Thread: Freelander Diff Ratios

AFAIK the ratios are the same.

Mark

Thanks Mark - thats what I thought - except for the slight change from 99 to 00 to fix the Viscous Coupling/IRD failure problem.

However the book lists the rear diffs having ratios of 4.2:1 for petrol, 3.647:1 for the L series Diesel, and 3.182:1 for TD4 manual. Hence my logic said that front diffs should be similar to the rears. If the IRDs are all the same ratio and the vaious models have different rear diff ratios, then in theory the VCs would have to work real hard on some models to prevent transmission windup and fail after an extended period.

I am at the point of putting a 01 model IRD into my 98 car and the dreaded thought that the IRD ratio might be all wrong crept into my head.

Thanks for the info. - Hope you are having a great trip.

Garry

Hmmm.... OK. I wasn't aware of any difference in the drive train between them.

I don't have any of my Freebee stuff with me but if you wanted to get a decent answer, pop a note onto the Freelanderclub Yahoo E-Group (http://groups.yahoo.com).

Mark.

Did it - Thanks Mark

Couldn't get any info on the Freelander's front diff ratios and when I removed my IRD today, I found some interesting stuff in counting input shaft rotations vs output shaft rotations. It would seem that when I stipulated a post 2000 version IRD from the wrecker to replace my buggered one, it would seem he mixed up L series diesel with TD4 diesel and I have one out of a TD4.

I would have expected the rear output shaft of the IRD to turn at the same speed as the input to the IRD but this is not the case. The rear output shaft of the IRD actually turns at about 2.333 times faster than the input from the gear box - so the actual diff ratios in the IRD and the rear diff are substantially different but generally balance out at the wheels. While the rear diff ratio is in a L series is 3.637:1, because of the increased speed of the tail shaft, the effective ratio is only about 1.565:1.

My investigation showed up the problem with the diff ratios in the 98/99 cars.

In the L series, at 1000 revs output from the gearbox (about 600 engine RPM), the front wheels are rotating at about 683 RPM (1.464:1) but the rear wheels are trying to rotate at 640 RM (1.565:1) so the viscous coupling is working constantly to take this difference out and after a time ends up failing which in turn causes the IRD and/or the rear diff to fail.

The TD4 doesn't have the problem of the 98/99 models - under the same 1000 RPM from the gearbox - the front wheels turn at 740 RPM (1.351:1) and the rears at 733 RPM and this difference is most likely because of my crude method of measuring (rotate the input shaft 10 times and count how many times the output shaft turns). The TD4 has a rear diff ratio of 3.182:1 which is an effective ratio of about 1.351:1 when the higher gearing of the tail shaft is taken into account.

As I now have a IRD out of a TD4, the rear diff ratio is all wrong. I have to do some work on the rear diff so if I want to retain the reliability of the TD4 drive train it might be simplist to replace it too - the end result will be slightly worse lower end performance but better cruising and a poorer Gazz.

Guess I will be front drive only for a while yet - at least until I can save up to buy a rear diff.

Gazzz

Originally posted by garrycol+--><div class='quotetop'>QUOTE(garrycol)</div><div class='quotemain'>Couldn't get any info on the Freelander's front diff ratios and when I removed my IRD today, I found some interesting stuff in counting input shaft rotations vs output shaft rotations. It would seem that when I stipulated a post 2000 version IRD from the wrecker to replace my buggered one, it would seem he mixed up L series diesel with TD4 diesel and I have one out of a TD4.
[/b]

Post 2000 is TD4.

Originally posted by garrycol+--><div class='quotetop'>QUOTE(garrycol)</div><div class='quotemain'>I would have expected the rear output shaft of the IRD to turn at the same speed as the input to the IRD but this is not the case. The rear output shaft of the IRD actually turns at about 2.333 times faster than the input from the gear box - so the actual diff ratios in the IRD and the rear diff are substantially different but generally balance out at the wheels. While the rear diff ratio is in a L series is 3.637:1, because of the increased speed of the tail shaft, the effective ratio is only about 1.565:1.

My investigation showed up the problem with the diff ratios in the 98/99 cars.

In the L series, at 1000 revs output from the gearbox (about 600 engine RPM), the front wheels are rotating at about 683 RPM (1.464:1) but the rear wheels are trying to rotate at 640 RM (1.565:1) so the viscous coupling is working constantly to take this difference out and after a time ends up failing which in turn causes the IRD and/or the rear diff to fail.
[/b]

Sounds about right....


<!--QuoteBegin-garrycol@
The TD4 doesn't have the problem of the 98/99 models - under the same 1000 RPM from the gearbox - the front wheels turn at 740 RPM (1.351:1) and the rears at 733 RPM and this difference is most likely because of my crude method of measuring (rotate the input shaft 10 times and count how many times the output shaft turns). The TD4 has a rear diff ratio of 3.182:1 which is an effective ratio of about 1.351:1 when the higher gearing of the tail shaft is taken into account.[/quote]

OK... The problems come from the difference between front & rear wheels rather than anything relative to engine speed. I don't s'pose you've tried counting the revolutions of the front wheels vs the revolutions on the output shaft (effectively pretending that the drive is on the centre prop shaft)?

<!--QuoteBegin-garrycol
As I now have a IRD out of a TD4, the rear diff ratio is all wrong. I have to do some work on the rear diff so if I want to retain the reliability of the TD4 drive train it might be simplist to replace it too - the end result will be slightly worse lower end performance but better cruising and a poorer Gazz.

Guess I will be front drive only for a while yet - at least until I can save up to buy a rear diff.

Gazzz[/quote]

I'd hope you don't have to do that. There's guys in the UK that are running the later IRD in the older trucks and AFAIK they haven't touched the rear diff. They've covered plenty of miles without problems and have better tyre wear.

Mark.

Camel Landy said
<div class='quotetop'>QUOTE</div><div class='quotemain'>OK... The problems come from the difference between front & rear wheels rather than anything relative to engine speed. I don't s'pose you've tried counting the revolutions of the front wheels vs the revolutions on the output shaft (effectively pretending that the drive is on the centre prop shaft)?


I'd hope you don't have to do that. There's guys in the UK that are running the later IRD in the older trucks and AFAIK they haven't touched the rear diff. They've covered plenty of miles without problems and have better tyre wear.[/b][/quote]


Have effectively done what you suggested ie pretend the drive is on the center prop shaft - answers are the same as the input shaft to the IRD and the rear drive output shaft are directly connected - geared together. Wheras the drive to the front wheels goes through the front differential.

I also have heard that the later IRD should go straight in and be compatible with the rear diff - but the logic doesn't hold - if the initial problem was caused by the difference in diff ratios - putting in a TD4 ird with a different diff ratio should make the problem worse. I am sure you are right about your experiences - then that begs the question was the initial problem the IRD - what if it was in fact the first lot of VCs that just failed and caused the IRDs to fail. What if the later VCs are better able to handle the different diff ratios - I am sure your friends who are running later IRDs are only doing so because the original IRD failed along with the VC and as such they put in new VCs.

Thanks for the tips Mark - I really appreciate your assistance.

Oh - Harveyg77 from the Yahoo Freelander Club sends his love 8O

Catchya later

Gazzz

Originally posted by garrycol

Have effectively done what you suggested ie pretend the drive is on the center prop shaft - answers are the same as the input shaft to the IRD and the rear drive output shaft are directly connected - geared together. Wheras the drive to the front wheels goes through the front differential.

Bugger.... [img]style_emoticons/<#EMO_DIR#>/sad.gif[/img]

Originally posted by garrycol

Oh - Harveyg77 from the Yahoo Freelander Club sends his love 8O

LOL... Great guy. He used to be in the navy too... :wink:

Mark.