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Worn motor mounts causing in CV joint destruction?

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Itsawykydtron View Drop Down
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    Posted: Feb/05/2019 at 5:37am
Leaving a snowy parking lot yesterday in 4 wheel drive while moving straight ahead through an intersection I gunned it a little bit and heard a bang and then thump thump thump. I was expecting front driveshaft or something but I was surprised to see my right front inner half shaft joint was pulled apart.

I replaced this axle with an aftermarket new part from Rock Auto in March 2017 after the old axle had a joint fail from a boot that had been torn from before I got the car.

I'm not overly worried but I would like to lessen the chances of this happening again. What I see as potential causes so far are:

1. Motor mounts are bad and motor torqued enough to pull the joint apart. Unfortunately I've never checked these but I plan on replacing them on this next go round of repairs.

2. Cheap quality axle. It's a surtrack/trakmotive. Lifetime warranty. Rock Auto will cover it. I ordered an extra one to put on the shelf since both sides are the same.

3. Broken spring? I do have a broken coil spring on the rf that I plan on replacing when I do all this work as well as new shocks. I don't see how this could be related but it's an issue in the same area.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Feb/05/2019 at 6:48am
You don't state the vehicle?
CV joints are not usually affected by motor mounts. Broken suspension yes.
Most failures are poor quality or lack of lubrication, cut boot or broken band allowing water in, or just inferior lubrication/manufacturing.
Now if your talking about a Jeep with u-joints on the outer front fixed axle, expect to change these every 2 or 3 years. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Itsawykydtron Quote  Post ReplyReply Direct Link To This Post Posted: Feb/05/2019 at 6:53am
Oops sorry. It's an 85 Eagle. The boots are in good shape. My thinking is the front diff is bolted to the engine so any torquing could pull on the shaft.

The inner joint is a tripod style and it pulled out. I'm supposed to get the half shaft and motor mounts today so hopefully I'll do the repairs later this week.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MacGyver Quote  Post ReplyReply Direct Link To This Post Posted: Mar/02/2019 at 8:36pm
Any updates on your repair??
Any indication of the failure being due to the manufacturing quality of the axles??
 
I'm in need of two new CV shafts to replace my current ones that have torn boots and are noisy...
 
I was just about to order those same RockAuto shafts because they seem to be the most economical choice!
Especially for me being in Canada where buying local is about double the cost of RockAuto!!  Not to mention the axles are NEW and don't require a core charge!
Too expensive to ship cores back across the border!!
 
I need new axles very soon!!!   It's my daily driver, and they're really starting to worry me!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Itsawykydtron Quote  Post ReplyReply Direct Link To This Post Posted: Mar/02/2019 at 8:53pm
I replaced that axle with another Rockauto axle and a week later it pulled apart again. We hashed it out over on eagles den and came to the conclusion that the surtraks have too short of an inner joint. Rockauto said out of 100 sold they've only had 4 returned but I wouldn't recommend them.

You should read our discussion and check out pics
http://forums.amceaglesden.com/index.php?topic=46566.0

I purchased a new axle from advance Auto parts online and it looks like it should be much better. I haven't used 4x4 yet though because I'm doing a complete front end rebuild now. Whatever you buy, I think the key is looking at inner joint length.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 73Gremlin401 Quote  Post ReplyReply Direct Link To This Post Posted: Mar/02/2019 at 9:48pm


3. Broken spring? I do have a broken coil spring on the rf that I plan on replacing when I do all this work as well as new shocks. I don't see how this could be related but it's an issue in the same area.[/QUOTE]

This is your answer right here. With a broken front spring, that side of the car is down, which puts the angle of the CV off from where it is supposed to be.
73 Gremlin 401/5-spd.
77 Matador 360/727.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote MacGyver Quote  Post ReplyReply Direct Link To This Post Posted: Mar/02/2019 at 10:41pm
Thanks for the quick reply!!
Some good info on the link you posted!!
(could have sworn I was a member of the Eagle's Den, but maybe it was the Eagle's Nest?  Or maybe it's been so long that I just can't remember my login...)
For some reason, I can't see the pics that you posted there...  Would have liked to see the differences!!
 
Guess I won't be ordering those axles that were already in my cart waiting for me to hit the Order button!!
Unfortunately, that means I'll have to order them from my local parts place, and probably pay double PLUS core charge without even knowing whether they're any good or not!!!
(I'd prefer to keep the cores for the stub shafts just in case I have issues!  Like you did! Wink)
At least any warranty issues will be local, and I won't have to ship them back over the border!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MacGyver Quote  Post ReplyReply Direct Link To This Post Posted: Mar/02/2019 at 11:25pm
Originally posted by 73Gremlin401 73Gremlin401 wrote:



3. Broken spring? I do have a broken coil spring on the rf that I plan on replacing when I do all this work as well as new shocks. I don't see how this could be related but it's an issue in the same area.


This is your answer right here. With a broken front spring, that side of the car is down, which puts the angle of the CV off from where it is supposed to be.
[/QUOTE]
 
73Grem:  Have you experienced this same problem with an Eagle??
 
My last Eagle had super saggy coils...  The control arms were almost touching the bump stops at rest on a level concrete driveway!  Sat almost as low as my Spirit!!  LOL!!
But even with the extreme lowest angle possible, I never had an issue with the CV shafts on that car...  Even banging on the bump stops driving over a dip in the road!!
 
My current car sits much higher in the front!!
Exactly the opposite angle on the shafts!!  Never an issue either, except for the rubber boots eventually cracking!!
 
Either way...   When the car is driving, and the front suspension is moving up and down, those CV shafts will experience ALL those angles!!
From bottoming out on the bump stops, to a full extension "dukes of hazzard" leaving the ground, the CV shafts should NOT come apart!!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Itsawykydtron Quote  Post ReplyReply Direct Link To This Post Posted: Mar/03/2019 at 7:45pm
You're welcome I was about to go to sleep and got the email alert. I wanted to make sure you didn't order them. I'm not up on image hosting on forums these days or I'd post the pics here, but I figured the least I could do was throw together an imgur gallery.

https://imgur.com/gallery/jVcGwli

I agree with you about the spring not being the cause. I'm sitting about 2 inches higher now on Javelin springs and if that was the problem it should be the opposite problem now! Haha.

Good luck finding decent axles cheap. The one I got from Advance was also new and about the same price after a coupon. Maybe they ship to CA.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 73Gremlin401 Quote  Post ReplyReply Direct Link To This Post Posted: Mar/03/2019 at 9:46pm
Originally posted by MacGyver MacGyver wrote:

Originally posted by 73Gremlin401 73Gremlin401 wrote:



3. Broken spring? I do have a broken coil spring on the rf that I plan on replacing when I do all this work as well as new shocks. I don't see how this could be related but it's an issue in the same area.


This is your answer right here. With a broken front spring, that side of the car is down, which puts the angle of the CV off from where it is supposed to be.
 
73Grem:  Have you experienced this same problem with an Eagle??
 
My last Eagle had super saggy coils...  The control arms were almost touching the bump stops at rest on a level concrete driveway!  Sat almost as low as my Spirit!!  LOL!!
But even with the extreme lowest angle possible, I never had an issue with the CV shafts on that car...  Even banging on the bump stops driving over a dip in the road!!
 
My current car sits much higher in the front!!
Exactly the opposite angle on the shafts!!  Never an issue either, except for the rubber boots eventually cracking!!
 
Either way...   When the car is driving, and the front suspension is moving up and down, those CV shafts will experience ALL those angles!!
From bottoming out on the bump stops, to a full extension "dukes of hazzard" leaving the ground, the CV shafts should NOT come apart!!!
[/QUOTE]

In a nutshell - yes.  I owned an 84 Eagle wagon 4.2/5 speed for a number of years. To be more specific, in your situation with both front springs sagging more or less equally, the deflection of the half-shafts from their normal ride-height state will not be as pronounced.  with a broken coil on one side only, that changes things a good bit.
Yes, the CVs are designed, by their very nature, to function normally within the range of the suspensions movement.  However, there is an optimal angle for them to function the majority of the time (ie, rolling down the highway) that the CV needs to be at the majority of the time. The situations the OP has described indicates that this is not the case, which means that at least one, if not both of the axles are being driven the majority of the time at a non-optimal angle.  Could bad motor mounts also be contributing to the issue? Of course - but I seriously doubt that it is causing this specific problem on it's own.
73 Gremlin 401/5-spd.
77 Matador 360/727.

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