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Help me investigate.


Car RamRod
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One of the kids on my local mustang board had quite the issue with his jeep.

Its an 89 wrangler, and basically the straps on the front DS broke and his ds spun around beating the crap out of the exhaust and floorboard.

 

My knowledge of these trucks is weak, but I'm thinking he mustve been in 4wd for this to happen. (Otherwise the t-case wouldn't be engaged, or did that have full-time back then).

 

Either way, let me know what could have happened here. If you want to see some pictures, click here: (slight language warning)

 

http://www.listangs.com/forum/viewtopic ... &sk=t&sd=a

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He said... "the hubs must have been locked because it was in 2WD" :shake: ... At least there was someone on there smart enough to respond and tell him that he doesn't have locking hubs. There must be a locker of some type in the front to make it spin. He was probably in 2WD as he was able to strap the shaft up like that & drive it. If it was in 4WD...he couldn't have done that.

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oh.... yea that's me with the yellow car in the signature. Most of the guys are just clowning around, but some really don't know anything. Oh well.

 

What I thought up until now was that he either had it in 4wd, or he had a locker in the front (or both). What else could it be?

 

At first I thought it must have had a front locker, causing it to constantly spin, but then I realized that after the break, the thing kept spinning, causing the damage to the floorpan and such. But then somehow, he was able to tie it up.

 

All this makes me think it must have been in 4wd.

Any other input would be great.

 

Matt

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It is quite possible that he was in 4WD when it broke and, realizing too late that he screwed up, put it back in 2WD after the damage to finish the drive. He then cooked up the story thinking that no one on a Mustang board is going to know any better anyway.

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lucky that it did not dig into the road and flip him :ack:

 

I guarantee that wouldn't flip it. There would be an awesome trail of transfer case and maybe transmission bits to follow. :clapping:

 

Willy

 

Can I ask why not with as long as the front DS is and with the weight of a YJ behind the T-case??? I know there would be an awesome trail of t-case bits, but with highway speeds think it could have been a fun drive

:clapping:

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lucky that it did not dig into the road and flip him :ack:

 

I guarantee that wouldn't flip it. There would be an awesome trail of transfer case and maybe transmission bits to follow. :clapping:

 

Willy

 

Can I ask why not with as long as the front DS is and with the weight of a YJ behind the T-case??? I know there would be an awesome trail of t-case bits, but with highway speeds think it could have been a fun drive

:clapping:

 

For it to catapult like that the transfer case would need to stay intact. The aluminum front output would shatter with that much force at highway speeds. I could foresee the driveshaft becoming a blunt spear progressing through the floor pan after it destroys the transfer case and inflicting some major injuries to any possible rear seat occupants.

 

This was also attempted on Mythbusters. It wasn't the exact same scenario as they used a full size '70s sedan and impaled the front of the rear driveshaft in a pothole at highway speeds. But, it pretty much ended up with the driveshaft coming up through the floor and shooting into the trunk. It did result in some awesome damage. :thumbsup:

 

Willy

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This was also attempted on Mythbusters. It wasn't the exact same scenario as they used a full size '70s sedan and impaled the front of the rear driveshaft in a pothole at highway speeds. But, it pretty much ended up with the driveshaft coming up through the floor and shooting into the trunk. It did result in some awesome damage. :thumbsup:

 

Willy

 

Yes I seen that show, but then I seen a LTD in 1972 drop it's DS and flip over in the road and slide to a stop on the top :clapping: WIll have to say that was cool to watch, even cooler watching the lady come out through the drivers window on all 4's and start the pee dance :yes:

 

 

But yes the DS could come up through the floor if the steel parts in the T-case did not hold in place long enough to get the backend started up in the air.

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Getting back to "How could this happen?" -- the '89 Wrangler had a vacuum disconnect on the front axle. If working properly, the right side axle shaft is disconnected by a sliding, splined sleeve when in 2WD. When 4WD is engaged, the transfer case ports vacuum to a switch that operates a vacuum-powered device (technically called a vacuum shift motor) on the front axle that slides the sleeve over to lock the inner and outer halves of the axle together. There are no disconnects at the hubs.

 

Usually, if the vacuum fails it happens during the long periods when the vehicle is being operated in 2WD and the result of a vacuum leak is that the front exle won't lock -- leaving you with a 2WD Jeep. However, I believe it also requires vacuum to disengage the axle lock, so it is theoretically possible (but unlikely) that the axle was locked even though the transfer case was in 2WD.

 

But that's the way all Cherokees and Comanches were made after 1990, and all TJ and newer Wranglers. The last Jeep with the axle disconnect was the 95 YJ (square headlight) Wrangler. The transfer case disconnects from the front drive shaft in 2WD, leaving the driveshaft to free-wheel with the front tires. There's no load on the drive shaft.

 

My guess is he had it in 4WD on pavement and didn't understand that the front wheels and rear wheels don't travel the same distance, which builds up stress in the drive line, until ...

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