The Diesel Stop banner
1 - 9 of 9 Posts

·
Registered
Joined
·
60 Posts
Discussion Starter · #1 ·
Couple of related issues possibly, with a 3500LB truck camper in the bed between 58-62 MPH I get a loud hum not present above or below that speed (OD on/off makes no difference), and at dead stop take off I get a shimmy sort of shudder (feels like the u-joints in the driveline are binding slightly).

E40D completely rebuilt by quality shop a month ago with all updates, shift kits, and TC ($4300 ouch but it was time), and just had all 3 driveline U-joints including carrier bearing with balancing done (assumed it was driveline for the take off shudder). no change after driveline work, and the 58-62 noise was there before Tranny rebuild.

Wondering how to troubleshoot this as it's only present with the camper loaded up, what kind of shop would you take it to for them to hear/feel it, maybe a Differential rebuilder? will they be able to duplicate without the camper load, as it goes away with it off?

Thanks for any thoughts in advance.
 

·
Registered
Joined
·
2,374 Posts
What if you accelerate above 62 MPH, then shift to neutral and coast down? Do you get the noise/vibration then? That would rule out/in the engine/tranny as a factor.

4x4 or 2WD? How far does the bed drop with the camper loaded? Maybe something's happening with driveline angles :dunno: .

Have you tried rotating the tires, to rule out/in tire imbalance? You wouldn't expect that to be dependent on weight load, but you never know.
 

·
Registered
Joined
·
60 Posts
Discussion Starter · #3 ·
I'll try the neutral test, however almost everything that would be spinning, will still be I think, Tranny was just gone through completely and it did it before that. I'm thinking maybe transfer case, and it's more pronounced with the drivetrain "loaded" vs. coasting back through that range.

Camper is heavy but there is still some suspension travel so I would (probably stupidly) assume that with new U-joints any angles less than bottoming out should be OK (4X4 capable in 2 Hi).

I don't think it's tires as it's "felt" up through the cab, but something else to check, Thanks.
 

·
Registered
Joined
·
11,887 Posts
They didn't accidently assemble the driveline out of phase, did they? (If it's possible on yours)
 

·
Registered
Joined
·
60 Posts
Discussion Starter · #5 ·
Nope, first thing he showed me when I came to pick it up (old Lou), I think he was stunned I even knew what he was talking about, (learned it from you guys). It was happening before I had the driveline serviced, had it gone through since everything was original, the carrier bearing was shot, and it needed a transfer case output seal, I was hoping it would also clear the standing start slight wobble issue that felt like u-joints but obviously was not. I want to be bullet proof with this camper.
 

·
Registered
Joined
·
1,847 Posts
I would look at the transfer case. Check the output shaft, and maybe take the rear drive line off and run it in 4 high to see if the vibration is still there. If it is then you'll need to pull the transfer case, and check the input shaft. the input shaft to the rear differential might be causing that, as well as axle bearings or carrier bearings in the differential. By running in 4 high, with the rear drive line removed, you eliminate all but maybe the axle bearings, since the rear wouldn't be under a load.
 

·
Registered
Joined
·
3,553 Posts
^^^^^ That would be a good shot at it.
With the extra weight it could very well be the axle bearings or even the diff carrier bearings.

The rear drive line shouldn't be effected, it would be more straight, not more angle, but the slip joint may be effected if it's bottoming out.

You have an F250. What do you mean by F350 rolling gear? Was the front & rear changed to a dually?
 

·
Registered
Joined
·
60 Posts
Discussion Starter · #8 ·
I will try the driveline drop, interesting thought for the take off wobble, not sure I want to run up to freeway speeds in that setup, seems like a lot of weight also for just the front diff/axles to be pulling? The signature talk regarding rolling gear I'll change as it's misleading but was in regards to bigger brake sub assemblies as I discovered; rotors/single wheel drums/pistons/calipers are all F-350 (non dually). I'm not sure why but perhaps the original owner ordered an upgraded brake package if that was an option.

Old Lou the driveline guy is also a Differential rebuilder, since I didn't mention it specifically I doubt he would have felt anything funny in the Diff as he was putting my driveline back in, especially since it takes weight to make it happen (versus a growling diff).

Final question is regarding the transfer case, I'll ask Lou but do Differential guys do Transfer case work typically as well, either end done correctly is beyond me.
 

·
Registered
Joined
·
11,887 Posts
I used to have the pleasure of fighting a lot of those high frequency hums/vibrations. They can be a royal pain in the rear. One of the first and easiest things to eliminate would be a bad rear wheel bearing. With the back axle up on jack stands and engine idling and truck in gear, use a stethoscope at the rear brake backing plate while yanking on the opposite hand brake cable to stop that opposite side wheel from spinning. Then reverse the procedure for the other side. (of course with limited slip they'll both be spinning) If one side is way louder than the other, you've got a bad wheel bearing. By your description, it doesn't sound like a differential problem, any component goes bad in a rear end and you get a howl or whine, not a hum type vibration. I'm sure your driveline guy mentioned that. Secondly, I'd dream up something to use as a shim, maybe an inch thick and slip it between the driveshaft carrier bearing mount and the crossmember, then go for a test drive and see if the hum is better or worse. Sure sounds like it's driveshaft related to me.
will they be able to duplicate without the camper load, as it goes away with it off?
That's generally the problem, unless the engine and driveline are pulling hard you usually can't duplicate the hum/vibration in a shop stall.
 
1 - 9 of 9 Posts
Top