the best MPG's.

Stage 2 can be used for general driving and light towing while stage 3 is not supposed to be used for towing. I would consider my boat OK to be towed in "2" if I wanted.

I pulled the boat home from Michigan last year (where I bought it) and over the 400 mile trip home running 70-80 MPH I averaged 14.5 MPG. I don't remember if I was in 1 or 2.

Empty on 2-lane roads @ 60 MPH I'm averaging 19-20 MPG.