Hi all as i was driving the car on 3rd gear .. car shacked and kept rolling but no power on the wheels.. i stopped and thought it was a clutch failure.. Unfortunately after removing the gears cover i noticed that the bearing holding the big main shaft was broken and the shaft was not engaging .. after removal of the lower sprocket and removal of the clutch cover .. i noticed the shaft moved alot like the video.. any ideas the cause or if its normal.. before removing the sum of the gearbox to have a look
The main shaft (item 1 in post #2) is broken/sheared (probably just past where the bearing 11 mounts). The 108665 bearing having failed is a strong reason for causing the main shaft to fatigue fracture -- with the 108655 bearing not supporting the end of the main shaft, there is a huge alternating-stress bending moment put on the main shaft that is not there when the 108655 bearing is OK.
From an earlier carb 308 SPC, but has the same general main shaft structure: Image Unavailable, Please Login
I feel the pain....10 years ago I needed an intermediate gear and at that time it was 780 £. Now a mainshaft is 3420 £ + VAT...shipping, work. I hope it will not be needed.
Really couldn't have been anything else based on the large angle that you could so easily move the shaft end thru and how easily it rotated in your fingertips. How did the 108655 bearing fail? Did the roller cage break and all the rollers just moved together to one side, or was it a more catastrophic destruction? On 328, they decided things were a little iffy (even if the 108655 bearing was OK) and added another bearing on the transfer gear case side of the lower transfer gear. However, even doing that is a bit of a design challenge having so many bearings so close together on a single shaft -- requires holding really tight tolerances on all the parts so that any stresses, due to all parts being non-perfect to some degree, are acceptable.
Rebuilding a gearbox properly is about half the cost of rebuilding an engine. Which is to say it's $15K but I don't know of many gearboxes needing major work like this. So maybe Rifledriver or Tim can add their voices.
i never had a problem in the gearbox.. this just happened out of a sudden... only bearing failure that managed the main shaft to move and bam got destroyed
I will say this. Find a tech that knows a lot about Ferrari gearboxes. I have worked on many old gearboxes that have had previous work and the things I find that are just done wrong is crazy. I know it is because they just didn't know it needed to be addressed differently. I have found things installed backwards, shafts that need to be held in place that were not, gear spacing completely wrong, mixed parts from different years that don't fit correctly. I have found that just the set up can be wrong on the forks and fingers and it makes shifting not very nice. It may cost a little more, but find a knowledgeable transmission guy.
a new problem appeared now after removing the shaft the shafts are different one is 46mm and the new one is 47.2mm does anyone know if the mondial came with different ratios... as evrything else is the same in the shaft Image Unavailable, Please Login
There is a normal shaft and a CH shaft...for Switserland. https://www.eurospares.co.uk/Ferrari/Mondial/Mondial_3.0_QV_(1984)/PartDiagrams/023/Main_Shaft_Gears
There are a lot of V8 cars that have been parted out and shafts are low demand. Destroying gears in one way or the other is pretty common but not shafts. There are a lot of changes for different markets and different years but find the number for that shaft and start contacting the used parts guys. Ted Rutland when he was still alive parted out a lot of V8 cars. Hes gone but his company is still around and owned by Motion Products Inc. Pat runs the parts department, get him or Brian and see if they have one. Since shafts are low demand don't be afraid to make them a counter offer and tell them I told you to. They both know me well. They are pretty rugged transmissions and I have only ever had 2 apart that needed a lot so this might not hurt too bad. If any syncros get replaced lap them to the gear. It makes a huge difference especially if its a new syncro on a used gear.
If you consider all the 3.0 shafts I am very sure there is more than 2. They have been juggling ratios on those cars since 1975.
