ZF4HP22/24 - Change of autobox

Blueman

Blueman

Member
Hi

I have a Rover 3500 1971 with a 4.6L engine. The gearbox is changed from BW35 to BW65 with succes.
But I have now bought a ZF4HP22 from an ambulance, and I have rebuild the ZF to a ZF4HP24 with parts from Ashcroft Transmission. But it still remains to install it in the car.
I know that some of you have done this before, for instance Guy Englishman.
Question is: How tricky is it?
I'll have to shorten the prop and make some new mountings. How strong must the mountings be? Does anyone have some pictures?

The speedometer drive is not the same as on the BW boxes. Is it easy to rebuilt?

I will also rebuild the exhaust system trying to use tubular manifolds and twin system that meets behind the box. How tight is it and is it possible to get a good and balanced system.

This was many questions, and I guess I'll come up with some moore as soon I have posted this topic. I am not in a hurry as my BW65 works well, but it has some hard days with the uprated engine. :angry:

Best regards
 
Phew!

Well yes it is fairly easy. I'm just about to drive the first of my two P6's with this conversion. Conversion was carried out by a sub contractor to RPI at Norwich. SO here goes with a bit of detail:

The box is a VERY tight fit in the existing tunnel. We finished up grinding off the stiffening ribs on the outside of the box.

The rear mounting is further back than the the BW, so we simply made a strap inside the tunel to carry the existing p6 rear mounting bush.

The speedo drive was provided by machining the existing BW angle drive to fit the ZF box - means you can use standard speedo cables.

Gearshift is provided by a Range Rover Classic (the 3.9 EFI variety - lots on scrap heaps!) change lever and cables. Looks quite natural on the P6 tunnel and plenty of space underneath. Does require a new tunnel finisher to replace the horrid Rover plastic item.

The exhaust is also a bit tight!! RPI have tooled up another of their contractors to produce suitable 4 into 1 tubular manifolds (we couldn't find enough space for 4 into 2 into 1). They then ran up a single pipe 2 1/2" bore system to go on the end.

And of course there's a shortened prop.

The big advantage of this set up is a) getting rid of the BW slushmatic and b) you get an overdrive top for relaxed cruising. (Essential with a 4.6!)

Does it work? Let you know in a week or two!

Give me a ring or e mail me and I'll let you have any more detail photo's etc.

I'd appreciate a lot more detail on the HP22 to HP24 conversion! (For the rest, the HP22 is standard on all Rover engined Range Rovers incl the 4.6, the HP24 takes significantly more torque. The ambulance sourcing is to get a 2WD rear end on the box rather than 4WD. Ambulance in question is LDV Sherpa 400 fitted with the Rover 3.9 V8 - yes, really, they're virtually standard in London.)

Chris York
 
Hi
Thanks a lot.
I am looking forward to hear from your experiance with this set up.

I would like some pictures, I am curious abot the rear mounting, does it work well with the strap. I would think it would be necessary to weld or bold in new mountings.
I'll send a mail to you.
There are not that many scraped Range Rover Classic here in Norway, but I think I would manage to get a hand on a proper change lever to use in the car.

And I still have some work to do on my tubular manifolds, and I still hope it will be possible to use my 4-2-1 after redesign.

The HP22 to HP24 conversion was easy but expensive because I did not to it myself. I bought the HP22 used in an ambulance, and ordered a rebuilt set from
Ashcroft Transmission.
The set contains of a set of internals at £325, set of friction plates at £50 and a rebuild kit at £ 35, (prices are + VAT).
I had a auto specialist to fit it all into the box.
This means that all the internals are (as) new, except the torque convertor.

The total length og the box will increase with 15mm longer due to the thicker pump assembly.

As Chris wrote, the HP24 takes significantly more torque, and can be necessary with an uprated 4.6 in the car. But it also depends that the rest of the car can handle the increased power.
 
Blueman
Had a bit of fun fitting the ZFHP22. I have an EFi 4.0L putting out 280hp (at last check) and the HP22 is adequate if you are driving sensibly.
During the fitting I noticed that speedo drive was damaged so I changed to an electronic speedo. The gearbox was origionally from a Jag, with a Discovery bellhousing which is a fraction slimmer that the RR for some reason! I have used a Jag 'J' gate shifter and it looks really good with a new wood surround.
I have also fitted a P6B with the 5 speed auto from a Holden (Vauxhall???) something or other. Not recommended as it does not suit the Rover V8.
A 4 into 2 into 1 system will fit, just run dual pipes and dont bother connecting them together. Sounds wicked!!!
Make sure that the prop shaft is shortened by a professional, and is balanced after or you will end up with all sorts of weird vibrations. :;):
Still trying to work the magic of the digital camera so am trying to get photos on the site.
Cheers
GUY :)
 
Hallo Guy

You must have been away for a bit - missed your posts!

With the Jag box what do you need in the way of controls? Obviously the J gate, but is there anything else needed fom the electronics? How do you arrange the kick down?

Which particular model of Jag did it come from, presumeably they are set up slightly differently between the 3.2's, 4.0's and 4.0 sports?

Regards

Chris
 
Chris
Been away for a while with work and have not had a chance to look in for a bit.
The fundamental gearbox is the same from Jag to Range Rover to Aston Martin etc! Individual manufacturers simply change the programming to the box and alter the final drive ratio to acheive the speed/ acceleration that they require. To that end the box is pretty easy to work with. All that is required is the appropriate bellhousing, and a basic program and the thing will work.
The J gate is cable operated and the kick down is via a switch under the accelerator. I run a MOTRONIC engine management system, which is programable through a PC or laptop. This looks after such things as engine management (sampling at 5000 thingys a second apparently) and allows different settings to be inputted, such as high power (rotten idle but goes like the clappers) to everyday driving. The gearbox is managed by the same black box (well silver really), and controls the gearshifts in response to the settings that the engine is running. I have set up three settings called Normal (boring everyday), Economy(great for long runs on the motorway) and Silly (optimises power at the expense of economy but is a lot of fun). With each of these settings the gerabox behaves differntly, Economy tends to shift to top soonser and loafs along, Normal has us just doing our thing like a normal car, Silly lets the engine get to 7000rpm before shifting up and is very aggressive.
To get started, if you are running a basic EFi V8, and a ZF4HP22 then the standard Range Rover/Discovery ECU will get you going and provide a base to play with. If you are just using the car as an everyday car the basic programs will be perfectly adequate.
As to the model of Jag the box came out of it arrived covered in dirt and grease on the back of a truck! I honestly have no idea what model it was out of.
Cheers
GUY :)
 
Hi Guy

Thanks for excellent replies.
My gearbox is from an ambulance, without the programming option, but with a kickdown cable. Would have been interesting to do an rebuilt to the alctronic management. The mechanics in the box is probably the same.

What car is the Motronic engine management system from?

Best regards,
 
The Motronic system is an aftermarket management system used for specialist and high performance uses. It is available from most speed shops and is one of a number of systems on the market.
They are popular with the Boy Racer crowd since it makes dialing in the turbo easier due to the programable nature.
Not cheap I'm afraid, i think my whole setup was AUS$3200. This included the management module along with a million and one sensors (including a set for when I decide to turbocharge the car!!!). I also had a custom wiring loom made to fit the car and gearbox combo.
Hunt around, there are a number of similar bits of kit on the market, and most are not too expensive.
Cheers
GUY :)
 
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