Worn drive shaft couplers/splined sleeve

[SirFallalot]

Heya, I need some advice on clearances for fabbing up some parts to repair my 80s Antonio Carraro Tigre 2700.

TLDR : I think the engine-to-tranny shaft is too short (bad repair? looks welded) and the couplers wear out because they're only working with ~1cm (less when the tractor flexes). There's ~2cm of clearance between the shaft and the engine/tranny spindles when the tractor is level, I was thinking if I made the couplers 1cm longer this would be fixed, or if it was a strong spring that caused the problem.

Half a year ago it started making a baaad whine in top gear, we avoided it but it soon spread to all, upon inspection we found it was a worn spindle sleeve that couples a shaft between the engine and tranny.
My dad had one made for 100€, ouch, put it back together and it was cured. I wasn't around and he doesn't remember/didn't document much about it.
Yesterday I noticed it was overruning downhill, once at the bottom it wouldn't move cept in lowest gear, and I could hear the "metal autodestruction" noise.

I took it apart and the new coupler was destroyed. The coupler on the engine side is also worn but looks quite old.


This is how the shaft fits in with the couplers, two springs maintain tension on it to keep it centered.
I think the reasons the new part wore out much quicker this time is on the first repair my dad lost a spring, the one he fitted is longer and stronger, forcing the shaft to the opposite side, the spindle looks like it was only working with 1cm, and even less when the tractor flexes, one of the retaining circlips on the shaft was also not in place, letting the coupler be pushed even further.





When the tractor is level if I put the shaft against one of the spindles, there's 2cm of clearance on the other side. Sorry for the bad pics my jacks are broken and I couldn't drive it on top of anything.


Although it's straight, one end of the shaft looks different it looks like there's some welds on it, I'm worried it was damaged and repaired but made shorter, so the couplers don't have much to hold onto.




I'm blaming the stronger spring on one side and circlips out of place for the fast wear, but in preventing further damage, I was thinking to get both couplers done 1cm longer (they're currently 5cm). The spindle coming out of the tranny is showing signs of wear and I don't want to damage it further.
I'm not sure if what we paid for the coupler (100€) was good or bad, machinist said it was a "much stronger material" (not as strong as whatever the spindle is made of lol), hoping it's not double that now.
Photos in album

https://ibb.co/album/0CDHSf

 

[SirFallalot]

Hey all.

This has happened again. Unfortunately the machinist forgot to make the couplers longer. Unsure how many hours it lasted, running pto stuff doesn't appear cause damage, but I could hear the screechy noise in 3rd, so I just avoided that gear. Unfortunately, the slightly lower pitched screech it sometimes makes in 2nd appears to be the same.

Only one coupler is worn, so I will make it 1.5cm longer (I'm afraid if it's too long it'll just hit, or I won't be able to fit the shaft). The spline clearance was very tight too, so I'm unsure if they were moving freely. The other coupler looks as new.

Unfortunately newer, even used, tractors are increasingly expensive, and I have no idea how people are affording them. 8-10k for a 20yo 25hp tractors.... 30-40yo's are still going for 5-8k. New ones 15-20k. I'm at a loss here. The vineyard is starting to look more like an expensive hobby than a family tradition.

 

[Tinhack]

I think keeping them greased would extend the life of the couplers. I don't see any grease fittings, but it looks like there was grease in there at some point. The couplers should be softer than the splines, so I'd drill and tap them for fittings. Give them a squirt every few days of use. My only other suggestion would be to convert to U-joints but even those need maintenance too. Grease is your friend, don't be afraid to use it.