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742 Ring and Pinion setup
https://slantsix.org/forum/viewtopic.php?t=66603		 Page 1 of 1
Author:  Rick Covalt [ Sun May 22, 2022 2:06 pm ]
Post subject:  742 Ring and Pinion setup
I have been trying to get some sort of a decent pattern on the 4.86 gears I have and my pattern was way to the heel of the of the tooth. After making a couple adjustments I got the pattern moved more towards the center of the tooth on the drive and coast. But it is too close to the top land of the tooth. Not sure how to move it closer to the root of the tooth?

742 rear. I started with the stock large shim and it was @ .090. Went to about .102 and it wasn't the right direction. Went the other direction to @ .078 and the pattern moved to the location on these pictures. All back lash settings were at .008.

What am I missing here. Trying to learn from all this assembly and disassembly! :D
I think I need to go to about .070 and try it but I'll wait for a response from the experts
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Author:  DadTruck [ Sun May 22, 2022 8:10 pm ]
Post subject:  Re: 742 Ring and Pinion setup
Rick, in doing my recent 742 diff set up I found:
1) To get a decent readable pattern on the ring gear teeth I had to keep the excess yellow paste off the pinion gear teeth. Having paste on both sets of teeth leaves a smudge and not a clean print.
2) I really had to rock the ring gear several times hard back and forth across the pinion. That gave a nice clear gear mesh print.
3) I found a good gear mesh indicator to be the print left on the un painted ring gear teeth that was left on those ring gear teeth by the next revolution of the pinion gear teeth that had pick up paste from the coated ring gear teeth. Like what is shown in the first photo on the first unpainted tooth.
4) What is the torque to turn on just the pinion? I found that after the pinion bearing depth was set properly and the pinion torque to turn was right the consistency and readability of the gear mesh pattern improved. Dr Diff specs for torque to turn and pinion nut torque are slightly different from the FSM for the 742.
5) Is that set of 486 gears new or used? If used it may not be possible to get a ‘normal’ looking print.
If new I would contact the gear manufacturer, as I agree with what you are saying, shims and backlash can move the print across the tooth, but there is no specific set up to just move the print deeper.

From what I read on gear set up, the drive side is the main side to use as a target. And under a hard load the pattern will move across the tooth in the direction of the outside of ring gear to the heel. With those two concepts in mind I think your set up looks close to OK, but I would want to see another go at a print with less paste and more back and forth rotation or a better look at the mark by the pinion on an un coated tooth
Author:  Rick Covalt [ Mon May 23, 2022 3:12 am ]
Post subject:  Re: 742 Ring and Pinion setup
Thanks John. Used set of gears. I think my torque to turn the pinion is @ 22 " lbs. I will give another go at the tooth marking this evening.
Author:  DadTruck [ Mon May 23, 2022 1:44 pm ]
Post subject:  Re: 742 Ring and Pinion setup
Being a used gear set, it will have a pattern already worn into it.
The pattern you see is your new set up intermixed with how the ring
and pinion are already worn in together. All is not lost though. Just get
the best looking pattern that you can on the drive side and go with it.
It will be fine. And if not perfect it will be as good as can be done.
Author:  Rick Covalt [ Mon May 23, 2022 2:20 pm ]
Post subject:  Re: 742 Ring and Pinion setup
Yes and since it is for the race car , noise is not a big concern. I just wanted to learn a little as I got it "close"
Author:  Rick Covalt [ Mon May 23, 2022 3:32 pm ]
Post subject:  Re: 742 Ring and Pinion setup
Went out and "re-wiped" the teeth as you mentioned John. A better pattern was seen on the drive side that was still a little high up on the tooth but had a nice large "V" down towards the root of the tooth that I could not see before. So that made me feel much better. Coast side was still a little high but was about 2/3 of the way across the tooth.

Painted it black and marked it "4.86". If I can afford gas I will put them in for the race at Farmington!
Didn't get a picture of the pattern because I left my phone at work. :D
Author:  DadTruck [ Mon May 23, 2022 8:16 pm ]
Post subject:  Re: 742 Ring and Pinion setup
Good progress
Author:  Doctor Dodge [ Tue May 24, 2022 11:34 pm ]
Post subject:  Re: 742 Ring and Pinion setup
Setting up rear end gears can sometimes be a real PITA....
You put everything together, take a contact pattern, take it all apart.... "rinse, lather, repeat"... a bunch of times.

One other thing I have used, especially with used gear sets... fine lapping compound. :shock: :roll:
Do not use a lot, keep it isolated to the gear teeth and be sure to clean it all out when finished.

What I have seen with used gears, installed in a different housing, is that a good contact pattern shifts slightly off the previous wear / contact area and that throws-off the current impression reading.
The lapping abrasive will work down any high spots and help the new pattern develop.
this does not "fix" a incorrect pinion depth or backlash setting but is a
another useful "tool" to help find a good contact pattern

As an FYI, the gear manufacturers, machine then hob / harden the ring and pinion gears, in batches, then make sets, to "lap-in" as final gear sets.
https://www.crownracegears.com/lapping.html
DD
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