MTFCA Forum

I'm in the middle of a rear end rebuild, I just ordered from Snyders there new style spooler set up, my question is when adding shims how do you know when the ring and pinion are aligned properly? I never set up a ring and pinion before, I know if they are too deep or too shallow it will cause wear or tooth jumping

I highly suggest that you purchase the "Rear Axle" repair book from any of our suppliers. It gives good, in-depth descriptions of how/why to do things and covers the question you asked, plus questions you have not yet asked. Do you know the acceptable tolerances of moving parts in the differential? Have you checked/repaired the dowel pins? Are your housings straight and square? Or how about another dozen things to check/repair along the way?

There are plenty of folks on the Forum who know how to rebuild a rear end, but unless they give you a 5,000+ word tutorial, they are going to fall short somewhere, on describing what you need to do or why you should do it. It won't stop people from trying, but advice to "just do this" or "just do that" will almost certainly be woefully incomplete given the knowledge deficit you're up against right now. There is more to it than just the depthing, and you'll really be doing yourself a huge favor by investing a few dollars in that booklet.

This is a big and important job that is not fun to do twice. Do you really want to work from a deficit of understanding and rely on random advice? I sure would not. I'd delay the project until the booklet arrived and then read through twice before beginning the depthing/backlash operation and then refer back to the booklet frequently. Once you've done one successfully, you will be an expert.

Good Luck

Jf:
By all means get the book (and read it) and follow Scott's suggestions.

My personal experience with the replacement pinion spool and bearing assembly and shims was to set the pinion and bearing location at the 'stock' location, then adjust the axle thrust washer thickness to bring the ring gear into correct mesh with the pinion. Of course you have to check pinion-ring gear mesh and clearance and get that is spec while doing the work, but I found with pinion set using the 'stock' shim pack the proper mesh and lash clearance were obtained by working out the thrust washer thickness. And it took at least 3 assembly/measurement/adjustment cycles to do this while keeping the pinion at the 'stock' setting.

I used prussian blue dye to verify mesh alignment and the thin copper wire strands inside lampcord wire to measure gear lash clearance. You run a single strand between the ring and pinion gear teeth at the inner and outer regions of the ring gear and then mic the flattened strand to get a measure of clearance. My experience was that clearance is not uniform over a full revolution but overall the variations were within spec as stated in the book.

Respectfully, jb

Jfmarkham wrote: ↑

Fri Mar 27, 2026 12:00 pm

I'm in the middle of a rear end rebuild, I just ordered from Snyders there new style spooler set up, my question is when adding shims how do you know when the ring and pinion are aligned properly? I never set up a ring and pinion before, I know if they are too deep or too shallow it will cause wear or tooth jumping

These are the instructions from Snyder's site --
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These are the instructions from the original Fun Projects website --
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While not Model T instructions or exact ring & pinion style, it should give you a visual of what your trying to accomplish. https://www.crawlpedia.com/gear_tooth_pattern.htm