Play in rear axle

[Burgamot]

I just removed both rear drums on my 31 Tudor as part of my restoration. When I grab the left axle it is solid no play. On the right side there is play (about 1/8 inch). In looking at Snyder’s catalog I don,t see a part to replace. Does anyone have a suggestion on how to address the play in the axle?

[Charlie Stephens]

If the play is up and down there is no problem. The axle is held in the center by the bearing. If it is in and out along the axis of the shaft I will let other more knowledgeable people comment. Which is it?

Charlie Stephens

[BillLee/Chandler, TX]

If the play is in-n-out, it means that the bearing surface inside the carrier where the axle gear makes contact is worn badly. I had a rear end on my car with the same symptom: OTOO 1/8" end play (in-n-out) and the bearing surface inside the carrier was worn badly.


Tom Endy has a lot of information regarding rear end assembly, etc. but one picture I have captured from one of his articles and it is attached. The bearing surface is outlined in red. On my rear end, that bearing surface was worn so badly that the spiral-shaped oil groove that can be plainly seen was almost completely gone.



Obviously, I replaced the carrier!


The question I have repeatedly asked and have not heard ANY rational explanation is HOW THAT WEAR CAN OCCUR! There is very little relative motion between the carrier and the axle, only when the car is turning a corner and the wheels are traveling different distance and speed. But that is very short-lived occurrence and relatively infrequent. How can there be much wear there at all?

[Dave in MN]

How can this surface become worn? One way is the use of the vehicle as a stationary power source. Attaching a drive pulley to one side, blocking it up and then using it for an extended period in this manner will create wear on one side of the carrier and on the spiders.

The photo below shows one use direct from the wheel without a pulley.

Good Day!

[BillLee/Chandler, TX]

Originally Posted by Dave in MN

How can this surface become worn? One way is the use of the vehicle as a stationary power source. Attaching a drive pulley to one side, blocking it up and then using it for an extended period in this manner will create wear on one side of the carrier and on the spiders.

The photo below shows one use direct from the wheel without a pulley.

Good Day!

Yes, that would be one way, but likely very uncommon.

[Tom Endy]

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Usually when the inside of the carrier is found worn it is in the area where the three axle shafts of the spider gear assembly are clamped between the carrier halves. The wear is caused by the backside of the spider gears rubbing against the carrier. When the two axles are installed the gear end of the axles push the spider gears up against the carrier. Often the wear is severe enough to cut a groove of 1\16" or more in the carrier around the holes. When there is this amount of wear the spider gears are pushed even more and will create thrust clearance in the axle shafts.


This is something I always check and I have discarded a number of carriers for this reason. Some amount of slight wear can be tolerated. The wear caused by the three spider gears is not always even. This why it is important to mark the carrier halves so they can go back together the way they came apart. When matching up orphan carrier halves wear patterns should be observed and matched
as close as possible.


Tom Endy

[Joe K]

Gears have a "pressure angle" - which is an average of the "ramp" between toe and root of the gear. Most have heard this in relation to spur gears with 14-1/2 as the commonly found angle, although 20 is common in newer machinery.

Pressure angle and forces resulting exist similarly with bevel gears such as the pinion/helical bevel driving the carrier and the spider/axle gears.

The pressure angle causes the two gears, drive pinion and driven helical ring, or axle gear and spider, to be forced "apart" when loaded.

In the case of the driven helical bevel gear, the force tends to push the carrier to one side of the pumpkin - resisted by the bearings the carrier rides in. I can't say I noticed one bearing more worn than the other when I rebuilt my rear end - but one imagines it was so. Both bearings were replaced with new in the differential setup and their clamping tension and the bevel gear position adjusted by use of various thickness gaskets per Tom Endy's method. (I think rear axle rebuilding and gasket shimming was first described in some detail and method by Rick Freeman in his Model A Shop Manual - which was the service instruction of choice in the 1970s.)

In the case of the spider gears, it can be seen that force will be equal and shared between the two halves of the carrier - two opposite and opposing forces. True the carrier and the spiders TEND to rotate together, but turning a corner calls the differential action of the rear end into play causing one axle to turn faster than the other and presenting wear to the inside of the differential carrier, which HAS to average the rotation of the two axles.

The differential action and resultant force between the spiders and the axle gears and housing is the same whether one is going forward or reverse.

One imagines that a car used continuously on an oval race-course would measurably shorten the life of the differential carrier compared to driving straight ahead.

Joe K