Just got my first Auto (Disco 2 TD5 - 2001 MY).
On a slope I thought an Auto should not roll back when in 'D' but mine doesn't hold at all. Is this normal or is there a problem? The slope is reasonable but not too steep.
Andy
Is that with the engine running or stationary? Either way, no, it won't. When running, you can hold the vehicle on the footbrake with the left foot whilst keeping revs up with the right (if necessary, e.g. for a hill start). When stationery, that's what P is for!
Stuart
The Rangie does. Im sure old Disco1 auto boxs do. Id check with the dealer..
Theres a girl with one here at work, Ill ask.
All autos seem to drive different. Some of mine would hold on a gentle hill, feet off all pedals in D, some wouldn't. My '98 Rangie which I think has virtually the same ZF 'box as your Disco will creep forward on the level in drive, and will also hold on a gentle hill. The downside to a vehicle that holds on a hill is it creeps forward on the flat so you need to keep the brake on! So long as yours is driving and changing smoothly, there's nothing to worry about.
Alan C
Drives OK, just wondered if there was some sort of 'clutch' in an auto that could wear with age?
In message , Andy writes
No - unless it is a DAF!!!!!! All autos (except a DAF) exhibit "drag" when ticking over in D, to a greater or lesser extent. There's nothing inherently guaranteeing that you will hold on a hill. Just a case of whether the drag is sufficient to balance gravity. My V8 auto Defender will hold on a fair slope. Put it in low ratio 1st gear and you have to be pretty hard on the brakes to hold it back, but I have the tick-over set a bit fast as I run it on gas.
On or around Thu, 29 Jun 2006 15:49:03 +0100, "Andy" enlightened us thusly:
only with the engine running fast enough to get enough drag from the torque converter. If it's at idle it shouldn't move, really, or only very slowly, and on any noticeable slope it'll roll back. a few more revs will partly engage the TC and hold it still. If you do that long enough, you'll overheat the transmission, mind.
"Andy" wrote in message news: snipped-for-privacy@bt.com...
Yes, there is. On the ZF4HP22 box (both early and later electronically controlled versions such as that in the Disco II), the "A" clutch (main forward drive clutch, engaged in all forward gears) is the weak link. Ironically, it's the smallest diameter clutch in the 'box, with the lowest surface contact area as well. This clutch wears at an accelerated rate due to main oil pressure leaking past the steel seals on the input shaft and applying a pressure to the clutch whilst in P, N and R, causing it to slip and wear. There are 7 wet-multiplate clutches in this box, A, B, C1, C, D, E and F. The life of the 'box can be optimised by never, ever revving the engine in P or N. What you should do is put the transfer box in N and select D on the main box, handbrake firmly on, if you need to do anything which involves revving the engine for any length of time. As for creeping or not, some will creep on the flat and not on, say, a 5% slope, others will roll back slightly on the same slope. It's down to the individual torque convertors and the clearances set within them when they are built/rebuilt. Just because one vehicle may roll back and another night not, doesn't indicate a fault in itself. If the oil on the gearbox dipstick is clear translucent red then you've nothing to worry about. If the oil is dirty or brown, check the bank balance! Incidentally, the ZF4HP24 as used in the P38 4.6 has an "A" clutch that is considerably larger in diameter with a correspondingly larger surface contact area (and a much higher torque handling limit), but it isn't a straight swap as the pump housing (and A clutch carrier) is 15mm longer, adding 15mm to the overall length. There is still the issue with the input shaft seals though. Badger.
So apart from having to lengthen / shorten the propshafts are you saying the ZF4HP24 fits the block without modification.
-- Andy
Physically, yes, it fits as long as you use the matching 4.6 torque convertor and engine drive plates. There's still the issue of the "24" being electronically controlled though, the way round that is to rebuild the "24" internals into the main case of a "22". Not the quickest of tasks, but the result is a super-heavy-duty box with the original hydromechanical control and no electronics. In my case (building one at the moment) I'll move the engine forward 15mm, it's easier to lengthen the exhaust 15mm than it is to modify and balance the props, and my engine sits 2" further back than std anyways. Badger.
On or around Thu, 29 Jun 2006 22:57:50 +0100, "Badger" enlightened us thusly:
Actual failure of the A clutch though, IME, takes under 100 miles from "slipping slightly under high throttle conditions" to "no forward drive at all under any conditions". You can still go in reverse, though, since reverse doesn't use the A clutch.
pity. both points...
Mind, I've only had one A clutch fail and that was a well-used box that I reckon had had a hard life before I got it.
By the time it starts to slip in forward drive at high throttle, the damage is already done! Most of the lining is worn by that point.
It's revving them in neutral or park that does the most damage Austin, to the point that most american states have special procedures for smog-testing any vehicle with a ZF4 transmission, due to their law-suit culture. Do a quick google and you'll see more info. Badger.
On or around Fri, 30 Jun 2006 19:36:15 +0100, "Badger" enlightened us thusly:
As a point of (at the moment, academic) interest, how much do you charge to do that (the rebuild I mean) - while I'm a good mechanic, I've not done an auto rebuild and I doubt it would pay me to acquire the necessary knowledge for a one-off, if I needed to do one.
The problem with rebuilding autoboxes is that if you replace every clutch pack, every sealing ring, torque convertor etc etc then it becomes extremely obvious that there are a lot of reconditioners out there that don't bother replacing ALL the parts, they couldn't make a profit otherwise! The parts alone to do a proper, full rebuild are around £400, and that doesn't include any "hard" parts such as clutch hubs if they are found to be excessively worn on the drive splines, they're alloy cast parts and the tangs of the clutch plates can wear into them, or the torque convertor stator spigot shaft. Labour would be another £180ish, making a total of roughly £580, but that's an extremely comprehensive build Austin. There are other mods that can be done, such as a modified sprag clutch assembly which eliminates the potential for losing 1st, this being another relatively common failure point on these boxes. That mod adds roughly another £90. To go the route of the extra 15mm and get the heavy-duty "A" clutch, you also need to factor in the extra expense of needing 2 gearboxes from which to build 1, you need a 22 and a 24 to amass all the necessary parts, and of course the relevant torque convertor and drive plate assembly. Badger.
Mine wont hold on a steep hill, but the wifes Touareg did, it had hil control so i guess they wont as standard?
Nige
On or around Sat, 1 Jul 2006 11:05:50 +0100, "Badger" enlightened us thusly:
Not silly money though, compared to some of the others in the market. I'd rather part with 600+ notes for a proper rebuild than 400 notes and not know.
true... does the 22 have to be fully functional? Mind, I scrapped the blown one I had here...
I can lay my hands on at least 3 blown 22's, they're not the hard ones to get! More of an issue is how blown they are with respect to how much (if any) contamination has got into the valve block itself, as that's a right royal pain to strip. Never wears, just sticks with the contamination off the burnt / broken friction linings. It's just too easy to get a machine-gun effect of springs flying around the workshop if you remove the wrong bit in the wrong order.!! Many years ago I was just over £600 for a recon Ford A4LD (Mk3 granada) box, one of the most disgustingly unreliable autoboxes ever made. I thought I was getting a fully rebuilt box but after taking the car back to Leeds 3 times (the firm that rebuilt it were in Leeds, it was easier to take the car to them than spend the time removing and fitting the box constantly, let them have the hassle!) I gave up and had it repaired properly by a firm in Preston. Good guys in that Preston workshop, they showed me what was what, I learnt a lot about autoboxes from them in only a few hours, but it was enough to overcome any fears I had about touching them. The biggest issue is finding someone who will sell you the parts, not the frictions they're easy to get but the "hard" parts. ZF4 is an easy box to strip and rebuild. Badger.
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