R65 Trans/Engine Mating

[Robb LaVelle]

I am 90% through a full restoration of my 1980 R65 and I am having trouble on the most mundane topic. I have rebuilt both the engine and the transmission but now mating the two is proving a challen. The tabs built into the housings of both parts seem to not align on the right side and, even though the input shaft mates well into the clutch assembly, there is still about an 3mm gap between the engine and trans housing on the right side. I have greased all the the edges that come into contact when assembled as well as the splines of the input shaft. I DID have the heat up the the shaft receptacles of the transmission housing to remove the shafts and, although clymer says not to use a propane torch due to potential housing warping, I know most mechanics do use this approach.

At this point I am thinking of milling some material off the the housings to force a fit because I have zero intention of buying a new housing.

Any ideas?

Cheers - Roro

[brownbmw]

Are those hex bolts holding your clutch assembly? They're supposed to be countersunk allen screws, and a specific one you get from a BMW dealer.
Even though the input shaft mates to the clutch splines, that doesn't necessarily mean the clutch is centered. Did you use a centering tool when installing the clutch?

[Robb LaVelle]

The hex bolts are original and yes, used a clutch centering tool (both a purchased one and the input shaft from the gear box)

[brownbmw]

Yep, my memory is slipping. Forgot that the early R65's took the hex bolts.
Hard to believe that the propane torch warped the housing unless it was glowing hot.
Is it 3mm off side-to-side so it won't start to mate, or is it mating up, but stops 3mm short of seating?

[Robb LaVelle]

Thanks for your help. The lip of that one tab is getting hung up on the rt side before I make much progress on mating the two assemblies at all. I spoke to my mechanic and he agrees - would have taken a blow torch to warp the case. I will remove the clutch again and re-center it. He also suggested installing the bolts and using that leverage to pull the assemblies together. It came off of the block only 3 months ago and I had the crankshaft & flywheel professionally balanced and re-installed so I can exclude that as the source. The input shaft could be the culprit (I rebuilt the trans) although I would think that the transmission housing and cover gear shaft receptacles - as well as the input shaft bearing - would ensure alignment.

I will try (and retry) and keep you posted.

Cheers.

[brownbmw]

You could try turning the engine approx 1/2 revolution. It appears the top-ends are off so you should be able to grab the flywheel/clutch assembly and spin it 180 degrees. If it's the clutch alignment the issue should move to the other side.

[Robb LaVelle]

Yup - i tried that - turned at the alternator lug but gap is still on the right side. Good deductive detective work will get us there!

BTW, that pic was pre-rebuild. It looks much prettier now.

[mark_weiss]

Remove the friction disc, test mate the transmission to the engine case.

[Steevo]

I would do the "install the trans without the friction disc" test before trying anything else.
There is no reason that the same parts should not mate the same way, and I have swapped around dozens of these transmissions and clutches without ever experiencing mis-aligned cases or bolt holes. Something is fishy.