Ok, went down past the lake, to a huge empty area that I test my truck at, for safety reasons. Since changing to 4.10 gears, the truck runs up to redline faster, so I decide to change my shifts from 5800 and 5700 to 5900 and 5800 rpms for the 1 to 2 and 2 to 3 shifts. So I retuned my predator and went to test out everything. I do about 3 runs, and like the way that it feels with the higher shift points. Decide to go home now, and get on it, and when it makes the shift into 3rd gear, I hear KaaBoom! and the vehicle runs up to redline real fast, and I let go of the gas. Coast for a while but the tranny is doing nothing, but revving up and the speedometer is revving up like crazy also. Come to a stop, look at the motor, nothing, look at the tranny, and I notice that my driveshaft is gone! Yoke hanging out of the tranny, and those little bullshit caps on the rear have warped out so that the driveshaft fell out. Call tow truck, and I look under my vehicle for about 15 minutes, and I can see where the driveshaft was bouncing around. SUPER LUCKY Pray to God, bounced off the frame a couple of spots, put a dent into my muffler, and that is it. Everything else is fine, gas tank, fuel lines, brake lines, diff, suspension, shocks, and rims and tires. It definately looks like my Flowmaster took the brunt of the damage, thank God for that muffler saving all the expensive parts. NO leaks from tranny or diff. Tow truck takes my truck home, and the diff is for sure fine. But now I need a custom driveshaft, and I don't have the money for a couple of months!! Once I get a new driveshaft I will then have to test the tranny to make sure that it is ok. I revved it through each gear, and the speedometer, showed fine, and I hear no noises what so ever, or any drag or what not. So I think my tranny is OK, time will tell! Looks like I will have to do some upgrades faster than I thought!

Will post pics later tonight, after I get back from dinner with family. Maybe after midnight. The drive shaft ripped into two parts. After looking at it, it looks like the teflon washer that they use that holds one of the caps broke apart, and the cap flew off, thus causing the driveshaft to rip out of the vehicle. Or one of the caps on the joint broke on its side I had to go back after getting home to find the driveshaft parts. Also the drive shaft hit the bed, and put a dent into it, right in the middle. I am not concerned with that since I am rhino lining my bed later, but will post that pic also!

 

man, that really sucks bad. glad nothing else got hurt in the process of it breaking apart besides a dent in the muffler. ?, can't you go with another driveshaft from a wrecked truck? seems that if you had it balanced it would work fine.

 

Damn, that sucks man Sorry to hear that. How much does a custom driveshaft cost?

 

Be glad that the front end is the end that stayed together! If the front would have came off and fell down, that could have been catastrophic to your truck and you.

An old fried of my dad's told us about his Blazer. The driveshaft fell off the yolk on the tranny, and caught something on the interstate. He sad the whole rear end of the Blazer came up and moved about 2 ft off course. He damn near wrecked it. He had just had the motor rebuilt and pepped up a little bit as well.

BTW .. this was an old 4wd Blazer, the ones when they put the 350 in them.

 

Who installed the gears? Sounds like they might have torqued the ujoint bolts wrong or stripped one or something.

 

did wranty fix the drive shaft sorry cant spell to good

 

Ok, here goes, BEEN THERE DONE IT , THREE TIMES, HAHAHAHAHA
That scenario sounds so familiar it's bringing back nightmares. I'll tell you my story and then tell you exactly how to fix it, do not do anything else except what I tell you and you'll be fine. Trust me, I just got thru with the same ****. If you want more info , go to my forum and look for my posts in the drivetrain area and racer's lounge about my shaft problems.

A while back i got my 4.10's installed by my badass friend joe over at jagperformance.com, he's awesome. First impressions were awsome, the truck was very torquey feeling and the shifts definitley were affected, they are over quick becuase of the quick revs. As soon as i get on the highway i notice a small vibe but don't pay too much attention to it.
Days past and i get some room on the highway to test them out, i'm going along and shift down into third, two seconds later, KABOOM, at 80mph, i about had a f@cking heart attack, scared the **** out of me,
My shaft broke right in the middle and hammered my flowmasters, ripped the two ujoint straps apart, and messed my trans bushing up (more on this later). Same as you buddy.
Now try going thru this two more times, but each time just waiting for the shaft to blow and it does, I'm still completely worn out about going fast in my truck, it still haunts me. i still can't confidently shift down into third and stretch it out as far as it will go. I have at the truck, and no breakage but i won't on the roads

Here's why it happen and here's how to fix it.

What happened to me and you was due to a theory for driveshafts called critical speed. Your truck wasn't designed to spin the shaft that fast becuase of those 4.10 gears, now in overdrive and third you're spinning it even faster, well, once it hits its critical speed , it starts to wobble in the middle and rips itself right in half. It's not your torque or power, it's becuase your stock shaft isn't balanced correctly and was never meant to spin like that. Now some will say, "i have 4.10's and it doesn't do it", well not all do, but mine and yours did.

Go to dennysdriveshaft.com and get yourself an aluminum HD shaft, mine cost $490, plus the HD 1350 series rearend yoke. That's the only one they will make you if you have about a 60inch ds. Exspensive, but after going thru 4 shafts , it was worth it, oh ya, three rearend yokes too, speaking of yokes,
Your rearend yoke is damaged and you'll need to replace it. If you don't, you're going to get vibes. When the shaft broke and was ripped out of the yoke, and spread those straps apart, it also, spread the two ears the straps bolt into apart. Everytime, that happended to me, it spread them apart about 1/16 of an inch.

Check your trans bushing that is in the tailhousing, it's very easy to replace and well worth it, messed mine up twice. Also, don't turn your trans with no shaft in it, not good for it, that internal trans shaft isn't stabble in there , the shaft keeps it centered.

If you're lucky, you didn't mess anything else up and you won't have any more vibes. I still have a very small vibe in mine and i'm still tracking it, but i guess that's what all those broken shafts do.

If it was a mistake on the mechanic's fault, this entire message is worthless, but i highly doubt it, shafts breaking in the middle in second/third gear is caused by critical speed, at least with trucks with our kind of power and 4.10 or lower gears.

Holy **** this is a long post!

I really hope you recover emotionally from the breakage hahah, if you do let me know how you did it, and don't test your truck out without a very good shaft in there, if you do, you face the chance of another breakage.

Good luck,

allen(broke 4 driveshafts)

 

Now I am scared to drive fast

 

Man I feel your pain man! When I tried to install those Billet Servos my stuff wouldn't go in and I got bent for $110 for the tow truck alone. Then I spent another $400 getting everything buttoned back up. Not fun and I FINALLY got that out of my hair. Imagine what $500 would have done for the truck...custom tune and an ASP pulley!

Glad you made it out okay man!

 

The drive shaft doesn't speed up or down with engine rpm, only speed.

It wouldn't spin any faster @ 80mph if you were in 2nd, 3rd, or OD.

I'm not sure I see that one .. although it sounds very possible, just under different situations.