How much backlash through differential is ok?

[rainer]

Hello.

I own a Touring 1916. It is currently placed on supports, so wheels don't get a flat spot over winter.

When turning one rear wheel forward and backward until the other one starts rotating in other direction, how much backlash is allowed along circumference? I assume this is also some indicator for wear of gears inside differential ?

Thanks in advance for your answers.

Rainer

[Norman Kling]

It's a bit difficult to diagnose without taking apart the differential.Several things could cause the problem. First thing to check would be end play in the axles. With the parking brake off, pull the wheel in and out toward the end of the axle. You should not notice any endplay. If you get a lot of endplay, you have a problem inside the housing. if this axle has not been rebuilt recently or ever, you most likely have babbit thrust washers at each side of the differential carrier and the inside axle bearing. If so, it deteriorates and will eventually cause the gears to fail and also transmission brake will not work when that happens. They should be replaced by bronze washers. Other causes is omission of the spacer washer between the inner ends of the axles and the differential. or possibly play in the universal joint.
Norm

[rainer]

Hi, Norman.

I am afraid you misunderstood... I have no axial play on rear axles.

The reason for asking:
I can turn one wheel backwards and forward approx 4-5" (approx. 12cm) measured on circumference until the other wheel starts rotating in other direction. With handbrake lever in neutral (= middle position and cold engine). This angular play does not change when closing the clutch (high gear). So this rotating play is more or less the sum of play of all gears inside the differential.

But I have no experience if this is normal or too much for my 107 years old Lizzy, therefore I want to compare with others.

I bought my T in this condition in 2020. It drives well, so I see no reason for taking it apart.

[Jerry VanOoteghem]

Rainer,

There is usually a considerable amount of backlash through the differential due to those gears and their clearances not being very precise. Consider also that the backlash in your entire drivetrain comes into play as well since you're not able to hold the ring gear from moving. The reaction forces within the differential will cause the ring gear to move as well.

[Norman Kling]

I think your lash is about normal. If the differential does not howl when you are driving in high gear, I think it is OK.
Nor,

[DanTreace]

Seems a bit too much IMO. Also you might have worn u-joint that contributes.


Just measured two rear axles, instead of measuring at wheel circumference, found it best at the brake drum, 8" or so from the axle center.


Did both vehicles the same, locked in high gear, both rear wheels jacked off the ground. Rotated one until the other wheel engaged.

To measure drew a pencil line on the drum, and strips of tape on the backing plate, marked black dot where rotation started and stopped.
Was approx. 20mm or so.

The brass oiler axle is fresh rebuild, not run. The varnished wheel axle rebuilt about 6 years ago or so.

[Kerry]

You will get old and turn your hair white worrying if you think that a T diff would be any better than what lash you are showing.

[Jerry VanOoteghem]

I think your lash is about normal. If the differential does not howl when you are driving in high gear, I think it is OK.
Nor,

When you're driving along in high gear you're not using the differential. You only use it when you turn corners and even then, the diff gears will never rotate fast enough to howl.

[Craig Leach]

Hi Rainer,
I would be inclined to agree with Dan's measurement ( that is inline with the rear I just put together ) Take the 2578E Housing plug out &
install a bolt with the same size thread & run it up firmly against the u-joint so it will not turn & test again. If you get the same result then
I would be inclined to think that the issue is in the rear end. If the play/backlash is greatly diminished remove the bolt & have someone hold
the brake pedal & check again. If the play is back then pull the trans cover & look for loose output shaft rivets, loose shaft to u-joint fit or
loose u-joint. if that all checks out good then go with Norms assessment.
Craig.