ZF 4HP22 - the journey.

WarrenL

WarrenL

Active Member
Well fellas, I now have a 4HP22 in captivity! Freshly removed from a 2.5 litre BMW E34, with about 130,000 kms under its belt.

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I took it straight around to my tame mechanic, who removed the pan and had a poke about and pronounced it a good box, as far as he can tell. He thinks even the A-clutch is in good nick, because there is no sign of shit in the very clean oil that we drained out. So! Now I have to find an LR/RR box. Then I'll have to do my homework and figure out everything else I need to do/obtain in order to effect the ZF conversion. For starters, here's a close-up of my tailcone:

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Comments?

So, fancy! Putting a German gearbox into that most English of cars, the Rover P6! There'll be BMW haters over at mg-rover.org who'd have my scalp for doing this.
 
Putting a German gearbox into that most English of cars, the Rover P6! There'll be BMW haters over at mg-rover.org who'd have my scalp for doing this.
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If it doesnt upset somebody it probably isnt worth doing!
 
Hello Warren,

Are the internals apart from the valve bodies within the transmission the same across the range of vehicles that the ZF was to be found? The Range Rover ZF will provide the bell housing and possibly the pan that you require? As for the valve bodies, which one do you go for? The torque converter will need a stall speed of 2200 rpm or so to be in keeping with the existing one in the BW transmission too, which of course was designed to match the torque delivery of the V8 engine. Other cars may well have had BW35 or 65 transmissions, but they did not have the same torque converter as was to be found in the Rover, which had a somewhat higher stall speed.

Ron.
 
Looks like a good buy Warren. What's your time scale for completion on this project? I know there are a few people waiting for someone to have a go first!

Ron, how does the torque converter stall speed affect how the car drives? Presumably a 2.5 straight six must throw out a fair amount of torque too.
 
i suggest you use the sump pan and dipstick tube already on this transmission. The RR and Disco ones are much too deep.

It will be worth swapping the valve block for the one out of the RR box in order to get the lower change up speeds.

You could equally argue, Ron, that the torque convertor from the ZF RR box is designed to suit the engine! So probably not worth getting too deep into unless there is an obvious mismatch on trial.

Chris
 
testrider said:
Ron, how does the torque converter stall speed affect how the car drives? Presumably a 2.5 straight six must throw out a fair amount of torque too.
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I'd guess it's exactly the same as the one I have in an E28 520i - 2.0 straight six with barely enough torque to pull the skin off a rice pudding. So I doubt if there'll be much of a mismatch.
Incidentally I'm watching this thread with interest as mine (in the BMW) is slipping badly and I'm trying to pluck up the courage to whip it out, strip it down and replace the A clutches or whatever's needed. Perhaps I should fit a Rover 'box in it...
 
Hi folks.

The exact path that I follow will is dependent on the RR box that I eventually find. According to mechanic John, the internals are all broadly the same across the 4HP22 variants, with the only significant differences being gear ratios. From what I've previously researched (and posted somewhere on the Forum), the BMW box uses the same ratios as the RR, and so I can mix and match the best bits from the two boxes. Since this BMW box appears to be in good condition, there's a possibility (for now) of swapping the bellhousing and valve body off the RR box. Initial information suggests that this might be easier than swapping the tail cone. I intend to use the sump and dipstick from the BMW box for the reasons stated above. I need to obtain a torque converter, since this box came without one (at 40 quid I'm not going to grizzle), so I might as well make it an RR/Disco one!

Anyway, as far as the Canonical Procedure For The Conversion Of The Rover P6B To A ZF 4HP22 goes, Step One is complete:

Step 1: Purchase an ex-BMW ZF 4HP22 (the non-electronic version). Store out of sight in the garage under a cloth.

Check back here in, say, 2012, to see if I've achieved Step 2.
 
I beleive to remove the valve block you need to do a complete strip, which I am led to beleive is a simple job.

Graeme
 
Likewise. John the mechanic's exact words were "piece of piss".

But as I said, all hinges on the quality of the RR box I eventually obtain; whether it's worse or better than the BMW.
 
all sounds so easy :LOL: The chap I talked to said he could change the valving block characteristics to suit my every desire, so it would seem that you could probably just mod your BMW valve block to achieve change up/down points and lock-up speeds as you require.

Graeme
 
Perhaps it's worth trying for just a bell housing, torque converter and flex plate? Who was the transmission guy you went to?
 
Automan Automatics, BQ (Before Quake) Cnr of leeds and Phillips St. ph 379 2266 dont know about AQ but the building still is there but I didn't look to hard when passing as to whether the business is still operating from there or not.

Graeme
 
I'll get in touch with him some time soon. Otherwise I'm keeping an eye on TradeMe for the RR bits.

This is fun!
 
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