The Case Of The Mysterious Slipping Axle


#1

The strange saga of my 1997 Nissan Sentra just seems to get stranger every day. Two weeks ago it died. My mechanic was “80 per cent” sure it was the transmission, but when he checked it out he said the front right axle had slipped out. He actually showed me where a piece of metal about 1/16" had sheared right off from the front of the axle. He said the tranny seemed fine, put in a new axle, but warned me that he wasn’t sure if the little piece that broke off was still in the transmission or not! The car drove great for three days then it died again. This time the same mechanic said I had a “trash transmission” and I needed to get a replacement. I had the car brought to another mechanic who had a lot of transmission experience. I talked to him about getting a used tranny and price, etc. He said he wanted to look at the car first. He called me back and said the tranny was fine, but the same axle had slipped out again. He insisted that the first mechanic had not put the axle all the way into the spider gears and I should get a refund. I went back to the first mechanic (this are both nice guys). He said he would replace the part, but he insisted that he had done hundreds of these, that it is a simple job, and that he was 100 per cent sure that the axle had clicked in properly. Here’s where it gets interesting. He is claiming that there is something wrong with the transmission (doesn’t know what) that is causing the axle to keep slipping out. He thinks it will probably happen again. The only reasons I know for an axle slipping are if it is too short, or if it isn’t put in properly; but he insists that there is some mysterious transmission problem that caused the axle to slip out both times. Does anyone have a clue about this. Thanks.


#2

I do not see how the second mechanic can be so sure the first mechanic did not fully seat the axle.

These axles are usually locked in by a snap ring that is located on the end of the axle. Simply push the axle in and one can feel the snap ring catch.

It’s quite possible that the original axle being loose and wallowing around could have worn the gear splines and snap ring groove in the transmission. If so, then an axle may never stay seated.

I think the second guy is jumping on the first one in a show of oneupsmanship.
(I will also tell you for a fact that doing this is not a rare thing to happen. Some mechanics always like to state or at least insinuate that the other guy is clueless.) Sad, but true.


#3

Thanks. This makes a lot of sense. I hope it isn’t true because I don’t want to have to replace the transmission. The second guy said he has some kind of a tool that allows him to look inside the transmission, but I don’t know if he is able to see if the splines inside are messed up.

Anyway, I’m taking the car to work today so I’ll probably know soon enough. What a nightmare this has been.


#4

Did either mechanic make an aggressive inspection of the motor mounts? i.e., torque load them in forward and reverse and look for deflection.


#5

There is another possibility. Although I admit it is rare and unlikely, it happened to me once on a Honda. The remanufactured axle had the wrong inner joint installed. It was identical in all respects except the groove for the retaining ring was located in the wrong place. For my application it should have been at the very end but this one was 1/2 inch or so farther in. Consequently, the retaining ring could not snap into its corresponding groove inside the transaxle. I did not notice this at first but it slipped out after being driven a few blocks.

That said, are we sure the broken stub is not still in place preventing the new one from seating?


#6

I drove the car around 200 miles in the past two days, careful not to take it on the highway and not to go over 40mph. It seems fine, but the last time the axle went it took three days so we shall see.

I called mechanic #2 and he says that he looked up into the transaxle with a “boroscope” and that the splines looked fine.

I’m still keeping my fingers crossed.

Thanks again.


#7

I highly doubt that they did this since neither of them mentioned it.

Thanks for this information.


#8

The broken stub definitely appears to have been left inside the transmission after the axle was replaced the first time. Mechanic #2 said he found it and that it was all ground up and “sitting right there” when he took the axle out. If the broken stub was the culprit, then this would be the best case scenario for me (provided it was removed and no further damage was done).

BTW, mechanic #1 is going to refund me the cost of the axle (not just the core) although not the labor. This seems fair (although I hope he includes his 30 per cent mark up on the part since I had to pay for this).

One follow up question. Mechanic #1 looked at the axle he put in that I brought back to him and said that mechanic #2 did not remove the dust covers and install them on the latest axle that he (mechanic #2) put in. When I spoke to mechanic #2, he said, “it’s on there”. Then I told him that #1 put the car on the lift and clearly showed me that it wasn’t, and he agreed with me. #1 is saying these are important (“or they wouldn’t put them on in the first place”)…to prevent particles from getting into the wheel bearings. #2 is saying he will put it on for free but that they can be more trouble than they’re worth because they often rot or rust off and cause a problem. (I believe #2 is applying the BS here, but I’m no expert). Do you think I should take him up on his offer to put the dust cover on the axle he put on? If these covers are so important, why aren’t they put on replacement axles? (I’m also a little hesitant to mess with this axle again if the car continues to ride well).

Thanks to all.

You have been most helpful.


#9

Well, you definitely have one of the most convoluted messes I’ve ever heard of.

Personally, I see no way a stub could remain in there. It is near impossible for me to picture the end of an axle shaft even breaking off.
Any problem may also not even be related to the splines; it may be more of a snap ring groove problem.

Regarding the “dust boot”; surely you don’t have an axle in there without the rubber CV joint boots in place?
If this is the case you should run as fast as possible from whoever would install an axle like this.

Any chance that you mean transaxle stub seal rather than a dust boot?
Same thing. If someone installed an axle into a hole that was missing the seal - run.
Will continue to ponder on this one.


#10

FYI, if you are referring to axle boots then all reman axles come with new boots on both ends. There should be no changing over anything.


#11

Most people find it very difficult to believe that the tip of the axles (not the ring) could actually sheer right off. Mechanic #1 showed me where the tip came off and said he had never seen anything like it. He said he thought it was a manufacturer’s defect. Mechanic #2 attributed the problem to metal fatigue.

As far as the dust cover is concerned, it is not a dust boot but a dust cover. It has nothing to do with the CV boots or with the seals. It is a circular piece of metal with a hole in the middle that goes near the end of the axle and is supposed to prevent dust and grease from getting into the wheel bearings.
It looks like a flat donut and the metal comes up about 1/4" from the axle. Mechanic #1 says that it comes standard with most axles but that the replacement axles usually don’t have them. He says some mechanics just say, “ah, they aren’t necessary”. He says whenever he replaces an axle he removes this dust cover (not the boot and not the seal) and slips it on the replacement axle. Mechanic #2 said they do more harm than good sometimes and he usually just puts in the replacement axle as is.

Hey, guys, I’m not making this stuff up!

Really!


#12

If I were to come up with my own description for that dust cover I would call it a removeable, circular metal collar, around 3" in diameter, that goes around the end of the axle and sticks up about 1/4" all around. The word circular metal collar describes it perfectly.

Thanks again.


#13

I think I know what you are talking about. This cover is on the outer joint and basically is a dust cover for the inner hub area. Usually there is a rubber lip around the circumference of the round plate. In my experience these have aways come with the remanufactured axle and not had to be transferred over from the old one. In any case, I would have it installed if it is missing.