'04 Ram 4wd 5.7 hemi 545RFE auto.

So over this weekend I did a road trip with the '04 1500 to pickup some stuff and haul back in the trailer. A couple of new quirks revealed themselves. I will throw them out here and see what you all think for ideas of what the problems may be.

First up, rear brakes and ABS. It has been very cold for months and roads here are pretty much the "compact snow with slippery sections" with alot of firm ice sheets. I have noticed that the rear brakes on the Ram are locking up with no ABS response, no clickity clickity buzz buzz. It can be unnerving as the rear tires locked can turn into a dangerous situation really fast. It seems like the rear tires lock up before the fronts begin to engage. There is no ABS light or any other type indicator alarm. Other than the handling, the truck thinks itself to be fine. This has never been a problem before, this is a new issue. I will not let anyone else in the family drive the truck until I've got this figured and fixed. Too dangerous. I am going to pull the tires off next weekend to check the rear for binding callipers, pad wear, and for anything obvious. Have you any ideas of what else I should check or look for? Is there a way to adjust front-rear brake pressure?

Next, driveline humming/whirring. I have noticed when running empty, normal driving, a new sound at 40+ mph. It is a humming. Like beginning signs of a bearing nearing the end. It is not loud or harsh (yet). Most people would not notice it, however I am in tune with my truck and know when something is different. The sound is similar to that of AT tires on the highway. I am sure it is not the tires because the sound is there whether I have the summer set or winter set of tires on. It is a separate sound. It seems to be coming from under the cab, mid point. Does it in 2wd and 4wd. No change. I know the CV on the front drive shaft is just about done, but still seems fine for now. As a test, I removed the front shaft and ran like that for a bit. No change, the humming/whirring is still there. Therefore it is not the tires or the front shaft. What else could it be? I was considering the rear drive shaft u-joints and they are nearing due, but this sound too much like a humming than the typical squeaky chirping and vibrations of a u-joint.

Finally, towing stuff. When pulling the trailer (7000+lbs) I noticed that humming sound to be a bit louder. I also noticed on heavy pulling, up hill or accelerating, there to be a slight but steady shudder. This is new, never had this before when pulling the same trailer and weight. I suppose it could be one of the four trailer tires as one was flat and needed to be topped when I picked up the trailer. However, it only does it when the truck is under heavier pull load. It is similar to the feel when one cylinder is not sparking, but there are no codes or other indications of such a problem.

Things I have considered;
- rear drive shaft u-joints. The mileage on it has me thinking it is time to replace, yet there are no visual or check with pry-bar signs of needing to. Joints are tight and smooth. This may be the shudders but will not explain the humming.
- front axle CV's. (not drive shaft). Were replaced about 60k ago. I see signs of light grease leakage from boot clamps. Boots are otherwise fine.
- electrical. Truck is due for spark plug change-out. There are no codes or indications of misfire etc. Engine runs super smooth and reliable.
- differentials. I was just recently in both the front and back doing oil changes. The sound was there before the oil change. Still there afterwards. The rear drained oil was fine, clean, no metal. The front had some metal, really fine particles.
- Tcase, recent oil change. The oil was fine, clean, no metal.
- Transmission, recent oil change. The oil and magnet in the pan was fine, clean, no metal.
- bleeding the brakes, fluid change out, all lines, done.

......... interested in your ideas.

 

2 or 4 wheel abs on your truck?

I am not real familiar with the 3rd gens, so, some questions back at ya.

Do you know where the PCM gets its vehicle speed signal from? If it ISN'T the rear wheel speed sensor, I would be tempted to look at that.... also, is it just one rear wheel, or are both locking up?

Humming: Likely a bearing going bad. May have to wait for it to get worse before you can isolate it. Probably wouldn't hurt to check t-case fluid.

Change the plugs, and whatever other maintenance you are due for, see if the shudder goes away.

 

Good questions.
- Not sure on the 2 vs 4 wheel abc. There is an abs plug on only one of the front discs, driver side. Then there are the speed sensors on the Tcase and one at the rear diff. There are no sensors on the rear wheel themselves.
- The rear lockup with no abs action occurs in 4wd for sure. I have not tried it in 2wd, as am in 4wd pretty much full time nowadays due to the roads. I will have to test this in 2wd. Btw, this is occurring on ice at slow speeds in around town at stop lights and intersections. Annoying but manageable for now.

Wondering if the following scenario may be possible: ... when in 4wd with one rear wheel brake locking up the abs does not detect as the front wheels and the rear driveshaft are tied together by the Tcase. The front wheels are not slipping, full traction, in this scenario. It may be that one rear wheel is locking by the brake and the other wheel is forced to turn in overspeed (by the diff gearing) as the drive shaft is still turning normal speed from everything else tied thru the tcase to the front wheels. On glare ice, I can see how this could occur with very little strain on the drive train. There is definitely a both rear wheels skidding scenario going on. I cannot tell from the driver's seat or the skid marks if both rears are stopped or one stopped and the other is over-spinning as described. More to this in a few days when I get time to pull the rear wheels off and inspect the callipers and discs. ...... The more I think about this, am suspecting now that I have one (or both) rear brake calliper needing attention and may even have a second issue with the limited slip not engaging properly or is somehow weak.

 

Ok, likely only RWAL, since you don't have sensors on both front wheels.

How do the rear brakes look? (disc, I assume?)

 

Yes, disc brakes all way 'round, all four. The rear discs look fine and near perfect, with the wheels on. No concerns about the discs, nothing obvious on front or back sides of the discs in terms of wear pattern. I will update here after I've had time to take the wheels off and check the callipers and pads. Am hoping that I find a stuck or sticky calliper that just needs cleanup and lubrication of the guide pins.

 

The shudder under load could very well be U-joints. My truck has a center carrier bearing too which I replaced them all when I was getting shudder when towing.
Mine was worse on start up at low speed when towing.