Whining when slowing down?

[Mockery]

Well this morning I helped Camilo (k1000o) to fit the VCU and prop-shafts on his 1.8L Freeby, a 2000 Model I think. So now it is actually four-wheel-drive.

Problem: there is now a whining gear-sounding noise which occurs when the car is slowing down. Engine braking or normal braking, it's the same. In fact it still happens if the gearbox is in Neutral.

I'm thinking this means the IRD output pinion was shagged already by the previous failed VCU and is why it was converted to 2WD (and sold on oblivious...)
Found rebuild kits available on evilBay, with all bearings and seals, so that's a direction for our next step; I'm just trying to think WHY would it only happen under deceleration?

[101RRS]

I suspect you are right - it happens on deceleration because the load on the gears is coming from a different direction - that is on acceleration power is coming from the engine to drive the wheels where on deceleration power is coming from the wheels to drive the engine.

Before buying anything further I would drain the IRD oil and check for metal and pull the pinion out and check it out. Then you can decide what to do.

Pinion rebuild kit or bite the bullet and get a new or second hand IRD - TRS in Adelaide is a good start. A few years ago new IRDs were $1800 from Landrover and good second hand ones were $1000-$1200.

Oh is the noise coming from the IRD or the rear diff? Sometimes the diff can take the hit when the VC goes.

I would not drive the car with the rear drive connected until you sort the issue.

Good luck

Garry

[Blknight.aus]

the gears in a diff are usually spiral cut (unless your talking about seriously old diffs)

when you accelerate they push (or pull) the pinion one way when you decellerate they pull (or push) the pinion the other this loads and unloads the bearings.

not having pulled diff on a freebie apart my guess is.

when you are accelerating the thrust is pushing the gears and bearings so that the correct CW+P alignment is being maintained and when you back off its opening up the tolerances and letting it howl. Both the sals and the stock rover diff so the same thing and its usually a good indicator that its time to overhaul the diff by way of bearing replacement.

This link (http://www.aulro.com/afvb/743795-post6.html) heads to a post that explains how the gears thrust off of each other, your interested in the bit below the 4 rough as guts descriptions of the crank shaft

[whyatts]

make sure there is no movement on the rear diff pinion
if there is you need to adjust the pinion pre load
this would cause a whining sound on de acceleration

if noise persists rebuild rear diff assembly and replace collapsable spacer

i'd be checking this first before replacing IRD!

[justinc]

Also, in addition to what Whyatts has mentioned, be aware that a NEW freelander rear differential is around $980 or so, hardly worth rebuilding it IMHO if the crownwheel and pinion is touch and go.

JC

[101RRS]

It will not be be the diff crown and pinion - it will be the IRD crown and pinion and specifically its bearings which fail causing the crown and pinion to no longer mesh. The diff has been in the car and working OK, albeit without drive to it. The drive to the rear would have been removed due top the rear drive crown and pinion and bearings in the IRD failing - when they have failed they cause heaps of vibration and noise but when the drive to the rear is removed and the Freelander is reduced to FWD, the IRD crown and pinion iand brearings are quiet as it is no longer under load.

The IRD pinion is easily (well relatively) removed for inspection.

Garry

[Mockery]

Thanks for the input guys, will see what we can see if the pinion comes out...

[Mockery]

Well, we dropped the front prop-shaft off and took a peek in the IRD...
Changed the oil and it came out looking exactly like pea-soup. No sign of excessive metallic bits though.
Took out the pinion, looks perfectly fine, although it engraved numbers on it as well as the stamped ones, so maybe it's second-hand?
Everything inside the diff looks fine also, except for a slight bit in the housing which could possibly be a bit chewed, but not sure how...
When re-installed, the output flange has about 1mm total play in both directions, would that be enough to indicate a worn bearing? It felt pretty fine in my hands, but I haven't held another one before that...

[101RRS]

Changed the oil and it came out looking exactly like pea-soup. No sign of excessive metallic bits though.

When you say pea soup - what exactly do you mean - colour or consistency - the reason I ask is that there is a small radiator inside the IRD that carries engine coolant through it - it is designed to carry away any excess heat generated by the IRD - if it is damaged inside the IRD if could be leaking (green colour) and and causing the IRD oil to be emulsified with engine coolant.

The engraving could be from a wrecker - if it starts wit TRS it is from Triumph Rover Spares in Adelaide - everything I have bought from them has been engraved - usually on the housing.

I cannot comment on the other issues you have mentioned. (when you talk about play in the pinion - are you talking rear diff pinion or IRD pinion?)

Cheers

Garry

[Matplat]

Did you eventually confirm what the problem was? I hadn't really taken much notice of it before but now I have read this thread I also have a bit of a whining when slowing down. It isn't really loud and is only noticeable at higher speed but now I 'm wondering if it is a problem....