Parts Compatibility 85 & 91

[benhanson]

I have an opportunity to pick up an 85 318i for a few hundred bucks for parts.  I'm in dire need of a differential, and I'm in Alaska where there don't seem to be too many 91 318i diffs floating around and shipping/freight is steep.  So my question is weather there are going to be many compatible parts from the 85 318i?  It has the m10 motor, so I know there won't be anything much there.  I'm thinking of things like fuel pump/interior parts/heater&ac parts.  The diff on the 85 is an unknown, so I'm trying to decide if other compatible parts will make the purchase less risky(in terms of value)

Anyone have any input?  Thanks!

[Slowered318]

I think the U.S. M10 318's came with small case 3.61, 3.91 or 4.10. I'm pretty sure the limited slip option was not available, these were not "sport" models. Although it's hard to assume what someone has done with a car pushing 30 years, It could very well have a 325ix LSD diff installed? Some things you will have to visually compare like the blower motor or heater core but the rest of the interior should line up. Your best option is to find out the last 7 digits of the VIN and cross reference the parts using realoem.com

[DesktopDave]

Both cars use a small case diff, so that might be an advantage.  It's not a 100% sure bet, but look up the build sheet of the '85 to see what it had originally installed.

The motor isn't very similar, but many of the fasteners are the same.  Some of the driven accessories might be able to swap as well.  Hopefully it's a manual transmission.  The transmissions are both Getrag 240s, though I'm told the pilot bearing is different (early input shaft is thinner).  Some mix and match might be required.  Shifters are different, but can easily be swapped.  The wiring harnesses are also a bit different.  Many connectors were changed over the car's lifetime.  I have an early-style speedo sender in my medium case diff, along with a matching plug that I spliced into the newer car.  I know it's a bit of a jury-rig, but that was so much easier than an EZ-out on the stripped bolts in the diff case!

Other than the rear arms (smaller outer bearings), and drive shafts (most likely no ABS on the early car), the chassis is pretty much the same thing.  Diving boards won't swap, but the grilles, hood and front quarters are the same IIRC. 

IMHO it's always good to have a spare car, and any E30 will do in a pinch.  Nickel and dime stuff like missing screws, wonky switches and interior trim gets to be far less of a problem.