Rear end finally let go

[EB]

I had the parts ordered and were supposed to be waiting for me to be repaired today and tried to get one more load out of it. Shouldn't have. Last Wed. I left for the Weatherford' Ok. area, delivered the load Thursday morning and was getting ready to start back and was asked if I wanted to go to Odessa and pick up a "doghouse" and bring it back to the location. I very seldom turn down a job so after a 480 mile deadhead I loaded up the doghouse and started back . Got to the location and could smell oil. Had a hole in the rear cover right at the bottom, the oil trail showed it happened about a mile from the location. Pulled the cover and had a handful of roller bearings. Needless to say I wasn't going anywhere. Called a friend and he said he would come to get me but I would have to drive back because he didn't have a class A license so I found a motel and he got there about 8 PM Sat. We went out the next morning and loaded the truck. After about 10 hours got back and unloaded the truck at the shop that had my parts. It was pulled down today and I had lost a carrier bearing on the driver side. Thought nothing else was wrong but found out the tone wheel was messed up and the speed sensor was cracked also. No other problems, after the other parts get here (tone wheel and speed sensor) I should get back on the road sometime Wed.

Shouldn't have waited as long as I did but it wasn't making metal and wasn't getting hot so I kept going. Moral of this story, if your rear end starts howling, get it checked, especially if your cruse control keeps popping off.

 

[MChrist]

Why does the cruise control turning off indicate a problem in the rear?

 

[AH64ID]

For a bad rear axle to cause the cruise to engage and disengage it must have had a slipping tone gear and the ECM was sensing either a 10 mph/sec increase or decrease.

 

[Nyoest]

Or that there was enough deflection Of the tone ring it lost signal. Or that the metal shavings built up thick enough on the sensor tip that readings were I intermittent or that EB runs a shade faster than the speed of sound and the sampling rate of the sensor can't keep up. .



My wife got fed up with me tonight so I'm here.

 

[MChrist]

That's interesting. I wouldn't have associated those problems with cruise kicking on/off. Good to know.

 

[EB]

Or that there was enough deflection Of the tone ring it lost signal. Or that the metal shavings built up thick enough on the sensor tip that readings were I intermittent or that EB runs a shade faster than the speed of sound and the sampling rate of the sensor can't keep up. .



My wife got fed up with me tonight so I'm here.

What he said, except for the part about running faster than the speed of sound. There was enough deflection that the tone wheel got against the rear cover and nearly cut through it. That is kinda hard on those little teeth. Actually I believe that happened after the bearing let go. Had a lot of deflection then.

 

[JHumphries]

What is your mileage?

 

[EB]

What is your mileage?

It's in the sig, I'm over 366,100 miles. I believe the exact miles is 366,140 something.

 

[cerberusiam]

Thats actually not to bad of mileage for the cheap bearings they used. I lost the facing on a carrier bearing race about 80k and that fixed the rest of the bearings with metal flakes.

 

[AH64ID]

Thats actually not to bad of mileage for the cheap bearings they used. I lost the facing on a carrier bearing race about 80k and that fixed the rest of the bearings with metal flakes.

The bearings are rated for a 50% longer service life than the bearings GM specs!

 

[cerberusiam]

The bearings are rated for a 50% longer service life than the bearings GM specs!

Somebody forgot to tell that to the bearing installed in my truck. :-laf



When you pull a failed one and look at what is written on it you will understand. Its not unheard of in these units to loose bearings or have other problems at low mileage.

 

[HBarlow]

EB,

Sorry to hear of your breakdown. I guess we now know that the service life expectancy of a typical Working AAM rear axle assembly is about 360k miles.

 

[EB]

Everything is back together and working again. Kinda hard for me to do the break-in the way I'm supposed to. Hopefully I won't get any real heavy loads for the next couple of hundred miles. Will change the oil to synthetic then. Does anyone out there have a temp probe in their rear end? If so, what is the normal temp when you are towing heavy. I can shoot mine with a temp gun but I'd like to know about temp ranges.

 

[AH64ID]

I was going to put a temp probe in mine, but after talking to a few people that had prob's pre and post MH covers there was no need with the MH cover. They do run pretty hot with the stock cover, over 200° IIRC. I'll see if I can find the posts that talked about it.

 

[TCDiesel]

My trueTrac and factory ran 150*/200* when towing (20K+) Heavy at 60/70 MPH,City traffic 140*/160*. My factory Pinion bearing failed at 104K.

 

[mpaulson]

My carrier gears failed at about 140k and ever since the magnet on the drain plug keeps coming up with chunks that look like old carrier gear bits and flakes. the pan has been off 6 times since checking and cleaning, including the axles and hubs pulled twice tryinh to make sure that all of it is cleaned out, but it is still coming!!!! And I don't tow to the extreme duty cycle that EB does. The next step for me is going to be getting a dif from a 5500 and modifing it to fit.

 

[TCDiesel]

I replaced everything in My axle , New Ring & Pinion Gears , new bearing Kit, with the TrueTrac. the Pinion gear was Not that bad,But WOW when you put in gear (AT) it slapped so hard that it would scare People in the parking lot, it was that loud,it sounded like a gunshot.

 

[ColemanR]

I guess I'm lucky then fliud changed roughly every 50k I just turned 484k mine runs about 175deg now your making me worry. LOL

 

[TCDiesel]

I guess I'm lucky then fliud changed roughly every 50k I just turned 484k mine runs about 175deg now your making me worry. LOL

At that mileage I would inspect all the gears (Ring & Pinion,Side Gears, Helical Gears) if all look good and spec out, I would install New Carrier Bearings,Pinion Bearing and Hub Bearings and run another 400k plus (Hopefully) if even 1 of the bearings fail it will most likely take the entire Diff with it.



Another area of concern is the CP3 with that Mileage,If the unit has not been inspected and a new seal kit install,I would make it a priority, Generally the shaft seals will not last much more then 400k without leaking (300k is safe) if they fail completely you will fill your crank case up with fuel in minutes without no warning.

 

[NIsaacs]

Everything is back together and working again. Kinda hard for me to do the break-in the way I'm supposed to. Hopefully I won't get any real heavy loads for the next couple of hundred miles. Will change the oil to synthetic then. Does anyone out there have a temp probe in their rear end? If so, what is the normal temp when you are towing heavy. I can shoot mine with a temp gun but I'd like to know about temp ranges.

EB, with a combined milage of over 700,000 miles of extreme duty between your two trucks, we are always interested in what you have to say.



There used to be a lot of complaints about the AM axles burning the paint off the covers, I was wondering if yours did that early on? Also did you need to change the ring and pinion or just the bearings and tone wheel? What is your oil change schedule and will you do anything different? Thanks



Nick