my first 742 case rebuild, need alittle advice please

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OK guys I need some help..this is making me nuts! I have hade this thing apart around 12 times now and I can't seem to get it right so right now I got 69 thou in shims my drive side don't look too bad but my coast is at the heel? My backlash is around 7 to 8 though and I have tried it tighter with little effect I post some pics ( I hope ) sorry about the blue marker paint but I have looked everywhere and can not find yellow so hopefully you can see what I am ignore the lighter color on the drive side and look for the dark pattern it's close to the middle why isn't the coast following? I have gone as low as 55 thou and as high as 77 thanks

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Yeah me too! It's called Prussian blue and it's all I can find I have been to three different auto parts stores and three wholesalers no one has the yellow they all have this blue crap I think I need to go to a art store and get some oil paint but they are all closed today it's a Holliday weekend here
 
I've heard of some people using latex paint. You may want to look into it. That prussian blue isn't cuttin it.
 
mopar56 said:
Yeah me too! It's called Prussian blue and it's all I can find I have been to three different auto parts stores and three wholesalers no one has the yellow they all have this blue crap I think I need to go to a art store and get some oil paint but they are all closed today it's a Holliday weekend here
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Randy's says the yellow pattern compound is a GM item, they sell it, a local dealer might be able to hook You up?
 
Thanks for all the thoughts funny for some reason I was thinking of calling gm to I will do that tomorrow but as far as the pattern goes I guess it's not clear enough for any thoughts? I am going to try again I am at 66 thou now and too high on the drive side so I will add a couple and see getting good at takin it apart lol but getting a little boring now
 
OK so I finally got some yellow gear paint this is 70 thou I still can't get the coast side to the center and the drive seems a bit high what do you think BTW getting tired of taking this damn thing apart but I'm determined lol

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your pattern is junk --- please do all here a favour and start over --- put the .090 shim in and then do a pattern check ---and adjust from there --- post the pics and we can help you better --- in the 40+ years i have been building differentials -- 742 cases are almost always in the .090ish shim range ,, unless the large pinion race was not seated completely into the case or the gear is cut way off tolerance.
you did check the bearing bores of the case for distortion/ high spots that can occur from driving out the old races -- i see that a lot and need to be corrected ( filed down ) before installing the new race.
you can see my work in kijiji ad 1235973203
 
Ok, fair enough, I respect what your saying, also I checked out your add and obviously you have done a few of these, ( nice jig for holding the diff by the way ), I have no problem putting the 90 shim back in, when I went back and read my notes I said with the 90 shim I started with the pattern was high, so I need to add shim, but I went the wrong way with shim, so I would agree it would seem I need more shim than I have however both times I have even been close I was around 70 thou, I also noticed you didn't post pics in your add of the coast side, is it not that important?, or just that it matches the drive side? Good point on the pinion race, I did inspect the bore and it looked clean in fact I bathed the housing in the solvent tank first and wire wheeled it inside lightly with a small power wheel so I could properly inspect and check for burs and the new race I installed seemed seated evenly however I will inspect again when the pinion is out, I will probably do this tomorrow and re-post pics, BTW I think I used WAY too much pattern paint I will back off on that to, lol, thanks for the help, I do appreciate it!
 
mopar56 said:
Ok, fair enough, I respect what your saying, also I checked out your add and obviously you have done a few of these, ( nice jig for holding the diff by the way ), I have no problem putting the 90 shim back in, when I went back and read my notes I said with the 90 shim I started with the pattern was high, so I need to add shim, but I went the wrong way with shim, so I would agree it would seem I need more shim than I have however both times I have even been close I was around 70 thou, I also noticed you didn't post pics in your add of the coast side, is it not that important?, or just that it matches the drive side? Good point on the pinion race, I did inspect the bore and it looked clean in fact I bathed the housing in the solvent tank first and wire wheeled it inside lightly with a small power wheel so I could properly inspect and check for burs and the new race I installed seemed seated evenly however I will inspect again when the pinion is out, I will probably do this tomorrow and re-post pics, BTW I think I used WAY too much pattern paint I will back off on that to, lol, thanks for the help, I do appreciate it!
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are these brand new out of the box gears or . brand new used ( badly set up by a previous owner ) gears.
order some pinion shims so you can do this right .
you want to get the best drive pattern for your gear set -- if the drive pattern is correct the coast pattern will follow --in other words if the drive pattern is correct dont worry about the coast.
lets start at .090 and run a pattern check and go from there.
you only have to apply gear marking compound to 3-4 teeth for a pattern check
 
The gears were used but low hours as the po went to a different ratio I do have a shim selection to add or subtract as required and yes I will use less paint as mentioned earlier my first try with this I am learning but learning is good thanks for the help
 
OK here we are back at 90 AND I removed the pinion race to check the bore for burrs there was one small one I cleaned up the bore and re-assembled it with the 90 and the pattern seems once again too high so I guess I need more shim? BTW backlash at 7 thou

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It looks like your going in the right direction with more shim. It is strange that it is still that far off with a .095 shim.
 
I agree, I have been doing lots of reading on these 742 cases it isn't unusual to have a thick shim pack I'm just not sure if I should push it as the pattern is more centered now.
 
Well if you go with what you have, it will for sure make noise, It almost seems that the gears are a miss matched set?
 
Because your pattern is all the way out on the end of the tooth on the drive side. Ideally you want your pattern in the middle of the face and flank of the tooth.
 
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