ZF 4 Speed conversion

[Johnh]

Hi All,

The new 3.66 (nearest to 3.7 they could get) diff from E J Ward seems very good, has a slight whistling noise noticeable at slow speed but after talking to Wards while up there handing over my old diff to get my deposit back they did say that this will go as the new gears bed in, 1 - 2 thousand miles. While chatting I learnt that they did look at getting a 3.45 diff built to the same standard as the 3.7 but there was not sufficient space in the box to achieve it. I am not an engineer but the new internals in the 3.7 box look very substantial and significantly heavier than the original's. Going by other reports so far I think I have made a good decision.

John H

[Robin Searle]

I had my 72 Mk2 Stag BW35 auto gearbox changed over the the ZF and noticed immediately two benefits MPG/MPL went up dramatically due to the RPM dropping significantly. BW35 70mph 4100RPM, with the ZF 70mph now only 2000 and it got rid of the BW5 clonk as it changed.

I kept my original diff and all seems to work happily together.

Robin

[milothedog]

I had my 72 Mk2 Stag BW35 auto gearbox changed over the the ZF and noticed immediately two benefits MPG/MPL went up dramatically due to the RPM dropping significantly.

BW35 70mph 4100RPM,

with the ZF 70mph now only 2000 and it got rid of the BW5 clonk as it changed.

I kept my original diff and all seems to work happily together.

Robin

That seems a little high, IIRC BW35&65 are just under 20MPH per 1000RPM and MOD just under 23MPH per 1000RPM but cruise better because the O/D on 3rd & top changes the sums .

Are you sure you have the correct 3.7 ratio diff

My standard BW35 indicates 70mph at or about 3500 RPM.

On a fast road I tend to cruise mine at 3000RPM and it hovers around 60-65 MPH so ties in with the information I posted above.

[DJT]

I had my 72 Mk2 Stag BW35 auto gearbox changed over the the ZF and noticed immediately two benefits MPG/MPL went up dramatically due to the RPM dropping significantly. BW35 70mph 4100RPM, with the ZF 70mph now only 2000 and it got rid of the BW5 clonk as it changed.

I kept my original diff and all seems to work happily together.

Robin

That seems a tad low, certainly for the 3.7:1 diff. With a 3.45:1 the revs on mine are 2,250 at 70 on an electronic speedo, verified by gps.

[mole42]

Agreed Dave, mine's got a 3.45 at the moment and 2500 at 70 is about what I get, but I'm on 185R14 60 section tyres, so that'll alter once I get the 80 section ones fitted.

Richard

[MandM]

That seems a little high, IIRC BW35&65 are just under 20MPH per 1000RPM and MOD just under 23MPH per 1000RPM but cruise better because the O/D on 3rd & top changes the sums .

Are you sure you have the correct 3.7 ratio diff

My standard BW35 indicates 70mph at or about 3500 RPM.

On a fast road I tend to cruise mine at 3000RPM and it hovers around 60-65 MPH so ties in with the information I posted above.

Mine is the same as Ian's 3500=70mph

[RobinLegin]

Mine is a 1977 auto with the BW65 box. At 70mph it looks like the engine is reving at 4K rpm. I would definitely like a ZF44 box!
Nigel

[Robin Searle]

Re what RPM at 70mph. Most automatics have in top gear the speed in mph needle parallel to that of the RPM, on on my Stag prior to the change over to the ZF it showed 70mph/4100rpm., needles pointing straight up With the extra higher gear when I notice that the two needles are parallel, then I know that I am in the ZF lower gear, not the higher one, so move the changer down one more notch, then notice the RPMs drop dramatically by 2000rpm.

As I mentioned before it has made a tremendous difference to the number of miles that can be driven on a gallon of fuel.

Robin

[milothedog]

Re what RPM at 70mph.

Most automatics have in top gear the speed in mph needle parallel to that of the RPM,

on on my Stag prior to the change over to the ZF it showed 70mph/4100rpm., needles pointing straight up With the extra higher gear when I notice that the two needles are parallel, then I know that I am in the ZF lower gear, not the higher one, so move the changer down one more notch, then notice the RPMs drop dramatically by 2000rpm.

As I mentioned before it has made a tremendous difference to the number of miles that can be driven on a gallon of fuel.

Robin

No they don't Why do you drive it in "3" and not "D" it must be simpler to just pull the selector fully back when you put it in gear

[RobinLegin]

Hi all,
Management is warming to the idea of a ZF 4 speed auto box. I have been in touch with Ian at Monarchs and the price is eye watering. However I am retiring at the end of this month, then downsizing house ( slightly) and may have a little bit to afford this.
I would therefore appreciate your views on:
1. Is this better motoring?
2. Assuming general law abiding road use in France will I need a front spoiler?
3. Will this devalue the car?
4. Should I keep the knackered BW65?
5. Is this exercise still worth it with the standard diff?
I believe Monarch use Mr Tate to fit the box. Is this right?
Cheers
Nigel

[Seaking]

You have the first part as you need a bw65 propshaft
Did mine myself saved a whole bunch of money yes better motoring more like a modern.
I would think it is better to go straight to mr Tate if you are not going to fit yourself.

Cheers Glenn

[Guest]

Pretty sure monarch will add costs over what Tate charge, but Evesham is a long way from Bournemouth? I have a manual car but EVERYONE who has a ZF rave about them. I can only see it increase the value of your car rather than devalue it.

Costly outlay but paid back if you do a lot of miles? I know I would do it.

[GDPR]

Hi all,
Management is warming to the idea of a ZF 4 speed auto box. I have been in touch with Ian at Monarchs and the price is eye watering. However I am retiring at the end of this month, then downsizing house ( slightly) and may have a little bit to afford this.
I would therefore appreciate your views on:
1. Is this better motoring?
2. Assuming general law abiding road use in France will I need a front spoiler?
3. Will this devalue the car?
4. Should I keep the knackered BW65?
5. Is this exercise still worth it with the standard diff?
I believe Monarch use Mr Tate to fit the box. Is this right?
Cheers
Nigel

Nigel

1) Yes - in ways that you haven't considered - more relaxed long distance driving, much improved mpg, less engine wear, smoother shifts.
2) In my own experience, the improvement to high speed cooling, especially in warmer climes gives increased confidence, reduces temp gauge paranoia, and improves steering stability at high road speeds.
3) Far from it - once you drive one with a ZF, it's hard to go back unless you are a purist
4) Not a lot of point unless you are thinking of refitting it before selling the car.
5) Definitely yes - effectively you have 2 extra gears, 4th being an overdrive, plus the converter lockup that is like a smaller overdrive on your overdrive - some consider having the 3.45 diff as too high a gearing with a ZF - I don't, but it depends how torquey your engine is.

Yes, lots of money, but as mine has been in 9 years, and with the mileage I've done, I reckon it's paid for itself

Russ

[RobinLegin]

Thanks everyone. All helps the decision process. Incidentally I did try contacting Tate through the SOC but got no response.
So Monarchs it will have to be.
Also which front spoiler do I need and where do I find this? Is it bolt on or welded?
Nigel

[Seaking]

Nigel most of us fit the tr6 one and it is bolt on

Still say you should use mr Tate try and contact him again

Cheers Glenn