Drivetrain 'Shudder' when backing up and turning. Rear Suspension, Differential, Transmission or what ?

[Brakelate]

There seem to be a lot of rear differential issues being experienced and discussed here.

Not finding anything precisely like what I am experiencing, what does everybody else think ?

I am wanting to get it diagnosed and repaired while still under warranty, though I am running out of time and miles on my factory powertrain warranty. Plus, it seems to be getting gradually worse, and I absolutely cannot have it fail where I live (over two and a half hours from a dealership) , or worse, when out in the middle of nowhere, off-highway or at the worst possible time and location. Out here that could be deadly.

Truck: 2018 Ram Power Wagon, drivetrain completely stock, with exception of a HD Thuren Rear Track Bar.
49k miles, with all but the last 9k on stock tire size. Currently on 35's.

Issue: Truck started to shudder when backing up while turning, as if backing out of a driveway or angled parking spot. Travelling slow, but under power. Not when coasting backward, in neutral. It has a cadence that is similar to what I imagine if the Ring and Pinion gears were gnashing or had slop in them. Will not do it in a straight line and didn't do it going forward. But that has changed, and just now has begun doing it for the first few feet as I roll out from a stop in a straight line.

My inspection could find no loose suspension components, engine or trans mounts. The fluids in the Trans and Transfer Case are perfect. Fluid in both Diffs are good, and I just changed out the rear fluid, with only a minimal amount of typical fine metal 'fuzz' on the rear plug magnet. Rear gears seem to have a nice, consistent wear pattern, though that is hard to tell just from looking with only the cover off. I am leaning towards it being a Rear Ring and Pinion Gear issue, or a Transmission problem.

Dealership found nothing, and I got the dreaded "Could Not Replicate" response. Though the dealership in Flagstaff, AZ wanted to charge me $125.oo for the 'Inspection' of a Non-Warranty item, despite it being there initially for the Front Steering Recall Repair. The next closest dealership (also over 2.5 Hrs away) is in St. George, Utah. I guess I will try them next, to continue to document my complaint, if nothing else.

Anyone experience a similar issue, or care to throw a possible cause / cure at me ?

Thanks in Advance !

 

[4xdad]

Brakes dragging

 

[Brakelate]

You know... funny you should say that! I totally forgot the only other change from OEM components made to the truck was the installation of Slotted Brake Discs and the addition of EBC "Yellowstuff" Brake Pads at all Four corners some time back.

Very, very interesting suggestion. I guess the quickest way to try and check that theory would be to drive it to a High Pressure Wash Station and thoroughly spray down the rear brakes, then immediately go and back it out of the stall and around the lot and see if there is any notable change.

There is a wash 65 miles from me (yes, I do live in the sticks). It is the perfect distance to have everything all warmed up from the drive over, and be able to do an immediate "before and after" comparison. I shall do that today! If you are correct 4Xdad, I will owe you big time!

Just for kicks, these are the parts that were swapped on. It would make total sense for a higher performance set of rotors and more aggressive pads to slightly stick and 'chatter'. Especially when 'warmed up'. Though I have never before in my life experienced such a thing, after many different vehicles, brake swaps and track days of all sorts and no drag can be felt from the driver seat or is revealing itself with any inability to seemingly roll freely on a slight grade or in reduced MPG. But, who knows, with such a heavy truck, I suppose it is possible.

 

[4xdad]

The inturnal park brakes slightly to tight

 

[mtnrider]

If it only does it when turning it's more likely an axle u-joint. Brakes are going to drag no matter what the orientation of the wheel is. Jack the front of the truck up, turn the wheels all the way to one side and spin the tires. If they bind or try to straighten the wheel out you have found the problem.

You could also jack the rear up and spin the tires to see if you have significant brake drag but I don't suspect that is the issue.

.

 

[buckeyexx]

You say you just changed the fluid in the rear end. I suggest adding some lubegaurd limited slip friction modifier to it. I know it says its not required for these rear ends but I had a similar issue where mine was doing it going forward and reverse immediately after I had changed the fluid in it. After doing some digging around on the internet I came across some other folks having the same issue and suggested putting the friction modifier in it. I added it to my my gears and low and behold it went away. The good thing is that it wont hurt anything even if its not the problem. Can get it at any auto parts store. Its worth a shot.

 

[62Blazer]

You say you just changed the fluid in the rear end. I suggest adding some lubegaurd limited slip friction modifier to it. I know it says its not required for these rear ends but I had a similar issue where mines was doing it going forward and reverse immediately after I had changed the fluid in it. After doing some digging around on the internet I came across some other folks having the same issue and suggested putting the friction modifier in it. I added it to my my gears and low and behold it went away. The good thing is that it wont hurt anything even if its not the problem. Can get it at any auto parts store. Its worth a shot.

But there is no "friction" going on in the rear axle. It's a helical gear limited slip and not a clutch type limited slip that relies on friction between the clutches and thus needs the "friction" modifier????

 

[Joshua Clark]

Im in agreeance with MtnRider.... Check your Ujoints bud. If you dont find one bad in one of your axles... check the driveshaft ujoints too. Brakes, trans, ring/pinion gear would all give issue in a straight line as well as when turning. One or more of your Ujoints is most likely gonna be your culprit here.

 

[buckeyexx]

But there is no "friction" going on in the rear axle. It's a helical gear limited slip and not a clutch type limited slip that relies on friction between the clutches and thus needs the "friction" modifier????

I agree and couldn't tell you the reason as to why it helped. Im not saying it is a fix for this situation but it did do away with my shutter or vibration I had. It has for what ever reason helped others too and its the reason I even mention it. It made zero since to me why it helped but I also knew it wasnt going to hurt anything so for the 10 bucks or so spent it was worth a try.

 

[22hemi13]

Wish I could hear if it’s making noise. My truck did this too “video somewhere” like you. In reverse not forwards. I searched and checked everythinggggg. Found it was rear lsd chattering some weirdly enough. I put fresh fluid in and it’s been fine. When it was doing it I could feel it and hear it. I removed driveshafts to figure out it was most def 100% in the rear. Just a thought with checking out.

 

[Brakelate]

Still scratching my head and searching for the cause. Wasn't brake drag.

I can almost (?) feel it sort of catching and clunking in the front end now. Does it hard enough that the shudder sent through the truck can now be visible in the form of a vibration of the exterior rear view mirrors now.

Original owner, truck only has 49k on it now. I just don't want an annoying thing to turn in to a major component failure out in the sticks, at the most inopportune time. I REALLY want to get it figured out before it runs out of the Powertrain Warranty, which will be in 11k miles / 4 months.

I don't mind the cost nor effort to install some super LSD friction modifier, even if it is just for giggles. I will also get the truck on jack stands and rotate the wheels individually, then turn the fronts full lock in each direction and spin those again slowly and see if there is any unusual drag, noise or rough spots in the rotation.

 

[Scottly]

My guess/bet is the front drive shaft joint where it comes out of the transfer case.

 

[4xdad]

Does it do it all the time or just under power or deceleration turn going straight over bumps. Does anything thing set it off

 

[4xdad]

When it happens try to slow it down or speed it up if you can then try to see if it’s in the same spot all the time sorry about the last post I didn’t read everything

 

[4xdad]

Then you could see if it happens in the same spot all the time

 

[olyelr]

Bad front axle u-joint? Seems way premature, but definitely check.

 

[Brakelate]

This seems very premature for a one-owner (non-abused) truck with such low miles.

The only thing consistent is that it only does it after driving ten miles or more at freeway speeds.

The front axle u-joints 'look' good, not that much can be determined by simply looking at them. But, there is no obvious damage, metal flakes, loss or splattering of lube, etc.
And the hard to find front driveshaft has been lubricated with the needle fitting, etc.

I do need to get it up off the ground and start doing some aggressive shaking, wiggling and spinning to see if there is any noticeable spots where it drags, or has abnormal freeplay.

I may also find a big empty parking lot where I could possibly make turns after mounting my GoPro in different spots taking a close look at various driveline and suspension components at all four corners. Then I can do a lot of tight figure 8 turns while slowly backing up. Then I could see if I could see any strange excessive play while also listening for any unusual noises.

 

[4xdad]

That sounds like a good idea

 

[danenus]

Process of elimination. Does your power wagon have a transfer case with a drive shaft to the front axle? Disconnect and remove the drive shaft and see if problem persists. If not. Ya got maybe a bad transfer case. If it does persists, ya got wonky ujoints at a wheel

 

[olyelr]

Process of elimination. Does your power wagon have a transfer case with a drive shaft to the front axle? Disconnect and remove the drive shaft and see if problem persists. If not. Ya got maybe a bad transfer case. If it does persists, ya got wonky ujoints at a wheel

Does a power wagon have a driveshaft to the front axle lmao