Heading west on I-10, our coach (U295) wouldn't move after spending the night at a truck stop about 30 miles east of Los Cruces, NM. After checking things over and finding the tranny roughly one gallon low of fluid, we resumed west. By the time we reached Tucson, we had added about 6 more gallons in order to keep limping along. By the time we reached Phoenix, the transmission gave it up. A truck repair shop found the driveshaft so tightly wedged between the drive axle and the rear housing of the transmission, that is was deemed to be unable to salvage the tranny. We are awaiting a refurbished tranny, but the shop has no ideas regarding why the driveline had jammed between the housing and the axle.
I have my own suspicions, but cannot prove anything. Anyhow, the drive shaft has been the correct length for nearly 25 years (1995 coach). Sure hope the driveshaft doesn't end up trashing the refurbished tranny.
Larry
Possible bulkhead issues, control arm bushings wore out maybe even incorrect ride height. Others can add to the list.
Bulkhead issues eliminated by Larry.
Extreme Graphics recently said our bulkheads were OK.
Check your motor and transmission mounts, short drive shafts require great alignment. Also check your ride height at the rear and that the driveshaft splines are free to move fore and aft, and may have a grease relief hole that is blocked. Ouch.
You have something that has shifted dramatically. What ever it is should become obvious whenever you change out the transmission. Did you notice any vibration or mis handling of the rear of the coach? Good luck with the replacement and diagnosis.
Do all of the above and think about taking the driveshaft to a drive shaft repair shop and make sure they are getting you a trans
with a retarder and get prices ahead of time.
U joints should be checked for binding or just replaced. I've got a car with a 7.75" driveshaft.
Larry sorry you're having such a expensive repair, I hope you find some answers!
Where did the fluid go?
The only way to tell on the bulkheads it seems is to cut back the fiberglass. Ride hight might be an issue next as the next thing I would look at.
My ? Is with that much wrong how could you not hear something or feel something?
What do you think happened, do
tell. Something has shifted rear axle or engine mounts. Going to be way more to it than a transmission. You sure need to know before installing a new transmission. Shouldn't be too hard to find.
I don't see how incorrect ride height (too high or too low) would "wedge the drive shaft between the axel and the transmission". The drive shaft has sufficient travel in the splines to accommodate any suspension position, full up to full down, without binding.
Incorrect ride height could result in a extreme operating angle in the drive shaft, which could damage the U joints.
Lots of questions to be asked and answered before this failure is fully explained.
Something "Moved" or "Broke" , Engine and transmission should be bolted together, drive shaft would be going forward to the differential, very short drive shaft, the rear axle must have shifted broken center bolt where the axle connects to the "Air Bag" frame?
I would not make any driveline modifications until I checked every part of the rear driveline... Be careful going under this coach, put safety blocks in place to support body. :o
The easiest one to understand this change is also one of the worst failure modes. Xtreme may have given the bulkhead a pass, but if the bolts are broken under the heads and there is no obvious separation, the bulkhead joint could still be loose. The normal unloaded position of the bulkhead joint even with no fasteners installed (on level ground) will be with the joint closed. It could drive normally and if you weren't sensitive to the feel of it, might go unfelt, and yet the retarder operation could be tugging the torque tubes (AKA trailing arms) with every application which could allow the driveshaft to be pushed against the transmission housing. It seems like that much movement in the bulkhead joint would be obvious just by looking, but... We will all be interested to find the cause!
Don
It's all about the typical diesel pusher short driveshaft length so ride height and alingment is critical, the u joints only have 4 breakover points when the driveshaft angle gets too steep to transmit pure rotary force without excessive vertical loads.. Front wheel drive cars use 6 bearing or more constant velocity joints on both ends. The off roaders with lifted jeeps experience the same issues.
Does rear bulkhead failure during rear braking extend or compress driveshaft, somehow I was under the impression that is what strechted the bottom of the bottom of the coach. IDK exactly as I have an ORED.
I'm confused also. Since the rear bulkhead is
forward of the rear axel, I'm trying to follow Don's comment and understand how the bulkhead joint
opening up can
decrease the distance between the rear axel and the transmission. I'm not saying he is wrong! He has extensive experience with the rear bulkhead construction and how it ties in to the rest of the coach framework. I just can't get the picture right in my head.
If the bulkhead joint is loose, use of the transmission retarder can apply considerable force trying to pull the bulkhead joint apart via the trailing arms as it tries to slow the coach via the drive wheels. If the bulkhead joint isn't stable, the trailing arms can allow the drive axle to shift to the rear as the bulkhead joint opens. When the axle shits to the rear, the driveshaft could potentially be driven towards the transmission. To a lesser extent, engine braking can do the same thing as the front brakes are not in play unless applies by the service brakes. Conversely, accelerating will try to close the bulkhead joint if it is separated. Similarly, if the airbags behind the drive wheels deflate for some reason, the airbags in front of the drive wheels push down on the front of the 'H' frame that carries axle which would apply a force tending to separate the bulkhead joint. This last only applies to the semi-monocoque Unicoach or Unihome with the eight airbag suspension. The attachment of the control arms, trailing arms, torque tubes... call them what you will, are what locates the drive axle as acceleration or deceleration forces from the drive wheels work to speed up or slow down the coach in motion. The above understanding came to me when I was repairing my bulkhead joint and I was able to separate said joint at will by placing two bottle jacks either behind or infront of the drive wheels. This is of course with no fasteners in place trying to hold it together. Think of a teeter totter with a fat kid only on one end or the other. In this case, the drive axle is the fulcrum and the bottle jack is the fat kid. I hope that I explained it clearly... It is difficult to put into words but would be simple to understand with a diagram.
Don
Edit: for clarity, I hope. I am not trying say that the above is the cause of the OP's issue, just that the dynamic forces of the drive axle through the attachment of the trailing arms to the bulkhead could apply force that might explain what happened. I am pretty convinced that my understanding of the relationships between the drive axle, the trailing arms, and the bulkhead joint is largely correct because I have done thought experiments which proved to be correct as I struggled with rebuilding the bulkhead joint. The use of leverage and mechanical advantage through the bottle jacks, allowed me to open and close the bulkhead joint at will. It was inspiration through sheer desperation.
Don could be on to something here. I would take a close look at the bulkhead
Changing ride height won't bother the driveshaft. That's what the splines are for. Driveshaft angles at each end should be less than 1 percent and not more than 3 percent for max life. This is the angle out of the pinion gear compared to the input shaft angle on the transmission, not the angle of the driveshaft. Vertical movement of the rear axle should not change this. It would take a failure or something major for angles to exceed this.
Pierce
All of that being said, a drive shaft expert can give allowable degrees angular +/- movement- based on driveshaft play length joint to joint before bad stuff starts to happen.
Larry, sorry for your problem. I am at a loss why I don't know what model year you are driving, so responding is not targeted.
Many years ago, Foretravel had a recall on our coach for driveline ANGLE.
Measurement were made with an angle measuring device, and adjustments to the angle made by putting a taller rearmost center engine mount that is below the crankshaft pulley, changing the angle of the transmission which is bolted to the engine. Ours had the mount changed to a taller mount
I think out of ANGLE drive shafts were damaging transmission end bearing.
Also, separately and likely not related to the driveline angle, Allison had a modification change for the part that keeps the transmission end bearing in place. I think the original part had one bolt and the revision had two bolts and the revised part came with the specified two bolts.
During an inspection, our end shaft was found to have some upward movement, that led to my Allison knowledge and our transmission end bearing being fixed.
Maybe your end bearing failed taking the seal with it, causing your early tranny fluid leakage. And from your description, if the coach was towed instead of being driven the transmission housing maybe could have been saved.
Also, I wonder why the end of the transmission can't be rebuilt, but maybe a whole rebuilt would be better and less expensive.
After hearing first hand stories of truckers damaging RVs that park in 'their' space, we never park among truckers at truck stops, Walmart, casinos, etc. What could they have done, no idea. We dry camp a lot, just not near truckers.
What Phoenix repair shop are you in? And how did the shop get selected. I think WW Williams is the shop that specializes in Allison.
Good luck.
I beg to disagree with your opinion, as u joints roll rover center when not inline, and my coach drive shaft is only about 16" long. So 1% to 3% total from the axle centerline to the to the transmission tailshaft has to be made up as the suspension moves up a down a couple of inches up and down from design ride height. For this reason I believe rear ride is important.
Let's wait until owner gets up and gives us more info,we can speculate but never know and we all want to know.Sounds like
whatever was causing the trans fluid to leak may be why they are saying the trans is shot.Were'nt there some posts a few years back
about the seal area on the trans wallowing out and causing a problem?The driveshaft is already out to work on the trans and u-
joint are not hi dollar I would get new ones to go with the tranny.We need to also know if the housing is broken or they are
saying something in the trans cannot be repaired.Think from what I know I would rule out motor mounts and axle movement,the motor mounts are big rubber washers with big bolts thru them and the axle is bolted so there is no front to back movement,unless
Don is right.Remember a few months back when David in Vegas had that torque rod bolt break off,he could have a couple like that
and not know it until now,that would throw things off some,when I redid mine I had to cut some of the bolts in 2 places due to parts
rusting and fusing together and mine did not look that bad,his may be worse.
Sorry for your loss.
Keep in the back of your mind that mechanics, for the most part, aren't paid to analyze problems.
I don't know where to start but some quality time spent closely examining everything from the bulkhead back is where I'd start.
It's usually something simple that's gone wrong, so I'd look closely at everything from the stuff that locates the rear axle to the stuff that locates the engine.
Jumping to conclusions is great exercise but it doesn't get the job done.
Take time to think. The best way to kill a fresh idea is to try and force it to the surface.
A "root cause analysis" is definitely required. It might be as simple as a failed transmission bearing, or a major suspension failure, or ?? Don't just replace parts without understanding the root cause!
No, the angle coming out of the rear end the the angle coming out of the transmission never changes as they remain parallel when the rear end travels up and down. The driveshaft angle changes but not the extended centerline of the pinion and input shaft for the tranny. For a conventional driveshaft (no constant velocity joint) 1 degree is ideal with 3 or 4 degrees the limit for long joint life. Note how to calculate driveshaft angle in the second image attachment.
So, while it's nice to have that 1 to 3 or 4 degree driveshaft angle (not pinion or input shaft angle), it will operate at angles exceeding this but it's not likely in our coaches while traveling down the road. Note the calculation for the real angle in the second image. It would seem much greater but when the measured 7 degree angle is actually calculated in relationship to the U-joints, it's only 4 degrees. While it looks like a lot, when you calculate it, it's only about half that much.
With proper rear end geometry, the rear axle assembly will NOT rotate as it travels up and down over bumps, etc but remain parallel with the centerline of the transmission output shaft.
Pierce
I believe this whole episode started back when we bought the coach. I immediately had the chassis serviced and the mechanic found some slop in the output shaft. After some research, I found that Allison had issued a service bulletin that the retainer torque, for the tapered roller bearing at the end of the output shaft, might not be properly torqued. I gave the new torque spec to the mechanic, but he said that was way too tight. He retorqued it to what felt 'right' to him.
Fast forward 5 years and 16K miles.
I tend to think the retainer loosened again and that the driveshaft 'worbled-out' the seal which then resulted in profuse oil loss.
We pulled into a RV dealership in Gilbert AZ. They suggested that they could take it to a Freightliner dealer and have them repair what I was fairly certain was the culprit. "Were'nt there some posts a few years back about the seal area on the trans wallowing out and causing a problem?" I appreciated their offer and took them up on it.
Fast forward a few days.
We went home to Augusta, KS as we just couldn't reconcile ourselves to a lengthy motel stay with two hounds...1200 miles from home...and tax time upon us.
Fast forward a few more days.
Freightliner called and said that the driveshaft had jammed into the transmission housing, and that the housing was damaged to the point where it would no longer retain a seal.
After some deliberation, I recalled that the RV dealer employees ALWAYS dumped the air to set their coaches lower for easier entry by potential customers. I recalled that it was just a reflex action on their part. They always did it.
So my guess is that when this RV dealer had an employee shuttle our coach to the Freightliner shop, he undoubtedly dumped the air.
At this point, I need to tell you that the air system in that old U295 is no longer robust (still easily meets DOT). It takes a while to get up to 110 psi. The old coach won't go to ride-height until you release the brake after hearing the pop-off valve. However, the brake releases arounf 60 - 75 psi if you wanted it too.
My quess is that the mechanic...always in hurry...released the brake as soon as the whistle shut off...not realizing that he hadn't attained ride-height...and drove (not crept) the dumped coach over the door threshold and caused the ensuing damage.
I've discussed this...over the phone...with James at FOT. He agreed that 'MIGHT' have caused it.
Anyway, I won't be sleeping too good tonight after reading some of your reponses.
Larry
I seem to remember Al & Sue McMurray had the same issues after MOT ferried their coach from southern Oregon to Nac to consign for sale......... It also was a 36 footer..
Regarding Xtreme...shortly after we purchased the coach in 2014, the bay door over the propane tank popped open...while driving...and damaged it. Ripped the rivet holes along the hinge-line like a failed zipper.
When we went to attend wife's driving school, Xtreme rebuilt it for us. After installing the repaired door, the fiberglass tech offered us a quick look-over (at no cost) for other problem areas. He then pointed out how the bulkhead repair had already been accomplished on our coach.
The bay door damage...and the bulkhead repair...is really, really sore point with me. Has NO ONE...at FOT...ever heard about such a thing as minimum edge-margin for fasteners? Grrrrrrrrrr...
Your theory about the tech driving the coach before acheiving ride height sounds plausible. Tire contact with the top of the wheel well by the drive wheels would also try to force the axle back towards the tranny. At any rate, you will sleep better when you know the root cause of the damage, so I hope your investigation brings you that closure. Everything looks better after a good nights sleep, so I hope you get that tonight!
Don
Larry,we all emphasize with you and wish this did'nt happen but you may never know the cause just the result of the problem.
Hate to say it but the root cause may be the air system not building enough air and loosing air.The coach is fixable,is there
any way your insurance would pay for a tow to another shop in case your not happy with this one?If the guy did not torque to
the right spec and his feel was off that's probably what happened with the oil loss.When you finally get the coach running make
an appointment with HWH in Iowa and they will go over your system free of charge,won't fix it for free but tell you what's wrong.
Keep us posted and what year is the coach.
I'm sorry for your loss, and you might understand my paranoia when dealing with outside "help."
A past friend of mine, Tony, owned a 1959 Cadillac Eldorado Biarritz Convertible and this automobile too had air bag suspension powered by a vacuum operated duplex air compressor. The final blow was a simple engine oil change at the dealership where the driver didn't want to wait for the air suspension to rise from its rest and crunched the engine oil pan on the lip of the garage.
This stuff happens more often than you think it does.
Let us hope that the Freightliner shop is more professional.
John, the coach is a 1995.
I really don't blame Freightliner for the situation. Most coaches, in that age range, don't level with air. I suspect that the tech (mostly used to working on trucks) may likely have never encountered such a situation. The shop has a good favorability rating, and they are quite cordial in keeping me abreast of what is happening.
There is much more to my story. My wife and I had been contemplating upgrading to a larger and newer coach for some time. This dealer had a consignment coach that came fairly close to matching our 'want list', so we bought it. However, it was a bit like a shotgun wedding. The 1995 has to be fixed before I can consign it in good conscience...assuming that I, indeed, do want to consign it. Turns out that the grass is always greener on the other side of the fence, and the newer coach isn't exactly paradise either. We are actually mulling over consigning the newer (2002) coach and keeping our old 36' 1995.
For example, I had always assumed that 450HP would move a 42' foot coach up the on-ramp rather assertively. It doesn't. It whimpers up the on-ramp. The C8.3 moves our old 36-footer much more assertively. Obviously, the 5.13 axle ratio on the 1995 is a HUGE factor when compared to the 3.91 axle ratio on the 2002 coach.
Anyway, I'm sure the epilogue on my gravestone will read that there is one thing worse than becoming old - becoming old and stupid!
Larry
I don't understand the infatuation with acceleration.* Never mind the number of long trips I've taken in antique automobiles, I once spent three summers driving my freshly built 1926 Ford to antique auto shows in New England. What could have taken 5 hours now took my 12 or more hours travel time. I enjoyed the day and gained an appreciation for just how much smaller our world has become.
That being said, recognizing that you aren't happy with a recent decision and having the ability to change your mind makes you intelligent.
*I have a very fast motorcycle for that foolishness.
Larry,
You should have your fuel pressure checked as your M11 40 footer should not let much grass grow underneath it. Something must be amiss that perhaps other owners may want to comment on.
I followed a 36' U320 M11 and while we were up at a little over 5000 feet, we had to have just the right upgrade for our Detroit to barely creep up on the other coach. The rest of the time, the six speed U320 was just faster, especially from stop signs where the perfect first gear in the U320 had them half way down the block before I crossed the intersection with our four speed.
Your coach should do almost as well as a 36 footer so get it checked out.
Pierce
I have no infatuation with acceleration...though it makes me sweat when a car bears down on me at 75 mph...driver texting instead of having eyes on the road...while I'm still doodling along at 25 mph.
Whitch coach you keep is up to you alone to choose,pros and cons for both ways.I would put it for sale here with your low price and see what happens before consignment,you can always try and sell without the trans repair as long as you disclose the problem.
Well if you want to go down that road, fuel filters can restrict the fuel flow enough to reduce power. 450 HP is a lot of fuel flow.
Larry, we have a 40'320 w/450 and it will move right along when you want it to, as posted above I would be checking fuel flow and pressure then possibly new fuel filters
Chris
And alot of intake and exhaust flow. Bigger rotating parts to slow acceleration. Colin Chapman nailed it with "simplify and add lightness"
Is the 42 footer a Foretravel? If so, that 450 hp has to move a lot more weight than your 36 footer with the 300 hp 8.3 Cummins. If it is not the ISM in a Foretravel, and an ISL, in another brand, torque will be lower and acceleration could very be slower than your 36 footer. Horsepower to weight ratio is important.
Yes, the 42-footer is a U320 with an ISM. Yup, the 36-footer with a C8.3 has a better hp/weight ratio.
Had a 34 footer with the ISC 350, faster than my 40 footer with a 500 hp ISM. Can't mess with physics, talking 14000 lbs difference.
Had the housing crack on one of our install trucks.. when they bolted the torque converter down they cracked the housing.. I welded it up and put it back into service. Dont know if that is possible but a cheap fix
Larry when I first drove our m11 I was unimpressed at the power.
Long list of changes made it much better. But we are at 36,000 pounds combined.
You certainly weigh more.
The 450 can probably be raised to 500hp. Brads brother Dave did his.
Exhaust, fan drive controller, good batteries, good alternator, solar to turn off the alternator during a drive, valve adjustment, cam position sensor, altitude sensor replacement, blue tech air filter, low rolling resistance tires, synthetic oil in wheel bearings.
Everything together made a fairly large difference in the engines ability to stay in gear up grades versus downshifting.
But at 10k more weight I would think it's still not impressive.
Brads brother Dave had friends at the Cummins dealer who may have bumped his power up even more somehow.
He's gone and no one knows. But the 500 hp is possible on the ISM