MTFCA Forum

Just wanted to check how close I need to be.
I've been told "side to side clearance of the carrier and thrust washer assembly inside the axle housings is small say 5 to 10 thou"
I've read and seen in the rear axle CD the axle should be snug with no side to side movement but easy to turn, I have .0075 movement, is this acceptable can I just add a .007 shim onto the brass thrust washer or should I machine a thicker thrust washer.

Agree,
Mounted and measured that way is the thickness of the Fibre washer between the Axle Gears and not the Crown Wheel assy pre load / end float. Alan In Western Australia

I add thrust washer shim(s) until the ring gear binds when I turn it with my fingers and then back off. You don't want any tight spots as you turn the gear. I've found nothing is perfect inside a T rear end. The flats inside the axle housings on which the steel washers ride are not uniformly parallel, the steel thrust washers may not be of uniform thickness or dished and the side to side width of the carrier bolted together is different at different places.
The last thing you want in a T rear end is close tolerances.
.

If you are asking about the small washer which goes in the centre of the diff casing between the two axle eands, then minimal clearance OK.I use an Australain $1.00 braass coin for the washer. These are sanded/filed down to a custom fit for the axles/housing being assembled.

Allan from down under.

Maybe The expensive $1.00 Coin Washer isn’t critical if you use Safety Hubs locating and locking the Axle locations?
Alan In Western Australia

Allan wrote: ↑

Wed Jan 11, 2023 3:51 am

If you are asking about the small washer which goes in the centre of the diff casing between the two axle eands, then minimal clearance OK.I use an Australain $1.00 braass coin for the washer. These are sanded/filed down to a custom fit for the axles/housing being assembled.

Allan from down under.

Agree.
If you are talking about the carrier & axle assembly in the 2 axle housings, the carrier should turn freely with no tight spots. .005 clearance is the target. .0075 (.0025 over) wouldnt bother me. You can narrow the brass thrust washer on the appropriate side & add back a .010 shim to get you back to .005" if it bothers you. I wouldnt bother.

I’m talking about the brass thrust washer that goes in the spider.
The way I have it set up on my mill, I pull one axle out as far as it will go and lock it down so the axle and differential can’t move than I can move the opposite axle in and out .0075”

The thrust washer between the axles was originally fiber. You are making yours out of brass. Spec wise you are probably ok, however, for the effort in making a thicker spacer here, I would. A minimum clearance is ok here. Were it mine to do, I would make a .005" thicker washer/spacer giving a .0025" clearance.
If using fiber, tight is ok because it will compress a bit when put in use.

What you've got there is just fine at .0075.

I have .002" brass shim stock, would it hurt to add three .002" shims, or should the trust washer be a single piece of the correct thickness?

Bruce

is it really that hard to accept "yes, it's OK" for an answer?

If it really is, then part off a disk on the lathe that is the thickness you want and be done with it. Adding in individual shims the thickness of notebook paper would not be a good idea as they will just wad up and create trouble.

What sort of clearance do you think a factory fiber disk would have after 500 miles being beaten to death on a rough road? There are some places where a couple thou one way or another makes or breaks a system; this isn't one of them.

It's a Model T. Don't sweat it. Enjoy it.

On to the next project.

Scott_Conger wrote: ↑

Wed Jan 11, 2023 9:02 pm

What sort of clearance do you think a factory fiber disk would have after 500 miles being beaten to death on a rough road?

I have never taken a rear end apart and found any traces of the fiber washer remaining.

exactly...

I agree with Scott, a single disc spacer of correct thickness is best for reasons cited. I have found numerous original fiber spacers in place in old differential cages, so these parts functioned to some extent in some instances. The rear axle rebuild guide suggests 'new' fiber discs are not thick enough, as you have confirmed. I found the same thing and machined a brass replacement when I rebuilt my '26 differential. jb