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Discussion Starter #1
Well, I thought I would be sending out pretty pictures of my first gearbox (105) rebuild tonight, but literally on the very last part something was wrong. The throw out bearing sleeve (picture below) in the bell housing is too large for the throw out bearing to fit over it. My question - how is that possible? Hasn't that sleeve been the same on every 105 hydraulic clutch car since the beginning of time?

The background is that I had to source another bell housing as mine was cracked. The one I got is for a 105 I assume...it mates up to my 2L block and all the hole distances match my old bell housing. But why would the throw out bearing sleeve be a different size? Not a big deal...I can just pull the one out of my old bell housing...but I am really mystified by this. It didn't even dawn on me to check it. Luckily I had just put the bell housing on, so the gasket maker wasn't too terribly set and reasonably easy to clean off the surfaces.

Can anyone solve this mystery?

Thanks.

1609523
 

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The release bearing part number is the same for all hydraulic 105 clutches. 1300 - 2000. I have a new one that I can measure if that would help.
 

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Did you get a new throw out bearing?

The Alfetta tob's are a smaller hole. But other then that they look the same.
 

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The ID of my spare release bearing is 31 mm.
 

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Discussion Starter #5 (Edited)
Mine measured same Ed...thanks for confirmation.

Yeah I have a new throw out bearing. It’s the standard Sachs 105 bearing from Classic Alfa. Fits just fine over the tube of my old bell housing, but doesn’t fit over the tube of my newly sourced bell housing. The tube in that “new” housing measures about 1/16 inch larger diameter than my old one.

It just concerns me that this “new” bell housing might be incorrect in some way, but I’ve measured it seven ways from Sunday and mounted it on my empty block and it mates up fine.

Thus the mystery of why/how that tube got in there and what it came from. Maybe someone just mistakenly put an Alfetta tube in there? Any other possibilities? I think Alfetta and 105 gearboxes were only hydraulic clutch boxes from 1969-1989, so seems only possibilities unless there is a variation of this tube within the 105 series.

Weird.
 

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My memory is of a straight tube of constant diameter whereas yours is waisted but it is larger where it fits in the bell housing. I wonder if the bellhousing has been repaired by boring that hole for a specially made tube?
 

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The more I look at that picture the more I think that the tube is weird. The wall thickness looks looks bigger than I remember.
 

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Discussion Starter #8
Well, I’ll get it figured out in the next few days and report back what I find.
 

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Maybe a PO could not purchase the genuine/correct release bearing ... and had a lathe. Is the clutch fork modified?

Also what do the mechanical clutch bellhousings look like?
Pete
 

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Discussion Starter #10
Mystery solved...well sort of...still not sure the PO's motivation, but more on that below. And if anyone knows if I can get the bell housing oil seal at a normal parts store in the US, let me know, as I will need to replace it again.

So I did some investigation and pressed out the T/O bearing sleeve. Small victory here, because often when I investigate things using my press, I break them. At any rate, the mystery sleeve is definitely different (pics below). It's longer and, as noted at the top of this thread, larger diameter (31.31mm vs. 31.01mm) because it is thicker metal.

So why did the PO do this? No clue, but as I went to press it out tonight and looked at it closely, I saw a thin residue of sealer which should have tipped me off. And when I pressed it out, saw all the residue...so it was definitely not OEM. The bell housing came from someone on the BB who races, so maybe there is some advantage to an Alfetta T/O bearing for racing? Who knows. Mystery solved at least.

Some things worth noting for posterity:
  • The correct 105 sleeve on mine is different than what's on later 105 models. Guessing maybe when Alfa changed to the screw-in reverse switch that maybe they changed to a different T/O sleeve...but that's just conjecture. What I do know is that mine pictured below is different than the one pictured here from an S4 rebuild. How to tell the difference? Well, the earlier ones like mine are flared at the bottom and have a collar like pictured below.
  • These earlier 105 sleeves press out from inside the bell housing (see pic below), which is different than the later model ones that press out from the back (gearbox facing side) of the bellhousing as noted in the S4 build thread above.
Ed - yep, great eye...you nailed it on the wall thickness.

Pete - to your questions, mechanical clutch bell housing does not have a sleeve at all...the T/O bearing sits in an arm attached to the bell housing itself which also attaches to the clutch cable. I don't have the original clutch fork, so no clues to be had there.

Incorrect sleeve is on the left:
1609600



Note how incorrect sleeve is thicker:
1609601


Earlier 105 sleeves have this collar (oil seal sits in it) and are also flared at the bottom as seen in the first pic above:
1609602


Earlier 105 sleeve presses out from inside the bellhousing:
1609603
 

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My guess is that your gearbox was probably used in a conversion to a vehicle other than Alfa, particularly as the length of sleeve is not stock. Before my Alfa days I modified a 105 box to fit in a Ford, replacing the original 4 speed unit - a popular upgrade in the days when 5-speeds were uncommon novelties. In my conversion, the greatest difficulty I had was related to the T/O bearing which had to fit a Ford clutch, yet operate off Alfa fork etc. The adjustment tolerances ended up being so tight that, on one occasion, I overheated and blew up the T/O bearing as it couldn't ever fully disengage!
 

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Richard Jemison
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With the Alfa hydraulic clutch design the TOB is always in contact with the clutch fingers. The spring in the MC keeps slack out of the rod/lever/TOB assembly.
 
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