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My 1999 100 series blew front diff pinion and crown. How do I check diff lock system?

Bushrat

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My 1999 100 series blew front diff pinion and crown wheel while pulling heavy lead in low range. It seems the diff lock is engaging rear diff only pushing too much power to front diff causing the problem. Does anyone know how to sort the diff lock system?
 

Steve Wright

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My 1999 100 series blew front diff pinion and crown wheel while pulling heavy lead in low range. It seems the diff lock is engaging rear diff only pushing too much power to front diff causing the problem. Does anyone know how to sort the diff lock system?
The front does not have a Diff lock on the front!
 

Bushrat

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One button locks both front and rear normally- but Ive discovered that the rear diff locks when gear moved from high to low- before Ive even depressed diff lock button... tks
 

Chris

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I don't think it does. The front diff is open. Locking the rear doesn't send any more power forwards either. Locking a centre diff will share the power front to back though. Are you sure the lock that you're seeing isn't the centre lock?
 

uHu

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It's the centre diff that locks when moving to low range, or by pushing button on centre dash; forcing front and read axles to move at the same speed (or pushing 100% of the torque to both axles). The later years didn't have the CDL kick in when engaging low range, and it has been common to disable that silly feature also on the early years. Not all 100s have a rear locker, and none had a front one originally.

The 2 pinion front diff of the 98-2000 was weak, and likely to break, especially when reversing. The newer 4 pinion is sturdy enough.
 

Bushrat

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I don't think it does. The front diff is open. Locking the rear doesn't send any more power forwards either. Locking a centre diff will share the power front to back though. Are you sure the lock that you're seeing isn't the centre lock?
Ive put the car on four stands, when engaging low range the sound of the solenoid engaging the diff lock is clear but you may be right- its the center diff lock engaging. And when the button is depressed the front and rear are engaged.
For 12 years Ive hauled my 6000lb 30’ boat out of the water no prob. Twice in the last month Ive blown front diff doing it. Only thing thats different is that I dropped gearbox to replace rear oil seal. ‍♂️ Maybe I got something wrong putting that bck after the seal change.
 
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Bushrat

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It's the centre diff that locks when moving to low range, or by pushing button on centre dash; forcing front and read axles to move at the same speed (or pushing 100% of the torque to both axles). The later years didn't have the CDL kick in when engaging low range, and it has been common to disable that silly feature also on the early years. Not all 100s have a rear locker, and none had a front one originally.

The 2 pinion front diff of the 98-2000 was weak, and likely to break, especially when reversing. The newer 4 pinion is sturdy enough.
First time the diff blew two spider gears went nd I rebuilt... this last time the pinion and crown wheel shredded and I put on load very gingerly-
 

Chris

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Can't point to what the issue might be but that sounds quite wrong. It's almost like it the wrong ratio. I'm not saying it is of course, but what would cause such catastrophic failure isn't clear.
 
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