Jump to content

Just bought first GM truck, looking for some advice


Recommended Posts

Just bought a 2005 GMC 3500 gas 4x4 dump truck. Right now it has a leaking fuel line - hoping I can get this replacement line from GM for a cab and chassis truck. Overall, its not bad...has 125k miles. The 6.0L seems pretty simple and long lived. What transmission does this truck have? 4L80?

 

The instrument cluster has flickering backlighting and sometimes the odometer displays and sometimes it doesn't. If you tap it, it comes back on. Bad connection? If I put a new cluster in, will the mileage keep? Or will it go to whatever the new cluster has?

 

The truck appears to have "dual zone" temp controls but the sliders in the middle are broken off. Can these be replaced or do I need a new HVAC head unit?

 

I'm sure I'll have more questions, but thanks in advance.

Link to comment
Share on other sites

4l80e

 

make sure you get the right line, as you've got a cab&chassis.  you might also want to check that you have good fuel pressure at the rail (right around 60 psi, both at idle and when the engine is at a higher rpm, like 3000).  also check how the top of the rear tank (behind the rear axle) looks, as mine had collected dirt and water over the years and the top of the fuel pump completely rusted through and was dropping crap into the gas...and the fuel filters that are part of the fuel pumps (both front and rear) aren't that good at actually filtering...you might consider plumbing an inline fuel filter between the front tank and the engine while you are replacing fuel lines.  The earlier models ('99-'03 GMT-800s) had an inline filter and bracket that works nice.

 

also check your brake lines, they rust bad where the 4 lines from the front end run to the abs unit under the cab along the frame rail as well as above the front fuel tank along the frame rail.  gm still sells new pre-bent nylon covered steel lines, but they don't include the 2 lines across the rear axle, various 3rd parties sell prebent stainless lines that include the rear axle lines.

 

-the ip is known to fail.  replacing it with another one uses the mileage from the new one (mileage is stored in the IP itself), so you'd need the dealer to transfer it

 

-the standard manual dual-zone I would suggest just getting another one from a junkyard if the sliders are busted.  they can't really be fixed.  main fixable thing with them is when the lights go out, but they are still a hassle as the lights are soldered down.

 

  • Like 1
Link to comment
Share on other sites

Well I can answer one of your questions. Are you good with a soldering iron? You can fix your instrument cluster pretty easily. They don't sell new ones anymore (you could get a rebuilt one from gm for $500) and unfortunately the mileage is stored in the cluster. Most people will send them to someone through eBay to have them repaired costing $150-200 and a few days turnaround. You can buy a kit online to rebuild it including lights and new stepper motors, which will eventually also fail if you haven't replaced them yet.

 

In my case, like you the mileage sometimes didn't show. It progressed to the point where it would never power up. I took it apart and took the board out into the truck and plugged it in. Using something nonconductive (I used an eraser) I started lightly touching different parts on the board itself. There were 2 little resistors, as soon as I touched them the whole thing powered up. I added a few drops of solder and it has been good as new since. 

 

Here's a video showing what I am talking about. In my case it was the same exact 2 resistors in this video, and others in the comments said the same thing. You can save a lot of money doing this one yourself..

 

Link to comment
Share on other sites

Thanks guys, really appreciate the advice. Both fuel tanks are plastic, right? The front one is for sure.

 

How do the tanks work? Does the rear tank automatically pump to the front tank? I don't see a switch for the aux tank. With the leak, the truck has to crank a bunch extra after it sits awhile to start. Once running, it runs fine.

 

The brake lines have been replaced once. I'm simply going to replace probably all of them which are bad.

Link to comment
Share on other sites

  • 1 month later...

Here's a little bit of a follow up. I haven't had a ton of time to work on the truck, so it's registered but not inspected. I've replaced upper and lower ball joints on the front, plus both outer tie rod ends. I've replaced the brake rotors, calipers, and pads at all four wheels. I can't believe GM makes you pound the studs out on the rear wheels to separate the rotor from the hub flange. That wasn't fun. I'm in the process of replacing brake and fuel lines. I have the OEM front fuel line, plus two OEM straps for the front tank. I bought a Dorman complete stainless steel brake line kit, but the lines that go across the rear axle are too long. I'm going to take it back today and probably just buy the factory GM kit. It's pretty tough getting at the lines (fuel and brake) that go under the cab. I also can't believe GM put the ABS unit on the frame rail towards the back of the cab. Why? So it can collect salt and mud? I've never seen an ABS unit not mounted under the hood somewhere near the master cylinder. Oh well. Oh yeah, and four new cab mounts that the rubber has collapsed on. Have the OEM parts, still need to do the work. Have 6 quarts of Mobil Super 5w30 and a Delco P46E filter waiting. Plus a muffler! Yeah, it seems like this truck needs everything. But its been a little fun working on it, anyway.

  • Like 1
Link to comment
Share on other sites

One of the computers in the truck (probably the BCM) monitors the fuel levels of both tanks, and automatically pumps fuel from the rear tank to the front tank as necessary.  I've read on other forums that it tries to keep the rear tank at approximately the same level as the front tank, but I don't know that for sure.  The fuel gauge indicates how full both tanks are.

 

Dorman's set probably isn't for a cab&chassis (rear axle is narrower than both the SRW and DRW trucks with pickup beds).

 

The GM OEM ones are nylon-coated steel, and don't come with the lines for the rear axle, and GM doesn't sell those lines.  You basically have to fabricate it yourself.

Link to comment
Share on other sites

The Dorman set specifically said it was for a cab and chassis, but it clearly wasn't. Anyway, I already got the GM set. The rear lines should be easy to make. Getting the original fuel lines out is very challenging, especially without a lift. You have to lay across the top of the engine to get to the rear vapor line which sits low down below the cylinder head near the bell housing. Once that and the actual fuel line are disconnected up top, there is a metal clip bolted to a bracket off the engine. I got the nut off by working both on top of the engine and laying below the truck. Next, there are a series of clips holding the fuel and vapor lines together than bolt through the frame rail. Mine were all very rusty, but every single bolt came out. I found out the ABS modulator needs to be removed from the frame (three very rusty bolts but again it came off) in order for the fuel lines to clear. Unfortunately, the fuel tank also needs to be dropped in order for the lines to be removed (they bend around the inside of the tank and frame). That's OK since I planned on replacing the tank straps anyway. The last obstacle is where the vapor line goes into the charcoal canister. The canister is located below the cab ahead of the tank and kind of above a cross member. The hose is plastic at this point with a plastic tab connector. The lower tab can be opened with a long screwdriver but the upper one cannot be accessed. I just carefully broke the original connector off since the new line has a new connector and it will just snap in. So I was able to get the original fuel lines off the truck but still have to install the new ones once the weather improves (another inch or two of snow and sleet on the ground from last night).

 

I also got a new muffler to replace the original which has a hole in the side. This one is a Walker with dual three-inch inlets and a single 3" outlet. Most parts stores carry it for around $250 to as low as $190 but I was able to buy it from Summit Racing with free shipping for $155. This muffler is a little shorter than the original and will take some slight modification to make it work, but it will work. GM wants $1300 for an OEM muffler.

 

I will update further as this project moves along...

Link to comment
Share on other sites

Would be a good time to do the rear brake line with the tank down...

 

Or if you have boards as a flatbed on it, removing the boards also works really good.  For my truck, the wood was screwed to the deck, so it was a pain to remove (basically had to cut up the boards, then cut off the screws).  I switched to clamping new boards to the deck, and now it's just a couple minutes to undo the clamps and pull the boards out to work inside the frame rails...made doing my fuel pumps and brake lines much easier.

Edited by davester
Link to comment
Share on other sites

Davester - mine is a dump which I can raise, so that part is very nice. I will replace the long line that goes to the back while the tank is down.

 

The weather is decent today (well, low 40's but not raining or snowing) so I'll take a half-day at my regular job and go home and work on this. Plan is to get the new fuel line installed along with at least the one brake line, then get the tank raised again and install the new tank straps.

 

I have also received a new climate control panel (the temp sliders are completely busted off on mine) and a new headlight switch to try and fix the flickering dash lights. Likely going to order a new instrument cluster with correct miles and hours programmed, since mine has a chunk out of the plastic, at least one gauge doesn't work, half of it doesn't light up, etc...but its $310. Pretty pricey.

Link to comment
Share on other sites

Well, I'd say changing fuel lines laying on your back with the truck on the ground is one of the most difficult things I've ever done. Having a lift might be a little easier, but still would be difficult. With the ABS modulator unbolted, and the tank down, you can route the lines along the frame and get them in place. But you cannot get the lines to "turn the corner" and slide up in the transmission tunnel between the firewall, bell housing, and back of engine. I ended up removing all the factory installed clips that hold the lines together on the replacement. Then I was able to run each line separately and then re-clip them. I still have about 3 clips remaining before I called it a day last night, but I'll be able to do them. I hooked up the fuel and vapor lines, primed the truck a few times, and she fired right up with no leaks.

 

With the tank still lowered, I'll run the long brake line from the ABS modulator to the rear axle, then raise the tank and install the two new tank straps. Definitely making some progress. Still need to do the following for it to pass inspection:

 

-Finish replacing all brake lines

-Install two new tires (I believe all the steel rims are interchangeable from front to back)

-Replace all four cab mount rubber cushions (8 cushions)

-Install slip on rocker on driver's side and do a little bit of bodywork there

-Figure out why some of the rear lighting (and cab clearance lamps) don't work

-Replace the muffler

 

My goal is to have the vehicle available for next Saturday. Hopefully everything goes smoothly and the weather cooperates.

 

I also installed the new (remanufactured Dorman) climate control panel and a new headlight switch. The headlight switch solved the flickering dash lights and as a bonus now the interior dome lamp works. The only downside is both the climate module and headlight switch are backlit in standard green and do not match the whitish-yellow factory lighting of the radio and cluster.

Link to comment
Share on other sites

It was raining and snowing on and off yesterday, so only did minimal work. Ended up ordering a replacement instrument cluster from Best Pixel Repair. On my existing cluster, someone had broken the plexiglass cover in one place, the oil pressure gauge did not work, and half of the gauges did not light up. Worst of all, the odometer display did not light up and would only intermittently work. I was able to get it to work long enough display truck mileage and engine hours. Best Pixel Repair has you fill out an odometer statement affidavit and they program the replacement cluster to your VIN, mileage, and engine hours. New one all completed should be in my hands next Tuesday.

 

I also removed the two worst tires, which for some reason were the duals on the passenger rear. I removed them and installed two brand new Sumitomo Encounter A/T tires in 10-ply E-range. However, what I'm doing is installing the new tires on the front, and the original, good condition front tires to the rear. Since the rims will now be reversed to fit on the front, they looked like crap. I used an engine degreaser on them first, then power washed them, dried them, taped them off, and put 5 coats of silver wheel paint on them. They look much better.

 

I also noticed the rubber pads were missing from both the brake and parking brake pedals...so I ordered new pads from Dorman.

 

Today, the weather should be OK and I'll take a half day from regular work so I can work on the truck. Goal is going to be to run the long brake line to the rear, finish the last three fuel line clips, reinstall the tank and new straps, reinstall the front driveshaft, reinstall the fuel filler and rear tank wiring...and if there is any time left, either work on the front brake lines or cut the stock muffler off and work on installing the new one.

 

Here's a pic of the re-painted rims:

IMG_3802.jpg

Link to comment
Share on other sites

Just another update:

Finished running all brake lines except the two short ones across the rear axle, because you have to make those yourself. However, I measured and cut the new lines to proper length. Had a buddy bring his flaring kit to work this morning and already have the new fittings on. So tonight I'll install these easy lines, then add fluid and bleed the whole system.

 

I got the rest of the fuel line clips on except for the final one up at the motor. Will finish that tonight as well. I was able to get the fuel tank re-installed with two new straps and the vent / vapor lines snapped back into their appropriate places. BUT...since I already had the fuel line connected to the pump, the neck on the pump bent a little and now their is a hairline crack...LEAK...at the neck coming up out of the pump. I'm disappointed...will try an epoxy but I doubt I'll have much luck. Also reinstalled the fuel filler neck / vent, the lines coming from the rear tank, and did a better job routing the wiring to the back then whomever was in their before me.

 

Also painted the two rear wheels to match the front, and reinstalled the front driveshaft. Tonight after work my plan is to install the two short axle brake lines, bleed the whole system, finish that last fuel line clip, epoxy the fuel pump neck, and maybe get the new muffler installed. After that, it's body work and sorting out the lighting. Tomorrow the new instrument cluster comes in and I'll reinstall the dash trim.

Link to comment
Share on other sites

Adding another update, if anyone cares. Finished installing the rear axle "home-made" brake lines, added fluid, and bled the brakes. The pedal feels spongy, but stops the truck. Since I've never owned a GM truck before, and this one had a split brake line when I bought it...I really don't know what it should feel like.

 

The muffler I bought really isn't designed for this truck. The dual inlets are the right size, but spaced much closer together than the muffler coming off. I've pulled the pipes together enough to make it work, and the muffler is clamped on and not leaking, but it is less than ideal.

 

The power steering pump is howling a bit. I'm hoping its just low on fluid. It looks like a lot of gunky oil on one of the lines coming off the pump. What are you supposed to put in the pump? The manual says "GM power steering fluid" whatever that is.

 

Now I've got to figure out how to fix some electrical issues. I have rear tail lights and backup lights, but no rear turn signals or rear four ways. I also have no cab clearance lights; otherwise all exterior lights work.

Link to comment
Share on other sites

Regular power steering fluid is fine.

 

You may want to flush the power steering system, as it is also used to boost your brake system (instead of a vacuum booster).  People think (including me, having done this) that flushing the system gives a little firmer brake pedal.

 

You might also need to bleed the ABS controller.  The proper way to do this requires something like a tech ii or Autogenuity with GM enhancement or something similar (they can command the computer to pulse the abs system a special way), then you bleed all 4 corners again.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.




×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.