Thread: LT230 rebuild now has backlash after 10,000kms.

May sound silly, but just check that the uni's in the prop shafts aren't failing.

Check wear on input shaft and input gear.

Originally Posted by workingonit

May sound silly, but just check that the uni's in the prop shafts aren't failing.

Check wear on input shaft and input gear.

Not silly at all. Have checked this. The uni's in the back a good (RRC shaft) the front are good and has recently been rebuilt - by a pro rather than I.

The flanges on the Front and Rear diffs get about 1/6 to 1/8 of a turn before they take up. The rear has recently been rebuilt with an Ashcroft ARB centre and shimmed by the book, also by a pro not me.

R380????
Did you put a new input gear in?
Could the lash be at the input to the box?

Otherwise is the lash gear wear between the mismatched wear between the 1.4s and the input?

S

I have a standard Rover diff ('84 RRC) on the floor and gives, at a guess, less than 5 degrees backlash rotation. You seem to be saying 45 to 60 degrees (1/8 to 1/6 rotation) at your diff?!

I've only ever installed Ashcroft brand diff lockers that don't require shimming, just backlash adjustment through tightening the bearings back and forth. Has the shimming on the ARB unit failed, allowing the crown to move away from the pinion, meaning you're gradually moving from riding the valleys to the tips of the teeth (so to speak), giving rise to increasing backlash? But maybe this is not the case as you indicate slop both front and rear, yet only ARB at the rear.

Out of curiosity why ARB rather than Ashcroft, for I assume a Rover diff?

Was your original ratio a 'Q' or quiet cut?

Originally Posted by workingonit

I have a standard Rover diff ('84 RRC) on the floor and gives, at a guess, less than 5 degrees backlash rotation. You seem to be saying 45 to 60 degrees (1/8 to 1/6 rotation) at your diff?!

I've only ever installed Ashcroft brand diff lockers that don't require shimming, just backlash adjustment. Has the shimming on the ARB unit failed, allowing the crown to move away from the pinion, meaning you're gradually moving from riding the valleys to the tips of the teeth (so to speak), giving rise to increasing backlash? But maybe this is not the case as you indicate slop both front and rear, yet only ARB at the rear.

Out of curiosity why ARB rather than Ashcroft, for I assume a Rover diff?

Was your original ratio a 'Q' or quiet cut?

Rover diffs are shimmed on the pinion only (sals is different), which determins pinion depth. Backlash is set by moving the crownwheel left of right by the use of the adjuster thingys (not a technical term).
It does sound like a lot of backlash though. From memory backlash is set between 0.1-0.17mm????

True, forgot about the pinion shims, which brings the front diff back into contention?

My understanding (correct me if wrong) is pinion depth is more to do with the degree of tooth overlap and position of overlap; once the pinion is set the backlash would be taken up by the diff centre 'adjuster thingys' or bearing adjusting nuts (as the BMW manual calls them, just looked it up). Only if you fiddled with the pinion after initial set up could you potentially introduce more/less backlash than required ie re-tightening the bolt too much or not enough.

Never installed an ARB, but vaguely recollect they are not always a perfect fit for Rover diffs and some shims were required fore or aft of locker bearings maybe, not just in the pinion adjustment - I could well be wrong? The Ashcroft diffs just slot in between bearing adjusters without any need for shims.

Yep, the mm adjustment is small, and can be a bugger to capture when tightening up.

Were both diffs given the expert treatment? Maybe the pinion nuts are loose on both diffs, and taking from Vern's comments, this could be a source of excess backlash?

Hard to believe, from what is said about the lt230 build, that this could be the problem.

Oh, and I believe crowns and pinions are paired. In theory you should not take a crown from another diff without taking the matching pinion.

Originally Posted by workingonit

I have a standard Rover diff ('84 RRC) on the floor and gives, at a guess, less than 5 degrees backlash rotation. You seem to be saying 45 to 60 degrees (1/8 to 1/6 rotation) at your diff?!

I've only ever installed Ashcroft brand diff lockers that don't require shimming, just backlash adjustment through tightening the bearings back and forth. Has the shimming on the ARB unit failed, allowing the crown to move away from the pinion, meaning you're gradually moving from riding the valleys to the tips of the teeth (so to speak), giving rise to increasing backlash? But maybe this is not the case as you indicate slop both front and rear, yet only ARB at the rear.

Out of curiosity why ARB rather than Ashcroft, for I assume a Rover diff?

Was your original ratio a 'Q' or quiet cut?

Sorry mate, the rear is an Ashcroft ATB - ARB was a typo. Not sure about the 'Q' i can tell you they are helical gears in all the diffs. Maybe a better way to describe the front and rear diff flange movement to be from 12 oclock to maybe 2 clock.

I don't think the shim would fail on the pinion of the diffs. I know the rear diff was adjusted as a front diff to make it marginally tighter.

Originally Posted by roverrescue

R380????
Did you put a new input gear in?
Could the lash be at the input to the box?

Otherwise is the lash gear wear between the mismatched wear between the 1.4s and the input?

S

Auto ZF4HP22. I didn't put a new input gear in, but i used the full gear set from the 1.4. All new bearings and shims.