ZF 4-speed auto .... problem?

Hello Steve As far as I know any changes to the ZF have to be made internaly i.e. hydraulic adjustments with gearbox out of the vehicle. I have had a number of diesel auto Discovery's with various lock-up speeds M reg.Tdi300 was 48mph very nice setting, S reg. SafariTdi300 was 52mph over the 50mph speed limits having to listen to the torque converting making the noise and wasting fuel. The Td5 was no better about 53mph again far too high. I wish all my Disco's had locked up well below 50mph I would have been very happy. Gordon

On or around Tue, 7 Dec 2004 18:52:33 +0000 (UTC), "Steve" enlightened us thusly:

has it always done this?

They're not all set the same. ISTR one or another variant being set to lock up early. Is it the original box for the vehicle?

However, my workshop manual says - in test 10 - that the direct drive clutch will only engage if 4th gear is engaged at 40 to 44 mph. Disengagement occurs at 39 to 42 mph. This suggests that mine locks up late

I have a scan of the page from the manual showing the shift pattern if that's of any interest. Other than that the manual only seems to mention setting the kickdown cable.

Richard

The first question has got to be - does it tend to stick in 1st gear when it's cold ?

The second question is, have you checked the oil level correctly ? (low oil often causes an early lock up) Before checking the oil level you need to cycle the box (while cold) through drive and reverse a few times then put it in neutral while you check the oil. (don't forget the handbrake !)

The lock up is caused by a number of things but primarily by the governor at the back of the box. The governor consists of a weight and a spring connected to a valve that spins on the output shaft of the gearbox. As the speed increases the centrifugal force opens the valve, eventually, in conjunction with the hysteresis valve, it will cause the box to lock up. The torque convertor also has an input on all of this too but IME it's unusual for the TC to cause this sort of problem.

One thing to note is that all this happens before the transfer box which should be an LT230 at that age. You should check that the transfer box is actually a 1.222 ratio box rather than a 1.4 as a 1.4 (or 1.6) would cause the box to lock up at a slower road speed if you are on standard (

You can also try adjusting the kick down cable as it's not unknown for these to be badly adjusted making the vehicle less responsive. The kick down cable effects the gearbox throughout it's operation and, if badly adjusted, it can cause the gearbox to lock up when it shouldn't. It can also effect the shift pattern and timing. If the gearbox hasn't been apart since it left the factory and the crimp on the end of the kickdown cable hasn't moved then the crimp should be about 1/8 of an inch from the cable outer with no throttle. If the gearbox has been apart/repaired or the kickdown cable replaced then there is a good chance that the little crimp is meaningless. That being the case try tightening the cable up a little at a time and see if that helps.

cheers

Dave W.

Since I've had it, yes.

I've no idea if it's the original box. Lack of leaks clonks whizzes and pings might suggest not, but then the speedo has only got 52k on it so perhaps it is. The speedo could be a new one too though, who knows! Maybe there's an OE serial number list that will match the box to chassis as it left the factory.

As someone else has pointed out, their ZF-4 locks at the same point as mine, so maybe there's nothing wrong after all .... which is why I put the question mark in the subject line. I suppose having it lock at 40ish saves it hunting when I get stuck behind the 45-53-45-53... (etc) mph Rover 412 (formerly Austin Montego ... inevitably green) road block. Now I just have to worry about the blue-rinse in a Nissan Micra doing 35-43-35-43...... grrrrr!

By the way Austin, the gas is sorted now (RR goes BANG! ... if you remember), thanks to someone on uk.r.c.f.lpg who sent me a scan of the installation and setting manual. It's easy when you know how!

Steve

Maybe that's why Haynes is quiet on the subject then. I guess I just need to live with it and enjoy the un-stressed burble.

Steve

My previous RR was an '88 and locked at the same point as yours does - which was why I wondered if this one had a problem. As an aside, changing from

If your workshop manual is correct then my current ZF box is about right on the money. Perhaps the later ones (somewhere between '85 and '88) changed their lock points but your manual isn't amended or pre-dates the change.

That's all I could find in Haynes too.

Steve

Not that I've noticed. It quite readily and smoothly goes up through the gears, even when cold. The only thing I've noticed (and this only happened once, last week during the "cold snap") was the shifter was stiff (ish) the first time I went from P to D in the morning. It only did it that once and on thinking "that was odd" and giving it a waggle up and down through the range I couldn't replicate it.

Checked, just a gnats whang below full - and it's pink (the oil, not the gnats whang ... although that might be pink too .... possibly ..... errr ....)

Tyres are 205's. I'll check the TX box, hopefully the sticker is still on there.

I'll bear this in mind and have a peep at the cable whilst I've got the thing up in the air to look at the TX box ratio. Thanks for the help.

Steve

These are the speeds my 86 RR locked up at. If hunting between gears bothers you on uphill stretches then it is good practice to pull the lever back to lock top gear out.

Huw