6 speed

[dmaxmule]

I am going to order a new d-max within the next couple of weeks, and I was wondering if people are still having trouble with the 6speed, or if the problems had been fixed.
I will gladely take advice on any other part of the truck also.

I would like to thak all the members of this forum. I have read this forum and studied it for over a year now while planning to order a truck. I have seen a lot of info that has helped me figure out what exactly to order. It is now just the finishing touches that I am thinking about.


THANKS

[James S]

Hey There,

Okay! First, can you give us all, a sneak-peak at waht kind of truck you are considering? It might aid us in offering you suggestions for: care, mods, options, transmissions, ETC. As you can see in my signature, I have a CC long-bed four by four, 2500HD, along with my mods. Transmission, depends on what you like to drive, a stick, or an automatic. Me, I've never gotten the hang of a stick, so got the automatic, however, both are vary good. I got the crew-cab, for my woodworking equipment, and versitility for carrying family and friends and all the gear. Alot of people who have the extended cab, seem to regret it, and would get the crew-cab next time, seemmingly for the added versitility and room. Many get the short box, given they don't need the truck for hauling, but more for towing. I got the long-box for hauling sheets of building material, cabinets, etc, and don't tow much. I haven't noticed a mager difference in handling between the CC short-box and the CC long-box. Given how much someone tows, determines whether they get the 2500HD or the 3500. Color, seating, stereo, trim, lighting, etc, are all options of personal preference. As far as upgrades and mods, I would deffinitely get, a tono/canopy, bed liner, running boards/bars, Invinca-Shield [actual bug deflectors don't DEFLECT], high-idle setup, exhaust, gauges, air filter, fuel filter, tires [personally, no more than 265/75 R16], synthetic fluids front to back, [Mobil 1 and Transynd ATF, are what I use], use either Stanadyne Performance or FPPF Total Power, as an additive for every fill up, magnetic drain plugs, and a Fumoto Valve. Power boxes, lifts, ETC, are all personal preference. Always use number-two diesel, or Premium Diesel. As far as cleaning, many of the car-care companies have polishes, waxes, washes, detailers, ETC.. My favorites are Zaino and Eagle1. That should give you some ideas, however, fire away and I will give you more, or explanations about the ones I have listed. Hope to hear from you soon!

James
PS, Enjoy your new baby, but don't forget to feed her, wash her, and change her diaper regularly!
smile.gif :D

[dmaxmule]

I will be ordering a GMC 2500HD 4X4 CC SB.

lly engine
6 speed (?)
all trailering equipment
bose radio
manual extend camper mirors
G80 locker rear end
cloth seats
rubber floor mats
SLE package
Silver Birch Metalic

[Jelisfc]

I love my ZF and would get another. No problems with mine so far. A creaky pedal and hard clutch after long drives but nothing to speak of. More problems are clutch and flywheel not the trans itself. I've got a vibration I can't quite figure out but it started after I put bigger tires on so I'm not pointing fingers yet.

[crafty]

I've had mine for 3 years and over 40,000 miles and I too would buy this truck again. The only trouble I had was with the flywheel which was replaced under warranty. I have had the hard pedal problem but not as bad as some and not all the time and my clutch has never squeeked. I dislike auto trannies and will always drive a stick. I get an averge of 19-20 mpg (imperal gallons) with a high of 25 on the highway and a low of 16 while towing a 10,000 lb trailer.
The final choice is yours but I would buy the 6 speed. :D :D :D

[JMPDMax]

It's my understanding that the LLY engine is not available with the ZF6. If you order a ZF6 equipped truck, you get the 300hp/520tq rated engine.

At least that's what I've been told....

Later....

[VA_Dmax]

I too have been really happy with the 6 speed. Im keeping my fingers crossed I dont have flywheel problems. Since it is part of the 100,000 mile warranty, I just hope if or when it goes its in that time period. Knowing that I complimented it, it will probably croak on me tomorrow. But its done everything Ive asked of it and more. One comment I do have is that I think 6 speeds run out of gear faster than the allison on the highway, I think once the ZF is in 6th and the allison hits 5th or OD that the allison runs at lower rpms. Anybody else notice that?

[CPMac632]

The gear ratio of the ZF in 6th is .72 and the Allison in 5th is .71.

[George Gozelski]

I think you would do better with the 6 speed than the Allison. I have a friend who has the exact same truck as I, a 2002 CC 3500 4x4, but his is equipped with the 6 speed and mine the Allison. He gets 3 mpg per gallon better than I do.

There is no auto tranny that is as efficient as the 6 speed; it boils down to what you like to drive. My buddy hasn't had a lick of problem with his (and he is hard on it) and it seems as though I have tranny related problems every other month.

If I get another Dmax, it will be with the 6 speed! :cool:

[VA_Dmax]

My paperwork for the vehicle when I ordered it lists out the gears as follows

1st - 5.79, 2nd - 3.31, 3rd - 2.10, 4th - 1.31, 5th - 1.0, 6th - .76

CPmac, is your 6 speed a .72? Just curious now if they changed in 2003?

[needbigtruck]

dmaxmule if the problems you are talking about are the hard clutch pedal and squeaky clutch pedal, no I don't think GM has fixed them, however neither problem is so big that it would force me to go buy an auto. That's because I enjoy shifting. I have had the slave cylinder replaced and heat tape applied to the hydraulic line, but still experience some hard pedal in the summer, usually while pulling my trailer. I have found that if I regularly replace the brake fluid (like every 4th tank of fuel or so) it's not a problem. I

[jjgmc]

I have 33,000 on my zf with no trouble at all. If I had to do it agian I would buy the zf.

[JMJORDAN]

I have had mine for year and a half now with no problems. I have 25000miles with some heavy pulling. Very happy with milage an power. Pulling my buddies pulling tractor around this summer. I scaled at 23,000 still got 12mpg. Everyday driving I average 18-19mpg.

[dmaxmule]

Thanks for all the replies. that was what I wanted to hear. I will probally order in the next few days. dmaxmule smile.gif

[Colorado Kid]

VA D_Max,
GM doen't seem to be able to figure out what the top ratio is in the ZF S6-650 as used in these trucks is. I've seen it listed in GM literature both ways, starting when the 2001s were still on the drawing boards and persting to this day.

What I know is this: My father-in-laws truck has an allison, 3.73 rear end and the same tires as my truck. At 2000 RPM his indicates 68 MPH. At 2000 RPM mine indicates 67 MPH. This tends to reenforce the thought that we have 0.72 as the top ratio in our trannys, as 0.71 in the Allison and )0.72 in the ZF should be too close to call, of just less than 1 MPH difference at 2000 RPM. The difference between .71 and .76 on the other hand would have me traveling 63.5 MPH at 2000 RPM.

In either case the point is more or less moot, because neither the Allison or 6 speed truck will "run out of gear" in high. They both hit the 97 MPH speed limiter while comfortably below readline RPM.

[dmaxmule]

I went to the dealer today, and I asked about a truck. {{Details under "New LLY d-max" post}}

The lly is available with the 6 speed. The 6 speed's numbers are lower is the only thing.

I did not think to ask about the transmission gear ratios. Sorry, maybe somone else can clarify the situation.

[VA_Dmax]

Colorado Kid, thanks for that info. Im gonna read mine on the way to work in the morning and see what it reads. Kind of curious if they did change them. I just seem to lose mileage FAST over 65 mph. Not sure exactly what RPM I was turning though. Do you and your father in law get similar mileage on highway? Just curious if it even makes much of a difference. Thanks

[CPMac632]

My fuel mileage drops fast above 65 to 70 also. If I keep it at 65 I have got a best of 24 and the best I have gotten over 70 is 19.8.

[VA_Dmax]

Colorado, CPMac, looks like my 6 speed does have the .72 and not the .76 as I ran right on 67 at 2000 which is what you said you ran Colorado. Thanks both yall for that info. Looks like GM has some mistakes on paperwork and listed on their specifications link on Chevy.com. Wonder why they have that listed?

[Colorado Kid]

I get WAY better milage than my father-in-law does. I get about 22 MPG at 70 MPG and he gets 14-15 MPG at the same speed, which probably has more to due with his trucks 496 cubic inch gasser than with his Allison Tranny. ;)

Towing the 5th wheels he gets 10 MPG if he's careful and the wind isn't blowing (even cross winds destroy MPG when towing). Under the same conditions I get 14 MPG, which means we're both ready to stop for fuel at 300 miles, even though his tank holds 8 gallons more fuel than mine. At that point his low fuel light is on, mines still off, but it's below 1/8th of a tank.

[luvthesmellofdiesel]

needbigtruck,

So that's the key to getting rid of the hard pedal is replacing the hydraulic fluid once in a while? That would be way cool if that's the case. I get the hard pedal, with the pressure point about an inch off the floor after driving on the highway for hours at a time...

Wasn't there somebody who posted a while back (I searched and couldn't find it) about replacing the DOT-4 w/ DOT-3 and it fixed this problem or am I thinking of something else?

dmaxmule,

As for the ZF/6, it's great once you get the hang of it. Having the GO gear right next to reverse is kinda dumb IMO, but once you're used to it, it's great and your MPG will likely be better than the Allison (depending on how you drive of course), and you save some major freight $$$ over the cost of the Allison. GM seems pretty proud of their Allison setup...

The flywheel/clutch issue hasn't been resolved that I'm aware of, as mentioned, and the flywheel is part of the 100K engine warranty so "when" it goes (around 16-20K miles probably), just take it in and tell them to replace the flywheel.

I hear there are some folks/companies working on aftermarket clutches and flywheels but until 100K miles, it's not a concern anyway. I suspect less than 5-10% of Duramax's sold have the ZF/6 tranny is probably why it's taking so long to see anything on the market.

If you're worried about power, buy a tuner...

With all the hoopla about fuel injector failures, you might want to consider adding a secondary fuel filtration setup (I have the ******** pre-oem CAT setup). It can't hurt and the price is right...

Tim