I've done a search and read through the threads and Barry's archive regarding rear end vibration. My coach is 1998 with 74,000 miles on it. I just bought it and put about 3,000 on it in the last couple weeks. I cruise around 63-64mph. At 65mph I can feel a vibration in the rear...at 70mph is when it peaks. It's not a tire or axle as the frequency is too high; it's drive-shaft or something spinning at that speed.
My coach is of the year, from the threads I read, that Allison didn't install the p3 carrier bearing or something correctly. Also, Barry said foretravel did some modifications on his old coach to adjust driveline angle. And he said he had a loose balancer.
I greased u-joints 2000mile ago and old grease flowed out of them with one pump indicating they were not dry.
I crawled under the rear end with a bar and pulled, turned, pried, and jiggled everything I could. Everything seems tight and there is no movement in the output/balancer on the transmission. There is a tiny clink in the rear when I turn the drive shaft back and forth with brakes on, but this seems like normal gear mesh.
At ride height (which is correct) the drive shaft angles down from the transmission to the rear slightly. The angles all appear to be small and not a problem. It does look like the transmission is "sagging" slightly and is not at a 90 degree angle to the ground, but this could be how the coach is sitting or as designed. I'm surprised there are no mounts under the transmission; instead it is only held by the bell housing.
I will try to contact the mechanic listed at Foretravel and another transmission mechanic recommended on this site. If my 1997-1998 md3060's are known for this vibration issue, I figure it is a matter of time before a repair is required. But at 63mph and below, I don't even notice it and the ride is smooth as can be. I'm wondering if it is something else.....or how long I can run it without doing any harm.
Any input? One thing I can try is going down the road and adjusting the ride height slightly to see if vibration changes.
Krush,
Check forums for retarder dampener failure. Check sooner than later. Are you sure you don't have an inside dual that is flat?
Pierce
in that speed range, I am always suspicious of tire balance or out of round tires - 55 - 70 MPH is where those issues tend to be most obvious.
We do not have any vibrations, and I am not aware of this being a known problem. This has to be difficult to diagnos. Even though you say it cannot be a tire, rotating tires may be an easy way to see if something changes. It seems that you cannot eliminate anything.
We did put a wired camera under our coach and on top of it while driving to try to find a noise. Cameras are inexpensive and can be a fun diagnostic tool. Pointing one at the U-joints, tires, etc may help. Our camera came with a long coax with a video RCA plug, which we put into our old VCR and recorded while we drove and later looked at the tape. It was interesting to see the brake mechanism move on tape.
I've read through all the forum threads which are also summarized here (thank you Barry!). The second paragraph says P3 bearing was a problem on these years. U295 Driveline vibration issues (http://www.beamalarm.com/Documents/foretravel_u295_driveline_vibration_issues.html)
I do not have flat or low tires, the axle is full of oil, no brakes are dragging etc. A 22.5 inch tire spins pretty slow and an out of balance or tire problem would be a much lower frequency.
This is much higher pitch, and though I don't have vibration equipment installed, I feel that it would be caused by something spinning the speed of the drive shaft. This is just from experience working on big fast rotating machines.
I checked the retarder damper, as stated in my first post. I went under and pulled and pried on everything. Nothing is loose.
Gary Omel has extensive experience with the carrier bearing issue. Send him a Pm and ask him to give you a call.
Mark
We have a vibration that generally peaks around 55 mph, but sometimes peaks at around 51 mph. I've had things checked twice at FOT. I asked them specifically to check drive shaft, universal joints, and transmission components for problems. I've also inspected the drive shaft and connected pieces for any signs of problems. Wayne at FOT claims the vibration is from the tires. We run Michelin XZA-1+. I've the have about 45K miles on them. I've had them balanced and added Centramatic balancers since the vibration started. Tires all look good, although at about 4 1/2 years on the coach, they are showing some weather checking on the sidewalls.
I am considering replacing the XZA-1+ with XZA-3 tire per Wayne's recommendation. Next spring will mark five years since we installed the tires. Some were almost one year old when they were installed.
This may be a very different vibration from your issue. I share it because we each experience a vibration dependent and the speed of the coach, and we've not found a solution.
With rear tires balanced and/or Centramatics, the next thing to check on the rear tires is RUN-OUT. You will have to chock the front wheels, raise the rear axle off the ground and disengage parking brake. Then check tire run-out.
Even a perfectly balanced "egg" shaped tire will-- roll like an egg.
Brett
That sounds like a good way to track the vibration. It's a new concept to me, but sounds very useful and productive. What would be the source for such a device? May I borrow yours? ;) Perhaps I should plan a trip to Virginia, a trip to NAC on your schedule, or somewhere else on your schedule.
That sounds like a good plan. I think Herman Power checked for proper seating of the the beads, and balanced the tires. I don't think they check for run-out.
All the ideas presented as responses to the problem are likely to applicable to krush's issue, as well as mine.
One way you might try to run it down using available hardware is to download a vibration sensing and analysis app for your smartphone. These typically will log the results into memory or a storage card. Then take the phone to an area where vibration seems most noticeable, duct tape it to a surface, and drive it at 5 mph increases in speed in intervals. Should give you the dominant frequency which will help narrow down vibration source.
I've used the accellerometer in these devices for many applications, they are amazingly sensitive and accurate.
Using this: Tire Diameter And Circumference Calculator (http://www.csgnetwork.com/tiresizescalc.html) (I know Michelin sizes a little unique), tire circumference is 125.108 inches= 10.43 feet/rotation. 70mph = 102.67 ft/sec. -------> 9.843 rotations per second (which would be 9HZ...very low)= 590.62 RPM.
MD3060: I found 6th gear is .65 gear ratio. My tach does not work (on list to get repaired, but lets say 1900rpm) 1900/0.65 = 2923 rpm ----> 48 rotations per sec...48 HZ
A tire would be a very low frequency vibration...which is not what I'm feeling. I appreciate the input, but I'm wondering if anybody did a quick check of the link I posted from Barry's site. My description of my vibration seems to match those on that link exactly.
Oil is full in rear end, u-joints are greased. Alignment is great. Brakes are not dragging (new right rear rotor and pads). Does it at 110psi and 100psi. I have 18,000lbs on rear and 9k on front axle with full fuel.
I can jack the tires off the ground and run it to 70 mph and see if I can find more facts. I can also pull both axles and run it up to 70mph going nowhere...and if it vibrates, well then we eliminated lots of things!
Thanks Mark, I'll do exactly as you suggest.
Perhaps our 99' has different rear axle, but the brochure showed as having a Rear Axle Ratio of 4.63:1
Don
Don,
For sure, but the data from the Beam Alarm page for the 98 270 clearly shows the rear axle as 5.13, that is what I was going by, if that is not the case, of course all numbers would be incorrect.
Having played the gear ratio's for many years vs tire size/rev per mile transmission gearing etc, I feel comfy in this arena, maybe wrong but comfy. ;D
Thanks for the info everybody. I spoke on the phone with somebody that chased vibration problems at 70mph in the past on a u270. I learned a lot of info.
My initial gut feeling/hunch was that the final drive on this coach is probably low, which causes the driveshaft to spin pretty fast at highway speeds. Looking at the specs: 1998 and older 8.3 equipped coaches come with mechanical 8.3 the md3060 transmission with .65 6th gear ratio and 5.13 rear end ratio. 1999 units come with electronic engines, md3066 with .67 6th gear and 4.63 ratio. U320 with M11 has 3.91 final drive and .67 OD (6th gear)
Assuming a 590 rpm for the tires at 70mph, here's what theoretical RPM of components would be:
tire rear OD drive shaft % dif engine % dif
590 5.13 0.65 3026.70 1967.36
590 5.13 0.67 3026.70 0.00 2027.89 -0.03
590 4.63 0.65 2731.70 0.10 1775.61 0.12
590 4.63 0.67 2731.70 0.00 1830.24 -0.03
590 3.91 0.67 2306.90 0.16 1545.62 0.16
From these quick calcs, we see that a 1999 U270 has a driveshaft (and transmission output bearing) spinning ~300 rpm slower. Also, engine cruise RPM is lower which rests better on the torque curve.
These facts probably won't be spoken about much, but design changes hint to what really happened. The MD3060 likely was designed to just work in school busses and trash trucks...all operate at lower speeds and don't have HP to go 70mph.
As for me, I'm going to check out a few things and see if I have some run-out on the output shaft/retarder damper. I'm going to try to find an allison distributor that knows their stuff and have them tighten up the carrier bearing....or see if I can tackle it myself.
And I may start looking for a 4.63 rear end out of a wrecked coach. It would help 60mph cruise as well. In my opinion, the final drive is too low and it shifts into 6th gear at 50-55mph.
Some issues are often unspoken.
Most coaches from FT are geared for. 65mph at rpm which produces max engine torque. (Usually the most efficient rpm in a diesel
Krush
I had p3 bearing replaced at inland truck repair Dallas TX, Option for me was bearing only with 6 month warranty or complete overhaul with 2 year warranty. I went complete overhaul which jumped it from 3 coach bucks to 6 coach bucks. It has been awhile but I think my vibration was from 50 mph up.
I tried new tires with balance new u joints, neither solved my vibration problem. Overhaul corrected vibration.
I would not go back to inland, Transmission, I a had leak they fixed it but gave me a bill
but finally agreed it should be warranty.
Call Stewart Stevenson (Allison Rep) Longview TX they were familiar with this problem and may give you some direction to go on.
Good Luck.
Larry
1998 U 270
You need to contact foretravel (James) about this problem, they can tell you how to properly check and correction this vibration problem, like adjusting ride height, checking the transmission bushing for proper bearing clearance and how to adjust the drive line angle at the differance and the tranmission.
Well now, thanks to this forum, I learn yet another tidbit about our coach and the differences between the different years. It can be very dangerous to make assumptions! But then, I knew that much already... ::)
Don
The rear axle will have a tag at one of the 3rd member fasteners with the ratio on it and possibly the number of teeth on the ring and pinion gear. Good way to tell what transmission is in it as the four speed in ours has a 1:1 fourth gear and a 3.07 rear axle ratio. If it had a six speed with a .65 overdrive sixth gear, the rear axle ratio would have to be a much higher number to come out with the same top speed. A diesel with the same horsepower but at a higher RPM would need a rear axle ratio with a higher ratio (number). A diesel with the same RPM but less HP would also need a higher ratio as it would not have the power to reach the same top speed (unless you went downhill). Tire diameter also makes a difference.
Yes, fun to play with calculations.
Pierce
You might check as to the cost for a shop to replace the gears only? I regeared many motorhomes
This seems to be the long term solution after ensuring the output bearing in the transmission is in good health.
I could buy a gearset and regear my rear with existing components. Or, I could find a rear that is 4.63 and just pull the axles and bolt it right in. This way, if I screw up, I can also put the original rear back in!
I find it interesting that in 1999 the axle was changed to 4.63 from 5.13. Sure, there is 25 hp more on the eletronic engines and a MD3066 with .67 instead of .65 6th gear. Design changes happen to fix problems--even if "there is no problem."
Yes, a wrecked RV with your 4.63 third member should be $500 or under and a couple of good mechanics (heavy third member) should be able to R&R in no more than an hour if all the gaskets release cleanly. At only 34 feet, you are much lighter than a 40 footer so it should be a good match. That ratio should increase fuel mileage as well. Check with your Allison dealer as you may be able to have them change your shift points.
Buying a gear set is always problematic. Takes a talented mechanic to do it right. Different torque for new vs used bearings, getting the pattern just right on the face of the ring gear, lots of stuff that many don't get right. More of an art than a tech school can teach. Bad setup can catch up way down the road.
Sounds like a good move to me. The only thing better would be a two speed rear end. HR or CC had two speeds in their top coaches over certain years. I would love to have one.
Pierce
I have to make some phone calls this week and check out a few things. I'm going to do some data gathering and data crunching as well to figure out what rear ratio would be the best. It may make sense to drop down a bit more (4.40, 4.30, etc whatever is available). This could make 6th gear as a true OD 65+mph and use 5th for around 55-60. Gears 1-4 are pretty spread out and low, so I don't think this would hurt acceleration much.
With full fuel and half water,half loaded with junk, and my motorcycle on back, I scaled right around 27k.
I'll have to analyze it a bit, though.
We were typing at the same time. As said, I'm thinking going down around 4.3-4.4 may make sense. I have no idea why they geared it so low with a 6sp transmission!
Allison 3000 and 4000 series transmission:
4th gear 1:1
5th gear .75 OD
6th gear .65 OD
Krush,
Is this vibration something you can feel at the driver's seat or do you have to have someone else go back to the bed area to notice it?
I feel it up at the driver seat (I travel alone, so I haven't been to the back underway yet). It just starts to be noticeable at 65. 70-75 it vibrates the floor slightly and I can feel it in my foot. It isn't "shake the mirrors" bad like some people with this same problem have had on other coaches.
Tires in the air and spin it up.
Check the DS (remove it) and check the joints
and
find someone that can verify DS balance.
Slow down and enjoy the ride until you get things figured out. pc
No progress on my problem/solution, but I did come across this: http://www.allisonelearn.com/lms/scorm_host/scorm_modules/1.0/en/tt-adv-3k4kevol01.0wbt/documents/01-wt-98.pdf (http://www.allisonelearn.com/lms/scorm_host/scorm_modules/1.0/en/tt-adv-3k4kevol01.0wbt/documents/01-wt-98.pdf)
It's regarding the upgraded retarder that came out in 1998. One thing that interested me:
* P3 Carrier P/N 29530458 must be used on MY 1998 uprated MD 3066 models due to that models HP and torque ratings. P3 Carrier P/N 29530458 can be identified by a circular raised rib on the rear face of the carrier (page 3)
Page 7 has an explosion of back end of the transmission. There are two identical bearings on the p3 carrier. #13 &27 (race) and 58/51. From what I see, #60 looks to be the retaining nut that people talk about not being torqued enough by allison at original construction. Looks like to get to it all that is required is remove driveshaft, then yoke, then seal.
As for replacing the bearings, it looks like #58 can be replaced fairly easily. #13 requires removing the retarder (if I read drawing correctly).
Edit: here is what it all looks like put together. The 2nd picture show each planetary set separated. p3 has the bearing on it: Allison MD3060 Planet Set Close Ratio | eBay (http://www.ebay.com/itm/Allison-MD3060-Planet-Set-Close-Ratio-/231285847102?pt=Motors_Car_Truck_Parts_Accessories&hash=item35d9b5f43e&vxp=mtr)
Good information there. So, it looks like the M70 X 2 retainer nut is the historically undertorqued part that can cause the bearing(s) to go out?
I have a Q for you. Does your retarder have what looks like a harmonic balancer on the output shaft? It's my understanding that some 3060 have this balancer and some don't, with the P3 problem usually showing up on units with the balancer. It's checked by gently prying up and noting excess play in the taper bearing. Since it's most likely the output end bearing would be the damaged item, it seems like it would be possible to replace bearing and seal in place though I wonder how one would lock shaft so the retaining nut could be torqued.
Are you positive that's your problem?? pc
Seperate from the diagnosis of your vibration issue I noted the 300 degree temp max in the test for the retarder itself without a degradation in effectiveness.
"Retarder capacity is reduced" past that not damaged.
Everything I've heard regarding "problems" has been second hand, word of mouth, etc etc. Some of it may be true, some not, some may be wrong. That's ok, I'm used to this as it's what I do for a living, lol. I haven't called up Foretravel or Allison yet because I've just been slammed with travel and work. However, I will talk to them.
In my earlier posts, I mentioned that I crawled under the coach and push/pried/pulled/banged on everything possible and didn't notice anything terrible. There may have been a TINY bit of up/down play on the balancer/yoke, but it only showed when using a pry-bar. My transmission does have the big balancer around the output yoke.
My vibrations start at 65mph and are not horrible. They don't shake mirrors or glass. But, I don't like it.
I may NOT have a failed part at all! To me, the "problem" is that the rear end gearing of 5.13 is too low and spinning the driveshaft too fast. There's little to no vibe below 60mph. See my quick number calc earlier in the thread to show what a different set of gears would do for drive shaft RPM.
I'm going on a short 500mile round trip over the next week. I'm just goign to stay around 60mph max. Once I get back and some time, I'll do some investigating. First, check yoke/balancer for runnout. Next, remove driveshaft and go up to 70mph on tranny. etc etc.
I looked up the part numbers for the bearing/race/nut/lock. $10-20 each for genuine allison on ebay.
The balancer in my coach has a slight amount of play in it when prying up with a bar. I would rather it have none but in conversation with Foretravel mechanic was told that a small amount is normal. I'd guess it at about .025". No vibration at any forward speed that I can detect. Vibrates a bit at idle in gear.
Hearsay that if driveshaft is removed for towing that it needs to be replaced in original orientation. I've wondered why this should be necessary, is it possible that driveshaft is somehow balanced/indexed to trans, diff? There's enough rotating mass there for an out of balance to show up as vibration. Seems like the axial thrust lines of trans wouldn't do it unless there is a major mechanical issue.
Our engines/transmission are not bolted directly to the frame but have mounts. They usually fail slowly and may transmit vibration to the rest of the coach at certain speeds when they do. Good to do a check here before going too far looking at a transmission shaft problem.
The generator is a good example. While the mounts may look in good shape from above, when you pull the generator out on it's slide and look under, the damage is readily apparent. Our generator vibration was all mount related as the rubber mount was absolutely shot underneath.
Pierce
Chuck, the reason for putting the drive shaft back in the same position is the joints must be "timed", in other words, the cross must both be in the same position or they will be fighting each other. So same position or 180 degrees out.
And how many tow truck drivers would pay attention? Another big reason to pull both axles to tow and leave the driveshaft alone.
Pierce
When purchased, my coach had 4 year old Toyo tires and it had a bad vibration in the front (feel thru steering wheel) and rear (feel thru seat bottom) starting at 55 mph. I thought it might have been balance and maybe drive shaft. Took the coach to my trusted chassis shop and what do you know, all six tires were badly out of balance (none had any weight on the wheels!) and 5 of the six had to be trued. Now all of the vibration is gone. So have a good shop check the run out and shave/true the tires if necessary. You would be surprised how many tires are out of spec and/or the run out spec is so large that it creates vibration issues.
I had a similiar problem on the 95 240 and found some idiot had put golf balls inside. At slow speed the front end wobbled like crazy.Once removed all was better.
JohnH
We just hit 300 degrees hot on a Colorado down mountain run. Did manually back off retarder a little several times, but the coach went down the hill slow & safe without brakes the whole way. The higher tranny temp did increase the coolant temp as the heat exchanger did its job. Downshifting to increase RPM to keep coolant flowing through radiator is a good idea.
Barry,
What road were you on in CO? I am getting ready to go through CO next week on my way to OR. I am concerned about taking 70 vs 80. Did you Trany temp reached 300?
Thank you,
AL
My limited understanding is it takes one hour over 300 degrees to start to damage normal old style ATF.
Transynd is probably more heat resistant?
Al, We were eastbound on US 160 between Alamosa & Walsenburg. We did fine. 300 is acceptable for our engine-tranny on major down hills.
I-70 has westbound climb up out of Denver and other parts have hills. Don't know about I-80, but it looks a little less windy on a map. Others will know more.
The old rule was petroleum lubricants can break-down above 250. Synthetics are MUCH higher and that is why transmissions, especially with retarder need to be using synthetic. And Allison Transynd is supposed to be the recommended synthetic, as it is made for Allison. There are other synthetics that say they are same or better, but why not use Transynd for that expensive part.
My Trany is on Transynd & most temp it showed was 230 while running it at 70-75 for a while on 95+ TX hot day trip.
I have been on 80 and it is easy enough. I want to take 70 west and I have been on some parts of 70 ... up to Vail area. I just don't want to struggle so much going so many up hill roads but 70 be fun i think. I will make up my mind when i leave Caste Rock, CO next Thursday go N or Go W ...
I can 2nd an earlier recommendation for Stewart & Stevenson in Longview to deal with the vibration issue. We had what I think was the exact same problem on our 97 U295 about 8yrs ago. As I recall, at any speed over about 50mph we would get a violent shuddering at the rear of the coach. It was notceable up front but really bad at the rear. It was an internal bearing/dampener issue in the transmission. I would have to look up the paperwork to remember exactly what it was called. Anyway, it was about a $2500 fix. That included a full conversion to Transynd. No problems whatsoever since then.
Dale,
Might be a good idea for a customer of Stewart & Stevenson to call them and nail down the cause of the problem.
What transmission, year, model, possible relationship to retarder, possible preventative check, what parts have to be replaced, Allison bulletin, etc.? Nice to be able to avoid a $2500 fix down the road.
Good for members to avoid wives' tales and get the information from the horse's mouth.
Pierce
I'm going to bet P3 bearing based on a number of 96-98 U270/295 36' coaches reporting this issue (if you search the forum for P3 bearing you'll get a number of hits and threads with good descriptions of the issue).
I spoke with my father to see what he remembered about this repair because he was the one that actually dealt with it. His recollection was that there was a batch of Allison transmissions with a design defect that, for a while, were repaired for free by either Allison or Foretravel. Ours failed after the coverage period expired so we got no help. I'm no expert on the construction of the transmission so hopefully this makes sense....the defect was internal at the input shaft. As Michelle stated, it was called a P3 Bearing or P3 Carrier and required some degree of tear-down to be repaired on our unit. Some only required adjustment or tightening but ours was too far gone and had damaged internal bearings. We didn't drive it long after the symptoms started showing up so if you think you're getting this type of vibration you should get it checked ASAP. Foretravel or Allison may be able to tell you if your particular unit is one of the unlucky ones with the defect.
Thanks to Michelle (and Berry Beam for the great work), here it is: U295 Driveline vibration issues (http://www.beamalarm.com/Documents/foretravel_u295_driveline_vibration_issues.html) and the Allison service letter: http://www.allisonelearn.com/LMS/scorm_host/scorm_modules/1.0/en/TT-ADV-3K4KEVOL01.0WBT/Documents/04-WT-05.pdf (http://www.allisonelearn.com/LMS/scorm_host/scorm_modules/1.0/en/TT-ADV-3K4KEVOL01.0WBT/Documents/04-WT-05.pdf)
Allison Mechanic's Tips for 3000/4000 models: http://www.utxchange.com/pdfs/MechanicsTips/MT4015EN.pdf (http://www.utxchange.com/pdfs/MechanicsTips/MT4015EN.pdf)
Prospective buyers might see it this has been done on the coach they are considering.
Pierce
To keep updated from the beginning of this thread: My 1998 u270 has about 75,000 miles on it. I have no slop or play at all in the output shaft of the transmission or retarder damper.
Doing some thinking and talking with people, it is obvious there was an application and/or design error. In our case, I really think it is an application error as the coach has very low rear end gears with 5.13:1. For now, I just stay slow at 60mph or so. But, in the next few months I'm going to change gears to 4.33 or 4.63....probably 4.33, but I need to do some analysis.
Experience and gut tells me that the p3 problem appears to happen on vehicles that do lots of highway driving. Trashtrucks and city busses likely don't have the problem.
To follow up on this thread, I did the rear end swap from 5.13 to 4.33. I have about 13,000 miles on it with mostly 70-75mph cruising.
The vibration is gone at 70-75mph.
It does come back up around 80-85. But I don't drive that fast, so it doesn't matter. However, this proves to me that the vibration is from the driveshaft. How do I know? The 80 mph is about 3000rpm in the driveshaft with 4.33 gears. 68mph was 3000rpm for the driveshaft with 5.13.
Remember, in 1999 or 2000, foretravel started putting in 4.65 gears.
See this thread for more details and analysis on the gear change: Rear end gear change from 5.13 to 4.33 on 8.3 Cummins u270 (http://www.foreforums.com/index.php?topic=22757.0)