my first 742 case rebuild, need alittle advice please

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mopar56

mopar56

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Sorry if this has been asked before and I am sure it has but bearings are expensive and only want to do this once, I have a 742 case, it came with NO shims, gears sure grip etc, I have a new set of Richmond 323 gears and a used cone type sure grip, and new bearings, I have plenty of tools, press, etc, I have installed new side bearings on the sure grip and need to install the pinion and set the depth, the manual I have ( written by Larry Shepard ) is pretty helpful but it says to use your old shim pinion gear marking and your new marking using a chart to decide on shims, but I don't know what the old number was, so I read through some old threads hear and most say with a 742 case start with a .090 shim and go from there, is this correct?, any other tips? thanks
 
On the different gear sets I have done the shim is anywhere from .020 up to .200. So .090 should be a good starting point kim
 
Thanks Kim, I value your input as with others here, this site is a world of help for fellow Moparians! also dumb question, but none of my shims are marked by size so out comes the micrometer, this is normal I understand
 
I found building 2 65 barracuda"s and stripping others 15 or better in my life once I became a FABO member there are no stupid questins but mabee a few different answers because these cars were made in 3 or more American countries, Mexican , and Canadian , . But there is a world of knowlage and many very intelligent pople that are willing to help you figgure the problem out , from touble shooting , to there own expeiriances in every phase of mopar buildingor finding old info . on the net ROK ON FABO FAMILY and MOPAR FANATICS AND MECHANICS AND MACHINIST AND FABRICATORS . winstoninwisc hagr812 ALL
 
mopar56 said:
Sorry if this has been asked before and I am sure it has but bearings are expensive and only want to do this once, I have a 742 case, it came with NO shims, gears sure grip etc, I have a new set of Richmond 323 gears and a used cone type sure grip, and new bearings, I have plenty of tools, press, etc, I have installed new side bearings on the sure grip and need to install the pinion and set the depth, the manual I have ( written by Larry Shepard ) is pretty helpful but it says to use your old shim pinion gear marking and your new marking using a chart to decide on shims, but I don't know what the old number was, so I read through some old threads hear and most say with a 742 case start with a .090 shim and go from there, is this correct?, any other tips? thanks
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for 742 cases if you do not have the original pinion shim start with the .090 shim for your initial set up ---
do not install the pinion seal until you do your final set up
install your pinion into the case and install the yoke and add some preload to the bearings to take up any slack in them
install your carrier and gear and set the backlash .006-.009
do a pattern check
if pattern is not correct,, remove pinion --- a shim change will have to be done - make shim changes in increments of .003 to see movement in the gear pattern
to move the pattern up on the teeth use a thinner shim -- to move pattern down use a thicker shim
adjust shim thickness until a proper pattern is found
once you have the correct pattern ,, start your final set up and select the right amount of shim to set the pinion bearing preload 20-30- inch/lbs rotating
with the preload shim selection is done -- do your final set up buy installing the seal and yoke and tighten the pinion nut --- check your pinion preload again
if correct then install your carrier and gear to set the backlash ,,, thgen tighten the cap bolts to spec. 90 ft/lbs
make sure all turns smoothly
once you have installed the diff into your car ,, do a proper break in for the bearings and gears .
 
wow, all good info here thanks!, just to be clear after reading the last post...shim the pinion head first to .090, install the carrier then apply pre-load, with only the yoke and NO front shims, check back lash and pattern and ONLY after that is right, shim the yoke, that is good to know I was going to install all shims right away, so is there a good starting point for the forward shim?, also I have been reading some people buy a second pinion head bearing and sand the inner part down to use as a tool to set depth, is this a good idea? thanks
 
mopar56 said:
wow, all good info here thanks!, just to be clear after reading the last post...shim the pinion head first to .090, install the carrier then apply pre-load, with only the yoke and NO front shims, check back lash and pattern and ONLY after that is right, shim the yoke, that is good to know I was going to install all shims right away, so is there a good starting point for the forward shim?, also I have been reading some people buy a second pinion head bearing and sand the inner part down to use as a tool to set depth, is this a good idea? thanks
Click to expand...

yes start with the .090 shim -- add preload to the pinion bearings without the pinion preload shims for your initial set up and also if you have to make any shim changes --- once the proper pinion shim is found that gives you a-- proper gear pattern -- then move on to selecting the amount of shim to give you the proper bearing preload,,, on 742 cases this could be from .030 - .050 depending on the gear ,,, measure your preload with the pinion only in the case ---the carrier and gear must be out of the case----- you can use old pinion bearings if in good shape to do your set up,,, hone out the centers for a light slip fit over the gear and proceed with your set up --
 
OK thanks that's what I needed to know unfortunately j do not have the original pinion bearing so I will have to buy another for shimming purposes oh well and again thanks!
 
do not buy a second rear pinion bearing , throw it in with a .090" and if you are lucky it will be good
 
so I finally got back to this last night and got my new races pressed in and 90 thou shim and bearing pressed on and put in the carrier I haven't checked the backlash or pattern yet but hopefully tonight, then it hit me... I don't have a spacer the one in my old case is too small a diameter and the 742 doesn't use a crush sleeve, I need a spacer right?, dose anyone know the part number for it so I can start searching? thanks.
 
Yes, You are correct, & a call to Randy's or Dr diff etc. should be all it takes.........did You not purchase a master rebuild kit for the install?
 
Killer6 said:
Yes, You are correct, & a call to Randy's or Dr diff etc. should be all it takes.........did You not purchase a master rebuild kit for the install?
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No I bought the parts separately unfortunately for us Canadians everything you guys get down there cost us 35% more here plus freight plus brokerage so it's cheapest to source this stuff at the local jobber BUT they don't have the kits but if I can't find the part here I may have to do that thanks
 
Ok so I have been doing some checking for this spacer and have been told that the 742 case because it uses shims dose not require a spacer, can this be correct? I even phone a diff only shop on the mainland? I looked on Dr Diff site and dont see one available either just a crush sleeve for the 489?
 
mopar56 said:
Ok so I have been doing some checking for this spacer and have been told that the 742 case because it uses shims dose not require a spacer, can this be correct? I even phone a diff only shop on the mainland? I looked on Dr Diff site and dont see one available either just a crush sleeve for the 489?
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the 742 uses shims to set the preload ---- NO crush sleeve/spacer --- as stated in my previous post -.030 - .050 depending on the gear --- ask around as someone may have some shims for a solid spacer used with 9 inch Ford standard pinion -- same shim --- go back and read my posts --you do not need the preload shims to check your pattern --just tighten the yoke enough to take out the slack in the bearings and add some preload -- then load your carrier and check your pattern
you need the shims to set pinion bearing preload when you do your final assembly AFTER you have established the correct gear pattern.
 
mopar56 said:
Ok so I have been doing some checking for this spacer and have been told that the 742 case because it uses shims dose not require a spacer, can this be correct? I even phone a diff only shop on the mainland? I looked on Dr Diff site and dont see one available either just a crush sleeve for the 489?
Click to expand...

if you cannot find the shims locally -- you can get them from Ratech Manufacturing --- ratechmfg@yahoo.com --- pinion bearing preload shim pack 742 case # 1107 ($12.00 US ) and pinion depth shim pack 742 case # 1108 ( $20.00 US ) or Summit Racing carries Ratech stuff as well.
 
Thanks John, I did read the post thoroughly I just wasn't clear on weather or not there was a spacer or not so thanks for clearing that up, I will check the back lash and pattern this weekend, I have located the front shims which I should have by Monday, I think I got this now, thanks again everyone for your help.
 
mopar56 said:
Thanks John, I did read the post thoroughly I just wasn't clear on weather or not there was a spacer or not so thanks for clearing that up, I will check the back lash and pattern this weekend, I have located the front shims which I should have by Monday, I think I got this now, thanks again everyone for your help.
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Sorry dude, I pooched My response to you, ......
You are correct there is no crush sleeve, there is no sleeve facsimile spacer either, the shims are the only spacers to set preload.
Thanks Marcohotrod for the fat red "X", lol!
There are some crush sleeve eliminators for other rears that would be what You described, but you're not working on one of those now are you....................:rolleyes:
 
Ok so here is where I am at, I put it all together set my back lash and checked my pattern, unfortunately it is high on the drive side and low on the coast side, so according to my pattern comparison in the manual I should remove some pinion shim, so I took it apart, ( even managed to get off the pinion bearing with out damaging it ) I figure I would take out 15 thou of shim as I started with 90 thou as recommended then I put it back together the drive side seems better maybe a bit high and the coast side is still too low so I guess it comes apart to remove more shim, any ideas how much to take out? I was thinking 20 thou which would take me to about 55 thou but that seems thin?
 
I use set up bearings that slide on and off with ease. I have one for the 741,742,489 case. Makes life a lot easier. When I start chasing a good pattern, I make .010 changes which I consider a large amount until I push the pattern to far past the pattern I was looking for. Then I'll make .003-.005 changes till I'm happy. Now the whole time I'm doing this, I don't set the preload every time I make pinion depth change. I only set preload after I get my pattern. I merely install the pinion and bearings along with the yoke and use the old pinion nut, and snug it down to get zero play and work on my pattern using this method. After I get the pattern I want, I take it apart and then use the small shims to get the right preload. I then take the yoke off one last time, install the new seal , yoke and new pinion nut and torque it. Make sense?
 
OK thanks yes that makes sense and that's how I'm doing it I have not installed any front shims yet just the one at the pinion head I just thought I would see more movement on the pattern with my decrease in shim but if you think 10 thou will make a difference then I will take only 10 more out I posted some pics hopefully they work I always have trouble posting pics on this forum thanks again

20170208_225730.jpg


20170208_225723.jpg
 
mopar56 said:
Ok so here is where I am at, I put it all together set my back lash and checked my pattern, unfortunately it is high on the drive side and low on the coast side, so according to my pattern comparison in the manual I should remove some pinion shim, so I took it apart, ( even managed to get off the pinion bearing with out damaging it ) I figure I would take out 15 thou of shim as I started with 90 thou as recommended then I put it back together the drive side seems better maybe a bit high and the coast side is still too low so I guess it comes apart to remove more shim, any ideas how much to take out? I was thinking 20 thou which would take me to about 55 thou but that seems thin?
Click to expand...

you are going the wrong way with your shim selection ---- on 8-3/4 diff to move the drive pattern up from the toe ( lower portion of tooth ) you SUBTRACT shim-- to move the drive pattern down from the heel ( upper portion of tooth) you ADD shim --- make your moves in steps of .003 so you can see the movement of the pattern -- you started at .090 and you had high heel contact--- go to .093 or even .096 then fine tune from there by going up or down on shim thickness to center your drive and coast pattern --
if you get the drive pattern correct the coast pattern will follow.
 
Damn, thanks John, well I guess that explains little correction with 15 thou I removed, like I said the manual I have isn't a factory one but it has been fairly helpful I was just following there pattern chart?, guess I will go the other way.
 
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