Another differential question

[Reno Speedster]

I have been out of town for work and am back on assembling the rear end.

I am setting the side to side play. All the parts are new and I have machined a couple of bronze thrust washers in trying to get it to fit properly. On turns freely using my thumb with a smidgen of drag and no side play (I can’t move it side to side in the case with a screw driver) and one is tighter. No gasket has been installed yet. Both have a tight spot in one location. Each thrust washer differs less than 1/1000 when measured in different locations around the washer, so they are pretty flat and parallel.

I can’t figure out why I would have a tight spot in one location. It would seem like having something high would bind all the way around.

So two questions: any guesses on what would cause this? Is this an issue that needs to be solved or am I good?

[Norman Kling]

Do you have the pinion gear installed and fitted to the ring gear? If so, there is a possibility that there is a tightness in the ring gear in one spot. The play should be about the thickness of a piece of newspaper between the gears. It could be just a bit too close, or if it is clear all the rest of the way and will still turn at the tight spot, it will wear in. As long as it wears just slightly, you have no problem, but if way too tight or the gears don't mesh properly, you might have big problems. Try some prussian blue on the teeth and rotate it one revolution and see the mesh pattern.
Norm

[Reno Speedster]

The pinion has been fitted using Prussian blue and a dial gauge, but the drive shaft is out so I can do the side play. So the tight spot is not caused by the ring /pinion gear fit.

[kmatt2]

I assume that you also checked the steel thrust washers for being flat and that they fit over the thrust plate pins correctly. Over time in hard service many a Model T rear axle housing has been bent or has worn where the steel thrust washer sits after the thrust plate pin failed. Check your axel housings for these problems because that could cause the problem of rotational tight and loose that you describe as a high spot gets to another high spot as you turn the ring gear and the housings are a little pinched. You may be OK if only a slight high spot because the gasket will add some clearance on final assembly. Be sure to get the get the gear mesh contact correct.

[kmatt2]

If you are using a Ruckstell is the ball bearing seating correctly ?

[Reno Speedster]

The steel disks and pins are new. The old pins were intact before being replaced. But I will check the plates to be sure. The two high spots lining up makes sense.

It is not a Ruckstell rear end. This car has a Muncie auxiliary transmission.

[Norman Kling]

You might try removing the outer axle bearings and then turn the axle in the housing. It should be centered in the housing. If it is high or low, you could have a worn inner bearing or the housing could be bent. If it changes from high to low as the axle is rotated, you could have a bent axle.
Norm

[Reno Speedster]

The housings are straight, the axles are brand new, and it’s being held vertically. No outer bearings are in it as it will have full floating hubs (which are not yet in).

I have taken things apart to check for variations in the thrust bearings and plates. Nothing so far. I have polished the steel plates with 1200 grit to make sure things are good.

It’s got me a bit puzzled.

[Dave Young]

I think the next step would be to blue the thrust washers and see how they are rubbing against the brass without the gasket in place.

[Jerry VanOoteghem]

The housings are straight, the axles are brand new, and it’s being held vertically. No outer bearings are in it as it will have full floating hubs (which are not yet in).

I have taken things apart to check for variations in the thrust bearings and plates. Nothing so far. I have polished the steel plates with 1200 grit to make sure things are good.

It’s got me a bit puzzled.

Look at the housing faces that the steel washers sit against. Pressing in the new pins can raise material around the pins. Try placing the steel washers over the pins and see that they are sitting absolutely flat and not "teeter tottering" over high spots adjacent to the pins.

[Atomic Amish]

I'll assume you're working with just the right half, with the differential/axles and ring/pinion set in and the driveshaft bolted in place with 3 bolts, as you're doing setup.

Is the driveshaft cotter pin installed? The last one I built I used too big of a pin and it would hit in one spot on the differential. Changing to a smaller cotter pin solved that.

The book says that there can be .010-.012" inches of runout, if I remember right? What is your runout?

I'm in the process of building one right now at the Village. Amazingly, this one seems to be going together with no issues... all that's left is to bolt the axle halves together and install the torque tube. I'm not holding my breath something won't go wrong before it's over.

Very Respectfully,
jason