Ferrari 355 Gearbox Adjustment Tool AV2731 or 95972731

Did you check the workshop manual? I'm not familiar with the 355, but for my vintage Ferrari the workshop manual has detailed information on how to adjust the linkage to the transaxle.

 

Ian- Maranello Classic Parts has it listed.

Part Search Results | Maranello Classic Parts (ferrariparts.co.uk)

 

I don't think that it is an adjustment issue. If you look in the repair manual, you can see that tool AM 105153 puts pressure on the shift rod detent springs so that the shift forks can be centered on the operating sleeves. This tool can be replicated by machining a piece of plate to load the detent springs.
The other tool AV 2731 lines up and sets the position of the control forks on the shift rods. This can also be replicated by machining a piece of steel to just fit in the control fork and make sure that all four forks line up, you could also eyeball the adjustment and set it up with a small straight edge.

Both of these settings are for fine adjustments of the gearbox, and would probably not cause your issue with the gearbox jumping out of gear.

When you move the lever side to side in neutral, does it move freely or up/down as you come across the gates? Is the gap between the shift lever and end of the gate the same in 1st, 2nd, 3rd, 4th, 5th, 6th?if so the adjustment is ok.

The gearbox is jumping out of gear due to wear/damage of the operating sleeve/sychronizing teeth on 2nd gear, or incorrect clearances (excessive end play/incorrect assembly of the gearbox shafts. Even if it was due to excessive clearances/incorrect assembly, now that it has been clashing and jumping out of gear for a while, the 1/2 operating sleeve and 2nd gear will be damaged and need to be replaced.

The gearbox needs to come out, have the shift/side cover removed and the cause of the fault diagnosed, and then a full disassembly and repair performed.

 

The adjustment in question require removal of trans and rear plate. There is no external access.

I have the tools but I could assemble and adjust the trans just as well without, it just takes an extra half hour. Also those tools do not really set depth of engagement of the shift forks which could be your problem. There is a chance it can be fixed without more parts but quit driving it yesterday and get it fixed by someone with a clue. That is not the current guy. In my opinion the 355 trans is the easiest of any Ferrari transaxle that requires internal adjustment with or without the special tools.

Nothing you are experiencing can be fixed without trans removal. Quit driving it now, its just getting more expensive.

 

355 Gearboxes are very complex and getting the adjustment correct is a multi step process. Rifledriver is correct in that it can be done without the specific special tools but the most important part is the tech doing the job. It is a MUST that they understand fully what and where to adjust.
The holes in the tool pictured are most important. I make my own tools for 308s, TRs, 355s, & others.
You will need to remove the gearbox and have some level of disassembly to get back in and have it set up properly. There are things that can be done that are not described in the manual that makes them shift better. Just find a tech that is very experienced with these gearboxes. This is not a DIY job.

 

Shift rod detent spring is #23
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Part of the reason for that is to Ferrari their dealers are a profit center. The tools are very expensive and many are just shipped automatically and added to your parts bill. As shop foreman of a very large store I had many made by a prototype machinist in Silicone Valley who didn't work cheap. He cost me a small percentage what the often garbage tools from the factory cost. As an example Ferrari forced us to buy an electronic torque wrench for $10,000 US. A comparable wrench from Snap On was $200. Now you know one of the reasons the dealer needs to charge so much.

 

Ian did the box work perfect after the rebuild or was it always not quite right? I’m a diy guy but fixed and rebuilt a number of 348 and 355 boxes. My 1st one just from the parts diagram. I don’t have any oem special tools successfully doing it by eye and with some home made tools. I have seen some strange damage and weird things in these boxes like man….how did that happen or that was never going to work. One of the great things about a manual box is the 100% mechanical nature. There are no surprises in there. Everything has a purpose and a right position fitting together like a puzzle that moves. So far all the problems I have seen almost jump out at you once the box is open but everything must be checked in there, clearances everything.

 

I remember our local dealer showed us that wrench...back in like 2002 or so? I wonder if they ever even used it...

 

Does anyone know how to use this AV2731 tool? Is it supposes to be precisely positioning something, similar to the tool for 360/430 F1 actuator positoining? Is it like being put on top of the gearbox and then some internal part is fit into the tool's concave?

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Are you talking about 2731? It aligns the selector forks. I have never used one and have done many gear boxes without it. Ferrari has a similar tool to do the same job on most of the transmissions. The notch in the selector is as I recall 16mm. It is the same diameter as a 308 water pump shaft. In the TR for example I have a piece of water pump shaft cut to the correct length. From memory I think the 355 selectors are not nicely lined up so seems to me I used a combination of things like a machinists rule water pump shaft etc. They are not in some odd order, they just need to be lined up with each other. Also the shafts need to be immobilized to perform that adjustment and the shift fork adjustment. That is what 106153 does. It is quite simple because on 355 they did something very smart. The selectors and the shift forks are adjusted via 2 pointed allen screws. They screw into a pointed hole in the selector shaft at a slightly different spacing. Let one off a little and tighten the other a little and it moves the fork on the shaft one way. Reverse the process and it adjusts the other way. Once you understand what needs to be done and try it you'll see how simple it is. Those factory tools make it easier to do, they do not make it possible.

Looking at the pictures again I am sure 2731 can be done with a piece of round stock like a cut down 308 water pump shaft. You will have to cobble up something that can do the job of 106153 but I think a piece of flat stock and some stand offs bolted to the case can do that.

And I suspect 2731 is bolted down. I see a hole in it where it straddles a boss on the case. But maybe not. Its exact position is not critical, keeping the selectors in line is.

I am betting youll see dimension D is 16mm.

 

Thank you so much for the explanation Rifledriver,
If I understand it correctly, the only measurement that matters or need precision on this tool, is the notch's width and depth and length,
i.e. D, R, H, and maybe E.
Am I understanding it correctly? Me and Qavion are trying to reproduce this tool.

 

I was right and wrong. I just measured a water pump shaft derived tool. It is 15mm and not as I remembered 16.

So looking at your latest picture I understand the tool a little better. It is 2 pieces. Did not see that before.

D needs to fit with some small interference fit in the selectors.
The notch H needs to fit around a selector turned sideways.
And I drops into the other selectors.

P only provides clearance for an allen socket to get to the adjusting screws for the selectors. And in fact it would work just as well without the second part.

As I have said this make it easier but it can be done with as good a degree of accuracy without it.

If you happen to have a hunk of steel and a milling machine handy it would be easy to make one.

The selector forks need to line up so the selector bell cranks # 1,2,3,4 line up so # 10 can swing all the way up and down without hitting any of the bell cranks.
That is the entire objective to this adjustment.

All 4 are adjusted at the same time. As for the adjustment screws (yes # 36), its quite easy. Once you are actually doing it you'll understand completely. They get moved back and forth via the screws until with just a little push it will go into all 4 at once. A tool compressing the spring detents must be in place during the adjustment process to hold shafts stationary.


As far as making this tool , I included a picture of what I made to do this job. This was done at the suggestion of one of the technical guys at Ferrari. In his own words "It works just as well as our special tool. The angle ground at the end same as on diagram.

By the way, the only internal difference between an F1 and a manual transmission on 355 are pieces 32,33,34,10, 35. It was found with the hydraulic shifting they were breaking. I think in later gearboxes they were all the same.
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I just reread part of the thread. Are you having problems with it jumping out of gear? Or ?

That would be a poorly adjusted shift fork, a worn shift fork and or slider or a worn out gear and slider.