Thread: Freelander - constant4x4?????

Repeat after me .
The front diff is effectively HIGHER than the rear so the car will feel like a Front Wheel Drive for those poms graduating from a Fiesta.
The rear is NOT higher.
That is if this post is correct that is.
http://www.aulro.com/afvb/technical-...ff-ratios.html
Regards Philip A

Originally Posted by PhilipA

Repeat after me .
The front diff is effectively HIGHER than the rear so the car will feel like a Front Wheel Drive for those poms graduating from a Fiesta.
The rear is NOT higher.
That is if this post is correct that is.
Freelander Diff Ratios
Regards Philip A

OI, easy tiger. Did you bother to grab a calculator?

(Sorry in advance gary, i cant make heads or tails of that thread)

Gary has stated the wheels turn at 683RPM at 1000 RPM gearbox output shaft. 683 wheel RPM is about 88km/h. Even in fifth gear, 0.649:1 that places it at 650 engine RPM. Not likely.

Using the numbers below, from the Rave manual...

Take for example, the 2.0L diesel, 1000RPM in fifth gear gives 36.5km/h.

1000 engine RPM -> 1000 / 0.649 = 1540 Gearbox RPM

1540 GBox RPM -> 1540 / 3.647 = 422 Gearbox Output RPM

422 GB Out RPM -> 422 / 0.828 = 510 IRD Countershaft RPM

510 IRD CS RPM -> 510 / 1.762 = 290 Drive shaft RPM

290 Dr shaft RPM -> 290 * (27 * 0.0254e-3 * pi) * 60 = ~37km/h

Remove calculation rounding etc and, coincindence? It lines up with given figures.

My original Q was simply the ratio of the rear, but now im interested.
If we do the same calculation for the rear,

1000 engine RPM -> 1000 / 0.649 = 1540 Gearbox RPM

1540 GBox RPM -> 1540 / 3.647 = 422 Gearbox Output RPM

422 GB Out RPM -> 422 / 0.828 = 510 IRD Countershaft RPM

510 IRD CS RPM -> 510 / 0.553 = 922 Propshaft RPM

922 Propshaft RPM -> 922 / 3.214 = 286 Drive shaft RPM

286 Dr shaft RPM -> 286 * (27 * 0.0254e-3 * pi) * 60 = ~37km/h

If you include the final drive ratio, of 3.647:1, use the different IRD and rear diff ratio, it brings it back to ~286 drive shaft RPM. much closer and around 1% less than the front drive.

So to confirm what Gary says, yes, the rear actually does go slower, contrary to my initial thoughts. This suggests that under straight line conditions, no power at all is transferred back. I was under the impression the rear was set faster, to give rear drive under normal conditions, but figures suggest its the other way.

The rear is more like a donkey on a rope, you gotta drag it. So if its for onroad use only, take the VC out and leave the handbrake on... :P

Cheers! Hope this clears it up a little!

FINAL DRIVE
Ratios:
1.8 ’K’ series with MPi 4.200 : 1 ........................
2.0 ’L’ series 3.647 : 1 ...............................

Road speed at 1000 rev/min in top gear:
1.8 ’K’ series with MPi 31.7 km/h ........................ 19.7 mph
2.0 ’L’ series 36.5 km/h ............................... 22.7 mph

INTERMEDIATE REDUCTION DRIVE
Ratios:
IRD input shaft to IRD countershaft 0.828 : 1 .............
IRD countershaft to Front driveshaft 1.762 : 1 ............
IRD countershaft to Propeller shaft 0.553 : 1 .............

REAR AXLE
Ratios:
Propeller shaft to rear driveshaft 3.214 : 1 ...............

Since those posts I have confirmed the actual front diff ratio is 1.81:1 and the rear diff is actually 3.214. The IRD which feed drive to both the front and rear has its own gearing that makes the effective gearing of the diffs similar but not the same.

On the 1.8 4 cylinder, the rear differential ratio slightly "taller" than the front (3.214:1 v. 3.188:1) so that some torque is always going through the rear wheels, even in the absence of any wheel slip at the front. Source Land Rover Freelander. There are differences with the engine and gearbox fitted.

I have to admit different (and conflicting) information exists in the literature. One day I am going to strip my spare IRD down and see what exactly is going on because having looked at this over the past few years it is as clear as mud - I might even have a look inside the IRD next week.

Garry

EDIT - just noted the previous post - be wary of the 2005 posts - at that time I had NO information and was being given the run around by a whole bunch of people and I good not accept at that time that the effective front diff ratios could vary so much and keep the rear ratios the same - the rear diff ratios id 3.214:1 for all FL1s (FACT). The mystery is the gearing in the IRD. As I said I will try to pull my old one apart next week and solve the mystery.

Yeah, the rave manual numbers seem pretty good.
They come to a result of...

Rear diff - 3.214:1 (tailshaft in to drive shaft out)
front diff - 1.459:1 (thats IRD in to drive shaft out)

Propshaft pinion - 0.458:1 (thats IRD in to propshaft out)

Proof of this is that 0.458 * 3.214 is VERY close to 1.459

Rave gives no alternate ratios, but there is definately room to play as its soo close. It shows the manual gearbox has different final drive ratios depending on engine, but the numbers for the IRD are the same.

That magazine article does not agree with my numbers, as changing to 3.188 results in almost EXACT alignment of front and rear wheel speeds, while 3.214 is dragging the rear a little. Either way, no forward torque is transmitted to the rear. Also, i might suspect that the closer ratios are on the 1.8 due to the limited power, and dragging the rear would be dreadful for highway performance.

If you have varying numbers, post em up and ill calculate out the suspected combos if you like.

Cheers!

Originally Posted by garrycol

the rear diff ratios id 3.214:1 for all FL1s (FACT). The mystery is the gearing in the IRD.

Well that throws one of my theories out the window on the gearing differences between the V6 and the TD4.
RAVE lists a Final Drive Ratio of 3.66 (V6) and 2.91 (TD4), which I thought was in the diff ratio, but must be a combination of the actual diff ratio(s) and the gearsets buried in the IRD.



I think we are getting into a far too serous area, all maths and smoking sliderules

On the diff subject, I have found most of the time the TCS looks after you pretty well if you get the line, speed and throttle control right, but more positive drive wouldn't hurt. I had thought about the Dana internals and looking into LSD sets but I think you could look for a long time before you found anything. Last weekend I went out with my brother in his Jackaroo which does have a rear LSD, but no traction control, he got hung up in basically the same way as you can in a Freebie, cross axled with 2 wheels spinning, the clutch pack in the LSD obviously still allows plenty of slip, so the result was the same. A rear air locker would be interesting, but so would a suitably setup Rangie.

Momentum is your friend, but comes with lack of comfort and possible damage!

The final drive ratio appears to be at the output of the gearbox. Selected to suit the engine. The ratios in the IRD are as listed above. Although im not sure of age variations.

from what i can guess...


\

My suspicion is that the LH drive shaft goes up the guts of the input shaft, meeting the differential in the right of the IRD. Which would result in...



Cheers!

he got hung up in basically the same way as you can in a Freebie, cross axled with 2 wheels spinning, the clutch pack in the LSD obviously still allows plenty of slip

LSDs need some traction to bias it towards the other wheel.
The stated fix is to pull the handbrake on a bit. Same with Torsen.
Wish I had known that when I had my old Jackeroo.
You can also do this with an open diff.
Regards Philip A

Originally Posted by SuperMono

but no traction control, he got hung up in basically the same way as you can in a Freebie, cross axled with 2 wheels spinning,

In this respect a freelander should be no different to a D2 or a D3 with out diff locks - when you get crossed axled with 2 wheels spinning, traction control should kick in and drive transferred to the non spinning wheels.

Well it does on mine albiet with a bit of ooomph on the accelerator peddle.

Garry