Thread: Discovery front diff backlash problems

Hi,

Just going through a complete front diff rebuild, fitted a new locker, all new Timken bearings, all seated & pressed in well, brand new 3.54 ratio CW&P.

Mechanical run out, on the back of the new diff / gear face, is 0.03mm which is well within spec, spec is 0.1mm.

My problem, is that I set the backlash at 12pm, 0.10mm, 3am, 0.13mm, 6am, 0.14mm, 9am, 0.14mm, I just can't get a uniform figure, over the full 360deg of the gear.

Anyone else ever seen a pattern of numbers like this before, blue contact is middle of the tooth, and centralised on the anti clockwise face / tooth. Coast side is ok.

The pinion head bearing / cone I pulled out had a strange wear pattern, not 100%, like you normally see, but constant for 60%, then a gap with no wear, then wear for 20%, then a gap with no wear pattern. Main reason for the rebuild was to fit the locker.

Starting to think I've got a pinion inbound bore issue.

Will try and upload a picture of the bearing race.

Any ideas guys, should I just leave it, or try and source a new diff housing?

Jim

Now you're testing my memory....

From memory, the locker comprises 2 main parts.
- A short 'half' that just has a carrier bearing journal, and flange that the crownwheel bolts go through, and
- A longer 'half' that contains the guts of the locker, carrier bearing journal and a mating crownwheel flange that butts up against the other half.

The 2 parts are located together by a recess in one part, and a protruding piece in the other.

I think if you take out those 2 countersunk screws you refer to (without the crownwheel fitted) the 2 parts come apart and you'll see what I mean.

With mine, there was significant clearance between them, rather than a close locating fit. Enough clearance for it to be audible over the phone to Ashcroft.

With mine, turning it 180deg didn't fix the issue, as each part is machined concentrically and it was just the clearance that prevented them locating nicely. Only solution in my case (without paying freight to send the whole unit back to them) was to fit the crownwheel loosely, and gradually tighten up the crownwheel bolts while adjusting the runout with a copper hammer until I was happy with the runout.

Long drawn out PITA process. I thought they would have sorted out the fit in the next production run (unless yours is an old locker), but may just be a simple case of 2 parts at the opposite limits of their machining tolerances.

Don't loctite the crownwheel bolts for the setup or you'll confuse things with loctite running between the flanges. Remove/loctite/torque them individually once the setup is OK.

I wasn't 100% happy at the time, but in 40K km's I've had no issues. Diff is quiet and the locker works perfectly any time I engage it.

Steve