SO what did you you do with your Stag today?

[HersnotHis]

Good mpg is that mainly down to ZF box do you think

mole42's drive would have been 80% + on motorways, the ZF is I believe the same 1:1 in top. Perhaps as his screen-name implies he has a "soft" foot. As an experiment I "soft footed" my modern Jaguar on a 150 mile journey and achieved an over 30% better fuel consumption compared with the same journey but "using" the car.

H

[DJT]

mole42's drive would have been 80% + on motorways, the ZF is I believe the same 1:1 in top. Perhaps as his screen-name implies he has a "soft" foot. As an experiment I "soft footed" my modern Jaguar on a 150 mile journey and achieved an over 30% better fuel consumption compared with the same journey but "using" the car.

H

ZF 4HP22 is 0.73:1 in top, hence the low revs and good fuel consumption.

A-type OD is 0.8:1.

BW boxes are 1:1

[mole42]

mole42's drive would have been 80% + on motorways, the ZF is I believe the same 1:1 in top. Perhaps as his screen-name implies he has a "soft" foot. As an experiment I "soft footed" my modern Jaguar on a 150 mile journey and achieved an over 30% better fuel consumption compared with the same journey but "using" the car.

Unfortunately I'm not soft-footed! In the 1970s I did forest stages in a 1275 Mini. The Stag isn't always a quiet beast!

The trip from Bristol only uses motorway until Swindon (about 40 miles), then it's mainly fast A road. It's the ZF gearbox that helps - top gear is about the same ratio as overdrive top in a manual.

Richard

[Stagdad]

Hi Gordon, I made a short link, too link out the inertia switch if it gives trouble , but only to be used as a diagnostic tool or in a emergency. Do not run for long as if you are in a accident the fuel flow will not cut out and your insurance may not pay out, but it may get you to a safe spot to have a proper look at the switch.
[ATTACH=CONFIG]37224[/ATTACH]

To bypass the inertia switch you can just use a standard size blade fuse, it has 2 male blades.

[Jeff]

3 speed BW auto, 4 speed ZF auto = no brainer re fuel consumption, pretty obvious I would have thought.

[GRD]

Thanks for the tips all points duly noted. I'll get the connectors later on today and make up the link tonight. This is what makes this forum so useful

[jbuckl]

trv8 is ohv! (& ohc)
is yours an rv8 then?

Put final touches to readiness for Drive it Day event tomorrow. Went to local shell station to fuel up but found road closed and petrol station also closed ! Therefore headed for next nearest station via A14 and promptly showed off Stag performance to several moderns. Got a thumbs up from one as I slowed down in sliproad!

However am becoming concerned that the engine sounds more top end rattley (if it was OHV I would say tappety) since having changed oil to VR1? (Previous Halfords classic).

H

[Stagsongas]

3 speed BW auto, 4 speed ZF auto = no brainer re fuel consumption, pretty obvious I would have thought.

Jeff,

A 3 speed and 4 speed 'box could have exaclty the same final drive ratios ( in top gear) but differerent 'spread' of the intermediate gear ratios.

Even so, the ZF has true Overdrive when the Torque converter is locked up, the output shaft has greater RPM than the input.

Regards

Steve

[Jeff]

But the engine revs are higher in top gear with the 3 speed Steve as you know hence my statement re: fuel consumption.

Jeff.

[DJT]

ZF 4HP22 is 0.73:1 in top, hence the low revs and good fuel consumption.

A-type OD is 0.8:1.

BW boxes are 1:1

Jeff,

A 3 speed and 4 speed 'box could have exaclty the same final drive ratios ( in top gear) but differerent 'spread' of the intermediate gear ratios.

Even so, the ZF has true Overdrive when the Torque converter is locked up, the output shaft has greater RPM than the input.

Regards

Steve

But the engine revs are higher in top gear with the 3 speed Steve as you know hence my statement re: fuel consumption.

Jeff.

I'll expand upon my earlier post #408:

ZF 4HP22 Gear Ratios (2 types in existence but both have direct drive 3rd and o/drive 4th):

A	2,48	1,48	1,00	0,73	-2,09
B	2,73	1,56	1,00	0,73	-2,09

BW35
1st 2nd 3rd
2.39 1.45 1.0

Type A
1st 2nd 3rd OD3rd 4th OD4th
2.995 2.10 1.386 1.135 1.0 0.82

As can be seen, the ZF has a higher ratio top gear than the MOD in OD.

[KOY 23]

Jeff,

A 3 speed and 4 speed 'box could have exaclty the same final drive ratios ( in top gear) but differerent 'spread' of the intermediate gear ratios.

Even so, the ZF has true Overdrive when the Torque converter is locked up, the output shaft has greater RPM than the input.

Regards

Steve

Steve.
Why do you mention final drive ratios? I agree that 3,4 or even 10 speed gearboxes could have the same top gear ratio, but this is not relevant to the topic.
We are talking about gearbox input to output shaft ratios, and in particular the ZF 4 speed which has overdrive 4th gear, not just an overdrive lockup. 3rd gear on ZF is similar to 3rd on BW35. The 4th gear on ZF reduces fuel consumption.

Dave thanks for clarifying, must concerntrate on typing.

[Carl Reading]

Took it for its MOT. It passed.
Couple of advisories:
Hand brake cable starting to fray
Loose baffle in one of the silencers

Can the baffle be repaired or is it a new silencer?

[Paul Kelley]

Left it in the garage again as still sleeting/snowing/raining/sunny and about 2 degrees. Gritters still around chucking the corrosive stuff about with gay abandon (can you still say that these days??!). Grrrrr! Roll on spring, never mind summer!
PK

[StagJonno]

Left it in the garage again as still sleeting/snowing/raining/sunny and about 2 degrees. Gritters still around chucking the corrosive stuff about with gay abandon (can you still say that these days??!). Grrrrr! Roll on spring, never mind summer!
PK

Ditto - it's unbelievable
Changed Winter to Summer tyres Monday on the daily driver - should have waited a few more weeks.

[Stagsongas]

Steve.
Why do you mention final drive ratios? I agree that 3,4 or even 10 speed gearboxes could have the same top gear ratio, but this is not relevant to the topic.
We are talking about gearbox input to output shaft ratios, and in particular the ZF 4 speed which has overdrive 4th gear, not just an overdrive lockup. 3rd gear on ZF is similar to 3rd on BW35. The 4th gear on ZF reduces fuel consumption.


Dave thanks for clarifying, must concerntrate on typing.

Jeff and John,

The way I read Jeff's post suggested that the choice between a 3 speed and a 4 speed box was a 'no brainer' in terms of fuel consumption.

I've just tried to show that whatever number of intermediate gears are present, that gives no indication of the final drive ratio, and that may well be identical in both 'boxes. It's more for readers on the side than Jeff himself, who I'm sure knows more about it than I do.

Whatever, after the 130 mile Drive it Day last Sunday I can confirm that my ZF dramatically increases the Stag's MPG when a good portion of the journey is over 52mph, i.e. when the TC locks up just like it did in the XJ40 I took it from.

Regards

Steve