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ZF fault diagnosis


bill van snorkle

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Automatic Tansmissions, beyond servicing or outright replacement are one component I have always managed to keep my oily mits out of, until now. Last night I had a bit of time to fiddle with an 89 RangeRover that I bought cheaply a few weeks back. The transmission has a problem, in that when first started, the vehicle will move in all gears on light throttle but will slip badly at larger throttle openings, and after a few minutes will slip so badly that the vehicle will stop moving altogether. Swictch off engine, wait a few minutes, restart engine and vehicle moves again as before for a couple of miles.

Last night I drained the trans fluid, which was quite clean, removed crossmember, removed trans oil pan which wasalso quite clean. I then removed and peeled open the filter. The plastic sheet filter element was blocked with scum but wasn't full of clutch material or much in the way of metallic particles. I cleaned the filter and tepped it back together (I'm cheap), refitted everything, and filled her up with new trans fluid .

The transmission drives a bit better now but still slips a bit in all gears, which suggests to me that the clutch packs are badly worn due to the previous owner continuing to drive the vehicle with a blocked filter, but something happened this morning that is confusing me a little. I pulled up at a set of traffic lights and put the selector in Park for a minute or so. When lights turned green I put it in drive and attempted to move off, but the engine labored and bogged down almost to the point of stalling and the Rangey really struggled to move.

Once up to around 20 MPH the car moved freely but I could still make the trans slip a bit. To hazard a guess I would say that due to sticky valves or a partial blockage,hydraulic pressure was being applied to 2 or more gears simultaneously and the different gear ratios were fighting each other.

Would anyone care to offer their insight as to what the problem may be ?

Bill.

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The labouring when moving off at the lights sounds like the box might be changing up into top gear, is the kickdown linkage ok?

It may have tried to start in high, but if the clutch packs or pump was knackered I would have thought the trans would just slip and not bog the engine right down to almost stalling point.

Kickdown linkage is OK too.

Bill.

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It may have tried to start in high, but if the clutch packs or pump was knackered I would have thought the trans would just slip and not bog the engine right down to almost stalling point.

Kickdown linkage is OK too.

Bill.

Sounds a bit likw the problem with cams that ashcroft mention on their website. they upgrade them when reconditioning apparently.

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Sounds a bit likw the problem with cams that ashcroft mention on their website. they upgrade them when reconditioning apparently.

That's the cam inside the sprag clutch. When that 'flips' you can't put the vehicle into drive but have to cycle through the gears (1,2,3,D) to drive it.

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Automatic Tansmissions, beyond servicing or outright replacement are one component I have always managed to keep my oily mits out of, until now. Last night I had a bit of time to fiddle with an 89 RangeRover that I bought cheaply a few weeks back. The transmission has a problem, in that when first started, the vehicle will move in all gears on light throttle but will slip badly at larger throttle openings, and after a few minutes will slip so badly that the vehicle will stop moving altogether. Swictch off engine, wait a few minutes, restart engine and vehicle moves again as before for a couple of miles.

Last night I drained the trans fluid, which was quite clean, removed crossmember, removed trans oil pan which wasalso quite clean. I then removed and peeled open the filter. The plastic sheet filter element was blocked with scum but wasn't full of clutch material or much in the way of metallic particles. I cleaned the filter and tepped it back together (I'm cheap), refitted everything, and filled her up with new trans fluid .

The transmission drives a bit better now but still slips a bit in all gears, which suggests to me that the clutch packs are badly worn due to the previous owner continuing to drive the vehicle with a blocked filter, but something happened this morning that is confusing me a little. I pulled up at a set of traffic lights and put the selector in Park for a minute or so. When lights turned green I put it in drive and attempted to move off, but the engine labored and bogged down almost to the point of stalling and the Rangey really struggled to move.

Once up to around 20 MPH the car moved freely but I could still make the trans slip a bit. To hazard a guess I would say that due to sticky valves or a partial blockage,hydraulic pressure was being applied to 2 or more gears simultaneously and the different gear ratios were fighting each other.

Would anyone care to offer their insight as to what the problem may be ?

Bill.

Hi Bill,

I would guess that the 'A' clutch at the front of the box has burnt out,

it will drive a bit when cold but when the oil gets thinner it slips,

when badly burnt and the friction material has all gone they can friction weld, this may heve been what happened when it locked up,

either way when they start slipping they usually need to come apart,

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