IRD Fail???

Here are some more pictures of the removed IRD and CV
While a little blurry the splines inside the gearbox are all okay:



Not sure if it is how it is meant to look but the middle set of splines only have spline at the bottom of that part but the CV still splines in and rotates nicely.

All the splines look good on the IRD itself:
All shafts rotate okay, not sure if more disassembly is required to see if there is more damage but it all spins nicely without grinding or any bad noises:

The bearing on the small gear looks a little worn but nothing excessive as I cannot feel a lip on it.

The splines on the CV Axle look okay not bad, still there, none missing or twisted:
Albeit blurry I can confirm all the splines look okay, I took a look at the UJ's under the boots which looked good too.

Does this mean the Failure is likely to lay in the Trans/gearbox or in the CV which I cannot see/tell?

Thank you for all the help, just trying to work out what is broken and needs replacing

Though the more I look around and at the below picture:



The more I think it is stripped as the splines where the IRD would go (The smaller set of splines) it is smooth but with little bit of spline at the end. this picture illustrates this Red being the beginning of the splines, blue being what is left of the splines and green being smooth area.



Note that the blue and green does go all the way around.

This would mean I need a new gearbox right?

Thank you!

So...

The weekend has been busy got a few people together and managed to replace the gearbox in a day, lots of stress and hard to reach bolts but it's back in and I can confirm that the front drive now works, the splines on the gearbox had sheared off.

To remove the gearbox though I had to cut the exhaust as at the time I didn't realise I'd be dropping the subframe to make my life easier.

But once it was all back together I started her up and it sounded like a v8 straight from the headers to down pipe with no cat but she idled quite rough which I assume was because the ecu was super confused now with the o2 sensors not showing the right numbers..

Now the bad bit. She has to move, I reversed her and while loud sounded alright, coolant was all good, all oil had been filled but it suddenly started dying she got to about 250 revs then died as i put the clutch down and pressed the gas but suddenly sprung to live at 1100 rpm then died almost immediately and then snow from under the hood... engine very bad.

Under closer inspection the smoke was coming from the air intake (stock) but quickly subsided could I safely assume that it backfired into the intake and burnt some of the filter resulting in smoke or should I replace the gasket assuming I didn't just bend my conrod?

I haven't tried to start it since as I fear for water in the combustion chamber

Let me know what you think I should do to diagnose the issue wether it was just smoke from a Backfire and just needs the exhaust replaced or if the head gasket went out if I just ruined the engine.

Thank you