416C loader slow to lift.

I have a 416C s/n 5yn6433 , the loader has gotten slower while lifting. From the lower point its ok , it seems like when the bucket auto level starts to work it slows the lift cycle. The tilt roll back works fine . I put a bucket of material up in the air while taking a break and it never came down a bit , so I think my internal cylinder seals are ok. I wonder if the valve is out of adjustment or needs to be rebuilt , tractor has about 4400 hrs. I have had a few people tell me to trade it off , but it really has been trouble free for the most part , I usually spend about 1000$ a year on it replacing worn hoses park brake , things of that nature. Is there a procedure to check the linkage for the loader valve. It does have the multipurpose bucket on it so it has an extra valve as well. The backhoe operates fine as well. And the hydro filter was changed at 4000 plus hrs.