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Discussion Starter · #1 ·
Hi,

Have a spare gearbox for a 1995 164 3.0 24v, with an inch hole in the diff casing where the diff blew.

Understand the gearbox itself was great before the diff let go, so wondering if a Q2 limited slip diff could be purchased to replace it and the casing repaired. Have heard some Q2 gear grinding required to get the speedometer to work properly with it.

Any advice?
 

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Unfortunately your gear case is destroyed. No practical way to repair it. I had the same happen to me twice.
Charles
 

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2015 Chevy (Holden) SS, 1989 Milano (Shankle Sport), 1991 164S
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Well, couldn't the case hole be welded back up, then the Q2 diff installed, or, was the case additionally damaged?

In your failures, was it the spider gear shaft moving (the retention pin falling out) and impacting the inside of the case, assuming the whole geartrain stops suddenly?

I wouldn't want this to happen to our 94LS. It's too bad that diff case cannot be removed separately, or at least just the inner parts out one side so that one could check the spider gear shaft retention.

Actually, the diff housing, and the inner diff gears, can be removed from the tranny case, but I don't think there is enough room with the engine in the car.

Is that true?
 

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Discussion Starter · #4 ·
Hi,

The casing was punched through at very low speed. The pinion on the diff had broken and dropped down in the diff, jamming it. The garage crew force pushed it to get it on a ramp and that was when the casing went. A significant hole but don't think at a structural point, hence thought it could be repaired.
In worst case, have possible access to a second 24v box with other issues to steal the diff casing from that. Can these just be swapped over?

Thanks for the help.
 

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When the diff pin backs out it impacts the center of the bellhousing not the diff case. I seriously doubt the bellhousing could be relied upon ever again, even with serious cast aluminum welding skills. If you have access to a whole nother trans, just put a Q2 in it. A later model trans is supposed to be engineered stouter so that would be a preferred gearbox to have anyway. If it has other issues, than think about having it repaired. If it is in one piece it is already an improvement over what you have. I have pics of the type of damage resulting from this failure in threads I have posted regarding the issue and you will be able to see what I am talking about.

edit: image added

Was yours inpacted differently?
Charles
 

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Discussion Starter · #6 ·
When the diff pin backs out it impacts the center of the bellhousing not the diff case. I seriously doubt the bellhousing could be relied upon ever again, even with serious cast aluminum welding skills. If you have access to a whole nother trans, just put a Q2 in it. A later model trans is supposed to be engineered stouter so that would be a preferred gearbox to have anyway. If it has other issues, than think about having it repaired. If it is in one piece it is already an improvement over what you have. I have pics of the type of damage resulting from this failure in threads I have posted regarding the issue and you will be able to see what I am talking about.

edit: image added

Was yours inpacted differently?
Charles
Thanks, Charles.

Because mine went at walking pace while the mechanics were pushing it the hole in mine is, I think, in the diff housing. Will take a pic over the weekend.

Cheers.
 

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While evidently Alfa/Fiat did stiffen up and reinforce the 164 diff casings for the later models, it does seem that the main problem is not distortion of the casing but the spider gear shaft retention roll pin (I'm assuming it is a roll pin) backing out, and letting the shaft drift to one side, thus releasing a spider gear and also allowing the shaft to hit somewhere in the bellhousing.


Don't know if there is a service bulletin or improved retention method for that problem. Sounds like, though, that if the tranny is pulled to replace a clutch or whatever, the diff should be inspected for roll pin migration.

Maybe a second retention pin should be installed on the other side to add redundancy.
 

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I think it will really have to come apart to inspect the insides of the case, diff and bellhousing for damage. May not be impossible to fix. I have a spare diff cover if you need one and various other trans parts. Just let me know if you need something. Trans parts are generally hard to come by, but I have many items loose in a box.
Charles
 

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I did notice on the Fiat eper parts program that the diff rear casing is not shown or listed, suggesting that it is sold with a bell housing, probably matched and line bored, similar to cam clamps and heads being matched and line bored.

This suggests that care should be taken to match things up as best as one could.
 

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I did notice on the Fiat eper parts program that the diff rear casing is not shown or listed, suggesting that it is sold with a bell housing, probably matched and line bored, similar to cam clamps and heads being matched and line bored.

This suggests that care should be taken to match things up as best as one could.
I'm sure you are right, good point.
Charles
 
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