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Discussion Starter #1
I've a 1993 GMC K2500 4x4 6.5l diesel, about 94K miles. Hardly driven for several years, but well taken care of. I've done stuff to it to keep it up. I really like it, but......

Tonight going about 40 on nice straight road, as making a right turn suddenly a really loud thumping and shaking occurred. It felt like someone really smacked us in the back.

I got out, nobody there, but the front of the rear drive shaft was laying on the ground. I told my wife to but it in Park, doing so the tranny sounded like grinding gears. I then told her to turn it off, then in Park, and set the brake.

Looking underneath, the driveshaft pinion, lying on the ground looked perfect. Also, very little oil leaked from pinon shaft hole. No noticeable damage to transfer case or tranny housing. In other words, nothing looked broken.

I had it towed to the place that replaced the seals in the transfer case, which was done about 2 years ago. Since then I've never been in 4 wheel drive.

Will be Monday before I can learn from that shop what happened. I would like to be ready with possibilities before I call them.

Thus what comes to mind that caused this?
 

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Bolts were not tight on the differential coupling, causing them to loosen up and the saddles to fall of, and then subsequently the driveshaft.
 

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Discussion Starter #3
JohnH123,
TY for your reply. To make sure I understand, the differential coupling is in the transfer case? If so, then transfer case needs removed to determine cause and action?


The driveshaft U-joints looked good as did the front yoke.



Hopefully be looked at Monday. Once done, I'll forward cause and options to repair.



Likely part of the noise was the front of the rear drive shaft hitting the road. I'll have this checked too.



John
 

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Wait so you're saying that the shaft came out of the transfer case and was still attached to the rear differential?
 

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Discussion Starter #5
Yes, drive shaft is still attached to rear axle.
 

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Assuming stock suspension and such, Is your rear axle still properly attached? Only time I ever saw that happen the U bolts had broke and the axle was able to roll.
 
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Discussion Starter #7
Is all stock.



I should know the specifics tomorrow. Remembering what happened I'm leaning towards the rear axle either failing, or as you stated, losing position. For that yoke is really long and to come all the way out was shocking to me and the tow truck driver.



I'll post as I learn cause.

TY
 

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Could you tell from looking at the slip yoke where it had been running? Maybe someone in the past installed the wrong shaft and you have just been lucky so far?
 

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Discussion Starter #9
The yoke is pretty long. About the first half of the yoke is shiny and clean. Will be most interesting to learn happened.
 

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They are usually in way more than half so it will be interesting to see if something moved or you got the wrong shaft.
 

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Discussion Starter #11
Repair place was closed today. So I went for a look. Immediately I could see the driver's rear tire not centered to inner fender. Looking underneath both U-bolts were rusted to almost nothing and are broken. Passenger side is almost gone also.


Releasing the E-brake truck rolls easily to the push. The yoke's inner splines look good. I could not see the splines in the transfer case.


Engine started fine. Earlier I learned that with the driveshaft removed and going into PARK will make a grinding noise. The person I talked to said he has heard of these bolts rusting to the point of breaking before on GM trucks.



I left a note with details to auto shop. I will advise of results.


Nonetheless, we need to keep an eye on these bolts, perhaps all of our vehicles.
 

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If the rear axle u-bolts are broken, I HIGHLY suggest not driving it anywhere until they are replaced...

...and the axle moved back to where it's supposed to be...
 

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It sounds like you got pretty lucky.

Back in the early ‘80s, my roommate had a Chevy Nova. While we were driving down Hwy 19 (4 lane, divided, with curbs), one side of the rear axle let go. The sudden application of rear steering caused the car to swerve right towards the curb. At the same time, the slip yoke at the front of the driveshaft pulled out and the front of the drive shaft hit the ground as the front of the car went up the curb. The drive shaft planted against the curb, pole vaulting the back of the car approximately 5 feet in the air and ripping the rear axle off the other rear spring. Since my roommate was already steering left from the initial swerve, the car re-entered traffic leaving the driveshaft and axle behind with the back of the car dragging on the ground. Luckily, the front brakes worked just long enough to stop the car as much of the brake fluid left via the rear brake lines that had ripped loose. Amazingly, no injuries and no damage to anything but the Nova. As the passenger, it ranks as one of my top 5 wild rides.

So yeah, I think that you got lucky...

Eric
 
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Discussion Starter #14
Yes, very, very lucky. I talked to several mechanics and each taken aback about this. One has seen this before on GMC trucks made in the 90s. My truck is rusted underneath, but I'm in WV, which is at borderline for serious rust issues.



The U-bolt I kept was rusted into a very small taper. The end was rusted, meaning already broken. This looks like a two prong garden rake.


Repair shop looked at everything, and except for the U-bolts and mounts it seems to be ok, DS is straight, and yoke is fine, transfer box has no damage, and leaf springs ok.



Of course replacing the bolts and mounts. With the drive shaft off I asked they replace U-joint bearings.



They're recheck tomorrow. The cost is $450. Given this I believe its a very good price.



If something happens as tested I'll add another post.


Most important point is to check these U-bolts, perhaps every other oil change. Any questions, replace them.


As Ewdysar said, this was a very wild ride..


I'm very happy that the truck will be back and ready.


Thanks to each of you.
 

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So yeah, I think that you got lucky...
.. agreed....

You should inspect the brake lines, suspension and steering linkage if the rust is that bad.
 

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It sounds like you got pretty lucky.

Back in the early ‘80s, my roommate had a Chevy Nova. While we were driving down Hwy 19 (4 lane, divided, with curbs), one side of the rear axle let go. The sudden application of rear steering caused the car to swerve right towards the curb. At the same time, the slip yoke at the front of the driveshaft pulled out and the front of the drive shaft hit the ground as the front of the car went up the curb. The drive shaft planted against the curb, pole vaulting the back of the car approximately 5 feet in the air and ripping the rear axle off the other rear spring. Since my roommate was already steering left from the initial swerve, the car re-entered traffic leaving the driveshaft and axle behind with the back of the car dragging on the ground. Luckily, the front brakes worked just long enough to stop the car as much of the brake fluid left via the rear brake lines that had ripped loose. Amazingly, no injuries and no damage to anything but the Nova. As the passenger, it ranks as one of my top 5 wild rides.

So yeah, I think that you got lucky...

Eric
Please tell us your roommate did not pursue a career in automotive maintenance?:eek:
 
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Discussion Starter #17
Quick update. The lower mounts took time to find, but repair shop says the leaf spring is broken. I can understand that, for felt like we got hit by a big truck.


Can't replace one leaf spring, need both. Adding, the rear axle is on the floor, this draws attention to the rear brake lines and E-brake. Likely these may be damaged too. And not yet driven to see if tranny or transfer case damaged. Given that I've told them to remove the rear axle cover. If gears are trashed, then trucky is on life support.


Jnlperformance is right, if this lives, then I'm into new brake lines. If it dies then I'll need your advice.
Will keep advised,
Humbled
 

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Discussion Starter #18
Rear Axle cover removed and everything looks good. Shop is getting leaf leaf-springs on-line, didn't say where, so might be this week.


Question: Are the front axle U-bolts suffering from same poor design? Irregardless, these should also be looked at.



Will keep advised, and always check axle U-bolts !!!!!!!!!!!!!
 

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Discussion Starter #19
Final update:
All parts installed, including new leaf springs. Mechanics test drove and said everything checks out very well. I'll get it tomorrow.

Cost $1050.

I'll do rear shocks and replace brake lines. I like Bubba', K2500 4x4 6.5L is definition of a truck :thumb:

My thanks to each of you for your advice. Best to your and yours for the holidays, and KEEP AN EYE ON THE REAR AXLE U-BOLTS !!
 

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Discussion Starter #20
Important update: About 500 miles since the rear axle U bolts rusted and axle shifted causing the rear drive shaft to pop out of the transfer case, then had it fixed. My brother in law drives it a bit, not me. It is not used very much, especially with all this virus stuff.
I drove it yesterday, hit a bump and the whole truck shuttered. Hit another bump and did it again. Looking, I noticed the right rear lower axle leaf spring had moved, not any of the bound leafs. Two miles away I very, very slowly limped it home. Called the shop that replaced it, out of business.
The local auto repair, I use a lot, looked and the wrong U-bolts where used. These are too wide. Might need to order. My points: Check these U-bolts, if badly rusted replace them, if you do shocks maybe replace these bolts, and always use the correct parts. You don't want the drive shaft to pop out of the transfer case and then cause you to be killed.
I really like my buddy, nothing like the smell of diesel in the morning...LOL.
 
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