IH 986 Clutch/input shaft

I am working on 986 clutch.Here s the issue.I installed a new disc and pressure plate.Set the clutch adjustments to service manual specs. After 10 Hours you can t shift it without grinding high low or rev. Adjusted linkage 4 differnt ways, nothing helps.First clutch/Allied Installed second clutch. HY-Cap Same thing.You can only shift without grinding after you stop and first 2-3 shifts upon start up. Has anyone run into this before? The input shaft splines are worn. Could this cause the disc to hang and drag? Thanks Ben

It sure can cause that disc to drag. Can't say that I have ever split a 66/86 series for clutch job where that IPTO spline wasn't badly worn.
Also be sure T/A dump valve and transmission brake are adjusted properly. Check cab mounts also.

Input shaft splines can be a direct cause of this failure mode. A worn disk patterns the splines with specific indentations and edges to them. as it wears toward failure, these become deeper and are sometimes deep enough to prevent the new disk from releasing at all. The new disk will not have contact in the same spots. as it heats in use these contact spots can move such that it drags (ever more seriously) If the wear is present, but not more than a.001" to maybe .0025" (compared to the unworn spline, I think it could be dressed out of the shaft. Doing this might be more time consuming and costly than replacing the shaft with good used (have it measured to be certain that you are buying a substantially better shaft!) But it could be acceptable. Splitting a big horse is not a casual task, so choices are made to avoid it.
Also check that PTO/hydro drive spline. Jim

Did you have the flywheel remachined to insure that you have a true surface with the correct step?

A worn out transmission brake will also not be very effective at slowing the transmission.

Yes the fylwheel has been machined to the correct step(1.400) and double checked.Adjust ments are correct and trans brake is new. Check out 986 on fixya.com same thing. 6 clutches,2 flywheels, cab mounts,brake,and new linkage.

Do the finger lay parallel to pressure plate. What is the thickness of the clutch disc. Some discs are thicker than new ones which will cause fingers to be tilted toward flywheel. Some rebuilt pressure plates have been machined too much and fingers tilt away from flywheel. Are all fingers the same, I always check with feeler gauge between finger and throwout bearing after tractor is assembled and in at least three different positions by turning engine. They don't always check out the same in all positions due to misalignment of clutch release brg on carrier. Also, did you assemble tractor with clutch bolted to flywheel or do it the right way and hang pressure plate on input shafts and bolt on from underneath to prevent damage to pressure plate or disc. Next thing, what disc, four pad, six pad. The six pads are not as good at releasing as the four pad. On the four pad, the trick is to bend the wings pads are on so outside edge of pad is a few thousanths of an inch from touching when laying flat on pressure plate. This allows pad to spring away from flywheel for better release. This was something IH came up with after having a tough time getting good clutch release on new 7 and 806 tractors and then again on later series. Also, lube the splines, preferably with molykote spline lube. Hey, I have been there, many times.

Did mine, if the trans brake is not set properly the trans continues to rotate causing grinding. Mine will not shift smoothly unless she is rolling smoothly. Nature of the beast.

Not sure of the pad demention but both disc s are the same thickness. Did the first one with a pilot tool and the second one with the bolt after rolling together method. Fingers on second clutch stand higher. Fingers are even. Also I have 3/4in to 1in travel on the throught out bearing and when you drive the tractor you can feel the clutch release in the top 1/3 of the pedal travel. Trans brake set on the tight side.

I drove a 786 this afternoon and it shifted like a dream. loose on the free travel tight on the brake.

I drove a 786 today that shifts perfect. Loose on the free travel and tight on the brake.