Throwing the Main Drive Shaft. Photos of the Aftermath.

[rsh253]

I felt a vibration for 15-20 seconds, and then it sounded like an explosion. It took a few seconds, but then I realized the engine wasn't driving the rear wheels any longer. Luckily, a 13,000 lb vehicle traveling at 50 mph can coast for a long way and I was able to pull off the road onto a nice grassy spot.

My driveshaft let go from at the axle flange, banged around on the frame and then the transmission yoke let go. On its way out, the drive shaft also hit and blewout one on the inside rear tires. I think the bolts on the rear flange were loose. When I replaced what was left of the shaft, the front bolts were not particularly tight.

One of the photos is of the truck frame with the very clear imprint of a Grade 8 bolt head.

Luckily I was able to get the truck home by engaging the front axle. I was able to buy a good used driveshaft on eBay.

It was an "interesting" experience.

-Russ

 

[BobM]

Holy Cow! That left a mark!

 

[oilcan]

Jumpin' jimminy!

I've noticed that if I reuse old locknuts they tend to work loose over time, especially on the drive shafts. Since the budget is limited and new nylok nuts can be hard to come by on short notice around here, I tend to squirt a little blue loctite on just about everything.

 

[powerhouseduece]

WOW!! looks like your frame has a new tattoo!

 

[cranetruck]

http://steelsoldiers.com/index.php?name=PNphpBB2&file=viewtopic&t=13558&highlight=trindal

 

[Pawnshop]

Driveshaft capture loops were required back in my Longhorn Speedway days, I assume they still are in the racing world. A lot of racers made them from chain so ground clearance was not an issue.

 

[papercu]

Be very glad it was the rear that went! When the FMTV first came out the front would drop, something about the vibration over a certain speed, killed several soldiers. Anybody remember how they fixed it? Wayne

 

[doghead]

It was an "interesting" experience.

Thanks for sharing it here. Very impressive photos.

 

[neilhendrix]

Looks pretty nasty Russ

Neil

 

[Big Mike's Motor Pool]

i had that happen to me once in a toyota on 44 inch tires. i was blowin down the road and the flange bolts at the trans came loose and the shaft dropped and continued to fling around untill i go the truck stopped. as we were pickin up the peices this pickup truck comes flying up the road and skids to a stop behind my truck. the driver was a bit mad and then i seen the hole in his windsheild where a u joint cap had blew through

 

[scooter01922]

WOW man, i don't even want to think how many TONS of impact force is has to take to make an almost perfect impression like that. Consider yourself REALLY lucky.

 

[jwaller]

ya. I was doing pmcs on the first deuce I bought and found every single drive shaft bolt loose. front and back and intermediate. glad I checked them first.

 

[FreightTrain]

And this is why I buy bolts by the 100 count box.If I need 3 or 4 I just buy a whole box for future use.Cause it always sucks to be doing something and then you find you need the same bolt from last week but it is 5:01PM and the store is closed.

 

[cranetruck]

Apparently, there is a mil spec for these self locking nuts and they only require 15 on-off cycles to meet it. MIL-DTL-25027 if someone wants to look it up.
Bottom line is that on a 30-40 year old vehicle it may be time to replace all those nuts....
I would think twice before using nylon insert types, at least until the chemicals that will attack nylon are listed, possibly solvents used along with painting may be bad and what about road salts, lots of exposure there.
Starting fresh, new all-metal lock nuts is the way to go (grade IMHO.

 

[cranetruck]

Checked the U-joints on the 757 and it uses self locking bolts, so now I'm looking for info on them...one thing after another..still this should be considered an important thread and many thanks for posting Russ.

 

[DanMartin]

For your locking bolt needs:

http://www.stage8.com/home_indus.html

I use these on my exhaust for several projects, and they work great. Great idea, an great results.

 

[Scrounger]

There are several things that one needs to remember about fasteners. First off every fastener has a specific torque value. If a fastener is over tightened it will cause it to stretch and it won’t remain tight. The second is that just as lock washes wear out, lock nuts wear out also. That is why when one looks in the TM is usually has something about remove and discard, then use new when reassembling.
Most of the lock nuts on the M-series are called Flex-lock nuts. They are made by SPS fastener. They were originally made for aircraft use during World War II. The military found that they would be useful on vehicles and now they are what are specified. The Flex-loc nut holds toque at high temperatures and can be reused several times, but they do wear out.
As far as driveline bolts on these trucks most of them have been removed and reinstalled so many times that they are usually worn out and should be replaced if they are found to be loose.