Got my pinion problems resolved. I am now assembled and set to check backlash. 3:55 R&P conversion. Two info sources, shop manual and devestechnet, put lash at .005-.007. The printed directions with the gear set, Chev's of the 40's, have lash between .008-.012. Significantly different. Anyone have experience with the Chev's gear set, or an opinion as to why there is this variance? Also, what did you set your replacement gears at?
TIA
"it's only old if you can't find a use for it; otherwise it's cool and i'll use it."
I think it depends on how many shims were in there to start with ,if I remember the older ones had one shim and the newer tubes had two but I cannot remember the thickness of the shims they used.
Kevinski, According to your attachment, the earlier tubes used two shims. But the number of shims doesn't really have an impact on backlash. Given the 3.55 gear set is different from factory, the factory backlash wouldn't be the one to chose, but .008 isn't that much different than .007. I think I'd shoot for the low side of the spec that Chev's of the 40's instructions call for.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
Thanks. I ended up about .0085 +/- a little. This was my first fit so the prop shaft is not installed. It made it a little difficult to lock down the pinion gear, but it's within tolerance. The wear pattern looked good so I am off to install the prop shaft and hopefully a full differential. Once that's all in I will do a final lash check as I can lock the pinion by temporarily installing the trans yoke and holding on to it.
A side note, I had not noticed some of the info in the printed directions that came with the gear set. The directions that Chev's of the 40's provides with their gear set are the directions from Patrick's.
Last edited by bigedpa; 02/10/202612:07 AM.
"it's only old if you can't find a use for it; otherwise it's cool and i'll use it."
If you're dealing with used gears, using the factory specs for setting up new gears is a crapshoot. You're likely to get a gear whine unless you happen to hit the exact backlash the gears have been running previously. They establish a wear pattern over decades of use, and trying to use the original specs seldom, if ever gets them back into the previous alignment they're used to running. I always try to do a tooth contact pattern with white lead or Prussian Blue before disassembling a used gearset, photograph the pattern, and try to duplicate it on reassembly. Original specs will get you into the ballpark on used gears, but they're a long way from hitting a home run at times. A couple of thousandths of backlash difference on new gears probably won't cause any problems. Jerry
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