Allison MD3060R P3 Carrier Bearing Fix

Topic: Allison MD3060R P3 Carrier Bearing Fix (Read 1188 times) previous topic - next topic

Allison MD3060R P3 Carrier Bearing Fix

June 02, 2023, 10:17:39 pm

Well this post is long due. I spent countless hours researching this mysterious P3 carrier bearing retainer nut coming loose issue. Everything I found was about how this shop or that shop knows the problem and can fix it. I am always determined to fix what I can myself so I want to write this up. There is no reason anyone with basic mechanical knowledge could not do this themselves. (**IF you have the Allison specific tool, more about that coming up)

I spent all winter trying to find documentation on this repair and the tools needed. I ended up buying the Allison repair manual for the transmission. That alone was hard to find and cost almost $80. It came as loose sheets that a shop would put into their 3 ring binder. It actually is quite nice. Great giant fold out diagrams kind of like some the FT documentation. With more knowledge in hand I found the specific tools I needed. Only problem is the socket setup alone was going to $600, the repair kit that comes with the special seal press was over $1500. I stalked Ebay religiously for months and the lucky day came. Someone posted the repair kit, unused, prob from an auction or closing business. I wrote them a very kind message and asked if they would be willing to sell it for $750. They were so kind they sold it to me for $500! So with the new tools in hand, and some knowledge via research I dove into this late at night for 2 nights to fix it. Let's begin!

Items needed:

1- J-50863-A Allison Maintenance Toolkit (Read on, I will rent this out)
2- 29556870 Allison specific seal
3 - 2) o-rings that go behind Allen bolts (sorry I never got part numbers for these. I called a Allison service shop and gave them my serial number and explained what I was looking for and he found them in stock)
4- Large breaker bar wrench (3/4 drive)
5- Torque wrench (3/4" drive as well, use adapters if needed)
6- basic sockets, wrenches, and swivels

The first step (after properly lifting and blocking suspension at full height with safety spacers) was placing a pry bar under the large balancer and gently prying upward off the retarder lines. The whole assembly was very loose. I could move it up and down at least 1/4", maybe more. Obviously a problem. I've read that some folks will pull an axle shaft or lift one side of the rear tires so you can spin the shaft and make access to the bolts easier. I chose to be lazy and quick and just did it in place. Admittingly I would say it would have been easier if I could spin the driveshaft while doing this.

I thought I was going to take the rear u-joint apart to take the driveshaft off, I broke a ujoint cap in the process and quickly realized that was not even needed to take this apart. oops, ignore that part.

What needs to come off are the (8 I think) 14mm bolts inside the balancer. At this point the driveshaft and balancer are loose and want to fall and crush you. This thing is HEAVY. Like 100# and awkward. I muscled it out but if I was doing it again a handy pull strap and supporting it and lowering it down would be better. With the back end loose you can loosen the grease retainer ring and slide the shaft off the splines and set aside.

What you are left with is the mounting plate coming off the output shaft. It is held on by (2) larger Allen cap head bolts. (forget size sorry) There are 2 o-rings behind these bolts, keep that in mind as they will need to replaced as well as the rear output seal. Once the two bolts are out (I used a prybar across the bolts to hold while loosening them. I did this all with hand tools, no impacts, as it was late at night and didn't want to make noise. ) you can remove the plate by just sliding it off.

Once removed I pulled the old seal out, popped loose pretty easy like most rear main seals. What you are left with is the retainer nut and lock tab washer. My nut was finger loose. The tabs on the locking washer had no tabs bent over. Makes me wonder if they came loose and bent over or did the factory just never bend them over!?

Now comes the fund part, get to use these massive expensive tools. There is a very specific technique laid out in the manual on how to do this. There are two "sockets". One fits inside the other. One holds the output shaft and is splined. The other slides over and makes contact with "teeth" on the end that grab the spanner nut that tightens down and holds the bearing tight. If you look at the picture you can see my two bars. One is just a 3/4" drive breaker bar to hold the spanner nut (outer socket. The other is a torque wrench with a 1/2" to 3/4" drive adapter on it. You hold the spanner nut and turn the toque wrench COUNTER CLOCKWISE to tighten to 55 ft lbs. ( there has been debate over this number in multiple posts and things I've read. The manual has a much higher value of 105 ft lbs for the NON-RETARDER version of the tranny. Then is the section specific to my model it say a lower spec, I went with this)

After reaching this torque you have to remove the sockets and place a torque wrench on just the output shaft socket and test for tension/resistance on the shaft. It should turn with no more than 2 ft lbs. You also have to line up the tabs on the locking washer with the spanner nut and the book says go to torque, then go to next closet tabs. 2 need to line up. Then test for the shaft resistance. If spec is too high back off the next "looser" tab location. Mine torqued up, lined up, and was just over 2 ft lbs of resistance on the shaft. I went with slightly tighter being ok.

Then reverse. Install the main seal with the special seal pressing tool (machined aluminum, very nice). Install the backing plate with two new washers behind the Allen bolts. Then comes the fun. Be smarter than me and use straps. I wrestled the driveshaft and balancer back onto the splines, then bench pressed the whole thing back on to the plate while one handed holding the shaft and trying to line up a bolt. It sucked but I got it. Bolted everything back down snug, screwed the grease cap back on the driveshaft. Put some new grease in everything, and away she rolls!

Vibrations, GONE! Very very happy with the repair.

Now the great news for anyone else who needs or wants to do this. I will offer the tools for rent! Please PM me and we can work out the details.

I hope this is helpful for someone else. I spent sooo many hours on this researching and really hope this saves someone down the line a ton of time!

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #1 – June 03, 2023, 12:08:16 am

Nice write up, great job.

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #2 – June 03, 2023, 09:00:08 am

Big job for sure. Glad there was no other damage other than the u-joint issue. Sad to hear that the tabs were not engaged preventing this from happening, probably happened breaking for lunch during original assembly. So that gland nut is for tension on the bearing preload im assuming? How much did you have to rotate the nut? Im guessing it had backed up as far as it could before contacting the outer shaft inserted over the inner shaft. Amazing those two smaller bolts keep the entire assembly secured to the shaft.
Scott

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #3 – June 03, 2023, 11:04:45 am

I am hopeful there is no other damage. I guess I could have pulled the bearing out but I just needed it to be drivable for the weekend! The nut was probably about 1 full turn loose at least. You are probably right that it had turned itself out until it hit the backing plate shaft. I was also amazed that all this torque is held by 2 bolts. There really isnt any force in that direction though, so it does make sense. The backing plate has a huge splined shaft that fits over the output shaft on the tranny.

It is really hard to tell in the pictures just how big all this is. Those special sockets are MASSIVE. Biggest tools I own now besides my 600# 4' torque wrench. That output shaft is almost 2" diameter. The driveshaft alone weighs so much with that balancer on there.

I am a little nervous for the next big road trip only because if the bearing was worn and I just tightened it back up I may be in for more problems soon. I do have a nice 4 hours trip coming next week, then a couple short trips again in July before we hit the big road in August. Hopefully that will be enough to work out any kinks.

I was able to scan a few pages today from the manual for reference as well.

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #4 – June 03, 2023, 07:55:27 pm

That is great. I got our 97 u270 home on Thursday. I see that the steering box is leaking, so will have to address that problem. I haven't had time to check the p3 yet. Thank you for the detailed write up. When I was working for Foretravel as a tech during those years, we had to install the dampener if there wasn't one.

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #5 – June 17, 2023, 09:12:30 pm

Well folks, bad news to report. The vibration came back within 200 miles. I was able to crawl under this evening and sure enough, back to square one. I took it back apart and the retaining lock washer that is supposed to hold the spanner nut in place has somehow bent the tabs back again allowing the nut to turn loose.

I am really stumped on this one. How could the nut be under enough pressure/torque to force those tabs to bend back over? This makes no sense. I had made sure 2 of the tabs were bent into the locked positions. (see attached picture) The nut somehow backed itself off hard enough to bend those back out. What am I missing?? Could the bearing itself be shot? If you look close at the pic the spanner nut is seated on the inner part of the roller bearing. If the bearing is shot I guess there could be force enough to spin the retainer?

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #6 – June 17, 2023, 09:24:41 pm

I can't tell from your pictures but the tab washer should be indexed to the shaft that it slides over, or an inner nut, much the same as a wheel bearing set up. Seems like I see a grove in the shaft Could the inner tab be broken off? It has to be held in place somehow, otherwise it's just a washer regardless of the tabs.

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #7 – June 17, 2023, 09:30:15 pm

Ohh my gosh, duh!! I bet you are right, although why would the tabs be bent back over? Wouldn't the whole assembly just spin? I think I need to take it apart one step further and see what is going on behind there. You might be on to something.

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #8 – June 17, 2023, 09:41:30 pm

The bearing cage doesn't look centered in your picture. Could that have anything to do with
the nut coming loose.

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #9 – June 17, 2023, 10:51:03 pm

Well im sorry to hear this. If that shaft is loose enough to walk around who know what else could be damaged by it. Is there other special tools required to tear down father? Please keep us in the loop. Im curious to what the fix will be
Scott

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #10 – June 18, 2023, 09:24:01 am

Think we are on to something here. I took the assembly apart and the locknut retainer is shot. It was worn down thin from being loose. Then some of the tabs broke off (where did those end up?) but the good news is everything inside looks great. No scoring or wear marks at all. The bearing looks and feel good. No signs of wear, the race was smooth and looks great. There does not appear to be a ton of loan on this. It seems to be just a support for the internal P3 carrier assembly. I think that is what is saving it.

I am going to order a new locknut retainer and if I can find it probably the bearing as well just to be safe. I'll report back when I find parts.

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #11 – June 18, 2023, 10:08:10 am

It is difficult to determine in photos but it looks like its worn 50% threw the lock tabs Im willing to bet Allison recommends replacement every time you remove it. I probably would have fell into the same trap myself. Think you may have it resolved
👍👍

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #12 – June 18, 2023, 11:15:05 pm

Looks as though you have found the problem. 👍

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #13 – June 19, 2023, 02:31:09 pm

I found the part numbers via a local supplier but he could not get the bearing quickly. Has the retainer locknut coming in tomorrow. I placed a backup order through Diesel Dash online and paid for overnight air shipping. A 2nd retainer and the bearing will be here tomorrow!! I will continue to post updates as I learn more.

Part #'s:
retainer locknut - 29506386
roller bearing - 23046437

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #14 – June 19, 2023, 02:40:24 pm

I think changing the bearing is a good idea as I have put in crappy retainer locks and never had one
fail.

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #15 – July 05, 2023, 01:03:56 pm

Happy update: I changed out the bearing, the retainer washer, and the seal again. Tightened everything back up to spec and took it on a 250 mile round trip this past weekend. All seems to be well. No vibrations. I need to crawl under and check for any slack but I'm doubtful I will find any. I hope this is the final fix on that issue. Taking it all apart again was not fun. I did use a strap this time to hold up the driveshaft, it was very helpful.

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #16 – July 05, 2023, 11:20:55 pm

Quote from: nbluesky – July 05, 2023, 01:03:56 pm

Happy update: I changed out the bearing, the retainer washer, and the seal again. Tightened everything back up to spec and took it on a 250 mile round trip this past weekend. All seems to be well. No vibrations. I need to crawl under and check for any slack but I'm doubtful I will find any. I hope this is the final fix on that issue. Taking it all apart again was not fun. I did use a strap this time to hold up the driveshaft, it was very helpful.

So was there any visible damage to the bearing and race?
Sounds like a good start to a permanent repair

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #17 – July 06, 2023, 09:03:09 am

Blue loctite on the nut may help.

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #18 – July 06, 2023, 09:10:48 am

No obvious signs of wear on the bearing. It did seem slightly worn perhaps compared to the new one but hard to tell with those tapered roller bearings. The cage is so loose on them even when new. No scoring or anything like that. It sure does drive smooth now

I thought about locktite but I was worried it would get in the bearing. It really should not move now, hopefully that is the case!

I might take it another shorter trip to Iowa for a softball tournament next weekend just to put on some more miles before the big 3 week trip in August. I also have the new steering gear to install sitting on the shop table...that's for another thread.

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #19 – July 06, 2023, 09:53:12 am

Think the new tab washer/lock was the answer.

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #20 – June 02, 2024, 06:27:14 pm

Super disappointed and frustrated to report the driveline has vibration again (although now totally different than before) and the output shaft is loose again. I can't believe it. I only put on maybe a few hundred miles. I don't have time to work on it now but I will follow up when I know more. So frustrating...

Previously the vibration was mostly bad in 4th gear and higher, I could also engage the retarder and the vibration would go away. Now the vibration seems to be at all speeds but becomes terrible over 60mph. I drove the last trip at 55-60. Brutal.

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #21 – June 02, 2024, 09:39:00 pm

I trust you are going to take it apart and see what's going on?

Re: Allison MD3060R P3 Carrier Bearing Fix

Reply #22 – June 03, 2024, 12:27:52 pm

Man, I hate to hear this. Almost seems like there's an outside force at work here, bad U joints, clocking wrong, engine tranny alignment angle or parallax to rear end input , driveshaft balance? Work performed looked meticulous.

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