1999 Land Rover Freelander vibration on acceleration

Could be clutch and if applicable DMF (DUAL MASS FLYWHEEL)

Could it possibly be the vcu?

Could be , many possible causes i.e ,

Land Rover Freelander VCU Viscous Coupling operation, repair and thoughts
I’ve done a lot of reading up on viscous couplings recently:

VW used them to drive the front wheels of their “synchro” vans. They have many of the same issues with tyres etc as Land Rover Freelander VCUs. VW Viscous couplings can leak (not a problem for LR VCUs) causing no drive to front wheels, or gellation of the fluid causing constant drive (as with LR).

From: http://www.syncro.org/VCTest.html
There appear to be two primary causes for the VC to engage when it should not: (1) having tires that are not all the same size and wear (all 4 must be the same), and (2) age…VCs appear to have a nautural life span, at least where subjected to routine high operating temps.

Also, I would wager the below (form the link above) is the primary reason for LR Freelander VCU failure, especially as the early vehicles gearing meant the unit was constantly slipping and hence heating the fluid:

A typical scenario leading to a cooked VC would involve a syncro with tire sizes that vary slightly in treaddepth. The syncro is regularly driven at highway speeds for hours at a time over a period of time. Eventually, the driver notices binding in the drive train whenever she pulls off the highway into a gas station for gas. It may be subtle at first. Eventually, though, as the fluid gets cooked and ruined, the wheels seem to stiffen or bind much easier than before, and ultimately at the slightest turn of the wheel. When it gets bad, the drive train may lock up completely in the parking lot at very slow speed upon a relatively slight turn of the steering wheel. This total engagement of the drive train puts tremendous strain on the components of the drive train when the van is moving at speed under power. With continued use, the transaxle soon fails, the drive shaft and CV joints are also strained.

See also: http://www.vanagon.com/syncros/technica/ for some more info.

It would appear Land Rover VCUs (like VW) suffer from “Gellation” where the fluid spoils and goes thick, causing transmission wind up (perhaps due to the unit constantly accounting for the mis match in gearing). So even if a car passes the “VCU test” of jacking up and turning a rear wheel, the fluid may still have spoilt to a certain degree and be causing a load up of the Diff and IRD – i.e. its not totally solid but is dragging.

I suppose the test should be changed to “if the rear wheel is hard to turn” – you would need to compare a new VCU to yours to tell – if yours is harder to turn then the new VCU it might be on its way out. But I would like to see other evidence like wear patterns on tyres and the reverse skipping tyre test. I would say going by the expense of new IRD and diffs then prevention by fitting a new VCU to a car that has the reversing issue and scrubbing rear tyres would be wise.

This does negate the common belief that if a Freelander is used off road a lot then the VCU will be healthier – unless of course regular “cycling” of the fluid helps keep it in good condition, but I do not know enough of the chemical composition and properties of the fluid to comment on this.

This link indicates it is possible to refurbish a VCU: http://www.vanagon.com/syncros/technica/vc-expert-interview/index.html You can imagine drilling out the fill points on the VCU, blowing the fluid out with an airline, fitting brake nipples or similar and refilling with fluid. However it seems the sticking point would be locating a supplier of the correct fluid! We have no idea of the exact composition of the fluid Land Rover used.

These guys refurb them and sell for £200 – they must get their fluid from somewhere – but £200 seems pretty reasonable if they have a warranty:
http://www.bellengineering.co.uk/5.html