Most lathem clocks have just two areas that need service:  The most common is the motor.  Less common is the movement. 
It it is noisy and losing time, with the printed time always matching the “face“ time, then you need to replace the motor.
If the “face“ is on time but the printed time is falling behind, then the movement needs to be replaced.  We bill about $125 for that, you need to ship it in, we rebuild the movement and give it a good cleaning, and a guarantee.

Regarding all mechanical Lathem time clocks - if the case is metal, then this is the solution:

The Lathem time clock motor is easy to replace.  It starts with a rumbling, then one day it is squealing.  The lathem time clock motor can be replaced with just two tools: A flat blade screwdriver, and a #2 Philip's head screwdriver. 
Simply remove the movement by popping off the “C” clip on the upper left hinge bracket, then pull the movement out.
Next, loosen the two Philip's head screws that hold the clock frame to the case, on the left and right.  Loosen or remove, either way is the same result.

Now taking the same screwdriver, loosen the two screws that lock in the motor.  In very old models, you will have to remove the screws.  The motor will now lift out - or you may have to pry it out using that flat blade screwdriver, again.  Disconnect the power leads, rotate the copper “S” spring counterclockwise to remove it.

Reassemble everything, squirt some oil in to the movement.
If you have a wire brush handy, Scrub the lint and ink off of the print wheels.
Wash the movement with WD-40, dry it with a hair dryer (get it hot!) for 5 minutes.
Let it cool down, and reassemble the machine.

We have the motors, we have all the parts. 
We can even do this for you and guarantee the work.