Hole in differential

Hi,

Do you think you can post a picture of this hole? That could change my opinion because I suspect the hole happened shortly before you found it. I mean like seconds before you found it. I highly doubt a vehicle would drive normally on a test drive for them with a hole in the differential, let alone you would not notice it for 130 miles. What made you finally discover the hole? Was there a loud noise or did you just look under the car and find it?

Let me know if you can get a picture and then about some of these questions and we can go from there. Thanks

The car is actually still being repaired, but I can ask them for a picture when I speak to them again. Actually, I wrote up the whole story for insurance purposes so there's a little more detail. I'm just trying to figure out exactly what happened and where it all went wrong. Sorry for the length:


In early June I drove on a ten hour, 600+ mile trip. I had been told by my local Honda service center, that a rear axle boot was leaking and to set up an appointment for repair. A couple weeks before the trip, my AWD service light also began coming on whenever I would drive for more than a few miles at a time. To avoid any issues on the trip, I set up the appointment for the axle boot repair and mentioned to the service center the issue with the AWD light. In a couple of days, the car was returned to me presumable fixed and ready for the trip.
There were no issues for the first part of the drive, but as we got closer to our destination, the AWD light came on again. The car also began shaking and making a slight grinding sound at slow speeds. Traveling with an infant and wanting to avoid any issues on the return trip, I set up an appointment to have the car serviced at the local service center to ensure that it would be okay for the 600 mile drive home. I dropped my car off on June 5th and a few hours later I was notified that the car was ready; I picked it up on June 6th. The invoice shows that I informed the service department that the AWD light would come on and the car would seem to shake at slower speeds. When the service was reviewed with me, the technician stated that they had ‘cleared a code’ and test drove the car without the AWD light coming on. When I stated that the light only comes on after several miles, they stated that sometimes it’s just a faulty electrical system or low current and that the light was not an indication of anything seriously wrong with the vehicle. They also stated that the car was fine and safe to drive.
After retrieving the car on June 6th, I didn’t drive it again until June 15th when we planned to drive the 600 miles home. About 100 miles into the return trip, the AWD light came on again and, being told it was a faulty electrical system, I continued driving thinking nothing was wrong. When hitting slow traffic, the car began to shake again and to make a grinding noise. We got off the interstate as quickly as possible and upon pulling into the gas station, the car began to grind and buck to the point that I felt like it could no longer be safely driven.

It was towed to a place where the service manager told me that I had hit something and there was significant damage to the undercarriage, including this hole. I remember actually hitting what was a piece of another car in the road some time about a month before this trip and I feel like this was the initial damage. The service manager acted like he was shocked that the previous (2nd) service center hadn't seen anything. But I don't know what would have been reasonable for either the first or second service center to have seen.

Wow. This would be hard to believe that this was not found. However, I also I am surprised you were able to drive this far with a hole in the rear end. Unfortunately, it sounds like the first shop just didn't give this much attention. If what you said they did was clear a code and drive it, they may have never even put the vehicle on a lift to inspect it and if it was there they would not have seen it.

Clearly there is a lot that could have happened and I don't like to make assumptions about shops that may or may not have done something properly. All I can suggest is to maybe find another repair shop which it appears you have done already.

Oh absolutely, I understand not wanting to speculate on the work that a shop did or didn't do, and at this point it really doesn't matter as it's mostly taken care of. I just like to know, when things go wrong, exactly how it happened in case something similar happens in the future. And not knowing anything about cars really, I had no reference point for whether this is common or not or what to really expect from service shops in the future. I did add a couple of images too.. it's hard for me to tell really what I'm seeing here. :)

I completely understand wanting to know what happened. I am the same way. As for the pictures, the first two are of an under vehicle cover or mat. It is simply to keep the under body components clean and protected. The hole in it was caused by running over something. This by itself if not a big deal because it is just a heavy fabric. The last picture is of the rear differential. It is hard to see but I circled what appears to be a chunk out of the case. However, it is hard to tell if it actually put a hole in the case. This may explain why they didn't see if because if it is not an actual puncture through the case, then there was no fluid loss which is why I could not understand how a shop would miss this. If there was not fluid loss then they would have needed to actually inspect it to find it and if they didn't see a need to look at it because they didn't experience any issues on the test drive then that is not uncommon.

I suspect what happened was the grinding and jerking that you felt was the rear differential engaging when it shouldn't. This could have been caused by the damage but it is what we call an intermittent concern which is why the one shop did not find anything wrong. So when this is acting up and the light comes on the AWD system activates and when slowing down or turning it is grinding because it is normally off at this point. You have a system called a full time 4WD/AWD system. This means it is always in 2WD except when the computer determines the rear wheels are needed.

I attached the operation specifics of your system. As you will see on dry pavement from a take off, you should only have a MAX of 20% power going to the rear wheels but in most cases you will have none. If the AWD system is applying too much torque to the rear wheels then the clutches in the rear end will grind causing a noise and vibration.

I hope this makes sense. Please let me know what questions you have and I will do my best to explain further because this gets pretty far off into the weeds of technical information. Thanks

Yes, thank you, this is very helpful! It does make some sense and explains why it seemed so much worse when I was in slow, stop-and-go traffic. I guess there's no way of really knowing why the car's computer would've activated the AWD system when it didn't need to be? These intermittent problems must be extremely frustrating! :) By the time I stopped my car, something had definitely deteriorated...the grinding and lurching got worse to the point where I actually thought I was dragging something underneath my car. Was that just too much power going to the back wheels? Or do you think that could have been caused by fluid loss? I attached a better, closer picture of the damage to the case if that's more helpful at all. Thank you again!

Okay. So there was a hole in it but I assume this is after it was all cleaned up because if the fluid leaked out it would be covered in an oily mess.

Yes. if the fluid leaked out then it will only get worse because the clutches inside are meant to slip and they can only do that if they are lubricated. When they don't have the fluid they lock up.

Hi, I took my car for a 20,000 service to a dealer and they called me later right before picking up to let me know they found a hole in the differential. We’ve driven the car the night before 40 miles and didn’t notice anything. Is it possible that the service shop broke the differential when doing the service which included oil change and tire rotation?

It is unlikely that they would have caused this by just doing that but something sounds fishy. Clearly I would go down and put it on a lift and have them show it to you. If it wasn't making noise and drove fine then I am not sure how they would do it but something doesn't sound right.

Let us know what they say and we can help make sense of it. Thanks