8 3/4 pinion depth
- Thread starter MikeH
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It depends entirely on what ring and pinion you use.
Nominal pinion depth = designed pd for a perfectly machined carrier & pinion. Shim is most likely 0.030".
This must be one of the closest guarded secrets in all Mopardom!! I have searched every where I know of to no avail!!
If I were home I could give you that info. The depth setting gauge kit I bought has
very helpful instructions that came with it. They give you a pinion depth for most factory gear sets. If you can wait till the weekend when I'm home I'll be able to help you.
very helpful instructions that came with it. They give you a pinion depth for most factory gear sets. If you can wait till the weekend when I'm home I'll be able to help you.
Well if MoPar's machining tolerances on differential cases was anything like deck heights, there's no "nominal spec". lol
If I remember right(and at my age that is a problem) the instruction sheet gives three different starting points for the three cases.
replicaracer43
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That's 100% correct!!! I just normally use whatever shim came out of the gears set I removed, then check the pattern, its usally good for me. I personally feel the shim is to correct for the casting variations in the cases, as the gear sets were most likely machined to a tighter tolerance that the cases themselves....but, I am no gear set up expert either
Your right, unless you buy a set of gears without the original shim and your starting with an empty case to build. That is what I always liked about Dana gears. They have a number either positive or negative that gives you a starting point when selecting a shim.
805moparkid
Slant and AFX Guy
haha!
replicaracer43
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Yeah, I get what your saying, I know aftermarket gears like Richmond have the pinion depth marked on them, but it would be a pain to get that right unless you had a "set up" bearing for the pinion, that was slip fit...
replicaracer43
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I also see .028 to .030 on most "489" cases, for whatever that's worth.....
I did just that I bought the set up bearings from Randy's. One for the 741, 742,489. They slip on and off, makes life a whole lot easier.
Don't forget to use the hogged out old front pinion bearing to center it up for a clean depth measurement...
I'm sure some ivory tower, know it all will be in shortly to say you should never do it that way and imply that I'm telling you do set pinion preload with the old bearing too... which isn't the case. :mrgreen:
I'm sure some ivory tower, know it all will be in shortly to say you should never do it that way and imply that I'm telling you do set pinion preload with the old bearing too... which isn't the case. :mrgreen:
Yup I can see it coming soon.
805moparkid
Slant and AFX Guy
god damn it you never use...
lol
lol
And to stay on track with this. .028-.040 seems to be a range that pops up a bit.
I hone the big bearings on all of them I do. Long as the bearing is good, that's a good way to do it.
Supershafts
Well-Known Member
It's .020 for the NPD.
69MOPE
Well-Known Member
It is .029". That is with a "factory" gearset. That is with a perfect 0.000" machined housing and a gearset marked -0 or +0. The problem is the housing is not marked ever! The only way to determine the housing mis-machine is to do the math on a rear that has never been apart and never had noise. Say you tear down a rear and the gearset is marked -2 and the shim is a .027", that means the housing is mis-machined .004" shallow. Or if it marked +2 and the shim is .027 the housing is perfect .000". If it is marked +2 and the shim is .031" is housing is .004" machined to deep. This all goes out the window if you are using a aftermarket gearset marked with a pinion depth number. You then need a set-up to measure pinion depth, then shim, then recheck. I have been setting up Chrysler diff's since 1975 and the I have never been able the "read" the marking compound method. I have even tried reading the marking compound pattern then checking it after using the pinion measuring tool and found the two methods not even close. I hope this helps you.
Both patterns look good. I like the .009 little more.
Who's kit did you get? I bought a Summit & I think I could get closer with a tape measure!!
I went ahead & mocked it up w/original shim-0.031". The original pinion was marked (-1), so I used original shim,thinking nominal PD was 2.765 & new PD @ 2.769, that I would end up 4-5 thousandths deeper. Perfect for a drag style R&P setup!
I agree on the 0.009 BL, it has more contact area..........TKS, Mike
Exactly!! Knowing the nominal PD & shim, you can interpolate the new shim from the original pinion marking & shim. It can be done! The proverbial fly in the ointment is the rear pinion bearing & race stack height. I always compare & adjust as necessary.
I - and don't hold this against me - I am an old Ford tech, starting in 1972. I started reading patterns & went to PD gauge about 77 or 78. The two methods are not comparable to each other! You set one up w/PD gauge & then ck pattern you will be disappointed! But I can't remember ever having one noisey!!...........TKS, Mike
Karl piper
New Member
Hi I have a 489 and I've taken out the 2.76 gears and replaced them with a sure grip and 3.23 gears it had a 20 thou pinion spacer and the new gears had no markings for pinion, I put it back together and set back lash with existing spacer and I had pretty good markings,I'm getting slight noise at 30mph and quite loud on coast to slight load from 45_52 mph,I'm thinking pinion is slightly out I saw sum guys say try 28_30 thou any thoughts or help would be very appreciated
.....I did a 742 case with 2.76s it had a .200 shim I was blown away as the thickest I ever used b4 was .060.........put in 4.10s and used a .088 shim stack............kim........
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