norseman
Well-Known Member
NO, Ratae (post # 17) has got it right.
Auto-boxes have changed over the years, there was a time when you could 'bump-start' an auto by pushing it with another vehicle but not these days
From her post the box failed whilst being driven offroad. I suspect the friction plates in the forward clutch were already worn & trying to drive it out of where it was stuck just finished them off.
We haven't been told what mileage it's done.
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Henry_b
Think outside, no box required.
To check the fluid correctly the Disco must be on level ground with the 'box in neutral and the engine running..
The ZF4hp22 has a habit of blowing the Sprag clutches, put her in 1st "manual" and see if she moves..
Does the fluid smell burnt?
is it black or just brown?
The ZF4hp22 has a habit of blowing the Sprag clutches, put her in 1st "manual" and see if she moves..
Does the fluid smell burnt?
is it black or just brown?
jamesmartin
Well-Known Member
it doesnt blow them they are rollers and ramps you get excessive wear so it doesnt lock or just gummed up which can be sorted with oil changes
Henry_b
Think outside, no box required.
It's the cams in this one way sprag clutch that "flip" the unit will slip both ways resulting in the vehicle only pulling off with the shifter in position 1 and not Drive
The sprag clutch fail's its sprag clutch (A) IIRC, its usually a combination of wear and abuse, if D is engaged from neutral with the engine in fast idle or revving high etc in the sprags are engaged suddenly and instead of wedging they will go over center and flip. when 1 is engaged a clutch plus the sprag clutch engage hence the ability to start in 1 when the sprag is inverted the drive is provided by the clutch only.
So offroad, you alternate from D-R quite alot i assume..
could of been dropped into Drive at high RPM or at another unfavourable situation.. etc etc
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jamesmartin
Well-Known Member
thats not exactly true they cant go over center theres a weak concertina spring a ball and a ramp if reversed the ball goes up the ramp and jams the outer ,if it doesnt do that ie wear so ball rising up the ramp is not enough to jam or ball doesnt rise as its stuck then clutch doesnt lock ie no drive, thats what i see when i rebuild them,they are never blown but when you counter rotate between your two palms worn or gummed up one will rotate both ways instead of only one, a rinse in paraffin cures gummed up ones, ive read that on ashcrofts and wondered what boxes they were talking about,though the fact one way clutches fail is real as is common failure of clutch A, which would generaly be the one clutch that needed replacing whether failed or not during a rebuild as they were allways showing signs of slipping ie plates darkening
Henry_b
Think outside, no box required.
jamesmartin
Well-Known Member
depends on oil colour ,black clutch pack ,dirty brown perhaps one way clutch and a few flushes,with a mechanical govenor controlled box the issues with the govenor flushes can give,but that can be fixed by removing the rear housing without stripping the box or removing it from the engine
