Ferrari Mailing List: Re: [NFC] Ok so it?s done (Matt Boyd)

[Peter Rychel (dino308gt4]

You mean the driveshaft is turning, but it will not actually move the car? That is weird and doesn’t make sense. There’s not much to a differential. You have two gears at 90 degrees to each other that are completely meshed. The differential gears are also completely meshed. Unless there’s some sort of sprag clutch mechanism thrown in there, it should be rotating both ways…

When I’m diagnosing pumping issues with the tanker trucks I work on, there are those with a physical drive shaft connected to both the pump and transmission. They’re connected 99% of the time to a “hot shift PTO” which is an air operated mechanism where you DON’T need to press the clutch pedal to engage. You just flip an air switch and voila, the PTO is engaged. There are times when the air cylinder, or air supply, or the clutch fork is damaged that the PTO gives the impression that it’s fully engaged when it’s not. I’ll go under the truck and CAREFULLY grab the shaft with my hands while it’s turning (yes, yes, completely disregarding the safety labels not grabbing moving parts. Hey, I’m a professional, I know what I’m doing! Ha!). When the PTO has failed in a way, I can actually stop the shaft from turning with my hands! I’ll declared it’s f’d at that point. Thing is, there is enough drag in the system from the various parts that will make the shaft turn, almost at full speed without it being engaged.

Consider my above statements about getting under running vehicles and moving parts as a disclaimer about injuring yourself, but it’s one thing to check. I’ll wash my hands off of this from this point onwards! Ha! 

Let us know what you find out…

Peter

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From: Ferrari <ferrari-bounces+dino308gt4=hotmail.com [at] ferrarilist.com> on behalf of George <ygpz4re [at] hotmail.com>
Sent: Tuesday, November 1, 2022 4:19:44 AM
To: PeterGT4 <dino308gt4 [at] hotmail.com>
Cc: The FerrariList <ferrari [at] ferrarilist.com>
Subject: Re: [Ferrari] [NFC] Ok so it?s done (Matt Boyd)

 

Peter - excellent edit, wish I'd thought of that...  But, if "shaft or gear could be split or sheared", would the driveshaft still turn in reverse?  That it does seems to imply, as Matt pointed out, that the gearbox is working, but something in the diff is not....  But I'm no expert by any stretch....

Matt - other NFC topics, and why I suggested trading "helps":

Beetle - reverse lights don't work.  Circuit is simple - power from coil, through a fuse, through the reverse light switch, out to the bulbs.  Fuse is good, bulbs are good.  So either there's a break in a wire somewhere (and I'd need that extra set of hands to help ohm out each wire) or the switch needs replacing (probably most likely).

"Old Blue" - back on the 8th, I drove it over to a "downtown" event in Gordonsville, VA.  Missed my location so had to turn around.  In the process of turning around, my forearm hit the horn button (which protrudes quite a bit, as you'll recall) and the horn blew - and blew and blew and blew, and did not STOP blowing!  Long story short, pulled horn feed wires from the horn relay just to shut them up.  So I'll need to remove that horn/trafficator "thingy" from the center of the steering wheel and see if there's something obviously wrong in there.  I'm hoping to be able to find it and correct it, because I understand those "thingy's" are NOT CHEAP these days.....  (side benefit is, with that "thingy" out, I can shift the wheel on the splined shaft and straighten it up a bit.)

gp

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From: Peter Rychel <dino308gt4 [at] hotmail.com>
To: Matt Boyd <ferrari308driver [at] gmail.com>
Cc: The FerrariList <ferrari [at] ferrarilist.com>
Subject: Re: [Ferrari] [NFC] Ok so it?s done (Matt Boyd)

I edited the subject line so now it?s legit (to talk about non-Ferrari content ?)

In nearly every transmission, reverse runs on a third shaft (main gears run on main and lay). The shaft or gear could be split or sheared.

Peter