8 3/4 742 case setup questions
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moper
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I wasn't really thrilled with the pattern posted. I'm less happy with the backlash. The spec is the distance between the pinion and ring gear tooth, but it should be the same distance at all points around the gear. The fact that it's got a .003" swing tells me something isn't right. That will effect the pattern too. Probably in the ring gear seating on the diff, or in the carrier bearing preload.
I've never owned a tool. I use new checking bearings on the pinion and start with whatever came out..lol.
I've never owned a tool. I use new checking bearings on the pinion and start with whatever came out..lol.
Well max run out where ring gear is mounted is .003 in service manual.
moper
Well-Known Member
That's nice. I stand by what I said. While I have found variances during setup, once completed none had backlash that varied depending on where one measured around the ring gear. I'd never let it go that way.
Just put the spec out there not what to do.
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You always get a perfect reading on backlash with absolutely no variance? Hell, it's rare to get a perfect run out reading on the carrier flange let alone a perfect reading on backlash! And even if you do get a perfect reading on the carrier flange, you can still get a variance on the backlash. If I get a perfect run out on the carrier flange and more than .003" backlash on the gears, I'll send them back but if the run out on the flange is .003" and back lash is say .005", I'll change the position of the ring on the flange and see if the backlash improves. If not, I'll get another carrier and go from there. All machined parts come with a tolerance. Some are in tenths and some are in thousandths but sometimes you get lucky and have perfect numbers.
Cranky I wonder if some of the variance in backlash is from bearing preload? Just curious what do you think.
vintage chromoly
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Also, on that note, how is carrier bearing preload set?
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The carrier and case are pretty stout unit and don't really see how bearing preload could affect it any....unless maybe you're really getting down on the spanner wrench.
Backlash should be checked when the preload on the carrier bearings have been set. If the backlash isn't right, I just move the carrier which ever way it needs to go with the adjusters. If I have the preload where I want it and the BL isn't right and need to move one way or the other....for every notch loosened on one side, the other adjuster gets tightened that much. I also will smack the carrier in the direction it needs to go with a large dead blow hammer and see if the adjuster is still good and snug. Timkens are very forgiving but too loose isn't really an option. Mine are snugged up pretty good and I use a smaller dead blow hammer on my spanner and give the adjusters a couple of pretty good smacks. Don't rear back and kill the spanner though lol. If the locks are off a bit, I turn the adjusters a bit tighter if going tighter is closer and loosen if that's closer. The adjusters can be moved a little either way too....and use Loc-Tite on the screws. You may have noticed that the carrier bearings do not move too easily if the caps are torqued down? I won't torque the caps completely down until things are where they should be. As for determining proper carrier bearing preload.....seems like I read somewhere how much torque a finished 3rd member should take to turn it but dang if I remember what it is or where to find it. Might could try an internet search on that one. After doing so many you just get a feel for it. A 3rd member with new new guts should be tighter than one that has 2 million miles on it though
Carrier preload is simple. Set to zero lash. Tighten opposite adjuster to obtain .006-.008 and your done. If the pattern is off at this point the pinion is at the wrong depth.
Doug
Doug
vintage chromoly
Well-Known Member
Update on the gear swap:
Ended up with .093 pinion shim and .055 preload shims.
Achieved what I think is a good pattern and managed to get backlash between .0085 and .010 depending on where I put the indicator. I set up the indicator at 12:00, 3:00, 6:00 and 9:00.
Got it all back together and took it for a spin and the gears are as quiet as a church mouse!
Hopefully, they wear in and perform as they should.
Thanks to all that took the time to participate and lend advice. It is much appreciated.
Ended up with .093 pinion shim and .055 preload shims.
Achieved what I think is a good pattern and managed to get backlash between .0085 and .010 depending on where I put the indicator. I set up the indicator at 12:00, 3:00, 6:00 and 9:00.
Got it all back together and took it for a spin and the gears are as quiet as a church mouse!
Hopefully, they wear in and perform as they should.
Thanks to all that took the time to participate and lend advice. It is much appreciated.
vintage chromoly
Well-Known Member
Where do you live old bee? I grew up in west park cleveland near Lakewood.
vintage chromoly
Well-Known Member
I'm in wellington. 30 mins east of Norwalk right off Rt. 18
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