Ird

Following on from the VCU thread ...............

Ordering my new VCU today.

Spoke to my local land rover dealers over the weekend about the whole drive train issue.

He said that various improvements were made but couldnt remember the exact time.

He said, the rear diff was improved by using stronger journals. The VCU remained the same and the ratio in the IRD was changed. He gave me the part numbers for the 2 IRD's but couldnt tell me exactly when they changed and also pointed out that the part number isnt on the unit so its imposible to identify which one you have.

he said the only way to tell bar removing it would be to check one against another noting the revs at a given speed say 70mph. He couldnt remember what the figures were but thought it was something like 3100 rpm in 5th at 70 mph for the old type and about 2800 rpm for the new or the other way around - not much use really !!!!

So, anyone here want to tell me what RPM they get at 70mph on an L series diesel ??

As I said he wasnt sure of the dates but said that a 2001 model would definately have the new ratio IRD.

Chris

In top?

In 5th - 70mph

cheers

I get about 2800 at indicated 70mph with well worn 215/65R16 wheels.

Can i ask why you need to know? at this speed on the road , or any speed, the IRD is not contributing to the drive It will either be driving the rear prop 8% slower than the front drive or at the same speed as the front drive depending on the one fitted. This should have no effect on the road speed vs revs. The difference here will be in the gearboxes which have different ratios for L series and TD4 . The TD4 revving slightly higher per mph in top than the L?

The ratio change in the IRD is to do with the difference between front and rear output shafts and this difference was reduced at some point circa 2000/2001.

The chap was telling me thet on the early freelanders the failure of the VCU and the assiciated symptoms could, in part be put down the the ratio in the IRD.

He said, that the later models with the revised IRD ratio didnt suffer (as much anyway) from the symptoms ie braking effect on lock, castelation of the tyres etc etc.

Im about to replace my VCU and was just trying to find out whether or not I had the old or new IRD.

Cos the part numbers arent on them he suggested that this checking of rpm should indicate which unit I have.

Ideally I need to compare early and late L series engines, not TD4s.

On the other had what he said may be a load of rubbish, in which case im wasting my time !!!

Chris

I'm not sure when the IRD ratios were changed but I know that the significant difference was the reduction in ratio difference between front and rear and this would not alter the road speed/rev ratio as the change was to up the speed of the rear drive. This reduction does have a positive effect on the VCU as in the early models the vcu had a constant speed differential of about 8% between the two ends causing it to slip constantly. This was not enough to lock it but seems to have had an effect on its life/performance.

By the way mine is a 2000 model I think it was registered in July and its on its second VCU its done 140K and appears to be OK. hope this helps.

Rob

Thanks rob

Mine is a 99 but only one week off being a 2000


As far as I know its on its first VCU


Although its free I'm sure its not as free as it should be so will change it to be on the safe side !!

Just noticed a new noise as well. See new post

Cheers

Chris in wigan

Good luck.

By the way they are supposed to be stiff. See other posts about testing then. They involve rotating the rear drive line by putting a big wheel brace on the back wheel while its in the air to get the VCU to slip when the front end is on the ground. The the way to determine which IRD you have is to get all four wheels off the ground and rotate the front wheel the rear will rotate less , detectable after a few turns and calculable if you mark the tyres.

Rob