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I just installed a new tach drive gear and noticed that the threaded brass retaining ring is rather loose when set for allowing the drive gear to feely rotate. If you tighten, the gear binds. If you don’t tighten, the entire assembly rotates very easily and could work its way out.
Is this typical?
Is there a standard procedure for adding some pressure to the threads so they hold position?
From: At my Bar drinking and wrenching in Lafayette Colorado
You have to custom shim the crossgear so it has some lateral freeplay when the brass bushing is fully tightened and seated. This may also required custom machining of the housing crossgear thrust surface or the machining and fabrication of a custom thrust surface insert.
So, the length of the cross gear+the brass button+the washer is longer than the current space created by the brass bushing, yes?
Could I start by removing material from the washer and/or button? I took out the original plastic button. Perhaps that would work better, since it’s thinner than the brass?
thanks for the reply
Originally Posted by lars
You have to custom shim the crossgear so it has some lateral freeplay when the brass bushing is fully tightened and seated. This may also required custom machining of the housing crossgear thrust surface or the machining and fabrication of a custom thrust surface insert.
From: At my Bar drinking and wrenching in Lafayette Colorado
Don't use the brass button supplied by many of these "kits." They are junk, and will shred themselves very quicky. If you still have the nylon thrust button and it's still intact, use it. Then adjust any further lash with the thickness of the washer located between the crossgear bushing housing and the crossgear.
This is what the brass button will look like after just a few thousand miles of service. All that shredded brass goes right down into the bottom of the distributor and trashes your lower shaft bushing:
I haven’t had to deal with a distributor cross gear for 15 years but at the time the ones sold were not good.
They had a small brass tip on one end and they didn’t mesh properly with the main shaft gear. I recall speaking with the vendor that I bought several from- now retired-who told me that the brass tip had to be filed to fit the shaft gear. I was suspicious of that but did it one step better by facing the gear in my lathe. I went through several facings and didn’t get any positive results. I then made a new brass tip and started over with the same results. I returned all of them and found a good used GM cross gear that worked perfectly. Just another example of junk sold for the past 20 years.
well … The brass button did get used, but I made sure the tip of the gear was super smooth and there was some space for grease between the surfaces.
Originally Posted by lars
Don't use the brass button supplied by many of these "kits." They are junk, and will shred themselves very quicky. If you still have the nylon thrust button and it's still intact, use it. Then adjust any further lash with the thickness of the washer located between the crossgear bushing housing and the crossgear.
This is what the brass button will look like after just a few thousand miles of service. All that shredded brass goes right down into the bottom of the distributor and trashes your lower shaft bushing:
I ended up shaving about .020 off the brass end of the cross-gear, then smoothing it off. It’s the best I can do with the tools I have. It has a small amount of lash, so it should be good.
the gears on both replacement parts (dizzy shaft and cross gear) seem to mesh Ok, so hopefully this will work for a while.
Originally Posted by GTR1999
I haven’t had to deal with a distributor cross gear for 15 years but at the time the ones sold were not good.
They had a small brass tip on one end and they didn’t mesh properly with the main shaft gear. I recall speaking with the vendor that I bought several from- now retired-who told me that the brass tip had to be filed to fit the shaft gear. I was suspicious of that but did it one step better by facing the gear in my lathe. I went through several facings and didn’t get any positive results. I then made a new brass tip and started over with the same results. I returned all of them and found a good used GM cross gear that worked perfectly. Just another example of junk sold for the past 20 years.
I hope it works for you. The ones I had would bind up badly. If I had attempted to use them, they would have failed. I would have liked to see how the ones I had were "fit" since no way were they working for me but I also didn't get any resistance from the vendor either.
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Tach Drive Lash Question
