E30 Diff swap advice

[pnosker]

This is to help those swapping E30 diff's into the 318ti. I originally went by the Notebook's guide (http://318ti.org/notebook/diff_conversion/index.html) and BlueBimma's guide.

My project was to swap an E30 eta 2.93 diff into my car while reusing the halfshafts and flanges.

Advice for old diff removal:
I tried the PB Blaster that everyone loves, and it probably helped with the overnight soak, but two of the driveshaft bolts were still impossible to remove. So I pulled out my Oxy-MAPP torch and heated it up with Propane-Oxygen (Couldn't find MAPP gas). That got them right off. Be careful, but this works very well.

That was the easy part. Remounting the flanges was also very easy, except I had a terrible problem fitting the new half shafts in because the flanges were still not quite 100% in. After they "suck" themselves in, hit them with a hammer to make sure they're seated properly. There will be no gap between the flange and the differential after.

I jacked the new diff into place and stupidly started the diff ear bolt first, instead of any others. That was stupid. None of the other bolts lined up after that. SO I had to dismount and waste over an hour trying to figure that out. Remount and start the top two instead. Even the bottom two would be better. After it was all mounted in, my stock halfshafts wouldn't fit. I searched for a while and saw Steve (Administrator of this forum) couldn't do it without E30 halfshafts. I said screw that, I need to use my car, so I dismounted the diff except for one of the lower bolts (which was loose) and the driveshaft, used a screwdriver to pry the diff as far over as I could, and stuck the half shaft in. I bolted the other side lower bolt in and removed the original side to do the same for the 2nd shaft. I needed to hammer the half shaft in so that it could fit. It was close, but a hammer was needed to do the trick. I found that this method worked well and I could reuse my shafts.

I bolted it all up by using a screw driver to pry the diff right under the correct bolt holes. This was tricky. I used a screw driver on the diff ear mount to pry forward and backward, and near the lower bolt region to move side to side. This got it to line up perfectly. The rear ear bolt couldn't fit and was over 1 in away from the right place, so I jacked the rear of the diff up to make that fit.

And so, after thinking it was a 1-2 hour job, was extremely sore after 8 hours of work.

Moral of the story:

Don't mount the diff without the half shafts completely in. Don't attach the ear-bolt first. Make sure someone can help you (Dad had to help me position the diff with the jack). And prepare to spend more time than you thought you needed.

I used Mobil 1 75w90 LS and it seems to be working fine.

I love the lower revvs. My Stromung exhaust made my car very loud at 65 mph. Now it's so quiet! 4th gear is like how 5th gear was. I can still spin the tires at start at around 2500 rpm and it doesn't really seem much slower. I don't have to shift at 58 mph anymore though! Oh, and my gas mileage appears to be at least 3 mpg higher now.