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# ZF 4HP22 step by step.

- Thread starter WarrenL
- Start date May 25, 2013

#### rockdemon

##### Administrator

Staff member
May 28, 2016
#61
May 28, 2016
#61
PeterZRH said:
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.
Click to expand...
Just about all automatics including the modern ones suffer this to some extent. My mate has a 2011 range rover sport 5.0 supercharged that does exactly this, then overreacts and changes down too far.
I tend to knock the box into 2nd on the bw coming towards a roundabout as you get engine braking and acceleration in 2nd.

#### drabbers

##### Member

May 28, 2016
#62
May 28, 2016
#62
rockdemon said:
Just about all automatics including the modern ones suffer this to some extent. My mate has a 2011 range rover sport 5.0 supercharged that does exactly this, then overreacts and changes down too far.
I tend to knock the box into 2nd on the bw coming towards a roundabout as you get engine braking and acceleration in 2nd.
Click to expand...
I remember my Grandfather doing just that in my car - knocking back into 2 for some tight (slow) corners - then back into D.
I guess it would have gone round in top otherwise.
Mark.
M

#### mikecoombs

##### Active Member

Jun 22, 2016
#63
Jun 22, 2016
#63
Peter, Have you gone any further witht he Crossmember? I'm building my collection of bits up and that is one of the last ones...I'm very interested. I'm being a little different in going for the 2200 diff ratio (3.54:1). My spare late model diff is off to get the new gearset next week.
P

#### PeterZRH

##### Well-Known Member

Jun 22, 2016
#64
Jun 22, 2016
#64
Hi Mike, I'm waiting on John in NZ and for a window in my schedule to collect the box and other parts from Andy as it involves a trip to the UK. I do know that the cross-member is off Warren's car at the moment for John to make the jig for others to get a copy. I'm assuming this takes a bit of work. Not heard from him for a week now.
The final drive ratio idea is very interesting. That'll give you an effect 0.83:1 instead of 0.73:1 in 4th. I wonder if that'll give you more "go" in gear as it would with a manual. I'm not sure with a torque converter transmission as they tend to have massive gearing and then use the fact they can slip 2:1 or thereabouts, it's not like these are "fixed" as such. That's why even an oldish transmission like this which locks up can when cruising be more economical than a manual car of the era as you effectively have a 6-speed gearbox range (OK usually not the case).
What I can say with experience of the ZF in my BMW is that gearing is important. The speed limit here in urban areas is 50kph, the car would never sit comfortably at this speed hunting from (presumably) 2nd to 3rd or more likely just creeping upwards pushing you over the limit - I have the tickets to prove it. The problem is not always behind the wheel of a BMW
Anyway one thing Warren hasn't posted here is that the exhaust needs to be re-routed from behind where the downpipes join to the second section of the exhaust. Basically the neatest way is to make it a 4 piece system with a new second piece custom made - it's just a simple bit of pipe so not so difficult but again it all adds up workwise. I'm really hoping Warren will post a close up or two of this, how the speedo kit is mounted and how the cooler pipes are routed.
I'm really looking forward to the silence and smoothness as much as the overdrive and lock-up.
M

#### mikecoombs

##### Active Member

Jun 23, 2016
#65
Jun 23, 2016
#65
My exhaust is bespoke anyway and it needs some tidying up. from memory it is 1.5" from the heads to four 2" into two 2.25" into one 2.5" through two straight through resonators (I couldn't find a muffler that'd fit in that size. The headers are good but the left bank is incorrectly grouped and it is a tad noisy) the final join is just to the rear of the BW35 and immediately ahead of the first muffler which is only 1.5" larger.
P

#### PeterZRH

##### Well-Known Member

Jun 23, 2016
#66
Jun 23, 2016
#66
I'm hoping to go for a custom exhaust too when funds allow. A twin system either side of the gearbox like the Triumph Stag with a small balancer pipe. I wonder if anyone has done something similar.
M

#### mikecoombs

##### Active Member

Jun 24, 2016
#67
Jun 24, 2016
#67
I think Sowen did a twin system for his twin cam conversion. There isn't much room under the battery box though on the V8 so one would have to for go the last muffler. Also the fuel lines are on that side so it would need to be well insulated where it goes over the axle and De Dion. That was why I settled for one 2.5" pipe. The main thing with twin system design is to get the crossover pipe in the right place, mind you same issue with the 4 into 2 into 1 arrangement. The last joint is critical as is the design of the actual joint portion. Best reference on exhausts is A.Graham Bell's Book - Four Stroke Performance Tuning (Haynes books). It's been reprinted about twenty times.
P

#### PeterZRH

##### Well-Known Member

Sep 16, 2016
#68
Sep 16, 2016
#68
Chaps. I now have everything and I'm ready to go. Mine will be the only LHD ZF car and the only Series 1. Unless you know different... Are there more than 2 confirmed conversions on the road yet?
Anyway, let's talk exhausts. The auto exhaust needs to be slightly re-routed to clear the rear of the ZF (still waiting for pictures of this). Anyone know if the 3500S exhaust will clear this without mods?
Could be a good time to fit 3500S manifolds and exhaust....

#### Demetris

##### Well-Known Member

Sep 16, 2016
#69
Sep 16, 2016
#69
PeterZRH said:
The auto exhaust needs to be slightly re-routed to clear the rear of the ZF (still waiting for pictures of this). Anyone know if the 3500S exhaust will clear this without mods?
Click to expand...
As you can imagine i don't speak from first hand experience, but i can tell you that the manual gearbox is significantly narrower at least at the bottom than the BW35 equivalent.
Therefore i doubt that the 3500S exhaust could fit.
H

#### harveyp6

##### Well-Known Member

Sep 16, 2016
#70
Sep 16, 2016
#70
3500S frontpipes run each side of the gearbox, joining behind it, and so as the 3500S box is very short, and the 35box longer, and the ZF box longer still I can't see the the 3500S frontpipes fitting without being lengthened, that's without the width issue mentioned above.

#### cobraboy

##### Well-Known Member

Sep 16, 2016
#71
Sep 16, 2016
#71
I made a twin system using 3500s manifolds and the downpipe bends, these were cut Just as they go straight and a flexible balance pipe joins the two. they then run back parallel each side of the tunnel with two 4 " cheery bombs and exit just before the rear wheel.
I have a heat shield over the fuel pipes. Ground clearance is tight, but would be fine with stock ride height.
M

#### mikecoombs

##### Active Member

Sep 18, 2016
#72
Sep 18, 2016
#72
The Auto gearbox tunnel is offset to take the pipe down one side but I think the ZF pan is narrower, though the tilt might negate this. My exhaust runs pretty low, partly below the floor level in order to allow access to the pan bolts without taking it off (originally it was all welded together as one piece). the final 2 into 1 join is just beyond the rear mount and is rather too steep a joint angle really but I was limited by the length of the resonator. I'll need to alter everything when I install the ZF no doubt. I'm just debating whther to buy a transmission jack or a two post hoist first...
Have you thought of running short sidepipes exiting downward in front of the rear wheels on that rocket of your Cobraboy?
P

#### PeterZRH

##### Well-Known Member

Dec 13, 2016
#73
Dec 13, 2016
#73
Hi all, just an FYI, mine is now officially work in progress! I'll take a few pics! Anyone else going down this path made progress?

#### Keith Fry

##### Member

Dec 13, 2016
#74
Dec 13, 2016
#74
Hi I gave a ZF4 HP22 on my series 1. It is so much better than the old BW35 and seems absolutely suited to the V8. You will not regret it.
P

#### PeterZRH

##### Well-Known Member

Dec 13, 2016
#75
Dec 13, 2016
#75
Hi Keith, looks like we have quite similar tastes both 1970 S1s and a desire to make a great car even better! PAS is coming (but standard in my case). S2 instruments also. Have you thought about a bigger ARB? At £120, the best Christmas present anyone can give you....
R

#### roverp5Bcoupe

##### Active Member

Dec 14, 2016
#76
Dec 14, 2016
#76
I just finalized the ZF conversion on my P5b. I fitted an LDV box, fitted a separate transmission cooler, and used a Jaguar XJ40 shifter cable and kept the P5b schifter. The box got a Jaguar sump and dipstick/filler tube. It drives superb. Only need to do something about the speedo as the speed it shows is far too low.
Peter

#### Keith Fry

##### Member

Dec 14, 2016
#77
Dec 14, 2016
#77
Hi Peter
Yes exactly that- making a truly great car just the d's b's!
I have thought about the arb, but Mark Gray suggested stiffer rear springs first. So those will be fitted (especially as I tow a caravan) and I will see what happens and maybe go for that later in 2017.
I have considered a Weber carb from rpi, but at the moment I am not committed. What do you think?
P

#### PeterZRH

##### Well-Known Member

Dec 14, 2016
#78
Dec 14, 2016
#78
Keith Fry said:
Hi Peter
Yes exactly that- making a truly great car just the d's b's!
I have thought about the arb, but Mark Gray suggested stiffer rear springs first. So those will be fitted (especially as I tow a caravan) and I will see what happens and maybe go for that later in 2017.
I have considered a Weber carb from rpi, but at the moment I am not committed. What do you think?
Click to expand...
I have a complete EFi setup in the basement but the Weber setup is probably the more sensible approach. Part of me wants to keep Rover components and use the more high tech approach. What both the Weber and EFi will give you over SUs is better throttle response and not having to retune it each time. You can get the SUs to give you as much power almost but as soon as you change anything you'll be back on the rolling road.
I'll respectfully disagree with Mark over the ARB. In truth you want both.
M

#### mikecoombs

##### Active Member

Dec 17, 2016
#79
Dec 17, 2016
#79
Peter, RPI used to do a set of P6B headers. they are 2x4 into 1. Not sure if they still do but they may have some ideas on where to put the crossover/final joint.
I did a 23mm ARB in the mid eighties and even that made a huge difference and the ride stayed the same (but I think the car has the Heavy Duty Australian spec springs)
P

#### PeterZRH

##### Well-Known Member

Dec 22, 2016
#80
Dec 22, 2016
#80
Anyone else found their propshaft UJs to be completely shot when changing the transmission? Mine were rusty, but I can't imagine the BW35 "clonk" doing them a whole lot of good either. The ZF is much gentler on the drivetrain.
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