QT Fr Diff Guard...bolt sheered off
 

OK...here is my problem. Last month, (at MAR laying in a field) I was trying to install my QT Front Diff Guard. I was having some trouble getting the grade 8 bolts the came with the guard to thread into the 2 holes in the bottom of the front differential, but I figured that under the circumstances (dirty threads, limited clearance, etc.) the problem was most likely me, so I just kept going. After several attempts, I got one of the bolts started and began cranking it down to install the guard. Much to my dismay, just a few revolutions shy of being completely tight, the head sheared off the bolt.

I spent the next few minutes calling the bolt, the diff housing, and myself a bunch of ugly words. Finally I enlisted the assistance of a friend who is also a Rover mechanic who politely pointed out that apparently the grade 8 bolts that came with the QT Fr Diff Guard weren't quite the right thread. (He also took the opportunity to call me a few more well deserved names...:o)

So, I drove home from MAR and decided to ignore the broken bolt for a few days until I was a little less annoyed. Fast forward to this week. I've found and sourced the correct size bolts from Fastenal (m10x1.25x25mm Gr10.9) and have spent the last couple days (between meetings and at lunch time) trying to drill out the old bolt so I could insert an extractor and back the broken stump out.

Well, I finally drilled all the way through the bolt (hooray!), inserted the extractor per the instructions, started to turn it with a wrench, and after an ever so slight movement of the bolt, the extractor snapped off. (Doh! Did a lot more swearing. :mad:)

So here is my question...do any of you guys have any suggestions for how to get this bolt out? I've considered heating the diff, but I'm concerned that this will cause problems with the integrity of the housing.

I'm guessing I will have to drill out the extractor, and try another one, but I'm a little frustrated at the moment and hoping someone can offer up some alternative ideas. Thoughts?

I hate those cheap extractors they will snap every time. Drilling that out will be fun as they are very hard. I assume the bolt is flush with the diff housing?

Personally, I'd drill the whole thing out, and re-tap the hole for a little bit bigger bolt.

If you decide to do that, go slow, take you're time and don't screw it up. When you have the new hole drilled, and the new threads cut, make sure you flush out the diff to get rid of any metal shavings.

Drill and retap a size larger bolt.

FWIW, these holes are the ones that the harmonic balancers mounted to, so they don't actually open into the interior of the diff.

Drilling it out wouldn't be too bad, but doing it while laying on the ground in the driveway complicates matters...

Actually, there is approx 1/4 inch of bolt sticking down. Just enough to be really annoying, because I can just grab it with vice grips, but not enough to hold on and twist.

Looks like I'll be doing more drilling and tapping this evening. I'll let you know how it goes...

You are still running the balancer too, I hope, your your truck will want to vibrate at certain speeds.

Weeelllll, no. I pulled the balancer from my rear diff when I installed a LR Rear Diff Guard (all while laying in that same field at MAR). I have it and could put it back on, but had several folks tell me it wasn't necessary.

If there was ever a balancer on the front diff, it must have been removed by the PO. (I really only referenced it as a way of describing which holes I was using in the front diff.)

I do have a slight vibration when on the highway from 73-80mph, but that occurred even before removing the rear balancer.

You have several friends that don't know what they are talking about. I would suggest your put it back on. As for the front, Rover never had one on the front of a Disco, wasn't needed.

get a nut the size/pitch of the stuck bolt, thread it onto that 1/4" sticking out, then tack weld it to the broken bolt.