Rear end thump, what to do.

Topic: Rear end thump, what to do. (Read 1508 times) previous topic - next topic

Rear end thump, what to do.

April 09, 2023, 12:09:31 pm

Hello forum members, I have been doing pretty good keeping Jor's old 34' going down the road. This is out of my knowledge though. I will post pics, I think I have that part figured out. We are at Enid Lake Mississippi. Very nice Corps. campground. Yesterday driving we started hearing some thunking, I just thought something was rolling around thumping in a cabinet. It got worse, wife says coming from underneath. It does seem to thump letting up, and then pressing down throttle pedal. Which I would imagine, could be what I am seeing in pics.
We were headed to Biloxi, but thinking at the every least we should head back towards home, which is about 600 miles to Missouri. Any knowledge and help would be much appreciated. Kim and Elana McCoy

Re: Rear end thump, what to do.

Reply #1 – April 09, 2023, 12:17:25 pm

So Kim in your first photo you are pointing out the driveline slip yoke. With it raised it is normal to see a shiny metal. Mine also has a layer of grease on it from over servicing both it and the joint about every 7K miles. To the left of the picture on that same shaft is a big round metal disk just past the rear U joint. I would take a prybar and side load it and see if there is any free movement side to side and up and down. Since you say you have a 34 foot coach Im guessing it is a 270 coach with a 8.3L engine and a 3060 Alison transmission. They are problematic for having the dampeners coming loose. Free play will indicate this as I understand
Scott

Re: Rear end thump, what to do.

Reply #2 – April 09, 2023, 12:32:01 pm

Thanks Scott, I haven't figured out how to put coach info, on my profile. 97 270 34' 8.3 mechanical. I will see what happens when I do as advised, and post outcome. Kim

Re: Rear end thump, what to do.

Reply #3 – April 09, 2023, 12:38:59 pm

Yup, exposed shiny metal normal-- it extends/contracts to account for movement between axle and chassis.

Check both U joints as well as transmission dampner.

Re: Rear end thump, what to do.

Reply #4 – April 09, 2023, 01:18:39 pm

Looks like drive line could use a bit of grease also.

Re: Rear end thump, what to do.

Reply #5 – April 09, 2023, 01:47:48 pm

Quote from: golfnut – April 09, 2023, 12:09:31 pm

Yesterday driving we started hearing some thunking, I just thought something was rolling around thumping in a cabinet. It got worse, wife says coming from underneath. It does seem to thump letting up, and then pressing down throttle pedal.

"Thunking" is such a vague description. Do you hear a thunk once upon changing direction? Say when you go from coasting to accelerating? One thunk is okay. Steady vibration deserves some observation and analysis.

The shiny area your yellow arrow points to is the drive spline in its extended position. That's a part that's often overlooked when running around with the grease gun, because if it doesn't have a grease fitting of some sort it needs to be pulled apart to be re-greased. If there is a problem with the drive shaft as others have said you can grab it in you hands and move it. If it doesn't move, no problem.
One thunk? Keep driving.

Re: Rear end thump, what to do.

Reply #6 – April 09, 2023, 01:58:12 pm

I can turn dampener and u joints slightly left and right. When I turn forward facing u joint, on rear end side, slightly to the left and then clockwise I can here a clunk?? Seems to be inside housing, normal?? will post pic. Not sure where to pry on the dampener. Anyone have a pic? So use a steel bar? Thanks for all the reply's!!

Re: Rear end thump, what to do.

Reply #7 – April 09, 2023, 02:10:55 pm

The damper does'nt come loose, the bearing in the trans housing does and may need to be tightened and or replaced,had mine
repaired in Memphis at a very good shop,there is an elbow towards the bottom of the trans under the damper,you can gently put the pry bar there and check end play,grease the u joints and shaft and see if that helps with the clunk,make sure the trans fluid is topped off.

Re: Rear end thump, what to do.

Reply #8 – April 09, 2023, 02:34:30 pm

Quote from: Old Toolmaker – April 09, 2023, 01:47:48 pm

The shiny area your yellow arrow points to is the drive spline in its extended position. That's a part that's often overlooked when running around with the grease gun, because if it doesn't have a grease fitting of some sort it needs to be pulled apart to be re-greased.

Every Foretravel driveshaft I have worked on/inspected DID have a (one) grease zirk on the spline and two on the U joints. Grease either of the U joint zirks, as both are drilled to the same center of the cross.

Re: Rear end thump, what to do.

Reply #9 – April 09, 2023, 02:40:46 pm

Quote from: golfnut – April 09, 2023, 01:58:12 pm

I can turn dampener and u joints slightly left and right. When I turn forward facing u joint, on rear end side, slightly to the left and then clockwise I can here a clunk?? Seems to be inside housing, normal?? will post pic. Not sure where to pry on the dampener. Anyone have a pic? So use a steel bar? Thanks for all the reply's!!

That would be the gear backlash and normal doing what you describe. The bearing Scott talks about is at the other end of the driveshaft and in the tailshaft of the transmission. You need to find a place to pry that damper sideways or up and down.

Re: Rear end thump, what to do.

Reply #10 – April 09, 2023, 02:46:31 pm

As I recall from earlier threads, if the transmission dampner needs replacing, several have used the Allison shop in Longview, TX.

Re: Rear end thump, what to do.

Reply #11 – April 09, 2023, 03:04:26 pm

Also make sure your differential lube is topped off.

Re: Rear end thump, what to do.

Reply #12 – April 09, 2023, 03:10:05 pm

Quote from: wolfe10 – April 09, 2023, 02:46:31 pm

As I recall from earlier threads, if the transmission dampner needs replacing, several have used the Allison shop in Longview, TX.

Stewart and Stevenson?

Re: Rear end thump, what to do.

Reply #13 – April 09, 2023, 03:13:31 pm

Sales + Service Locator

Stewart & Stevenson Power Products, LLC
4935 Whitehurst Drive
Longview, TX 75602
903-758-5562

Re: Rear end thump, what to do.

Reply #14 – April 09, 2023, 03:18:55 pm

Of course pry bar is one thing I don't have, and grease gun LOL. I do have this, just don't have any idea how much muscle to use. Is this where to try for movement?

Re: Rear end thump, what to do.

Reply #15 – April 09, 2023, 03:23:34 pm

Yes see if there is play there. It should not move.

Re: Rear end thump, what to do.

Reply #16 – April 09, 2023, 04:50:55 pm

Quote from: golfnut – April 09, 2023, 01:58:12 pm

I can turn dampener and u joints slightly left and right. When I turn forward facing u joint, on rear end side, slightly to the left and then clockwise I can here a clunk?? Seems to be inside housing, normal?? will post pic. Not sure where to pry on the dampener. Anyone have a pic? So use a steel bar? Thanks for all the reply's!!

That would be the pinion bearing and if it were problematic you could wiggle the drive shaft up and down. Turning from one side to the other is the backlash between the pinion and the ring gear, and not to belittle your concerns, but I'm wondering if what you're hearing is normal. Sometimes as we become used to a new machine, as we become comfortable in its operation we begin to notice "new" noises and vibrations. These were always present but buried under the noise of all the new sensations that come with new machinery.

Now the output bearing on the automatic transmission, if you can find movement there, you have something to be professionally addressed sooner rather than later.

Re: Rear end thump, what to do.

Reply #17 – April 09, 2023, 04:57:05 pm

I leaned on it pretty good, I am not getting any movement. I will check tranny fluid, stop somewhere buy grease and gun, which I was wanting something better anyway, see what happens I guess. Any more words of wisdom, please share, I appreciate it very much. Thanks

Re: Rear end thump, what to do.

Reply #18 – April 09, 2023, 05:04:46 pm

I have put about 4 thousand miles on the coach, we haven't heard this before, it is pretty distinct. No movement on the dampner that I can produce. The dampner and yokes will slightly turn counter clockwise and clockwise. Thanks Kim

Re: Rear end thump, what to do.

Reply #19 – April 09, 2023, 05:06:18 pm

I will see if I can move shaft up and down.

Re: Rear end thump, what to do.

Reply #20 – April 09, 2023, 05:29:51 pm

I can maybe very very little move shaft slightly up and down. I just realized, I bought a pair of overalls for this occasion, now that I have my clothes all full of grease. Par for the course.

Re: Rear end thump, what to do.

Reply #21 – April 09, 2023, 06:59:44 pm

Transmission Dampener
Barry seems to have a real good handle and understanding of this since he has been threw it. Would certainly think if it has been repaired or had the upgraded parts installed it should be with the prior records. Allison may even have history if they did the repair. I just reread the post and they go into good detail about it. You say that you think that there may be some play in it, I personally would want to get in front of it before it does any damage. Sounds like they changed the bolts and doubled the torque requirements on them to prevent. 4060 trans doesn't have these issues and was a contributing factor to wanting a 4060 rather than a early 3060 for me. Regardless if you don't know it's repair status it may be worth looking into farther. Please keep us updated.
Scott 🤞

Re: Rear end thump, what to do.

Reply #22 – April 09, 2023, 07:01:27 pm

Ken, I would recommend buying a grease gun with a pistol grip pump--you can hold the hose on the grease fitting with one hand and pump with the other
Just my thought
Chris

Re: Rear end thump, what to do.

Reply #23 – April 09, 2023, 11:27:47 pm

I can recommend the "Lock N Load" grease gun with an accessory easy lock coupler. Bought grease gun at Tractor Supply and it is designed to self bleed the air when changing over grease cartridges.

LockNLube Grease Gun Coupler locks onto Zerk fittings. Grease goes in, not on the machine. World's best-selling original locking grease coupler. Rated 10,000 PSI. Long-lasting rebuildable tool. Amazon.com: LockNLube Grease Gun Coupler locks onto Zerk fittings. Grease...

These two are worth the money in my experience.

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Re: Rear end thump, what to do.

Reply #24 – April 10, 2023, 07:02:52 am

Some other possibilities that can cause a thump to occur.
Does this happen in third gear? with the 3060 it could be a shift solenoid.
Check your motor mounts, epically the rear.
Look at your trailing arms for a broken bolt.
Have you recently had the wheels off? With your coach being a '97 you should have Budd wheels check torque on lug nuts. They changed to metric wheels on coaches between 5209 and 5212

Feeding the grease worms like have been touched on is a good start.

Mike

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