Have you checked your bearings on the diff cup?
Also what is the condition of your motor mount, is it locking in properly are you getting any movement if you try to rock the can side to side or up and down?
If you install the driveline without the pinion in place and spin the wheels is there any binding or clicking?
If you spin the motor with it not in touch with the spur is it smooth, give it half throttle and listen for any noises?
Are your driveshafts straight?
If you just run the pinion and spur gear together in your fingers do they mesh nicely, or do they catch at any point? Do this with them not attached to the car just run the spur around the pinion or the pinion round the spur?
Also make sure that the grub screw isn't hitting the spur gear, when you mount it all up push the spur back and forth and make sure it can't contact the grub screw.
There should always be a little bit of slack between the spur and pinion, I like to rock the spur gear back and forth, you can do this from underneath the chassis. You should hear a tiny knocking noise when you rock it, do this the whole way round the gear. Rock it, spin it a little, rock it, spin it a little more, rock it and so on, if you have a spot that you don't hear the knocking, you'll have to loosen the mesh I tiny bit. Then test it again.
Thanks everyone for the feedback. Going to try and reply in order to get some help!
The bearings have been replaced with Fast Eddy bearings on the diff so they are good to go, checked and running true and free.
No clicking or anything with the pinion out of play. Everything seems smooth. The driveshafts have a little wobble in them but nothing offensive.
The two gears mesh nicely but I think I discovered an issue, will post pics below.
Grub screw is recessed below the pinion and doesn't contact the spur gear. It's now also stripped a bit, so I have not figure out how to get that out... sigh.
So doing your test, but out of the car (I held the spur in the aluminum HR diff center, so the spur/pinion/motor are like a unit outside of the truck, there seems to be varying mesh as I rotate it. I noticed this somewhat with it in the vehicle but once removed it was more obvious. Pics below.
Man. I have never seen a spur gear so destroyed.
@Notorious J will like this one.
Keep in mind your pinion may be damaged from destroying the 2nd spur gear.
I had replaced the pinion once already for that reason. I have the 20T pinion to try and check with next to see how that does in terms of alignment.
Damn, just nom noming that spur gear like the cookie monster. Seems like something is moving...here are some possibilities: motor mount has play on the slider, diff bearings are blown/extremely worn down, maybe the plastic that holds the diff bearings down from the top is/are melted or worn allowing the diff to move, the center piece to the diff not fully tightened down, loose screws underneath that go to the actual diff mounting brackets, loose screws underneath to the motor mount bracket, waaay too tight of gear mesh, blown motor bearings.
I would put it on a stand and run it slowly, gradually increasing speed, and see if I can see what's happening.
Edit: One more thing, I would put your diff in your aftermarket mount, slide the motor back off of the spur, remove your two center driveshafts, tighten down the top cover as your normally would, and make sure your diff spins freely in the mount. I have and aftermarket diff mount/motor mount, and I did have to do a fair amount of filing in a few spots to make it spin freely....I wouldn't think it would be enough to brake off spur teeth, but who knows if it's completely bound up.
Good call - I did notice the screws that mount axially to the motor that hold it to the motor bracket slider thing, were a little loose. I ended up removing them and replacing with M4 stainless torx plus fasteners I have on hand, all tight now, but still some run-out in terms of mesh.
When I put it on a stand and run it slowly/25% throttle things seem sane, but when I give it the beans, it grinds or makes a noise I do not think is ideal.
Diff spins very well and is held fairly tight in the aftermarket diff mount. The bearing movement in the aftermarket diff mount is next to zero and also spins true and free.
Ouch. Looks like your spur gear has been doing some meth.
Something is moving way more than it should - definitely check for bad center diff bearings and that the top cover is fully seated (not just on) so that there is no up/down play on the center diff.
I agree. And, I think I may be on to something.
I don't know if its a flaw in the spur gear or if the motor shaft is bent or motor bearings are toast, but check this out:
With the "16T" upside down (for indexing reference), check out the tooth gap between mesh:
Notice that there is a decent air-gap between the pinion and spur. Notice too that the pinion teeth seem a little more rounded than I would expect? Perhaps this is from some iteration of things being loose/out of whack, not sure. Now, not moving the motor at all, I rotate the pinion gear about 180 degrees:
The mesh gap is much tighter. I think this is my issue. However, I can't tell what's causing it - but as someone mentioned above, the mesh is moving as it rotates. It seems to be in 180 deg phase to the pinion, so more likely the pinion than the spur gear side as I doubt the spur gear moves in and out of
spec every like 20 degrees of rotation.
By the way, the images above in this post, the differential is fully held by the opposite side bearing bracket. The near (camera) side attahes to the chassis but the other side bottom is part of the motor bracket assembly and so the lid is clamping the diff in place relatively well/tight so the drift/gap movement is not the diff moving around as I am holding it firmly in place.
I need to remove a stripped grub screw (any pointers other than drilling?) and running the motor w/o the pinion and seeing if the motor shaft/bearings are the culprit or what.
Thanks for the replies all - have a 3 year old dying to play again and a 2 week old freshy kiddo, so I've been meaning to reply but haven't had the ability. Appreciate the feedback.
