For Ty. Duramaxes.

[cleatus12r]

Here is a little bit of comparative information regarding the Duramax/Allison combination. I didn't write too much about the Dodge/Cummins only because what experience I do have is limited to owning a '94 5-speed for about a year. A year of which I was impressed with the off-idle grunt, fuel economy, and..........that's about it. The dang thing came from the factory with 4.10 gears. Why in the world would a company build a vehicle (with an engine that stops making torque after 1800 RPM) with 4.10 gears? It makes no sense. I could drive 62 MPH and still get 19 MPG religiously.....but step it up a bit to 67 MPH (after 2100 RPM) and it would go to 15. Dang thing would move any load desired up until 1800 RPM....I learned to "short shift" really good. The truck was bone stock.

I work on Duramax-equipped trucks a lot. Most of it's warranty work, and most of it is due to electronic/wiring issues. The control modules that have to communicate with eachother to make everything work right........don't most of the time. Most of the work I do is fixing communication and electronic component problems. It's those damn Indonesian parts. The actual "hard parts" such as the engine, transmission, and drivetrain are nearly bulletproof. Case in point, in the 10 years I have been doing this, I've come across THREE Allison transmissions that have failed under day-to-day use. One simply needed cleaned out and a new torque converter installed. One had a broken tailshaft housing (bad u-joint caused it) and one had a torn 3-5-R clutch seal. I replaced one engine piston that was melted due to a leaky injector, one head gasket, one injector cup, three turbochargers, and a couple CP3 injection pumps....along with a lot of injectors.

The Duramax engine is hell-for-stout. The head gasket issue everyone talks about, well......what issues? Yeah, some fail, most don't. The bottom end is nearly indestructible for most easily attainable power levels. The pistons have actual oil cooling channels in them.....which is better than the standard "squirt oil at the bottom of the piston head" approach of the 7.3s. The common rail injection system is very quiet...moreso on the LBZ and LMM ('06.5-current) and is very reliable. The LLY-LMM ('04.5-current) trucks have a variable geometry turbocharger that works surprisingly well too. It's not nearly as reputable for failure as the 6.0L PSD turbo.

Injector issues? Not really too bad anymore. The only ones that really have problems are the '01-'04.5 LB7s. Most of those are few and far between now....or have already been fixed. Hell, most of them are warranted for 200K (under certain failure modes) and once they've been changed, they are usually good for another 100K + miles. The LLY-LMM engines don't have near the trouble...and the injectors are easier to change since they're not under the valve covers like the LB7s.


As far as the rest of the drivetrain goes, the transfer case is standard fare....some suffer from mysterious fluid disappearance and subsequent range fork disintegration. A lot of them used for daily town driving activities suffer from oil pump locating ear protrusion through the rear case half and run out of fluid when the thrust clip falls out of it's spot. It's easily fixed with an updated thrust clip on the pump.

The rear drive axle is a monstrous 11.5" AAM full floater. These are the same axles that are underneath the rear of the Cummins-equipped trucks....the housing is a little different though. The axle tubes taper to 3.5" at the ends vs. the Dodge's constant 4" diameter. In other words, it's tough.

The front differentials have suffered the same fate as all of the retarded General Motors IFS center sections...they love to eat bearings. Pinion bearings, side bearings, they just don't last.

The front suspension is my biggest gripe, but also puts food on my plate. Lower ball joints, inner tie rod ends, and alignments keep me busy. They ride nice though....

Interior....kind of bland. The CD players aren't known for their reliability and the factory speakers in the front doors are very prone to failure (buzzing voice coil/magnet interference). The coating on the radio and HVAC control knobs wears off insanely fast.

The power-extending camper mirrors are junk. The field of vision is terrible and they don't always extend or retract....don't break one off either backing out of your garage. They are stupidly overpriced to replace.

What else? Transmission oil cooler hoses, power steering pressure hoses, and gasser oil cooler hoses. My favorite since I only replace a dozen or more sets a week. Why can't GM make a cooler hose that will not have a leaking crimp? I wish I knew...replacing those gets old.


So, which Duramax is the best? Personally, I'd pick an '03-'04.5 truck. Why? First off (and the biggest reason), they don't have EGR. Ask anyone why EGR on a diesel is bad. There's a reason EGR delete kits are big money. The LB7s get better fuel economy than any later D-max. A wastegated turbine housing (fixed geometry) is standard. They've got plenty of power and upgrades to it are EASY and make a world of difference. The reason for an '03-'04.5 over the '01/'02 trucks is the transmission control overdrive override switch. The early trucks didn't have an option for selecting 4th gear. They would hunt between 4th and 5th gear under load....and there wasn't any way to keep it in 4th. The '03 and up trucks had a 5th gear inhibit button. There is an upgrade kit for the old '01/'02 trucks....think early E4OD and the pushbutton on the dash.

The Allison hasn't changed much. Sure, it received a 6th gear. However, it's only for lowering the RPM at highway speed. The basic Allison transmission is nearly the same save for some planetary gear teeth angle changes and a few thrust bearings vs. thrust washers. There are a few pressure control changes as well, but it's still the same basic transmission. The gearing is about spot-on for the Duramax. Every WOT shift occurs at 3300 RPM....and drops the engine RPM 700-900 RPM per shift. It's absolutely perfect. However, on the '06 and up, the "tap shift" is really cool. It allows the driver to select the highest gear that the transmission will automatically shift to. It also allows forced downshifts at the touch of a button when decending a grade. If I could have that with an '03, I'd be all over it.

Any questions?

[Pullin'Fool]

All that is real impressive....they do run pretty good, and sound real good with an open exaust...but nothing beats the aforementioned IFS, watching the front tires point at the license plate and and self destruct.......It happens on a weekly basis at a pulling track near you......Kinda feel a little sorry for the mis-informed, unprepared, budwiser-fueled bubba that finds out the hard way that it is definately the weakest link.......Thanks for your post, very infomative



http://www.youtube.com/watch?v=iT6Lqj-_eSo

[kokopellimotorsports]

Thanks for posting this Cleatus, I finally saw it.this is some great info. I will post some questions later.

Ty

[Corey Cohron RIP]

Ty, when you get a minute, check out this thread.

KICK A$$ POST WRITTEN BY CODY

[cleatus12r]

Thanks, Corey, now I'm blushing....and I don't do that often.

Actually, that thread was written before I knew a fraction of what I think I know now.....which is still a very small percentage of what there actually is to know.

[kokopellimotorsports]

Holy cow Cody! I really need to pick your brain some more.

I appreciate the articles, great reading. Please keep them coming.

I am compiling a list of questions that I will PM you soon.

Thanks

Ty