Rear axle and diff

Russell Reay

Russell Reay

Well-known member
When I first bought my car a couple years ago, I tore it all apart and discovered the damage on the left rear axle shaft. Following instructions in the red book, I removed the left housing, installed a good shaft , and reassembled using a new gasket the same thickness as the original. The car still isn't road-ready, but it drives OK in the yard. Before I head out out for a test drive, is there anything I should do regarding the diff and axles? The previous two owners drove it around town fairly often, but I don't know about long trips.
 

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Hopefully you set the pre-load on the bearings as the new housing may, or may not be, identical to the old one. This may not be critical as Ford parts were made to an exact standard, run it and see how it acts.
 
I have read about setting the preload, but have never done it--or thought I needed to. Note--I didn't change the housing, only the axle shaft. I also seem to recall that the spider gears had to be removed, and I very carefully replaced them in the same order.
 
You may be fine. Check out Tom Endy's descriptive of rebuilding the Model A rear.

https://www.santaanitaas.org/wp-con...rential-Rear-End-Restoration-Revised-2014.pdf

The business of pre-load is important - but not necessarily fatal.

Google query:
What are the objectives of preloading?
To improve gear engagement accuracy by increasing bearing rigidity. To reduce smearing by eliminating sliding in irregular rotation, self-rotation, and around
the- raceway revolution of rolling elements. To minimize abnormal noise due to vibration or resonance.

I would say if assembled you can "turn" one wheel and have the other wheel turn in the opposite direction (i.e. a normal function of a differential) then you're probably fine. If it turns "hard" then you got problems. If it turns too easy then you have problems too - but not like hard.

Joe K
 
One thing you need to pay attention to is how the key goes into the slot. I don't think the red book mentions that, but according to Bratton's "Worn or broken keys can cause many problems. Taper end of key toward differential with the taper down. (Keep a spare key in your tool box"
 
You might grap the end of the axle and see if there is any in and out play. This would mean that you don't have any preload. If the axle cannot be moved, it means the bearing on the axle shaft is up against the race. This may be good or bad because you don't know what load has been placed on the bearing when you tightened the banjo bolts. At this point you might as well fill it with 600W and hope for the best.

Getting the correct preload is a time consuming process. It requires separating the torque tube from the banjo, removing the carrier parts (spider gears) so that all you have assembled is the axle shaft and axle housing to the banjo. Now you reach in the drive shaft hole where the pinion gear used to be and turn with your fingers the ring gear. The intent here is to use the correct number of paper gaskets between the axle housing and banjo so that you can turn the ring gear with some light force. Please get Tom Endys 2013 Rear Axle Rebuild Paper. Ed
 
Having set up quite a few 90 degree gear boxes with Timken bearings, I recommend using less preload on good used bearings. They still need preload but they can be 20% less than new bearings. Try to start with the same shim gaskets. If not, measure the old ones for thickness. New ones will compress some, but you have to start somewhere.
 
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