Thread: Bolt head in rear diff..

I'm thinking it is the head off a bolt holding the crown wheel. If it has broken off, what are the others like? As a first step consider jacking up a rear wheel (chock front), handbrake off, remove the level plug and see what you can see as you rotate the diff. If it is a salisbury, remove the rear cover to have a look. If it is a Rover diff, you can fairly easily remove it by pulling both axles, disconnect prop shaft and drain it.

With either diff type, you need to be certain where it came from. If you are lucky, it is a leftover from a previous repair and no further work will be needed. If it is one of the bolts holding the crown wheel on, replace all of them with new ones, correctly torqued (ff a head has broken off, were they overtightened? or faulty bolts?). I am not sure, but you may be able to do this (one at a time) without further disassembly. If it is quiet, and this is the only repair needed, then you should not need to make any adjustments.

Yes as noted its a crown wheel retaining bolt (well the head anyway). The P38 diff if you work them, towing, offroad can break them. When you pull the diff out you will likely find bolts next to it broken and bolts on the opposite side of the crown wheel broken.

Good time for a rebuild, while it may not be noisy yet I would say there will be plenty of backlash in it.

Thanks, Ill pull the diff out in the morning, definitely crown wheel bolts. its at 200,000k of hard off road and towing, so I think I will go an Ashcroft conversion, but will renew all CW bolts in the mean time.
Are there any Ashcroft diffs available in the country or are they an order in from OS?

Originally Posted by Summiitt

Thanks, Ill pull the diff out in the morning, definitely crown wheel bolts. its at 200,000k of hard off road and towing, so I think I will go an Ashcroft conversion, but will renew all CW bolts in the mean time.
Are there any Ashcroft diffs available in the country or are they an order in from OS?

*Direct from Ashcroft it wont take long to get here, the new ATB for the P38 doesnt need the spacer ring fitted.
*Replace the bearings while you are there.
*Also if as you say hard offroad and towing, its likely going to need a new crown wheel and pinion.
*Once carrier is removed, check the bite pattern and amount of wear on the teeth.

G'day Summitt,
If your crown wheel bolts were like the ones on my front diff, (2002 Td5 130) they have serrations under the head face, the serrations dig into the cast iron carrier over time, and allow the bolts to loosen. I replaced mine with ARP bolts, with a smooth face, after needing to replace my crown wheel and pinion after it chewed though a few bolt heads. In my opinion using serrated head bolts against cast iron was a very poor design.
arp-bolts.com

Cheers,
Mick.

Well, every bolt had sheared off, and amazingly none had gone through the CW/P. Given the vehicle is off road nearly everyday, everything is in perfect condition.
Ive put it all back together with new HT bolts and will look into a new locker and fresh bearings etc.
Its incredible that the vehicle showed no signs that anything was wrong with the diff, zero noise or backlash, probably got it just in time before it exploded all together!

Wow!
Buy a lotto ticket!!

Were the bolts sheared (failed between C/W & carrier) or the heads detached? Which would most likely be due to overtensionedor faulty bolts.