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Dumbass mistake

K5Jimmy

K5Jimmy

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I changed driveshaft in my 89 w/12B/Auburn...I had a CV shaft built to get rid of a vibe gremlin that I've chased from time to time.

Anyhoo...the CV shaft cured the vibe and I've driven the truck probably 3K miles towing my boat,etc. I recently headed to my lake house and had a failure that started with the 700R not wanting to lock up....then I picked up a small vibe and wouldn't shift into OD which proceeded to turn in to a larger vibe that "rang" the driveshaft revolution wise.

I just got around to pulling the thing apart to find 2 large teeth busted off the pinion. I looked for a reason and discovered that the damn $400 Driveshaft Superstore driveshaft was 1 3/4" longer than the stock that I replaced. It went in easy and with no issues, so I don't know how I missed it.

Good news is that the Yukon gears must have taken a beating for 3-4K before breakage....I have a Transfer Case saver instead of the stock C clip on the output shaft of the 241, so I have no TC damage.

I am hoping that is the extent of the damage as I can rebuild the diff. I just sold a van width 14SF w/disc and 4:10 because a guy offered my $500 more than I paid for it....dammit. LOL..Oh Well..I guess that's Karma.

I don't need or want a FF....just wanted to share a dumbass oversight. My 89 is a "pristine" DD.
 
That sucks! and...where the hell have you been man? I saw the user name and thought maybe it was a 5 or 6 year old thread some n00b had drug up from the depths! :haha:

Rene
 
K5Jimmy said:
OK....That was my first best guess...what do you think caused it?
Click to expand...

It's a 12 bolt, they aren't super stout. Anything could've caused it, too much stress on it probably.

Sometimes a bolt will come loose and get between the teeth which will cause them to break off like that too.
 
Or as it gets old the bearings on the pinion can loosen up and change the preload. This could allow the pinion to pull into the ring gear and break teeth. The vibes you had earlier could have contributed.

Dik
 
38377k5 said:
It's a 12 bolt, they aren't super stout. Anything could've caused it, too much stress on it probably.

Sometimes a bolt will come loose and get between the teeth which will cause them to break off like that too.
Click to expand...

I should say that all this Began and happened in just a few minutes. There was a slight growl, then a vibe so I pulled over (in the rain) to check. Turned around to get to a town (45mph) and the vibe worsened and then turned into a rotation related "ring" thru the DS. All this within about 8-10 miles. It got me back to civilization (with the wife) but it's the first time ever I ever took one home on a wrecker $254 from Durant, OK to McKinney, TX.

I know they aren't all that stout, but mostly because of the carrier. This 12B is one I had laying around when it got built. I used Yukon gears, Auburn Pro and Moser1340H axles and then had it built by Stan Hopkins. He is The rearend guru in these parts.

This diff has about 80K on it since built in 96. I put the CV shaft in it about 3-4K ago. Because it is 1 1/2" longer, I'm thinking that upon compression it was stressing/jamming the pinion bearing on one end and the TC output shaft on the other. The pinion bearing evidently was he weak point. I cannot feel any movement at the pinion, but I agree that the preload change on the pinion caused the failure. All bolts, etc are intact within the diff. At the TC end (241) I replaced the spring clip at the output (notorious for breakage) with a bolt on Saver. There is no evidence of anything out of the ordinary at the TC end, which again puts me at the pinion bearing being the weak point in all this.

I've had some version of a K5 since 1975 as a DD, with this 89 being my 5th. I've had Gov Locks blow for no reason whatsoever, but never had a pinion go without some sort of noise. Just like most everyone here, I know every nut and bolt, rattle, shake, squeak, and quirk that we all love about these (my) trucks.
 
K5Jimmy said:
I should say that all this Began and happened in just a few minutes. There was a slight growl, then a vibe so I pulled over (in the rain) to check. Turned around to get to a town (45mph) and the vibe worsened and then turned into a rotation related "ring" thru the DS. All this within about 8-10 miles. It got me back to civilization (with the wife) but it's the first time ever I ever took one home on a wrecker $254 from Durant, OK to McKinney, TX.

I know they aren't all that stout, but mostly because of the carrier. This 12B is one I had laying around when it got built. I used Yukon gears, Auburn Pro and Moser1340H axles and then had it built by Stan Hopkins. He is The rearend guru in these parts.

This diff has about 80K on it since built in 96. I put the CV shaft in it about 3-4K ago. Because it is 1 1/2" longer, I'm thinking that upon compression it was stressing/jamming the pinion bearing on one end and the TC output shaft on the other. The pinion bearing evidently was he weak point. I cannot feel any movement at the pinion, but I agree that the preload change on the pinion caused the failure. All bolts, etc are intact within the diff. At the TC end (241) I replaced the spring clip at the output (notorious for breakage) with a bolt on Saver. There is no evidence of anything out of the ordinary at the TC end, which again puts me at the pinion bearing being the weak point in all this.

I've had some version of a K5 since 1975 as a DD, with this 89 being my 5th. I've had Gov Locks blow for no reason whatsoever, but never had a pinion go without some sort of noise. Just like most everyone here, I know every nut and bolt, rattle, shake, squeak, and quirk that we all love about these (my) trucks.
Click to expand...

What is this "saver" you are talking about? Everytime I have seen a shaft too long that has bottomed out it damaged the tcase or the adapter it had not effect on the rear. I think it was more likely a problem with your 12b and not your dshaft.

Dik
 
sandawgk5 said:
What is this "saver" you are talking about? Everytime I have seen a shaft too long that has bottomed out it damaged the tcase or the adapter it had not effect on the rear. I think it was more likely a problem with your 12b and not your dshaft.

Dik
Click to expand...

I've had 2 of the snap rings at the output shaft break in the past...then I found this Transfer case saver, don't leave home without it, DIY and save money! - Drivetrain.com

I haven't had a broken snap ring since installing this about 9 years ago. I agree that I may be overthinking this, but then I'm the one who
removed the driveshaft and played a bit with clearance measurement after I found the broken teeth. It may well just be a worn bearing letting go, but I'll shorten the driveshaft about 1 1/2" just for peace of mind and cheap insurance. It may not be direct cause and effect, but the DS may have been an extenuating circumstance......or not...it's just what I found.

The very first symptom was that it dropped out of OD and wouldn't go back...so I may well have gacked something else and just haven't found it yet. Or it may be coincidental.

Since I'm fixing to move out of state, this may be a blessing in disguise since I know people I can trust to handle things beyond my skill level. (tranny diff)
 
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