Replaced P-3 Carrier and Bearings

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Replaced P-3 Carrier and Bearings

August 13, 2016, 06:13:24 pm

After feeling a vibration that got worse with time, I took our 36' 1997 U295 coach to Stewart & Stevenson in Longview, TX, for evaluation and repair. When I first noticed the vibration, it was at about 55 mph. With time, the vibration was stronger, was present over a wider range of speed, and was strongest at lower speeds. When I arrived at S&S, the vibration was noticeable from 40 to 55 mph, and strongest at 47 mph. The folk at S&S checked the output end of the transmission and found: the bearing fastener was tight (that's good, some fasteners get loose with time); the P-3 carrier, bearings, and races were worn. They replaced all worn parts, replaced filters, replaced fluid with Transynd, and pronounced the problem to be fixed.

I drove 260 miles and found the vibration to be remarkably less. I think I still feel a bit of vibration at about 48 mph. I think that may be a "normal" vibration.

James Williams, the service manager, was personable and effective. He is very familiar with the issue, and has managed a lot of work on Foretravel coaches. In phone conversations prior to my trip to Longview, he said the problem was most likely in the P-3 carrier and he estimated that it would take about four days fix the problem. I arrived at the shop at 8:00 a.m. on Tuesday morning and left about 1:30 p.m. on Friday. The cost of the repair was a bit under $5,000. I stayed in a local hotel during the work since the coach had to stay inside the shop and was not habitable. They can keep a coach plugged to power while they work, but were pleased that I arrived with an empty, warm refrigerator that was not in operation.

James reported that they have not had a "second failures" of the P-3 carrier and bearings. Our coach is at about 140K miles.

Re: Replaced P-3 Carrier and Bearings

Reply #1 – August 13, 2016, 09:15:07 pm

Stopped in at the S&S shop in Longview a few years back. They were recommended by MOT to do a diagnosis on the transmission for a sending unit that was cutting up a little. They did the diagnosis through a computer hookup, found it was a sending unit, had me out of the shop in an hour. James was also the service mgr. at that time. They also had a couple of foretravels in the shop for service work. Very efficient operation, would recommend.

Re: Replaced P-3 Carrier and Bearings

Reply #2 – August 13, 2016, 09:46:31 pm

J.D.,

Unfortunately I can report a repeat failure. The coach we purchased in June was held up having James' crew do the repair. James told me it was the worst case he had ever seen (I knew there was more than 1/2" of end play as measured at the output harmonic balancer, and upon acceleration witnessed what felt like a 350 hp impact drill). There is a thread on this forum going back several years and everyone with a short FT (not U320 though) should read it carefully. I'll get back to that in a bit.

I was comfortable that we would enjoy another 86k miles with the repair being complete and didn't hesitate to proceed with the purchase. A couple of weeks after having it I was compiling its history from the very complete lifetime service records. I happened to discover a small invoice for a full rebuild at 45k miles (that was the first owner). Don't think my heart didn't skip a beat because I quickly recognized that the P3 carrier bearing had cost over 20 cents/mile over the coach's life. I had accepted a mental accrual of 10 cpm. This was new territory. I'm glad I missed it on the due diligence because I think we would have passed knowing about the two-time loss. We are happy we bought it.

Not to rationalize but I know the first one was luck of the draw. If people read the thread, it's clear to me that FT had a design serial defect on their hands and they did a lot of work in the late 90s to try and minimize the impact. Unfortunately the geometry of the driveshaft fatigue cycles the weak link in an otherwise very robust transmission. You don't hear about this in any other make or model. I suspect the owner at the time was unaware as it was out of warranty and probably didn't consult FT.

I am suspecting since the first rebuild was done on the West Coast, it wasn't in collaboration with FT like Stewart and Stevenson in Longview, Texas. So at best it probably got rebuilt as original with no upgraded parts or assembly process. Interesting, it was $5k.

Jumping forward to 86k miles, I am aware that when this coach left the West Coast for MOT, the HWH ride height was not working. So at least 1800 miles of potential abuse on the drive shaft system. I don't know how much more before that. So the second failure might not be such a terrible thing, but I will still mentally accrue 20 cpm and hope it never comes to pass.

But the real message ties back to the driveshaft vibration thread. There are things we all can and should do to minimize the risk. As I mentioned, DO NOT DRIVE in manual ride height mode. In case of HWH failure, it is a good idea to have your height measurements so that if you have to limp it somewhere, you don't do so causing more fatigue than necessary. Second, and from the thread, pay careful attention to the u-joints. I plan to grease them before every trip. It's tricky to get all four zerks from one position. I am going to try a right angle grease attachment. If that still proves troublesome, I'll change the zerks from straight to right angle. Shouldn't take more than 5-10 minutes to grease them (and the splined shaft, which is easy) and clean the excess grease. I know I can get it quicker. My first time I got attacked by fire ants and suffered more than 50 bites across my neck and arms before I could crawl out. This is personal.

Finally, when under there greasing the drive shaft u-joints, check the output shaft end play with a big screw driver or crow bar. Shouldn't be any, but get used to knowing how to check it. Very easy if you have the harmonic balancer on the end. If end play is discovered (approaching 1/4") get to S&S if possible and have it checked. I hope that early detection of bearing wear can cut the repair cost down significantly. The thread kind of hints at that. If everyone does this, I think they will find it before a vibration becomes apparent. I can attest, there is no vibration now in ours.

S&S at Longview is probably the best place to go since they have such a rich history with this issue and tight collaboration with FT. Hopefully it never comes to pass, but I would like to believe I could drive across Houston to the S&S shop (50 miles) versus 270 miles to Longview. And for owners that aren't even in Texas, I would like to believe they could visit their local or regional S&S shop and have their representatives communicate with James in Longview. If the problem arises, we are all better off with proactive attention and seeking the best attention possible.

I suspect that these failures are still more pervasive than we first thought. There are a number of repairs that compare in cost to this one and so some might have just accepted it and moved on. This forum is great in many ways. Hopefully with heightened awareness, we can spare a lot of owners some unnecessary expense and grief.

One additional note, my conversation with James aligns with J.D.'s description. First class. My only frustration is that he told me they would put the old parts (almost everything in the planetary sections) in a box in the bay because I wanted to shadow box the bearing. They forgot to do it.

Alan

Re: Replaced P-3 Carrier and Bearings

Reply #3 – August 14, 2016, 01:10:28 am

Quote from: Oxbowgal – August 13, 2016, 09:46:31 pm

J.D.,

Unfortunately I can report a repeat failure. The coach we purchased in June was held up having James' crew do the repair. James told me it was the worst case he had ever seen (I knew there was more than 1/2" of end play as measured at the output harmonic balancer, and upon acceleration witnessed what felt like a 350 hp impact drill). There is a thread on this forum going back several years and everyone with a short FT (not U320 though) should read it carefully. I'll get back to that in a bit.

Alan

Why not the 320? I didn't read where you got back to that issue.

Re: Replaced P-3 Carrier and Bearings

Reply #4 – August 14, 2016, 06:03:05 am

Craneman,

I rambled on in that note and didn't provide the detail on the 320 (or U-295 that have the bigger engine). It comes with the Allison 4000 series transmission. The 3000 series is a brute in its own right. The drive shaft geometry induces some fatigue stress elements that manages to hunt down the weakest link. Since the 3rd planetary carrier bearing handles the final output loading, that is probably the weakest link. Might be so on the Allison 4000 as well, but we are talking about a much beefier system. The Allison 1000, 2000, 3000, and 4000 series are all the same basic design but grow progressively in size and weight. I would love to see the difference in the P3 carrier tapered roller bearing between the 3000 and 4000.

But since you ask, perhaps someone has had a failure in a 320?

I didn't mention it, and it is because it would be pure speculation, but one thing that differentiates the FT from most (not all) other brands that use the 3000 series Allison is the retarder function. It is a wonderful feature but does subject the driveline components to stress when used hard. That stress is not chronic (like forward acceleration and cruise) but perhaps more intense when called for. Which fatigue stress elements contribute the most to the failure? It would be interesting to see if a finite element analysis was done back in the 90s.

Alan

Re: Replaced P-3 Carrier and Bearings

Reply #5 – August 14, 2016, 09:01:11 am

Alan,

The two grease zirks on each U joint go into the exact same center section of the joint, so they lube exactly the same. They have two because one is always much easier to access.

Said another way, grease EITHER one-- no need to grease both zirks on a U joint.

And, only two transmissions used on the coach years you are referring to.

Allison 3000, up to and including the ISL
Allison 4000, only on engines larger than that

Re: Replaced P-3 Carrier and Bearings

Reply #6 – August 14, 2016, 09:39:36 am

Quote from: Oxbowgal – August 13, 2016, 09:46:31 pm

J.D.,

Unfortunately I can report a repeat failure. The coach we purchased in June was held up having James' crew do the repair. James told me it was the worst case he had ever seen (I knew there was more than 1/2" of end play as measured at the output harmonic balancer, and upon acceleration witnessed what felt like a 350 hp impact drill). There is a thread on this forum going back several years and everyone with a short FT (not U320 though) should read it carefully.

Alan,

Here are a couple of the earlier threads you refer to (to save everyone else the searching...)

Vibration in rear of coach

Transmission Dampener

U295 Driveline vibration issues

Re: Replaced P-3 Carrier and Bearings

Reply #7 – August 14, 2016, 10:21:34 am

Mr. Stevens - are you saying the vibration was felt throughout the coach? I have no vibration in the front, but in the bedroom it's kind of like an earthquake, albeit a small one. (How does one quantify vibration?) A paper cup left on my desk will stay in place, a soap dish in the bathroom will move around a bit but hasn't so far fallen off. Should I expect NO vibration in back?

One of the links that Michelle just posted states that the P3 nut problem was a 97-99 issue. Can anyone confirm or deny that?

Re: Replaced P-3 Carrier and Bearings

Reply #8 – August 14, 2016, 10:35:59 am

Quote from: Gayland Baasch – August 14, 2016, 10:21:34 am

One of the links that Michelle just posted states that the P3 nut problem was a 97-99 issue. Can anyone confirm or deny that?

In the links I posted - Jim and Gayle McNeece indicated it happened with their '96 U295

Re: Replaced P-3 Carrier and Bearings

Reply #9 – August 14, 2016, 11:35:23 am

Gayland,

Is the issue a vibration or just rougher ride in back?

Said another way, does it do it on smooth roads as well as rough ones?

Re: Replaced P-3 Carrier and Bearings

Reply #10 – August 14, 2016, 11:54:56 am

The difference between the u270/u295 and u320's is also the rear-end final drive gearing. I wrote a few threads on what I did to solve the problem...I changed my rear to 4.33.

My hypothesis for the p3 failure is that the transmission was never designed to run at such high output shaft RPM with the 5.13:1 rear end it originally came with (the 3000 was originally made for trash trucks and school buses!). Those that cruise at 55-60mph seem to have fewer p3 problems.

Anecdotal evidence only.

Re: Replaced P-3 Carrier and Bearings

Reply #11 – August 14, 2016, 12:40:33 pm

While the rear axle ratios may be high, remember with the Allison 3000 and 4000, both 5th and 6th are OD's.

.65 for 6th
.75 for 5th
4th is 1:1

Re: Replaced P-3 Carrier and Bearings

Reply #12 – August 14, 2016, 01:35:40 pm

I know I'll get the negative comments but seems to me this would be a good case to use synthetic in the rear end.
You have a bearing getting worn for whatever the reason,why would you not want to put the best oil in that area.
I realize the end we are talking about is in the trans but the other end of the drive shaft is in the differential.

Re: Replaced P-3 Carrier and Bearings

Reply #13 – August 14, 2016, 01:59:53 pm

Does anyone know if the drive shaft is the same length with the 3000 or 4000 series transmissions?

Re: Replaced P-3 Carrier and Bearings

Reply #14 – August 14, 2016, 02:20:03 pm

Quote from: wolfe10 – August 14, 2016, 12:40:33 pm

While the rear axle ratios may be high, remember with the Allison 3000 and 4000, both 5th and 6th are OD's.

.65 for 6th
.75 for 5th
4th is 1:1

Yes, and doing a double overdrive spins the driveshaft (and P3 bearing) very fast with a 5.13 rear end. Since nothing is perfectly balanced, the faster something spins, the more energy there is in vibration.

Re: Replaced P-3 Carrier and Bearings

Reply #15 – August 14, 2016, 05:21:24 pm

Quote from: krush – August 14, 2016, 02:20:03 pm

Yes, and doing a double overdrive spins the driveshaft (and P3 bearing) very fast with a 5.13 rear end. Since nothing is perfectly balanced, the faster something spins, the more energy there is in vibration.

The 1999 U320 has a 3.91 to 1 even with double over drive not spinning as fast as my old '81

Re: Replaced P-3 Carrier and Bearings

Reply #16 – August 15, 2016, 09:21:45 am

Brett - I would deem the roads I was on were very good, I 90/I 94 between ND & Washington State, but my experience is limited as I usually don't have anyone along to drive so I can check whats going on in back. I'm thinking I should see if there's a reliable place in Fargo where I can have it checked out, just for piece of mind if nothing else.

Re: Replaced P-3 Carrier and Bearings

Reply #17 – August 15, 2016, 02:54:23 pm

I am wondering if the amount of suspension movement up and down might be affecting the p3 wear issue.

I am assuming all the non u320's had bilstein shocks?

Less dampening on top of more rpms might be a factor.

The more up and down might also be wearing the watts linkage cross arms bushings allowing side to side movement of the rear suspension unit along with up and down?

Anyone had a p3 issue with FSD shocks?

My two cents

Re: Replaced P-3 Carrier and Bearings

Reply #18 – August 15, 2016, 04:04:07 pm

In the links Michelle posted in reply # 6 it appears to be a Allison issue and there were adjustments made on the cost of some of the repairs. Loose bolts was one issue.

Re: Replaced P-3 Carrier and Bearings

Reply #19 – August 16, 2016, 12:00:34 pm

Quote from: krush – August 14, 2016, 02:20:03 pm

Yes, and doing a double overdrive spins the driveshaft (and P3 bearing) very fast with a 5.13 rear end. Since nothing is perfectly balanced, the faster something spins, the more energy there is in vibration.

I would like to input my 2 cents worth on this thread. The rotational speed of the drive shaft and transmission output shaft is totally related to road speed and has nothing to do with the gear the transmission is in. The only way to change the rotational speed of the drive shaft is to change the gearing in the rear end as Krush has done. I'm not sure this is a good thing as the torque transmitted by the drive shaft has to increase to move the coach assuming conditions are identical. Does the increased torque put more load on the P3 bearing? I don't really know, but It would put more load on the U-joints, but they can probably handle it. On most vehicles the drive shaft, rear end, engine and transmission are in as straight a line as possible, so that the U-joints are used as little as possible, and to reduce the variation in rotational speed of the drive shaft. See this: Universal joint - Wikipedia, the free encyclopedia I suspect this problem is more related to the angle of the very short drive shaft than it is to the rotational speed, although I have no proof of that. I would agree that driving at a slower speed reduces the loads and reduces the chances of a failure. To the best of my knowledge, I have not had this problem, but like some others have not been able to go to the back of the coach when it is in motion. I grease the U-joints quite often because I think they get a good workout on the short drive shaft. We would have a longer drive shaft, if we did not have the retarder and less of an angle change when the rear end moves up and down. Exactly where is the P3 bearing? Is it before the retarder? I believe the retarder is a bolt on option, but I could be wrong; doubt if the P3 bearing changes position, but there must be a bearing at the output shaft on the retarder. Is that the bearing that is failing? This also brings up another point; since the rotational speed of the retarder is the same as the drive shaft and it's effect is much greater at high drive shaft speeds, reducing the drive shaft speed also reduces the effect of the retarder. Although in most cases doubt if it would be noticed. I once asked an Allison tech rep if the retarder added some drag/friction to the system when not in use. as compared to the same transmission without the retarder, and he said that it did. It's a small amount, though it does increase with speed. The vaned rotor in the vaned retarder housing is still working against air resistance. We would all get slightly better mileage if we didn't have a retarder. So Krush have you noticed a mileage improvement, slower acceleration, or ability to climb a very steep hill?

Re: Replaced P-3 Carrier and Bearings

Reply #20 – August 16, 2016, 01:01:50 pm

Quote from: Jerry Whiteaker – August 16, 2016, 12:00:34 pm

So Krush have you noticed a mileage improvement, slower acceleration, or ability to climb a very steep hill?

Same MPG, but I now cruise at 75 instead of 63-65. Better driving climbing hills because now the 1:1 4th gear at peak HP rpm (2200-2300RPM) is at a more usable 59mph. I wrote two or three threads summarizing everything, I'm not going to repeat everything here.

The 3000 series transmission is completely different than the 4000. Also, the 4000 u320's run a 3.91 rear end AND the transmission is much bigger and stronger than the 3000.

Around 1999 the alison went from the 3060 to the 3066. The 3066 looks to have a stronger output shaft design. Also, the u270's went to a 4.63 rear.

I don't have play in my output shaft, even when using a prybar. But I did feel a vibration over 65-70mph with the original 5.13's. I swapped to 4.33 and now if I hit 80 I get the same vibration. I believe it's driveshaft related. Regardless, with the 4.33, my 70-75mph is equivalent to going about 58-60 with 5.13s.

Anecdotal evidence and phone calls with other owners suggest that those that drive under 65mph have less p3 problems. Do what makes you feel good.

Re: Replaced P-3 Carrier and Bearings

Reply #21 – August 16, 2016, 04:38:53 pm

Quote from: Gayland Baasch – August 14, 2016, 10:21:34 am

Mr. Stevens - are you saying the vibration was felt throughout the coach? I have no vibration in the front, but in the bedroom it's kind of like an earthquake, albeit a small one. (How does one quantify vibration?) A paper cup left on my desk will stay in place, a soap dish in the bathroom will move around a bit but hasn't so far fallen off. Should I expect NO vibration in back?
...

I noticed the vibration while sitting in the driver's seat. I could feel in at my butt and I could feel it through the steering wheel. When I first started noticing it, I asked folk at FOT to diagnose it. They hardly noticed it and suggested that it was tires. There was indeed some cupping in the tires. Later, I asked Wayne to check for play in the drive shaft. He pronounced it to be tight and again suggested the problem was tires. This spring I put on all new tires. The vibration was still present and growing worse. I took it to Stewart & Stevenson in Longview, TX, for repair. They reported significant lateral movement of the vibration damper at the output of the transmission.

The following paragraph includes fodder for consideration with respect to some of the issues brought up in the thread.

The engine is Cummins C8.3-325 with Banks Stinger. The coach is at about 145K miles. I replaced the Bilstein shocks with Koni FSD shocks at around 70K miles. I used Dexron fluid until the recent repair. S&S installed Transynd during the service and repair event. To the best of my knowledge, the retarder did not come off the transmission for the repair. While the coach was on the lift, it was at (or near) normal ride height. The drive line was very straight. When conditions allow, we drive steadily at 65 mph. We only go faster than that for very brief periods of time. Engine speed at 65 mph is about 1900 rpm. We leave the "Retarder" switch on all of the time. We leave the joystick at position "0" except when we require some speed control on long descents.

Re: Replaced P-3 Carrier and Bearings

Reply #22 – August 16, 2016, 06:02:25 pm

Quote from: J. D. Stevens – August 16, 2016, 04:38:53 pm

The engine is Cummins ... blah, blah, blah ... joystick at position "0" except when we require some speed control on long descents.

... and we have a good time! We get to sleep in OUR OWN dirty sheets, use our own potty, take the grandkids to our place when we go to visit their parents, take our dog, and ... you know the drills.

Fix 'em up and enjoy the adventures when you can.

Yes, this post is off topic. I started the thread and this post gets past the technical details. It addresses the reason why we keep fixing things.

Re: Replaced P-3 Carrier and Bearings

Reply #23 – August 17, 2016, 08:43:56 am

I think there likely is a design or manufacturing flaw on the original 3060 transmissions. I heard rumors of some allison bulletins or at the very least, some shop knowledge. I think S&S is the place to have the repair done as they have done many of them. FT will never admit that these p3 repairs exist, including the well regarded tech guy at FT. Allison will never admit that some of these have been repaired, nor is there any multiple of p3 repairs, as that would show some type of flaw. This is common in all industries, and the truth it that your RV lasted nearly 20 years before having the problem. Sleep well knowing that it likely will never reoccur.

Re: Replaced P-3 Carrier and Bearings

Reply #24 – August 17, 2016, 11:48:48 am

If for some reason you think you may have the P-3 problem starting,take a oil sample of the trans fluid the bearing material
will surely appear.

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