BCM Community
Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: Nova Eona on March 15, 2022, 08:58:53 AM
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Hey all, I just woke the bus up from the winter and am hoping to take it on a few hundred miles' trip in two weeks, but I'm still chasing some vibration that appears at speed. Engine runs smooth and everything cruises nicely around town, but getting upwards of 40 mph there's a distinct vibration strong enough to rattle some of the windows (and the stove) and make the passenger side mirror visibly vibrate. Last year I had the driveshaft replaced (separate issue) and did the rear radius arm bushings, but have not yet gotten to the front radius bushings yet. Tires are two years old and were all checked on the spin-balancer to make sure they weren't the issue. Wheel bearings have been checked by a good shop as well. Haven't tried this specific test this year, but last year if I shifted to neutral while going 50-ish the vibration was still constant.
Question is, could bad front radius bushings cause that much vibration, or should I be looking at other potential causes as well? With just two weeks to work with I want to make sure I maximize my time working on it, it'd be a shame to focus on the front bushings only to find they weren't the cause.
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Could it be thumpy tires?
Jim
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Your mention of driveshaft replacement gets my attention. Have you examined the drive shaft since replacement? I ask from past experience. A bad universal joint can send vibration all through the coach and so can a sloppy slip spline on the drive shaft that is not kept greased well & frequently. There are other things it could be but wanted to make mention of what came to mind. I don't see radius rod bushings creating "vibrations" as much as thumps or clunks when hitting road irregularities. HTH.
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The speed of the vibrations can tell you a lot.
Jim
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Was the driveshaft tried 180 degrees offset from the current placement? I've heard of it causing vibration problems if it is mounted out of sync.
Do you still have the handbrake by the driveshaft? If so, is it possible that it's loose or missing a chunk?
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Your mention of driveshaft replacement gets my attention. Have you examined the drive shaft since replacement? I ask from past experience. A bad universal joint can send vibration all through the coach and so can a sloppy slip spline on the drive shaft that is not kept greased well & frequently. There are other things it could be but wanted to make mention of what came to mind. I don't see radius rod bushings creating "vibrations" as much as thumps or clunks when hitting road irregularities. HTH.
I have not looked at it too closely since it was done, but I'll give it a wiggle next time I'm looking at it. I had the bus at a heavy truck shop last summer and they found that one of the yoke pieces was out of round, so they had a well-respected driveline shop nearby fab a new shaft to replace it, did the pinion seal and new shocks while they were at it too.
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Was the driveshaft tried 180 degrees offset from the current placement? I've heard of it causing vibration problems if it is mounted out of sync.
Do you still have the handbrake by the driveshaft? If so, is it possible that it's loose or missing a chunk?
Have not tried that, how much of a nuisance are these shafts to rotate like that? I had the shop do the install last year, so it'd be a question of whether it's worth having them do it.
Handbrake has been removed.
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I'm assuming they balanced the driveshaft, right? Did they replace the u-joint bearings and such?
I think there are details about marking the driveshaft position when it's pulled to make sure it goes back the same way. Check the manual for details about total replacement re: position.
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check for bolts or caps coming loose. Especially be sure both joints are in phase. In other words, all four caps are in same location as other end. If front joints caps are 12, 6, 3 and 9 o'clock, rear joint should be the same. Also if any tires have nylon in casing, expect 20 miles to round them out again. Nylon flat spot when sitting and vibrate till warmed up. I don't know if they use that any more.
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It's not just nylon, although they seem to be the worst. Even modern tires can flat spot from sitting. If it's a thump about every time the tires go around that's probably it. If it seems to wobble about 4 or 5 times that fast it's likely the driveshaft. Look closely at what was changed first. U joints out of phase can happen. The front one and the rear one need to line up exactly, in other words if the caps on the input yoke are up and down the ones on the output yoke need to be up and down. Some shops build but do not balance. Look for new welded on balance weights as evidence that they did.
Jim
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I think I may have found the source of the vibration! Now, correct me if I'm wrong, but see attached pic - pretty sure the old parking drum's edges should not look like that!
Now, that brake is obviously not in use, what's the process for deleting that drum?
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Wow! No wonder it vibrates with half the lip gone. Easy to remove. Just remove all the bolts attaching drum to trans output yoke. About 8 of them. May be wire tied. Once drum is off, you can remove brake shoes and mounting plate. You'll need to disconnect driveshaft to do it. Be careful not to lose any needles in caps. You'll then have a nice increase in room in that area.
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Nice find. That's exactly why I was asking about the hand brake earlier. A missing piece like that seems like a prime suspect in your vibration.
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@Nova Eona
Do yourself a favor and just remove the circle of bolts at the very end of the driveshaft - both ends. These are the companion flanges which mate up to the output shaft of the transmission and the differential leaving the two u-joints totally in tact. The companion flange at the transmission end has to come off anyway to remove the parking brake drum. I done it this way several times. Remove the differential end 1st so the shaft can move away from the transmission. Keep in mind the prerequisite to doing it this way AND to remove the parking brake drum w/o removing the tranny is to have an enlarged hole (opening) in the bulkhead the drive shaft passes thru. I mention this because it was a common modification that lent itself to much quicker & efficient unit repairs in this area. I can post photos if it you'd like.
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@Nova Eona
Do yourself a favor and just remove the circle of bolts at the very end of the driveshaft - both ends. These are the companion flanges which mate up to the output shaft of the transmission and the differential leaving the two u-joints totally in tact. The companion flange at the transmission end has to come off anyway to remove the parking brake drum. I done it this way several times. Remove the differential end 1st so the shaft can move away from the transmission. Keep in mind the prerequisite to doing it this way AND to remove the parking brake drum w/o removing the tranny is to have an enlarged hole (opening) in the bulkhead the drive shaft passes thru. I mention this because it was a common modification that lent itself to much quicker & efficient unit repairs in this area. I can post photos if it you'd like.
Well the hole seems plenty enlarged already, so I suppose I lucked out there at least. Those bolts within the drum are not fun! Got all 8 of the drum bolts out and 6/8 of the flange bolts on the transmission end before I ran out of light today, was hoping I could get away with just doing one end but it sounds like I'll have to do the pumpkin end as well. Can't wait to see how much nicer it drives after all this. Anyone know offhand what the torque spec on those bolts should be when going back in?
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https://www.almabolt.com/pages/catalog/bolts/tighteningtorque.htm
We used self locking nuts on the bolts on ours. Tens of thousands of miles and never had them loosen. Replaced those nuts any time they are removed. No nuts- red loctite.3/8-24 grade 8 used lock wire first couple of times, but what a pita.
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Wonder why your mechanic didn't see that when installing the driveshaft?
Jim
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We've always used the same hardware except for adding new lock washers - never any issues. The companion flange at the tranny end is a pita due to space constraints but gets real simple like the differential end when drum is removed. I hope you don't need to do what I'm about to mention but NOW would be the time! Check the output shaft seal of the tranny while the parking brake/propeller shaft is removed as that is what has been taking all of the beating from an unbalanced parking brake drum. That big nut is 1400 ft. Lbs. BTDT after a parking brake burn at highway speed which fried that seal I mentioned above.
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Wonder why your mechanic didn't see that when installing the driveshaft?
Jim
Tunnel vision on the drive shaft! Us bus nuts have great peripheral vision when working on our beasts of beauty...
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Tunnel vision on the drive shaft! Us bus nuts have great peripheral vision when working on our beasts of beauty...
My thoughts as well - I've been back there plenty and never noticed it before, could have saved myself a lot of time if I'd caught it last year!
So, update - went back today and got the driveshaft fully unmounted from both ends along with the bolts on the circumference of the drum, however said drum is still on there rock solid. Does that big Jesus nut have to come off to remove it? I left it soaking in penetrating oil in the hopes that it's currently just held on with 60 years of rust adhesion, I don't like four figure torque values.
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Rusted to mounting flange just like brake drums on hubs. Spray with penetrant for 3 or 4 days. Then rap at 180 degrees locations. Use a short handle sledge or bigger if room. Don't waste time with small hammer.
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Air impact hammer is your friend.
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Forgot to answer your question on the big jesus nut - that holds only the transmission output shaft flange & preloads the output shaft bearing & has nothing to do with the parking brake drum. Once your drum is removed look for wetness & in some cases flooding behind that flange that the jesus nut is on. That would be an indication of the tranny output shaft seal leaking as I mentioned in an earlier post and would behoove you for replacement now otherwise you're going back together. You may notice if it's not completely buried in grease build up that there is a slobber tube 3/16" - 1/4" copper tube that directs any fluid leakage from the said seal away from the parking brake drum which in your removal of the drum renders it obsolete for that kind of protection. It's clocked at the bottom of the seal area behind the flange. Fwiw.
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Success! After much hammering, penetrating oil-ing, heating, and a bit of chilling, the dang thing finally came free, what a lovely little clunk sound. Wiggled the driveshaft around until I could get the drum loose and bolted it all back up, now just gotta go back and torque it properly to call it done.
I did not notice any significant signs of leaking from the transmission seal, which reinforces the fact I haven't had to top it up ever since changing it over to synthetic oil two years ago.
While it's fresh in my mind, here's a step-by-step for anyone else tackling this in the future.
1) Saturate the drum/flange connection with penetrating oil. Use an obscene amount. This can be done later but the sooner you start the better
2) Verify or make some kind of marking on the pumpkin end of the driveshaft to make sure the flange meets up to the exact same point. Mine already had a white line aligned with one of the bolt holes on both flanges
3) Remove fifteen bolts from the transmission end of the driveshaft and eight from the pumpkin end. You do not need to disassemble u-joints, but will need to get creative with extensions, u-joints, and wobble-sockets. A beefy impact wrench is your friend here, my Ryobi battery impact overheated itself but my Earthquake (HF) 3/4" breezed through it. Leave at least one bolt in the inner ring of the transmission end
4) Run a wire or rope through one of the empty bolt holes on the transmission end. You can't verify flange markings with the drum in the way, so this will ensure your transmission mating remains matched. Tie this off so it won't come undone, but leave enough slack for the driveshaft to move around a lot
5) Remove that last bolt on the transmission end
6) Knock the driveshaft free from the flanges and compress it if possible, then squirm under (blocking obviously) and wiggle the flange on the pumpkin end around until it's under the pumpkin. Doesn't hurt to tie it in place to keep it from sliding down to the ground
7)Apply a mixture of hammering, heat, cold, and penetrating oil to the brake drum until it comes loose. This may take a week of intermittent care
8 ) Wiggle the freed drum loose and down to get it out. Hopefully your bulkhead is already opened up to make it easier like mine was
9) You've probably got a rope or wire running through both flanges and the drum now, run a second one around the drum to make sure your mating remains matched, then remove the first so the drum can be thrown across the yard victoriously
10) Wiggle the driveshaft back into place, making sure the flanges meet the same boltholes they had originally.
11) Bolt it up using new hardware where available/applicable, fresh spring washers at a minimum. I'm using antiseize compound on mine.
12) (This part I have not done yet) Torque it down to spec, probably using a crowfoot wrench and applicable math as needed. The bolts are 7/16-20 Grade 8, torque to your preferred spec, I'm seeing 70ish for dry or 50ish for lubricated. Wire it up if you kept the castle nuts and are so inclined.
(https://lh3.googleusercontent.com/pw/AM-JKLWGUJoot1JWBILH5SZToE6B_vSfsiPBt0UTNTS8wPjptj8a3vpOYoP1bL_jDpcwyJNeg1zS-yBXQVuVqel3f_-iOTv5AFqID5TyBhJCO_0X2FJp8Uq-tt33Azy1WjKZ_2SR_h-iXdAtMUC3r4qGgq4ydw=w1080-h1440-no?authuser=0)
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Good news!
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Great news. :^
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Got everything torqued down and took it for a test drive today, all went well - still the occasional vibration or rattle, but much better than before! Now I can finally start spending more time driving this thing than fixing it hopefully!
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Great news again! :^
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We've always used the same hardware except for adding new lock washers - never any issues. The companion flange at the tranny end is a pita due to space constraints but gets real simple like the differential end when drum is removed. I hope you don't need to do what I'm about to mention but NOW would be the time! Check the output shaft seal of the tranny while the parking brake/propeller shaft is removed as that is what has been taking all of the beating from an unbalanced parking brake drum. That big nut is 1400 ft. Lbs. BTDT after a parking brake burn at highway speed which fried that seal I mentioned above.
How to you tighten to 1400lbs?? I struggle with 450lbs wheel nuts.
I see you have a hemi. Im doing lifter/cam job on sons at the moment.
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How to you tighten to 1400lbs?? I struggle with 450lbs wheel nuts.
I see you have a hemi. Im doing lifter/cam job on sons at the moment.
Used a 3/4" drive @ 650 Ft Lb torque wrench with a 4 to 1 torque multiplier - that's 350 ft lb at the handle.
Is the lifter/cam job related to any valve seat issues on that Hemi?
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Any recommendations for a torque multiplier? Would be handy for lug nuts.
Ive heard about seat issues on some of these Hemis especially if it overheats. This one is a 2011 and valves/seats are still in good shape. One lifer roller is seized and its cam lobe is rounded off. Cose examination of other lobes shows a few with pitting starting on nose. It reminds me of a wheel bearing race that's starting to fail. Lifter rollers for those lobe are still ok. I suspect its cam lobe breakdown that starts the process and lifter failure is the last stage.
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Don't know if this is advisable on a 4101 but we tracked down driveline vibration on a car by putting axle on jackstands and running it at highway speed. Ours was a bad ujoint install causing drive shaft vibration at tranny.
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Our torque multiplier isn't the lug nut style. It looks like a beefy socket ratchet with a 2' handle. It's 3/4" input & 1" output square drives.
The Hemi valve seat issue mostly disappeared with the 2009 model & newer. There were specific issue with 2011 models but don't know the details - wonder if the cam/lifter is part of that?
If we allow our bus drivetrain (drive shaft, & universal joint grease fittings to get deprived of regular lubing - the drive line will develop a vibration - especially on turns under a load. With regular lubing it runs smooth. I would contribute this to worn parts (excessive clearance) in the U joints and specifically the driveshaft slip spline yoke.
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also a worn out slip joint can cause it. Find a bigger drive shaft shop that can chuck the whole shaft assembly on their lathe.
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nut buster
removes bus tire lug nuts like they are fingner tight and no more air compressor or air lines and works great on all nuts
https://www.milwaukeetool.com/Products/Power-Tools/Fastening/Impact-Wrenches/2764-20
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Right been eyeing one of those. But how to torque them back down is still a problem for me. I mean a 5 foot bar and digital torque adapter is how I did it last time but its no fun.
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Might as well go with their 1" battery wrench. 1800 lb. ft. Torque.
I have Harbor Freight's 3/4" version. May not be quite as high torque as the fuel, but lots cheaper and works fine on my lug nuts.