MTFCA Forum

The instructions state to grind down the woodruff key so the top is only 3/4 inch long. This also removes a chunk of the key that fits in the slot in the drive shaft. This is so the key does not rub on the face of the bearing itself. It would appear that grinding off that much of the key means that there is less surface area between the key and the drive shaft, which holds the pinion gear in place. In the picture I have a key where I left 7/8 inch of key and when I install this key there is still space between the key and the face of the bearing, so the key should not rub on the bearing.

Is there a reason why the key is suppose to be only 3/4 inch long? Would the longer key be acceptable?

Dave, getting ready to do the same thing soon...
The way I understand it is the key needs to be shortened so the gear will tighten down on the taper of the shaft, and still put some preload on the bearings.
Also the taper holds the gear tight along with the key.
I have to dig up a good shaft as my nut was not tight from before and the taper is worn. Probably what led to the pinion gear loosing a tooth.

If the Woodruff key is too long it will stick out past the pinion gear and hit/interfere with the bearing. Steps 4 and 5 of the installation instructions say to make sure that the key does not protrude past the pinion gear.

4)Refer to Fig.1 and modify the Woodruff key by grinding or filing one end off until the key matches the drawing. Unlike the original installation- it is important that the key must not protrude beyond the rear surface of the pinion gear.

5)Temporarily fit the Woodruff key to the taper and"try"fit the pinion gear to the shaft to make certain that the key is not going to protrude behind the rear surface of the gear. See Fig.3. Remove the gear and key after final modification and fitting

If the Woodruff key is not sticking out past the rear surface of the pinion gear (or shims, adjustable modern pinion bearing) it will be fine.

I heard it from the best possible source that the adjustable version is for people who feel that they should have something to adjust.

I put my first one in this year
What i did was mate it up dry marked the ky removed the parts ground off 10 thousands more
No issues
The stock version the extra key lock the sleeve that basicaly all you need to removed
That simple

First, the disclaimer. I have never used one of the new improved pinion bearings, although I do think they are a good idea.
The original factory setup, the Woodruff key is supposed to extend slightly beyond the pinion gear for the inner bearing sleeve's notch to lock into and keep it from working or rotating on the drive shaft. As I understand it, the new improved bearing doesn't need or want this bit of an extension of the key as it would interfere with the new bearing and likely cause damage or failure.
I would not shorten the Woodruff key any more than necessary to give the new bearing the clearance it needs. But I had a T shear the Woodruff key (it was a fine looking new key when installed!) after only a couple thousand miles on the car. I suspect the key I had was defective since no other possible cause was found. But they do shear occasionally, and shouldn't be compromised by taking any more away than is needed for the new bearing.

Before you assemble the bearing setup on the drive shaft put the pinion gear on the drive shaft and tighten the nut down. Now take the nut back off. The gear should be tightly wedged on the drive. It should take a good whack on the back side of the gear with a brass hammer to get the gear off. This is extremely important otherwise the key can shear off if the pinion gear does not properly fit on the drive shaft

Stephen