Thread: TD4 VCU Faulty??

My Comments in Red in against the relevant area below

Originally Posted by psproule

I know this has been covered at some length on a variety of forums but there seems to be a lot of conflicting information. I agree

I suspect the VCU in the 2001 TD4 we have just picked up might be too tight (161,000km). On full lock it feels a little tight. (The is quite normal as long as it is just a little tight - it is the VCU working as it is supposed to detecting the front wheels (turned) turning at a slight different speed to the rears.) When reversing on lock - the engine just just load up a little - if it is a manual and the engine labours a lot or stalls then the VCU is suspect)

I have jacked up one rear wheel and can rotate it by hand (without a breaker bar) but only slowly and with a fair bit of force. (this is actually good - normally you would need some sort of leverage to move the wheel so if you and it would still be OK - if the VCU was locked you could not move the wheel). My VCU has been in for 100,000km and I have always needed a bar to move it.

I have also noticed it has broken a rear diff mount (the front one) (the rear of the diff is supported by two mounts sharing the load - the front only has one that is offset and takes a lot of load - I replaced mine when I did my VCU and it is beginning to knock again. easy - must a little fiddly to replace.

and one of the unis in front of the VCU looks a little floppy (can these be replaced like a normal tailshaft?). Yes - again I did mine when I replaced my VCU. I cannot remember but you might have to drop the VCU to do the UJs - probably a good time to do the VCU bearings as well. You will need the right Torx socket to remove the CV on the front of the front drive shaft

From my forum readings it would seem that there is no definitive way to test the VCU? Some sites simply state to replace it but at $1390 it might be wise for me to confirm the diagnosis first. Some sites (here included) state that the failures were usually only on the pre 2000 models? I know I can convert it to front wheel drive but I'm not keen to do that as it will be used in light off-road situations. I might remove the shaft in the interim though to prevent any damage. The VCU can fail on any model as it does not have an infinite life but the pre 2000 models placed extra loads on the VCU that caused it to fail somewhere around about 130,000km. Your VCU seems OK - check it every 5000km with either the wheel method or the whiteout marks (tippex test) on the tailshafts. Yes you can removed the shafts and VCU then what is the point of of having an awd. VCU prices are coming down - 5 years ago they were $3000 new - now $1300 less than the price of a major service on mine so test it and when it has failed put in a new one.

We also have the "3 amigos" situation with the TC,ABS, HDC lights. I'll look for a faulty brake switch or switch wire on the weekend. They come on from time to time - if turning off the ignition does not fix it the first identify the sensors on each wheel - in particular blow compressed air (or even high pressure water but then clear excess) into the air gap between the sensor and rotor ( if you can get at it) to blow any dust out of the air gap. Some sensors can come out easily so pull them out (they come out on my early FL1 - not sure about yours) and just blow it all clear - while you are at it check there are no breaks in the wire from the sensor up the wheel strut. If the problem continues then it is time to get expert help.

Thanks for any advice, & suggestions of who to source parts from are more than welcome.

Pat

Garrycol, thank you very much for your detailed reply. That puts my mind at ease a fair bit. It doesn't feel like it wants to stall the motor on full lock but you can feel it bind up a bit and on loose gravel it wants to push forward a bit. I'll fix the diff mounts and the unis and go from there. And as you suggest i'll check it regularly.

And thanks very much for the info re the TC etc - I'll have a chance to go through it on the weekend.

Reading the forum I have a growing list of things to do - clean out the intercooler & replace the crankcase breather, block off the EGR and tidy up some cosmetics. I like these things though - feels nice and solid, & the TD4 is fairly willing & able.

Cheers & thanks - Pat

I test mine the same as a RRC with 20Nm of force it should turn 25' to 30 degrees in a minute. I lock the front of shaft and put a torque wrench on the damper bolts and carry out test.

Woko, forgive me (and I am mechanically inclined), but which damper? I gather there is one in line with the driveshaft? I have only had one look under it so far so will have another peek this-morning.

Thanks - Pat

In theory you should be able to test the VCU via the use of a torque gauge of some sort if you knew what force is required to turn a serviceable VC. eg at normal temperature the VC should be able to be moved using xyz NM force - if it takes more or does not move then it is unserviceable. Unfortunately I have never been able to find what force is required to move a serviceable Freelander VC - hence the logic that if it can move and is not locked then the VC is OK.

Woko who has/does work on these has determined that a suitable force is 20nm and turning at a rate of 30 degrees a minute. I assume he is testing the VCU direct rather than the wheel method that has the diff gearing in the process.

If I read him correctly he will have one of the rear wheels off the ground and lock the front driveshaft (usually by leaving the front on the ground in gear, chocked with hand brake off). If you have a look at the VCU you will see it comprises two drums - a longer one with smaller diameter, and shorter one of larger diameter. I cannot remember which is which but I believe the smaller one is the VCU itself and the larger one is a rubber filled DAMPER. It has some large bolt heads on it.

With the front shaft locked you could put a torque wrench on one of these bolt heads and turn the damper which is also turns the internals of the VC - if it turns with the specs Woko has mentioned then the VC is OK - if you need more torque or it turns slower than 25-30 degrees a minute the VC is suspect.

Woko - where did you get the 20nm figure from? Frome tech data or based on experience working on these - as said I have tried to find this magic number but have never found it.

Garry

Ok, when I get a chance I'll climb under it with the torque wrench and some sockets and a stopwatch and report what I find. This one hasn't seized - I can still turn it.

I just got the service manual (ebay rip-off but appears to be the factory one). It doesn't seem to list any torque settings or ways to test the VCU. It does mention though that the damper is only fitter to the 1.8 K series motor.

Pat

Originally Posted by psproule

I just got the service manual (ebay rip-off but appears to be the factory one). It doesn't seem to list any torque settings or ways to test the VCU. It does mention though that the damper is only fitter to the 1.8 K series motor.

Pat

Go to the AULRO Forum shop (see the Shop menu above) and buy the Rave Manual. This a genuine manual.
Dave's Interesting Things

I would also buy the Haynes manual on ebay or at Repco. RAVE is excellent but the Haynes has more explanation for us "dummies". I find that they tend to complement each other.

As far as the torque figure - I have asked on many forums, ask mechanics, asked GKN (the makers) etc but never found a number.

All FL1's VCU, irrespective of engine,have the same VCU and DAMPER.

Garry

Yes I check it direct on the VCU. The figure I'm using is for a vcu on a Range Rover classic. I Cant find a freelander figure either. Ive been to freelander schools and those notes dont have figures either. I know its not the same as a freelander but my TD4 has 100K on it and it passes with in this range.