quote:

Originally posted by bigcat:
I can hear and feel the knocking noise from the the area standing over the differential.

Could it be a loose shock and or mount bouncing around?

Bill N.Y.

"....It also goes away when applying brakes."
-bigcat

"I wonder if you have a bad tooth in the differential or a bad pinion bearing..."
-Rusty

If the problem goes away during the coasting-and-then-braking phase, but exists under low speed, heavy-loading of the driveshaft phase, wouldn't this support the Rusty theory of problems in the differential? Seems like problems with the gear-mesh would be noisy under load and quiet when unloaded......

quote:

Originally posted by Lee:
"....It also goes away when applying brakes."
-bigcat

"I wonder if you have a bad tooth in the differential or a bad pinion bearing..."
-Rusty

If the problem goes away during the coasting-and-then-braking phase, but exists under low speed, heavy-loading of the driveshaft phase, wouldn't this support the Rusty theory of problems in the differential? Seems like problems with the gear-mesh would be noisy under load and quiet when unloaded......

"You talkin' to me? You talkin' to me?..." Robert De Niro, Taxi Driver

Total agreement there... let's face it though, he's not going to diagnose that for himself. He would need to take it to someone for additional diagnosis. If he couldn't locate this after checking the U-joints out he's now almost at the stage of professional help.

I'm not standing there listening to his noise and I'm also trying to gauge how far he's gone into his own diagnosis by asking these questions. I typed that he should jack it up and check but unless there's a load factor on it the noise might go away while lifted up.

I would drain out the fluid to see what came out after looking over suspension parts. While under a load condition the rear end flexes, while the rear is trying to bite into the pavement other factors besides the rear differential are at play. The suspension and shocks now have a forward load bearing twist/push to it. Loose or damaged suspension parts might make a noise that comes and goes with a torque factor on these items.

As stated earlier:
"The more information about your coach that you can give the better off I or someone else might be able to answer your questions. No detail is too small.

Additional items to check would be leaf springs, hangers, mounts, torque arms, radius rods, tires, rims and even exhaust pipes. Before I tell someone to go take it to there local garage I'd like to see him check the basics first.

Good luck to you bigbear and keep us informed.

Bill N.Y.

Bill,

This is one of those times when I chose to pontificate without having a clue what I was talking about.....

I do recall, as a poorly coordinated 14 year old, "experimenting" with the 2-speed axle on an over-loaded farm truck....It made sounds & had symptoms as described here. Pulling the rear diff cover revealed several ring gear teeth laying in the bottom of the pig......

That totally sums-up my expertise here

Yes, the load on the drivetrain is different if it is up on jacks. However, lightly applying the brakes while on jacks simulates a driving load. Applying the brakes while on the road loads the drivetrain a little differently.

BTW, even though I suggested listening with a stethoscope, I have found it devilishly difficult to locate problems that way myself. It is either my hearing or the peculiarities of sound transmission in axle housings. In a recent case, I ended up finding a bad axle bearing the old fashioned way....by removing it and feeling it with my hands.

quote:

Originally posted by Lee:
Pulling the rear diff cover revealed several ring gear teeth laying in the bottom of the pig....

Most of these coaches more likely then not would require one to remove the rear end if you can't take the cover off the back.

Looking under your coach you will probably see the bolts that hold the rear end in on the same side as the input/pinion shaft.

My 72 Nova requires me to remove a rear axle cover. Great if you want to peek inside the rear without pulling it out.

Most other rears requires the front bolts be removed to pull the rear to inspect it. Everthing comes out and there's no inspection cover to look thru.

quote:

Originally posted by Lee:
That totally sums-up my expertise here

Don't sell yourself short!

Bill N.Y.

I suspect that Breakaway has a Dana (80, mebbe), so the cover is on the back of the differential, which is actually the front of the differential, being it's backwards.

I'm going to replace the cover on mine with this, first chance I get.

Also going to backfit the transmission pan.

quote:

Originally posted by Rusty:
I suspect that Breakaway has a Dana...

Nice looking products Rusty. I looked for a C-6 tranny pan for myself but didn't see it. I figured the next time around I would replace the tranny pan with a deep sump pan and get one with a seperate drain and temp sending unit port.

Bill N.Y.

How about this? It even has a drain plug (How retro is that? But of course it's the almost perfect spot for a tranny gauge).

Thankyou Bill , Rusty & others for your posts. I did find the grease serts after removing and cleaning the shaft. I did replace the u joints which did not really need replaced. I agree with you guys that the problem looks like it might be the differential. I'm going to jack it up today or tomorrow and run it and if the noise is present I will be able to locate it. I was not able to find anything loose or broken such as shocks or any parts associated with the rear end. I guess I will probably end up taking it to someone to diagnose it if the noise goes away under no load. I suspected something wrong with the differential from the start.

quote:

Originally posted by Bill N.Y.:
I'll add that the cost of a road breakdown would be insane compared to new u-joints. I'm looking at an invoice right now from a trucking company who's driver stated that he heard the same noises you did for a little while before failure. The invoice cost him over $2,100

Of course you probably think I porked him - Far from it - It's easy to look at the total and think he got the shaft - He kept driving it to the point that there was a cascade event that tore things up...

What did he get for that amount?.. 6.75 hours of road side service. A new yoke for the back side of the front rear - A pinion nut - A driveshaft made up at a machine shop (slip yoke, stub shaft, end yoke assy) - broken down for 3 days because it happened after 11am on a Saturday - 2 new U-joints - He lost his load for the run because he had to sub it out - Repaired torn out airlines - Replace a beat up and leaking maxi brake chamber - And he lost over $2,100 - Ouch!

I think he got a great deal, Bill. I've blown a trailer tire when I was hauling a float with a large forklift on it, and it cost my company $500 for someone to show up with a tire and fix it during a rain storm. Mind you this was in the middle of nowhere, but $2100 for all the work you did? That's a steal.

Next time I have a major rebuild on the books, I'm just gunna drive it near your area, pull to the side of the road, and have you do an in-frame right there. I sounds like it'd be cheaper than taking it to a local shop!

The differential is a Dana 80. I removed the cover and found nothing. No broken teeth no metal lying in bottom oil level OK and oildid not smell burnt. I'm going to find a way to get this up on blocks tommorrow to see if can hear noise and if so to locate. Hope my wife does not run me over. Well on second thought maybe not, knowing my wife she will find the excuse liks saying OPPS so Better get a buddy to help.

Hey Bill H, what do you think about...

Preload on the pinion nut? Slop in the pinion bearing?

Bill N.Y.

Is this what you saw when you opened it up?

OOPS...
Looks like I can't find a good image that will allow remote linking - go to Google and do an image search under "Dana 80 rear ends"

Bill N.Y.

Bill the picture did not show. But probably . There is slop and I called a repair shop that only does differentials and was told maybe Ok or maybe not he needed to look.