Huh. How about where the trunnion attaches to the differential? If things were relocated by welding, you’re going to want to make sure everything is squared up. Those dimensions are critical.
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Yes, everything looks good. It was done in a jig specifically for this conversion, so I'd have to guess it was done right, but I have to wonder. Perhaps I got something wonky ( I was working kinda fast to get everything together) The trailing arms look like they are identical and can go on either side, either way. The A frame assembly can only go one way. I suppose its possible that something slipped when it was being welded, but I need to measure things out and make sure something is off before calling the guy who did the work.
Will'59 Alfa Romeo 101.02 Giulietta Sprint
'69 Alfa Romeo 105.51 1750 GTV (R.I.P)
'69 Datsun 2000 roadster Vintage race car
'88 BMW M3Comment
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I must have missed something - did you swap in a 105 rear end and trunnion? How different are they?
As Nader says, misalignment there can mess up the way it tracks through corners and make it a handful. What say the gurus of AlfaBB about this?Comment
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A lonely Sprint
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Its a 105 rear end (4.1 ratio, 54% lockup LSD) modified to fit a 101. There is no T shaped trunnion, but an A shaped arm that locates the whole thing. It looks like this...
The upper point of the A mounts to the differential, the bottom attaches to the body.
I'd think the trailing arms would be more prone to causing things to sit crooked, but they look identical, and are both the same length. Perhaps its something stupid that I'm over looking, but I'm not sure.
Will'59 Alfa Romeo 101.02 Giulietta Sprint
'69 Alfa Romeo 105.51 1750 GTV (R.I.P)
'69 Datsun 2000 roadster Vintage race car
'88 BMW M3Comment
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So the A-frame mounts to OE brackets on the body? Were they moved or bent at some point? If that's all stock and the bushings (and shims?) are right, it's in the diff mount...or the trailing arm bushing as you said. hmm..Comment
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If anyone is tuning in and hasn't seen one, this is the 105 rear axle "trunnion." It's a smart system - that lightweight aluminum arm (OEM is steel) serves as the short trailing arm and the lateral locator for the rear axle assembly. Long trailing arms mount to the bottom of the tubes and carry the spring perches. So the axle is perfectly located and can't rotate or tramp. It's an evolution of the design in the 750/101 rear suspension.
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Oh, I didn't know you were adapting a 105 axle/diff to a 101 chassis.
If you're confident that the trailing arms and A-arm mounts to the body are square, then the differential mounting adapter would be suspect. Looks like you needed a ball mount on top of the diff. How was that done?
If you were going through that much trouble, this would have been a good time to ditch all that and go with other locating systems like a Watts, Panhard, or my favorite, the sliding block.
These systems lower the rear roll center, allowing the car to corner flatter. My adaptation of the sliding block deletes the bar going across the chassis where the trunnion bar would have lived. Instead, I have a titanium bar reaching from the diff to the rear bulkhead sheetmetal (reinforced, of course) to prevent differential tilt fore and aft, while still allowing it to pivot and oscillate with suspension movements.
'91 325iComment
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Wow, that's pretty slick! I read that back in the day, the mechanics would grease that slide up before every race. Were you the guy that did the design with Delrin blocks?Comment
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That would be me. I have Delrin surfaces lining the yoke, and used Nylatron for the block. I learned a lot about UHMW plastics in my research for that project! (Most of which I've forgotten by now).'91 325iComment
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Nice!Comment
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A number of years ago, there was a Sprint race car running with us in SOVREN, red with yellow accents, that had a sliding block rear end. This was early in my vintage racing, before I had one, didn't know what it was, and I used to follow this thing on the race track, staring at that yoke peeking out from under the rear apron. What was that?! Mesmerizing to me, and definitely an inspiration for my own later adaptation.'91 325iComment
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Sliding blocks are cool, but not if you actually want to use the car on the street. I didn't want to change anything on the body, just adapt a rear end that had a good LSD and better gear ratios (because a 4.56 open with 160 hp is going to be useless) Larry Jr from Alfa Parts Exchange did the work. Really all that was done was the trunion mount was removed, and the correct tabs welded onto the housings. All the stock hardware just bolts on.
As far as I know, there is nothing bent. It was all straight when I pulled the old rear end off, and was still straight when I repainted everything. There were some big washers that came with the poly bushings I installed, but there was no way in hell the parts were going to fit with the washers in place. I was in a hurry to get the car back on the ground so I could move it to a safer location as the fires got close to St Helena. I do need to go back and look more closely at everything.
Will'59 Alfa Romeo 101.02 Giulietta Sprint
'69 Alfa Romeo 105.51 1750 GTV (R.I.P)
'69 Datsun 2000 roadster Vintage race car
'88 BMW M3Comment
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Did they ever make a Sprint in this green? It's sorta cool.
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