Front cv or diff noise

[ericos_bob]

G'day, been busy getting the syncro ready for a 7 week trip offroading and have been sorting out the mechanical quirks, torqueing all bolts and replacing fluids etc. Just my luck I seem to have developed a noise literally in the past couple days coming from the front left diff and/or inner cv. I replaced the inner cvs with new 944 type about 6 weeks back though haven't driven more than 1000km. If I remove the left inner cv from the diff it disappears. To try and further diagnose what is making the noise I've jacked up the left side of the car while in 4wd and run the engine with a gear selected. The diff/cv makes a constant knocking grinding noise. When I increase the revs the grinding sound becoems much louder. I've run the same test with the the right side of wheels lifted and there is no noise coming from diff. Can I rule out the diff being the culprit here? Any ideas?cheers

[Aidan]

Bob
I'm just working on a front diff at the moment that has got a worn diff - the internal differential gears have picked up and if you turn the diff it sounds really rough - the internal backlash should be only 0.03mm- o.17mm, this one is 0.47mm - there's very little chance of repairing it if it is this as the internal pinion set is just that a set of four shafts/cogs and the spacers between them are only available in a very limited range of sizes - the one I'm working on was built originally with the 2nd largest spacer in it so even 2nd oversize can't bring it back in spec, I spent all afternoon yesterday swapping diff cover plates and 3 of the 4 pinions and spacers and new thrust washers in different thicknesses to find a set up that would work and have had to give up.
The front diffs are only 2 pinion diffs so have the range of spacers, but it appears that the wear is in the diff casings; the rear 4 pinion diffs have a block type spacer that is only available in one thickness so when they are worn out that's it change the diff
Usually wear is apparant on the short side of the diff - the crown wheel side, which on the front diff is the right side, play at the other side would also indicate a worn diff - the reverse is true on the rear - usually there will be a little play at the output flange on the left side, often accompanied by weepy seal whilst there is very little movement on the right side

[ericos_bob]

Wow, thanks for such a detailed reply aidan. To be honest I've had to read everything twice due to my lack of understanding of the inner workings of transaxles. I don't appear to have any trans oil weeping on inspection. I have since drained the oil and there are no metal filings visible on the magnet or in the oil itself. The diff makes no noise when turning either end by hand though I thought perhaps this is due to there being no load on it. I am fearing the worst but still hoping for the best so will replace oil and try running a different left inner cv.

[ericos_bob]

Just checked my cv joint and turns out it is buggered. I mean to the point where when I try to move it by hand in any direction it just jams in that position. I can feel the grinding too. It seems all 6 of my brand new 944 cvs have now failed me in less than 1000kms. I have already converted my rear drive shaft to run 930s after the 944s failed me there. I can only guess my whole set of 944 cvs were a defective batch or I've done something wrong installing them. I'm going to switch back to the stock front inner cv joints and hope they cope with the angle of 2" of lift.

[ericos_bob]

Just checked my cv joint and turns out it is buggered. I mean to the point where when I try to move it by hand in any direction it just jams in that position. I can feel the grinding too. It seems all 6 of my brand new 944 cvs have now failed me in less than 1000kms. I have already converted my rear drive shaft to run 930s after the 944s failed me there. I can only guess my whole set of 944 cvs were a defective batch or I've done something wrong installing them. I'm going to switch back to the stock front inner cv joints and hope they cope with the angle of 2" of lift.

[ericos_bob]

Just checked my cv joint and turns out it is buggered. I mean to the point where when I try to move it by hand in any direction it just jams in that position. I can feel the grinding too. It seems all 6 of my brand new 944 cvs have now failed me in less than 1000kms. I have already converted my rear drive shaft to run 930s after the 944s failed me there. I can only guess my whole set of 944 cvs were a defective batch or I've done something wrong installing them. I'm going to switch back to the stock front inner cv joints and hope they cope with the angle of 2" of lift.

[Aidan]

tough break on the cv's Bob, standard works eh ? But at least it's not the diff