Noise in 4 wheel Drive
 

Hi again everyone -

I am a novice on this.

We may purchase a 2004 GMC 2500 4x4 diesel. It has electronic 4 wheel drive. My question is - when you are driving along and decide to put it in 4wheel drive (high) and press the button - should I expect to hear ANY (or what kind should I hear) noise? I want to make sure that I understand this before we take it on a test drive.

I have a 1500 Dodge with a manual lever to put it into 4 wheel drive so yes I hear a noise when it goes into gear

Thanks for all the information -- I truly appreciate your time


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I have a 2003, same running gear. I do hear a solid "clunk" as the front differential engages. I can't remember the speed, but you are only supposed to do it at 35mph or less. IIRC, there is a solenoid that is engaging the front differential. As such, it's either open or closed (on or off), kind of like your magnetic actuators for Silent Choice exhaust on a boat. Further, it doesn't ease into place like you would do with a manual floor shifter.

Depends on how cold it is out.. Steels the colder it is the thicker oil or gear lube makes them slow engaging and they will make some noise..slower speeds seem to clunk less..

Sydwayz - thank you so much - I feel like an idiot to some of these questions - an old fart is supposed to know this but I just don't have the experience. I hope this deal really goes thru - the truck looks like it came out of the box - it has 170k -- We have a couple of diesels - and to be honest they really don't get "really" going until after 100K. Our Benz E320 CDI 2006 has 135K and to be very honest at 125K it was like the car got hit with the fountain of youth -- fuel economy went up- which was great before, the get up and go is the best ever. down side it seems that I can't blow any smoke out the exhaust-- URGH

is there anything else that I should be looking at the trucks within a year or two

again thanks so much for your help

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LLY or LB7? They had both in '04. My '04 was an LLY so they referred to it as a '04.5.

My 08' you don't hear a thing. Turn hard left or right on pavement, it'll tell you if it's engaged!

I was hoping to learn that from the VIN number but so far I haven't been able to get the information-- I'm stopping by a GMC dealer tonight. It's a GMC 2004 Durmax 2500 club cab short bed- white with gray leather. Lord willing I'll test drive it Saturday and maybe drive it home Saturday afternoon. Do the designations that you reference LLY or LBZ have anything to do with the Transmission?

thanks

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The WORST issue on those trucks is the brake and fuel lines. They ALL rust out. Plan on replacing them, unless they have been done already. There are kits out there in coated and stainless steel.

My two 2500HDs have been 8.1L Gasser with the Alison Automatic transmission, so I can't comment on anything from the Duramax side. I've replaced brakes on mine, and pitman/idler arm. Also, they do have some main ground issues, especially with trucks that have been exposed to salt. I just had to replace my front bumper due to rusting from the inside out. The back one is probably next.

You'll be able to tell when the 4x4 actuates. I have a 2007 2500HD and can just barely feel it in the floorboard when it engages. I throw mine in and out of 2H/4H at any speed, as long as your front and rear axles/tires are moving at the same speed and you aren't making a bunch of tight turns. When using 4L max speed is 45 per the manual.

Sometimes when going from 4H to 2H, I have to get out of the accelerator a little to get the actuator to release, but I've always shifted all of my GM's at speed, at least the ones with matching gear ratios.

www.dieselplace.com is a good place for some research.

In 2006 they changed to the LBZ engine and 6 speed Allison trans. The 6 speed makes it sooo much better on the highway. The 5 speed will be at 2000 RPM's at about 65 mph which sucks for MPG's.

Seems that many LLY's were bad about running hot, some worse than others. Dad had an 05 LLY and I remember it would start climbing to 210 or a little higher towing a heavy loaded enclosed trailer if I was behind a semi on the highway. Pull out and pass or just get airflow through the radiator and it would cool back down. I was watching the temp on a Edge Juice with Attitude box in the dash.

Try to look at the service records/history if you can and see whats been done.

No, that is the engine designation. LB7 was the first gen engine with the injectors under the valve covers and a waste gate turbo. LLY moved the injectors above the valve covers and had a VVT (Variable Vane Turbo).

Which is more desirable, and for what reasons? Thanks.

There were issues with some of the transfer cases. Do a google search regarding some of the TC cases had holes worn in them from a pump rubbing.

TOTALLY forgot about that.

It's called "pump rub". There was at least one TSB about them.
https://www.google.com/webhp?sourcei...q=pump+rub+tsb

There is a fix kit for it.

Basically, the oil pump inside the transfer case rubs the casing, eventually causing a hole. The transfer case fluid drains out, and blows the transfer case.

I think opinions will vary. The knock on the LB7's was if the injectors leaked, you had diesel in your crankcase. It has been quite a few years since I followed the diesel sites so I'm not sure if the newer generation injectors all but solved that issue. As stated above, the LLY's had issues with overheating. I personally never had an overheating problem with my LLY but I only towed 10K in pretty flat land. If you towed heavy and in any kind of elevation it was a problem. LLY's also had some injector problems but they would not put diesel in the oil like the LB7's would. VVT's can have their own set of issues. I think it comes down to how much you are going to tow and what level of power you desire. I ran both a 40 and 60 HP tune (Diablosport Predator) on my LLY with no other mods and it was plenty for my needs. In fact, I couldn't keep tires on it as it was also my daily driver so a lot of in town driving would just roast the right rear. I'd get just a little over 20K out of a set of tires rotated every 5K. IMO, the LBZ was the best engine as it solved a lot of the problems the LLY had and was pre-DPF. But those are hard to find and command a premium.

Correct. Another thing to look out for. There were also some wiring issues with LLY but the problem escapes me at the moment. A quick search on dieselplace.com would find all the major issues.

8th digit on the VIN will tell you the engine. (1) will be LB7 (2) will be an LLY.

If it is an LB7 here are some things to lookout for from my experience.

Change your fuel filter every single oil change. The injectors are way too sensitive on the LB7 engine and any little bit of dirt will trash them. To replace all of them is usually between $3000 to $4000. Fuel filters are much cheaper. Also, if the do go out, call GM they extended the warranty on these injectors to 7 years/200,000 miles and have been known to reimburse past that.

Pump rub in the transfer case is possible, you will have no idea if yours is an issue until it is too late or if you open it up and have a look.

If you start feeling like the transmission is not shifting right whenever you put it into gear, then look at replacing the Neutral Safety Back-up switch on the side of the transmission for $80. They can go bad.

If the O/D button does not work it is more than likely and broken wire in the column where the gear shifter pivots. This happened on mine.

Injector cups can fail. It will look a lot like the same symptoms as head gaskets which will pressurize your cooling system and puke coolant. This can be tested for if the issue does present itself.

Make sure you have it looked at up in the air before you buy 100%! As above they either need, or have had fuel lines and brake lines replaced. Metal retainers at the top of the tanks rot out and piss fuel. Cab corners, rocker panels, and lowers of the doors need a good inspection or it will cost you some coin! Love the trucks though, front seats are just as comfortable as a Lazyboy

Re. the Benz E320 CDI 2006 - I've got 170K on mine and am getting the best mileage ever, and its always been good. Power feels the same but that's just a guess. My truck is a 2005 Dodge and I only have 65K on it, the Cummins is barely broken in.

[QUOTE=billpor930;4525487]Re. the Benz E320 CDI 2006

Fellow Benz owner -- yes, I can't brag enough about how it is running. It seems every time we go somewhere it gets better and better- I tease my wife and tell her -- they get this way right before they blow up! I'm really hoping that this GMC that I'll look at is everything the pics and documentation show -

only a couple more weeks till the boat splash season!!!

Be safe

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