cheapskate

Long story short; I had a transmission problem. I installed a 4.9fd this spring and have about 5k miles on it. I took it out to a local event, ran it really hard and noticed an "on power" whine noise while driving home. I pulled it apart the next day. I suspect the whine was coming from the diff bearings, they made a grumbling noise when spun by hand and the bearing to shim clearance was out of spec (.008 gap). I suspect that a diff bearing started to crap out and the clearance opened up, resulting in the whine when on power. I swapped new diff bearing onto the diff, which are silent, and order a new shim. I haven't noticed any other issues but there is some wear on the final drive. Does this look like a concerning amount of wear?

-Using mfg's recommended fluid
-Had correct amount of fluid
-Diff runout was .001 when fd was installed

Da1WiTsKiLz

If it were the FD I expect it to make noise at all times. I installed a final drive in a transmission that was so worn the identification marks were completely gone (do to a broken diff in a past transmission) and it made no noise at all. Did you check your other mainshaft and countershaft bearings?

cheapskate

I don't think the noise is coming from the fd, more concerned if I damaged it or not as I'd like to keep using it. I replaced all the bearings this spring with the exception of the diff bearings (which I just replaced). All the bearing still spin freely and quietly. I inspected it more today and took some better pictures. The one thing I noticed that doesn't seem right is that first gear, second gear, and everything between on the counter shaft is loose. I can wiggle first gear up and down roughly .008" and you can hear it moving around. Same with second gear. The synchro rings for first and second gear can be moved a lot with a finger. Is this normal!? I am going to take it apart tomorrow and inspect. Something between first and second gear either got smashed or maybe fourth and fifth need to be repressed on.

Any input is appreciated.

Ring gear wear:


Very small burrs forming on pinon:


Wear on pinon:


everything from second gear down is loose, can be moved up and down, especially the synchro rings:

theYBLEGAL

ROFL. I just had same issue

Look at my thread 'broken carbon coated synchros'.

I bet it was assembled without the distance washer that goes on the shaft first. Between the FD gear at base and 1st gear.

Edit, in pics it looks like the washer may have been there. There are 3 size thicknesses of washers, perhaps yours is too small.

Let me know!

turbonetics3597

did it make noise coasting in neutral thatd be diff bearings. depending on how much power and what your launches are like input shaft bearings are pretty common. i would assume it wouldnt be your fd because you replaced counter shaft and ring as a set and they look good. the nut on the input shafts like to come loose if not tack welded in place if it were that you should be able to see it in the case where the nut sits at the back of the case. use a paint marker and look at the wear pattern on the pinion and ring like setting a diff up make sure to do coast and accel will give you two different patterns. when i did mine the diff bearings were a little bitt thinner which i would have needed shims for so stayed with the oe ones in it

cheapskate

Thanks for the replies.

I measured all the synchro rings, gears, and double cone synchro and everything checked out. It was assembled with thrust washer on the countershaft. I pulled it apart yesterday and I didnt see anything concerning. The hubs, sliders, needle bearings, synchro rings, and synchro gears all looked good. I re assembled everything and measured clearances again. I have .005" between first gear and the thrust washer which is within the factory spec. However I can still wiggle first gear, second gear, synchro rings, and the hub. Is this normal!? It doesnt seem right...

The whine noise was only present when throttle was applied, it was non existent while coasting, clutch in or out. The lock nut on the counter shaft did not look like it slipped, the stake was still in the groove.

I have new diff shims and a counter shaft lock nut on the way. I cannot find anything else that measures out of spec or looks visibly damaged so I am going to put it back together and see if it still whines.

Please let me know if anyone has any other ideas.

Edit - I am using the offset inner race ball bearings for the diff which do not require the extra shims. I measured diff runout yesterday at .002".

turbonetics3597

dont quote me on this it was like 2 years ago i built mine but i believe gears press on and should not slide, not for sure but i remember they were a bitch coming off.