348 Won't change gears

Worn clutch my first guess. Failing diaphragm or failed syncromesh.

 

With car off put in gear ..then depress.clutch and try starting ..does car move forward ..if so your clutch is not disengaging

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It's the clutch

 

If you want to check if the bearing is not working well, start the engine, and with an ear near the pumpkin, ask someone to depress the clutch pedal: if a metallic whining noise appears.....worn bearing. A bad flange of the throwout bearing normally leaks liquid if broken and causes a massive fluid leak.
The bearing, once activated by the oedal, pushes the "fingers" of a diaphragm and disengages the clutch plate(s). Or there is something shot that wines or leaks;fluid from the small window under the pumpkin or the diaphragm of the clutch is not working well or the clutch disk is worn. Diaphragm and clutch disk(s) are normally sold as a new kit.
Once disassembled the pumpkin you (or your mechanic) will easily find out.
Did you try to give a throttle blip from standing still before trying to insert the first gear?

 

Perhaps the clutch does not fully disengage but the residual "bite" is not enough to move the car. Malfunctioning throw out assembly would either leak fluid or make noise, it would not cause problem like what you describe. The problem you are having could be due to a radial crack in the clutch diaphragm. If the diaphragm is good, you would feel a "peak" in the pressure you apply to the clutch pedal early in its travel and it wold then go down a bit easier over the rest of the travel. If the diaphragm is cracked, you usually do not have the "peak" but the clutch pedal gets somewhat heavier and heavier as you press it down.

In any case, get the clutch out as it is not possible to tell, based on the symptoms you are having, what the actual problem is.

 

It all starts with setup height. That's the clutch pack operational range. stuff effects the range...disc wear...broken fingers...failed T/O bearing. I can certainly be wrong. I'm just going by your post which isn't much data. I'm not there feeling what the car is doing. Sounds like You are just "at" the failure point.

 

I was just about to post to say I had the exact same symptoms and it was broken fingers on the diaphragm spring.

Initially, I was tempted to just replace the spring but ended up replacing the whole clutch, new flywheel and regreasing the flywheel (I'd previously replaced the slave with a Hills one). After pricing up new friction plates and the cost to recondition the flywheel and have it all balanced etc it seemed like the most sensible option.

Whole story below - hope it helps.

https://www.clubscuderia.co.uk/forum/index.php?threads/348-diy-restoration.45388/page-137#post-848334

 

You may be able to have the broken diaphragm spring locally replaced, see 348 clutch removal | Page 4 | FerrariChat.

Ernie, did the new diaphragm spring you got in Long Beach work well?

 

Broken fingers like that would cause the pedal to feel differently.
I also don't believe in rebuilding the pressure plate. Just buy a new clutch pack.

 

I used the same place that Ernie did for a friend of mine who had a 348 at the time. He said his clutch felt better with the new spring than the old one (before the failure of course).