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# ZF 4HP22 step by step.

- Thread starter WarrenL
- Start date May 25, 2013

#### WarrenL

##### Active Member

Aug 2, 2014
#41
Aug 2, 2014
#41
Hi Peter, and sorry for such a late reply. It's winter here in NZ, Brown Rover is hibernating the season out, and I've had a whole bunch of other distractions (a new MG6, plus the ongoing saga of earthquake repairs to our slightly broken house), all conspiring to keep me off the CRF. To answer your question, I have no idea what the cost of a turnkey conversion might be. I suspect it would be prohibitive for the ordinary P6 owner, which is why I undertook to carry out as much of the conversion myself as I possibly could, and why I've attempted to document the process here for the benefit of others. All up, I spent somewhere in the ballpark of NZ$4000, but then I didn't skimp where I deemed it necessary or desirable, so it's entirely possible to come out with less damage to your bank account if you can, say, fabricate your own custom rear cross-member, leave out all the plating and powder-coating, skip the transmission strip-and-overhaul, etc, etc. You might also spend a lot more, by leaving your P6 with a transmission specialist and telling him/her "please fit a ZF 4-speed - call me when it's all done."

#### WarrenL

##### Active Member

Aug 3, 2014
#42
Aug 3, 2014
#42
STEP 6: YOUR REAR END.
Having previously covered what's involved in mating up the front of the ZF to the Rover, we may now turn our attention to the rear of the gearbox. Things get interesting here, because there is more than one way to skin this cat. What you end up with will depend on the type of ZF that you've obtained as a donor for the 2WD rear end.
In my case, as previously stated, one of my donor boxes was from a BMW. This came about because cubed BMWs are a dime a dozen here in New Zealand, and their ex-gearboxes can be had for pennies. You might be considering, or have on hand, a Jag XJ40 or Sherpa/LDV version of the box, in which case your experience will be different to mine.
One of the first problems I had to think about was the mating of the gearbox output shaft to the P6 prop shaft. Looking back to this early picture, you will see that the BMW output flange has three holes and a rubber doughnut (I'll stick to the proper British spelling). This is incompatible with the Rover's 4-hole prop shaft flange. What to do?
Well, I'll cut the explanation as short as I can. Discussions here on the forum led me to the XJ40 flange, which is a perfect match for the Rover prop shaft. Furthermore, it fits right onto the BMW output shaft (the fitting of which is described a page or two back). I therefore spent a bit of time on the phone and the Internet, and I managed to track down a Jag flange for a reasonably agreeable sum of money. So why not be done with it and simply start with a Jag XJ40 box as the back-end donor? You're more than welcome to take this path. But bear in mind that I was feeling my way through this project, with no documented prior examples to draw on, so there was a lot of trial and error going on. In my particular case, I'd already obtained a BMW box, and XJ40 ones aren't so common in New Zealand. Furthermore, when choosing your rear end, you need to take into consideration one or two other factors. Eightofthem provides some useful information and very good photos right here at:
viewtopic.php?f=1&t=15069&start=135
You can see that the Jag housing is quite a different proposition to the BMW's. Importantly, the overall length of your Frankenstein ZF is a serious consideration. Not only do you have to think of the space in the transmission tunnel, but also the construction of your new rear cross-member, and the refitting of your prop shaft. My personal combination of BMW housing and Jag flange allowed the ZF to fit with a custom cross-member that bolted to the existing transmission tunnel brackets (more on this later) and required NO MODIFICATION TO THE P6 PROPSHAFT. The shaft just eased into place with the splines extended approximately halfway. Perfect! I can't guarantee that this would be the case with a Jag housing, and as you can see from eightofthem's photos, the Sherpa/LDV box, whilst incorporating a mechanical speedo drive which the others don't, is a lot longer, posing its own problems.
So, BMW housing and Jag flange it was. I then discovered a new problem. The Jag and BMW output yokes have quite different profiles, and this meant that the Jag yoke didn't quite sit properly in the BMW housing output seal. The solution, for me, was to take the Jag flange to a machine shop which belongs to a friend of a friend, and in a favour-swap, have 5mm removed as shown in the picture below (original photo courtesy of eightofthem).
So, I have now reached the point of possessing a complete and assembled hybrid box comprising all the appropriate Rover V8 bits up front, a BMW rear housing and tailshaft, and a Jaguar XJ40 output yoke/flange.
What's next? Well, we have to fit this box into the P6, by way of that aforementioned custom rear cross-member, and then pay attention to all the little details: oil cooling, gear shifting, speedo, dipstick/filler and throttle valve cable. Stay tuned!

#### Attachments

- Output yoke trimming.jpg
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- Output flanges.jpg
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#### Gus the Snail

##### New Member

Feb 20, 2015
#43
Feb 20, 2015
#43
New reply to old thread , but can you tell me if the auto cooler lines have a connector with a barbed fitting at all? My box has no cooler lines and cant test drive it without them. Lines and cooler obviously isnt an issue , just the fittings are.

#### WarrenL

##### Active Member

Jun 21, 2015
#44
Jun 21, 2015
#44
Gidday Gus. A new reply to an old question, and I do apologise for not seeing your question earlier, but I swore off the Forum a while ago in order to concentrate on driving and enjoying the car without getting sucked into the P6 vortex... if you know what I mean. It's been longer than I expected, but I really had to stop obsessing over the car and just use it a bit. I'm my own worst enemy in this matter. By logging in I've probably now opened my own personal Pandora's Box...
I'm not entirely sure of the answer to your question - do you mean the original lines? From memory, in my particular assortment of bits I had BMW cooling lines but not LR ones, so I popped into an LR wrecker and paid a few dollars for a set of lines and fittings, and then I had custom lines made by a mobile hydraulic hose man-in-a-van who popped into the workshop and bent some pipes into the right shape, attaching them to the LR fittings. It was pretty cheap all up. The custom lines run along the side of the block where the old Borg Warner ones did, and then connect to flexible hoses that complete the journey to the oil cooler. Does that help?
Regards,
Warren
V

#### v8 pop

##### New Member

Aug 15, 2015
#45
Aug 15, 2015
#45
could anyone please tell me were I can get the inhibiter switch for the early zf4hp22 gearbox cant find one any were . im doing a convertion from 3 speed sd1 box to a 4 speed jag box. loving this tread
E

#### eightofthem

##### Member

Aug 15, 2015
#46
Aug 15, 2015
#46
v8 pop said:
could anyone please tell me were I can get the inhibiter switch for the early zf4hp22 gearbox cant find one any were . im doing a convertion from 3 speed sd1 box to a 4 speed jag box. loving this tread
Click to expand...
Not cheap, and not available from most suppliers new I am afraid.
http://www.brit-car.co.uk/product.php/9 ... ox_rrc_dis
http://www.island-4x4.co.uk/inhibitor-s ... -3037.html
http://www.paddockspares.com/rtc4937-sw ... hibit.html
I do have some good used ones here though. ( the Jag box does not have the hole for the switch, so you will have to machine it out to take it ) although you can rig up a suitable alternative near the selector lever.
P

#### PeterZRH

##### Well-Known Member

Sep 30, 2015
#47
Sep 30, 2015
#47
Is this the basic box I'm looking for?
http://www.ebay.co.uk/itm/BMW-E30-320I- ... 419d446244
So I need a Jag xj40 tail shaft and the auto bellhousing/flexplate from a S1 disco and that's my basic hardware?
Can't help but think the e30 shifter would look OK in a p6 too, especially if the original knob can be fitted: http://s40.photobucket.com/user/vwsweet ... 5.jpg.html
E

#### eightofthem

##### Member

Sep 30, 2015
#48
Sep 30, 2015
#48
Without seeing the gearbox code plate, it's hard to tell.
Some are Hydraulic only, and some are Electro Hydraulic, so you need to check what it is.
P

#### PeterZRH

##### Well-Known Member

Oct 1, 2015
#49
Oct 1, 2015
#49
A few more questions.....
Firstly the box DEFINITELY does lock in 3rd? I'm guessing in general, non-motorway driving, it spends a lot of time in what was the old "top" so this is significant. I've heard talk of "mods" to get it to lock in 3rd and this set me wondering.
Secondly has anyone played about with the control valve bodies? I'm guessing the needs of a Range Rover 4WD offroader, an LDV van or a Jag with over 200bhp+ is going to be very different. Would something like a BMW 520i control give better results or are they all so similar it makes no odds?
Finally efficiency. Any estimates as to what the losses are compared to a BW35? Anyone did a 0-60 or 50-70 before/after?
E

#### eightofthem

##### Member

Oct 1, 2015
#50
Oct 1, 2015
#50
The box only shifts into lock up when FORTH gear is engaged, and only then whilst under light throttle.
Soon as you press harder on the throttle it will drop out of lock up and back into forth gear
I have stripped plenty of valve bodies and it is a minefield, there are many differences between them, and you have to be careful what you use.
Not done a 0-60 trial, but from feedback, the difference when cruising is amazing, and transforms the ride.

#### ghce

##### Well-Known Member

Oct 1, 2015
#51
Oct 1, 2015
#51
PeterZRH said:
A few more questions.....
Firstly the box DEFINITELY does lock in 3rd? I'm guessing in general, non-motorway driving, it spends a lot of time in what was the old "top" so this is significant. I've heard talk of "mods" to get it to lock in 3rd and this set me wondering.
Secondly has anyone played about with the control valve bodies? I'm guessing the needs of a Range Rover 4WD offroader, an LDV van or a Jag with over 200bhp+ is going to be very different. Would something like a BMW 520i control give better results or are they all so similar it makes no odds?
Finally efficiency. Any estimates as to what the losses are compared to a BW35? Anyone did a 0-60 or 50-70 before/after?
Click to expand...
The LR boxes lock up in 4th at approx 80KMH (50MPH), most other car variations seem to lock up at 100KMH (60MPH).
Lock up in 3rd is not just up to the box but the Torque Converter I am led to believe, nor is it available in all variations of the ZF 4HP-22
Graeme
P

#### PeterZRH

##### Well-Known Member

Oct 2, 2015
#52
Oct 2, 2015
#52
OK that's interesting anyone have a locking 3rd model then?
I refer people to this thread: http://www.aulro.com/afvb/technical-cha ... erter.html
Does any one know what is involved in making a ZF 4HP22 Lock up the converter in 3rd as well as 4th? As I do a lot of hill work and towing of heavy implements here would be good mod. I see LRA say they do them but I asked Andrew and he said they havn't done one yet Thanks Tony.
Click to expand...
......
The mod requires the valve body separator plate to be machined/ drilled slightly, and I am led to believe that there are a few differences in the landrover/ range rover 4HP22 over the years that mean some valve bodies aren't easily modified.
I had one done recently for a customer and it involved using a Jag XJ40 valve body, modified plate etc behind a 3.9V8i.
Click to expand...

#### ghce

##### Well-Known Member

Oct 2, 2015
#53
Oct 2, 2015
#53
PeterZRH said:
OK that's interesting anyone have a locking 3rd model then?
I refer people to this thread: http://www.aulro.com/afvb/technical-cha ... erter.html
Does any one know what is involved in making a ZF 4HP22 Lock up the converter in 3rd as well as 4th? As I do a lot of hill work and towing of heavy implements here would be good mod. I see LRA say they do them but I asked Andrew and he said they havn't done one yet Thanks Tony.
Click to expand...
......
The mod requires the valve body separator plate to be machined/ drilled slightly, and I am led to believe that there are a few differences in the landrover/ range rover 4HP22 over the years that mean some valve bodies aren't easily modified.
I had one done recently for a customer and it involved using a Jag XJ40 valve body, modified plate etc behind a 3.9V8i.
Click to expand...
Click to expand...
The blind leading the blind is my interpretation of that.
I can give you my version of the process but somewhat like their's mine is also Chinese whispers and no faith could you put in it, but here goes any way.
My understanding is that for 3rd lock up one of the valves and possibly the body needs modding, the effect is to allow a pawl or lever to engage with the torque converter to lock it up in third.
I agree this would be a good Idea for fuel efficiency reasons, also locking up early in 4th as per the LR valve body is a good thing too, little V8 but hi ft/lb engine on a 1260 KG car means early lock up can only be a good thing.
Graeme
C

#### colnerov

##### Well-Known Member

Oct 2, 2015
#54
Oct 2, 2015
#54
Hi, here's a question, If the vehicle is towing heavy loads or doing hill work as described would
lock up in third really be required? In those circumstances wouldn't the gearing advantage of an
open torque converter be advantageous? Plus as said with lock up in fourth releasing with the
application of more throttle and presumably it will do the same in third because the load is too
much, then it will be self cancelling?
Colin
E

#### eightofthem

##### Member

Oct 2, 2015
#55
Oct 2, 2015
#55
Modifing the valve body to obtain the engagement of the DDC ( lock up ) in third will have a knock on effect in the transmission, you are in effect asking the box to do something it was not designed to do ( hydraulic units ) unless you were to beef up the internals to 24 spec.
There are no Pawls or mechanical gizmo to engage lock up, it is all done by fluid pressure, and valve control and in effect is a pressure activated clutch plate, that activates on the impeller side of the convertor when the fluid flow is reversed in fourth gear at preset points specific from model to model.
When activated it is basically direct drive from crank to output shaft.
P

#### PeterZRH

##### Well-Known Member

Oct 5, 2015
#56
Oct 5, 2015
#56
I'd be interested to know if there is some objective measure for transmission efficiency. Obviously when it locks in 4th there is going to be a substantial difference. I wonder how this compares with the BW35 in general use?
Many 3500 (auto) owners report 95-110bhp at the wheels, which is a fairly sad state of affairs really. That's around 1/3 in losses. If the ZF can bring that down nearer 20% then you are talking the same kind of gain a fitting a fast road cam and best of all its pure efficiency not throwing more fuel in.
Secondly reading about this it appears shift points and the control gubbins work at least partly on road speed. Now we're all familiar with the BW35 changing up at bad moments simply by backing off, so I assume this is done purely on internal pressures in the old box. Being speed related would of course be a big advantage in day to day driving doing something as simple as approaching a corner and you not having to dive onto the brakes when you back-off? That'd be worth having.
I only have experience of a switchable electric version of this box in the BMW e34 (5 series). I remember being impressed when driving down a long descent in the Alps that it even managed to stay in low gear and give a little engine braking. I wonder how integrated these relatively simple and early electronic auto boxes were?
H

#### harveyp6

##### Well-Known Member

Oct 5, 2015
#57
Oct 5, 2015
#57
PeterZRH said:
Now we're all familiar with the BW35 changing up at bad moments simply by backing off, so I assume this is done purely on internal pressures in the old box. Being speed related would of course be a big advantage in day to day driving doing something as simple as approaching a corner and you not having to dive onto the brakes when you back-off? That'd be worth having.
Click to expand...
The BW35 is controlled by 3 inputs, selector position, throttle position, and roadspeed.
P

#### PeterZRH

##### Well-Known Member

Apr 25, 2016
#58
Apr 25, 2016
#58
Anyway, this old chestnut. Fate and a BW35 approaching imminent death has forced my hand somewhat. The logistics and costs of sourcing and fitting a BW35 here in Switzerland means the relatively small extra investment means the ZF is now "go". Perhaps my overenthusiastic enjoyment of my new, uprated ARB through the Alps brought on the demise.... Moving swiftly on...
I contacted John Weir at Canary Automotive about fabricating a copy of Warren's gearbox mount. He's currently looking into making up a jig in order to produce these more effectively to order. It'll be complete with mounts, bolts etc and be powdercoated.
So basically Andy's kit plus John's gearbox mount will give you have a more or less off the shelf option bar the speedo drive and cooler pipes. More news when I have it. I'm hoping postal costs don't kill the viability. Mind you given Swiss rates for labour and bespoke engineering, that will take some doing....
P

#### PeterZRH

##### Well-Known Member

May 1, 2016
#59
May 1, 2016
#59
If anyone is interested in a replica of Warren's gearbox cross member then please PM me as I am negotiating with him now it might help get a better price. It won't be a "cheap" option but it will be a properly engineered solution. You also get the benefits of Warren and John's time and experience and avoid any nasty issues that you might not have thought about. In addition to that you also have the reassurance that it is capable of passing the strict type-approval rules in New Zealand.

#### WarrenL

##### Active Member

May 28, 2016
#60
May 28, 2016
#60
It is all of that. It has also survived a couple of years now without twisting, torquing or falling out of the bottom of the car! But there is a considerable amount of John's time involved in fabrication, and the man has a family to feed, so don't expect a bargain. I still feel that it was very much worth the cost, and it was ultimately a relatively small proportion of the total cost of the project, which ran to about NZ$4000 all up, even though I did the bulk of the work myself.
Worth it? Well absolutely. As I've spelt out before, the fourth gear and lock up have utterly transformed the car, and the extra responsiveness of the ZF in the lower gears is also noticeable, and satisfying. I'd never go back.
Postage is comparative peanuts, Peter. We're only talking a small package weighing a couple of kilos.
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