OK, let me see if I have this right:
The shims included in the Fun Projects pinion bearing kit adjust where the gear teeth mesh.
Shimming either under the ring gear or between the 3 thrust washers set the gear lash, that is the gap between the teeth.
The proper mesh should be even across the tooth as seen with marking paint or grease.
The proper lash should be .008 to .012 as measured with a dial or solder squished between the teeth.
Right now I have even mesh using the biggest shim, but huge lash. I was thinking of adding a couple shims between the thrust washer stack. to close it up.
On another note, I had all this set up nice before I realized I forgot to put in the little fiber washer between the axles to take care of that end play. Now the whole thing is messed up and I cannot get good gearlash, which is odd since I had it before. Adding the axle shim shouldn't change lash or mesh because the diff gears sit on the housing and would be the same even if I took out the axles. Serves me right for doing this when I'm on Owl shift.
With the original setup pinion depth is set by how much material is faced off the front of the drive shaft bushing. The depth of the pinion gear can affect the gear mesh clearance, which in turn can affect the gear backlash (two different things).
I suspect that you may not have enough pinion depth to achieve the proper clearance. Perhaps the drive shaft bushing is not pressed in all the way, or it needs to be faced off some. I compared a new bronze drive shaft bushing to an original Babbitt one and found the new ones are much thicker than the old ones (I don't remember by how much). Or perhaps you just need to shim behind the thrust washer on the RH side, which is not uncommon. If so you may have to mill the thrust washer on the LH side to allow proper fitting of the differential between the thrust washers.
.008" - .012" clearance is a measurement that is OK for continued service on used gears. With everything new I would shoot for .000 to .002" gear mesh clearance. As soon as that T drives 100 miles on the new thrust washers it will have .005 - .010" more clearance than you have with all new parts sitting on the bench.
The fiber disc, or a brass washer to take its place, is necessary to maintain proper mesh on the spider gears. Without it there will be a lot of unnecessary stress and wear in the differential.
Royce and I have a couple areas of disagreement.
I don't believe the depth of the pinion is controlled by the face of the front driveshaft bushing. The torque on the pinion gear forces the driveshaft forward and the running depth is set by the geometry of the inner sleeve and the thrust bearing, which are fixed. You can distance the pinion away from the ring gear by adding a shim between the spool and the axle housings.
I also disagree that the ring and pinion gears should be set so close together. I've done a lot of rear ends, standard, Ruckstell and Perfecto and strive to set them at 15 thou lash for quiet operation. Last set up I ran was set at 17 thou and is the quietest of them all. I used NOS Ford gears, but I don't think that accounts for the difference since I've used Mark gears on the others with good results.
You are right about the pinion depth on the original setup. I meant to point out that with the Regan setup the drive shaft bushing can prevent the proper depth of being capable of being deep enough if the bushing is too tall or not pressed in all the way.
Compared to the original Ford Babbitt bushings, the modern bronze bushings have enough extra material to raise a couple of blisters on your hand when using the T-handled facing tool presently sold in the catalogs.
Thanks, guys. I think I have it now. I'll have to wait until I'm off owls to do anything. I need my beauty rest...and not make any sleepy mistakes that'll kill me later on.
Chris, you have me a little mystified. If you can add shims to the thrust washer stack, does that mean you have some slop in the there? If you add shims to one side and take away the same from the other, then it would make sense.
When I assemble a rear axle I like to make the new brass thrust washers .010 - .015" different in thickness when making up the shim stack. That way I can swap them from side to side to get some adjustment.
Hope this helps.
Allan from down under.
Are you using new or used gears? The measurements shown in the books are for new gears. If the gears are worn, you might find they are noisy with the original lash. You need to account for wear because the teeth of the pinion gear and ring gear are worn to fit and any change in the lash will put high areas against each other making the gears noisy and even possibly cause them to break. When you get everything set up, rotate the drive shaft. It should move very smoothly and without any binding. Turn at least one full turn of the rear axle, which will be between 3 and 4 turns of the driveshaft. If it is rough, you need to add more lash.
I am using used gears from a local club member. Allan: I have about .1" rotational free play on the pinion gear, but even mesh between the crown and pinion. I believe I have to move the crown more towards the centere of the unit.
Chris, if you have minimal play between the axles courtesy of the brass thrust washer between them, and minimal play with the diff centre assembly within the axle housings courtesy of the steel thrust washers and bronze thrust plates, there should be no room to add shims. To shift the diff assembly towards the pinion gear as you indicate, requires shims in the left housing, but the same amount needs to be taken out of the right hand side. That means taking some off the brass thrust washer.
Once the centre assembly is set up within the housings, the total thickness of all the thrust washers and thrust plates on both sides needs to be maintained.
Hope I have not confused you.
Allan from down under.