Ring and Pinion Backlash, What's everyone doing? Options

[Matt Romanowski]

For the folks who are rebuilding their own transmissions, what are you using for a backlash measurement? The manual says around .007, but that seems a little tight. We're trying to get some temperature out of the transmission and were thinking about running a little looser. Anyone tried that?

[Dr Evil]

I use the factory tool, or at least a clone of it. The factory states that .012-.018 (edit:McMark 0.12-0.18mm or 0.005-0.007") is tolerance. The way that the back lash is set at the factory is that the pinion is mated to the ring at a set design measurement "N" and then the unit is run on a machine and slowly adjusted out from the center line of the ring gear until the quietest operation is attained. This number is then scribed onto the pinion head, i.e. n=18 would mean that you need to set the pinion back from N +.018.

To do this correctly, you need the special tool. Varying in or out will not give you much in the form of performance and I do not think it will effect cooling all that much either. One can surmise that the quieter running factory setting is the least amount of friction one can get from the R/P.

[Jon B]

I use the factory tool, or at least a clone of it.

Photo below of factory tool, P258, with all accessories.
This tool will only measure pinion depth; other tools are needed to determine ring gear backlash and differential bearing preloads.

I'm curious to see the clones being made.



Jon B.
Vista, CA

[Dr Evil]

I use the factory tool, or at least a clone of it.

Photo below of factory tool, P258, with all accessories.
This tool will only measure pinion depth; other tools are needed to determine ring gear backlash and differential bearing preloads.

I'm curious to see the clones being made.



Jon B.
Vista, CA

Mine was made by a machinist and has the same dimensions as the factory tool. I only have to use it when replacing R/P for failure of inspection or traumatic failure. Most of the time, and I have covered this extensively here and in my DVD, I instruct people to measure gaskets and maintain factory set specs. The vib issues is not much of a concern in the small increments we deal with. It is mainly a nuisance. Many other manufacturers do not do the finite test in leu of just matching patters with dykem or other indicator to a visual pattern.

In a race box, though, I would keep as much friction and vibe out of your setup as fatigue will be highly magnified. Bearings wear and tolerances are quickly lost.

[0396]

I use the factory tool, or at least a clone of it.

Photo below of factory tool, P258, with all accessories.
This tool will only measure pinion depth; other tools are needed to determine ring gear backlash and differential bearing preloads.

I'm curious to see the clones being made.



Jon B.
Vista, CA

Mine was made by a machinist and has the same dimensions as the factory tool. I only have to use it when replacing R/P for failure of inspection or traumatic failure. Most of the time, and I have covered this extensively here and in my DVD, I instruct people to measure gaskets and maintain factory set specs. The vib issues is not much of a concern in the small increments we deal with. It is mainly a nuisance. Many other manufacturers do not do the finite test in leu of just matching patters with dykem or other indicator to a visual pattern.

In a race box, though, I would keep as much friction and vibe out of your setup as fatigue will be highly magnified. Bearings wear and tolerances are quickly lost.

Any pictures of these various copies of the P258??