ZF 4HP22

OK, makes sense. I mean, you can see the fluid oozing out around the input shaft but that, and the gap in the bottom of the housing, couldn't account for the volume that poured out. Now, as for method of removal, I followed exactly the procedure in the Rover workshop manual, which has you separating the box from the bellhousing/torque converter. However they appeared to a bit off the pace in two respects. Firstly:

"Lower the rear end of the gearbox sufficient only to give access from the rear, to the upper hexagon securing the fluid filler tube... Unscrew the upper hexagon securing the fluid filler tube to the gearbox."

Well you can't. The gearbox simply doesn't drop low enough to give you enough room to swing a spanner. Hence the hacksaw blade. Secondly, they mention something about a drain tray to catch residual fluid, but you are not warned that the contents of the torque converter are about to dump on you. They do, however, have a reverse procedure for offering the gearbox up to the bell housing/torque converter when reinstalling.

I assume when removing everything together, you release the torque converter from the flex plate via the aperture in the front?
 
I assume when removing everything together, you release the torque converter from the flex plate via the aperture in the front
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That's right. That's why there's a removeable panel on the bottom front of the bellhousing. I'm surprised at the manual's method, i've never known anyone to do it that way and getting it back together must be a nightmare. (try refitting the converter on one of your spare trans'. You have to align 2 or 3 splines and and the drive dog. It's quite a fiddle!) Also, if the bellhousing is still attached there is no need to remove the filler tube.
 
KiwiRover said:
Standard practice is to unbolt the converter from the flexplate, then separate the bellhousing from the engine. It's heavier but you won't get the spillage. And you will have to fit the converter to the box before you put it back in because aligning them is quite tricky. :)
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Not with a 35.
 
Harvey, are you responding to the first sentence or the second, or both?

Oh well! I've removed a couple of engine/gearbox combos from cars over the short course of my young life, but I've never dropped a gearbox out the bottom by itself before, so this was always going to be a learning experience. In fact, this whole conversion exercise is a giant learning experience because I only have the vaguest clue as to what I'm doing! Wish me luck, fellas. I'm going to need it.

I had a bit of a grovel under the car again yesterday to reappraise things, and despite the fluid spill and the problem with the filler pipe, on balance the method derived from the manual probably worked out better for me. There's not much room under there, and leaving the bell housing in place made lowering the gearbox out much easier with my contrived apparatus of trolley jacks and blocks of wood. The bell housing is a heavy POS and I only just lowered the box out without causing myself injury.
 
Just thinking out aloud for a moment. Looking at the amount of work that is required to fit the ZF box, has anyone actually calculated if this is a financially viable project?

WIth a normal open road speed limit in many places of 60 to 70 mph (100 - 110kph), engine revs will normally be in the region of 2500 to 3000 in round figures. Not high revs by any means, so with the overdrive on the ZF, that might drop the range to 2000 to 2500 for the same road speeds. What would be the projected fuel saving over say 10,000 Miles per year of country driving?

The cost of rebuilding the ZF is the region of 4 times more for the same sort of work carried out on either the 35 or 65. So in Australia where you might spend $1000 or less having your 35 or 65 fully reconditioned (say 650 Pounds), it will cost something like $4000 (2600 Pounds) to have the ZF reconditioned. That is a huge difference, so the ZF would want to last for decades and see 4 times the mileage between rebuilds otherwise the costs become rather excessive.

Ron.
 
Financially viable + Rovers = :LOL: :LOL: :LOL:

I appreciate what you're saying Ron but for the most part these are hobby cars and we do these things for the fun of it. It would make for a relaxing drive to watch that tacho needle drop on the motorway and it would be cool to tell people you've stuck a 4spd auto in your car. Justifying the expense doesn't really come into it (except to the missus).
The ZF would never have been my first choice for an upgrade but it was Land Rover's so it makes it the closest thing to a bolt in conversion we have. A preferable option might be a GM700R4 or Toyota AW71 but they would require expensive adaptor plates.
 
SydneyRoverP6B said:
Just thinking out aloud for a moment. Looking at the amount of work that is required to fit the ZF box, has anyone actually calculated if this is a financially viable project?

WIth a normal open road speed limit in many places of 60 to 70 mph (100 - 110kph), engine revs will normally be in the region of 2500 to 3000 in round figures. Not high revs by any means, so with the overdrive on the ZF, that might drop the range to 2000 to 2500 for the same road speeds. What would be the projected fuel saving over say 10,000 Miles per year of country driving?

The cost of rebuilding the ZF is the region of 4 times more for the same sort of work carried out on either the 35 or 65. So in Australia where you might spend $1000 or less having your 35 or 65 fully reconditioned (say 650 Pounds), it will cost something like $4000 (2600 Pounds) to have the ZF reconditioned. That is a huge difference, so the ZF would want to last for decades and see 4 times the mileage between rebuilds otherwise the costs become rather excessive.

Ron.
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Hi Ron, as Al says it's not about the cash, if it was we would all be driving Toyota Corollas.

With the relaxed and graceful demeanor of the P6, 3000 rpm is far to high an RPM range to make for relaxation and given the HP, torque and light weight body of the car it just offends my engineering mind to have what other wise is such a nice car spoiled by this design oversight.

Auto recons seems to be an area fraught with predatory pricing, variability and just plain rip offs. I was quoted NZ$300.00 for a ZF split, strip and A clutch replacement, any other parts that maybe required would be extra but on the whole very cheap very very reasonable pricing I thought, I doubt that the BW recon would be so cost free, That said other people getting auto boxes recond and repaired have paid way over the top for example my Suzuki box cost NZ$4,500 for a rebuild and pricing for other acquaintances has been 1500 plus.

I would hate to work out the labour cost for retrofitting the ZF to the P6 but can see at least 30 hours in it, hopefully if enough people do the conversion the knowledge base will reduce the install and modding time.

Graeme
 
Hi Ron. I think you misunderstand my reasons for converting the car to a ZF. Significantly, it is not based on economic factors. Let's face it, we're talking about an elderly V8 with the aerodynamics of a small building! I've already signalled my disregard for fuel economy simply by owning the thing! Brown Rover is a weekend car that I drive purely for pleasure, and it will never cover huge distances. If the ZF provides better fuel economy I will be happy, but if it doesn't I won't really care.

Any other form of financial viability is moot. If you own a classic car and lavish some money on it, financial viability is out the door and gone. I'm not sure any car is financial viable, but classic cars are the least viable of all. We all do this for love, let's face it. If cheap motoring was all that mattered to me, I'd push the Rover over a cliff and just tool around in the wife's Micra for ever more. We bought it 10 years ago, and apart from service items we've never replaced so much as a single nut. It never misses a beat, and it will last at least the next thousand years at the wife's current rate of mileage.

Secondly, the conversion is shaping up as not particularly onerous, or expensive. Throughout the course of this thread we've been zeroing in on the actual steps involved, and even I, a total babe-in-the-woods who can barely adjust a crescent spanner without help, am yet to be put off. Crank adapter, spacer, driveshaft, rear mounts and change linkage are the problems that require solving, and all should be relatively simple to sort.

For me, this is all about the driving experience. I love my P6B, in most respects an astonishingly good drive by modern standards. I have had numerous nice new company cars in the last 15 years to compare it to, and also my superbly comfortable Rover 75, yet the P6B has always remained my favourite. But I have long felt that the Borg Warner 35 lets the rest of the car down. The gearing seems very low for an engine with so much available torque (even in standard 3528cc/twin SU form) and with the torque converter slip and general slushiness it always seems like the rear wheels are connected to the engine by a big rubber band. I've always found the car unnecessarily busy at 100 kph. I compare this with my experiences of driving 4HP22-equipped Discos, P38 Range Rovers and BMWs. Bolted behind a Rover V8, the box is crisp, responsive, and the lock-up torque converter and overdriven fourth make open road cruising a completely different prospect. The ZF 4HP22 is nearly 30 years newer than the Borg Warner 35. It is a greatly superior box, and it can be made to fit in the Rover P6 with relatively little effort. Upgrading the P6 from the 35 to a manual box seems quite popular; I've seen several, usually with SD1 or Celica 5-speeds, but I like a self-shifter behind the V8, so the ZF is a no-brainer to me. It's damn close to a bolt-in upgrade.

I have to question your relative rebuild costs. I've had a completely different picture painted by my regular mechanic, and Graeme (ghce) has had some very encouraging prices quoted regarding work on the ZF. In any case, it's largely irrelevant in my particular situation. We're comparing a stuffed 35 in need of a rebuild (at whatever cost) with a 120,000 km ZF in good nick that can be plumbed straight in. I mean, there's always a risk it'll crap itself, but I'm prepared to take it. I know the car it came from (a well-looked after 5-series unfortunately squashed by a retaining wall in the Feb 22nd earthquake), and my mechanic has inspected the box for me. The ZF is a well-regarded, reliable box. The odds are good.

Finally, there has been a lot of interest in this thread and elsewhere throughout the forum concerning the ZF gearbox. There is a general feeling that the 4HP22 represents a worthwhile upgrade to the P6B, and the encouragement and advice has been forthcoming from all quarters. We can't all be wrong!
 
The lock up is going to improve economy and power in 3rd and 4th by about 20% from my understanding....
 
4th gear is 0.73:1. Compared to the direct drive BW35 that's a 27% drop in revs, isn't it? Taking into account the noticeable torque converter slip of the 35 even at open road speed it will be even more.

Dunno what that all translates into with respect to power and economy, but I can see a great improvement just in refinement.
 
in 3rd an 4th you'll have pull more akin to a p6 manual. People pay a lot of money to get an extra 30+bhp out of an engine but here you'll get that as a by product. I think it's well worth it.
 
WarrenL said:
a 120,000 km ZF in good nick
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Sounds good to me. The 5hp18 in my TDS is at 415 000 kms and, having had two oil changes in its documented life, feels indistinguishable from that of a FSH mature owner car with half the mileage. It has developed a slight leak from the selector mech is all. I like ZFs a lot and love the lockup.
 
rockdemon said:
The lock up is going to improve economy and power in 3rd and 4th by about 20% from my understanding....
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Mechanical 4hp22 is 4th only for lock up electric maybe 3 rd and 4th....unless any one knows better.

Graeme
 
I was looking at it from the point of view of being someone who uses their Rover on a daily basis. I certainly don't consider 2500 to 3000rpm or even higher as being high engine revs. I will concede that the 3.5 litre engine has to be driven with more throttle at those speeds and is certainly not as smooth as the 4.0 and 4.6 litre engines, so that would re-enforce the argument that to keep the revs lower would be advantageous. The factory fitted P6B camshaft though is of such a design that the engine really doesn't start to perform well in terms of pull until you exceed 2000rpm, and certainly 2500rpm really sees the performance improve.

I can also appreciate the argument that in standard form, the BW35 and 65 do feel rather sloppy, as Warren said, akin to having a rubber band between the rear wheels and the engine. So again the thought of a ZF does offer significant appeal which I can fully understand.

My thoughts are no doubt influenced by having driven 6 cylinder Nissan Skylines and Holden Commodores which had overdrive transmissions. They would constantly hunt between overdrive and the direct ratio on even the slightest rise if more throttle was used as the speed started to drop. They would then surge ahead, so you would have to back off again, very annoying after a while, and nothing like the no fuss driving of the Rover.

Ron.
 
Certainly agree with he last part especially in 4 and 5 speed autos, constantly chopping and changing when you want t be in cruise mode only, a real pet hate for me with auto boxes and the reason I prefer manuals but then again I don't even like kick down, when i need any performance boost I just change down with the gear selector.

Graeme
 
SydneyRoverP6B said:
My thoughts are no doubt influenced by having driven 6 cylinder Nissan Skylines and Holden Commodores which had overdrive transmissions. They would constantly hunt between overdrive and the direct ratio on even the slightest rise if more throttle was used as the speed started to drop. They would then surge ahead, so you would have to back off again, very annoying after a while, and nothing like the no fuss driving of the Rover.
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Ah, yes! Many years back I drove a '98 Falcon company vehicle, and its Borg Warner (IIRC) 4-speed would do exactly that. It was especially disconcerting when you were using cruise control. There is a particular wide sweeping bend going up a hill on the highway to Dunedin, a regular trip for me in those years. I learned to ditch the cruise control well before that bend because the car would slow, drop suddenly to third and accelerate madly for the second or two before the cruise control throttled back, nearly throwing you off the outside of the bend. First time gave me quite a fright, second time the lesson sunk in, the third time I remembered to release the cruise control before the bend. Pain in the butt.

A 2.2 litre Toyota Camry would hunt too, but it was desperately lacking in power. It needed to work the revs. However driving 3.5 litre Discos (several of them over the years), I've found the ZF a pleasant transmission, shifting in all the right places. It's been a while Graeme, but I'm sure I recall lock-up on third as well as fourth. To the uninitiated, it can sometimes feel like a 6 speed gearbox. However my memory may be confusing itself with driving later Discos with the electronic version of the box. My old man has an early 90s 3-series with the mechanical 4HP22; if I get a chance I'll cadge a blat out of him and see if it locks up in third.

Tor said:
WarrenL said:
a 120,000 km ZF in good nick
Click to expand...
Sounds good to me. The 5hp18 in my TDS is at 415 000 kms and, having had two oil changes in its documented life, feels indistinguishable from that of a FSH mature owner car with half the mileage.
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I'm working on the old principle "if it ain't broke, don't fix it". The indications are that the box is far from broken; however I'll take it on the chin if it gives trouble after installation, and drop it out again. There's nothing to lose other than the effort of a second removal and reinstallation. Pain in the arse if it comes to pass, to be sure, but not as painful as paying to have a perfectly good box stripped and reassembled for nothing.

I am considering the possibility of stripping down and rebuilding my secondary donor box, the Disco one, after this present project is all over and done with. I could do it myself given sufficient time and prodding about, learning heaps along the way, and it would be ready to install should the Beemer box give trouble.
 
Most of the Jappas I drive at work have a button on the gearshift to turn the overdrive off which is ideal for city driving, otherwise they will drop into 4th at light throttle at 25mph. The Rangie (which has the ZF) simply will not select 4th below 50mph so it's effectively a 3spd around town but once on the motorway it will sit at about 2200rpm at 65mph. Lovely.
 
I'm familiar with that button from various NIssans and Toyotas. I assume that you could, should you wish, alter the ZF's upshift to 4th by installation of the appropriate valve(s)?
 
Hi Warren, I can't remember which box you are using as the "primary" box? I seem to recall you had a BMW one? Don't forget that the disco box has the valve block with the lowest available speed setting for change into 4th. So get the installation right with the BMW box and see how the upchange suits. Then if not acceptable rebuild with the Disco one.

Chris
 
Yes, the BMW box is my primary donor, Chris, due to its low mileage and tail cone configuration. The current plan is to transplant the Rover valve block into it.
 
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