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Forum locked  This topic is locked, you cannot edit posts or make further replies.  [ 7 posts ] 
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 Post subject: 8 3/4 set-up
PostPosted: Thu May 02, 2002 3:57 pm 
I would like to put a new ring & pinion in my sons 8 3/4 rear. It is a 489 case. I have the shim kit, crush sleeve...etc, but do I have to have a special tool or fixture to set the pinion depth? Is there another way around this (the cheap man's way!!) I have a dial indicator and a set of micrometers.

I'd like to do this myself if I can, and use it as a teaching tool with my son. Actually 20 years ago I knew how this was done, but I have a poor memory! Man! I must be getting old.

Thanks for all your help.

Rick

rcovalt@innernet.net


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PostPosted: Thu May 02, 2002 5:20 pm 
(User Above) wrote:
: I would like to put a new ring & pinion in
: my sons 8 3/4 rear. It is a 489 case. I have
: the shim kit, crush sleeve...etc, but do I
: have to have a special tool or fixture to
: set the pinion depth? Is there another way
: around this (the cheap man's way!!) I have a
: dial indicator and a set of micrometers.
:
: I'd like to do this myself if I can, and use it
: as a teaching tool with my son. Actually 20
: years ago I knew how this was done, but I
: have a poor memory! Man! I must be getting
: old.
: Thanks for all your help.


Rick,

Are you putting-in an aftermarket ring & pinion?
Are there some numbers engraved or painted onto the new gears??
Do you have a factory service manual? Do you have impression and lapping compound?
DD


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PostPosted: Thu May 02, 2002 6:07 pm 
(User Above) wrote:
: Rick,
:
: Are you putting-in an aftermarket ring &
: pinion?
: Are there some numbers engraved or painted onto
: the new gears??
: Do you have a factory service manual? Do you
: have impression and lapping compound?
: DD


I'm installing new Richmond gears and they do have the numbers etched on them for pinion depth and backlash. I have the lapping compound, but I don't have the factory service manual. (Which I'm sure is what I should have.)
Thanks for your help,

Rick

rcovalt@innernet.net


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PostPosted: Thu May 02, 2002 11:12 pm 
(User Above) wrote:
: I'm installing new Richmond gears and they do
: have the numbers etched on them for pinion
: depth and backlash. I have the lapping
: compound, but I don't have the factory
: service manual. (Which I'm sure is what I
: should have.)
: Thanks for your help,


Rick,
That pinion depth number is the key you need to select the correct shim. If I remember correct, that number is the distance between the ring gear carrier centerline (capfaces) and the top of the pinion head. (2.750 inch range?) There are some special tools which makes shim selection real easy, (bolt this tool in and use the shims like a feeler gage, just find the one that fits snug inbetween the tool) or you need a depth micrometer and a calculator. You may want to call around to rearend / tranny shops in your area and see if they have that tool you could borrow or rent. Randy's sells that tool at a reasonable cost. (may-be we can split the cost, I need one!)

Trouble with setting-up rear end gears is that you have to make your "best guess" on the main pinion shim thickness, assemble everything, set the preloads and backlash, then take a contact impression off the gear teeth. If it is off center, you take everything apart, (including pressing off the main pinion bearing) and select a different shim based of what the contact pattern looked like. ( the shop manual shows these contact patterns and how to adjust)

If you are good, (or lucky) you get it right in 2 or 3 trys. I have had to do so many trial assemblies on these that I have a main pinion bearing that has the ID honed-out to a slip fit. I use that bearing to do trial assemblies and find the correct shim / gear pattern, then swap (press-on) the new bearing. (I measure both bearings to see if they have the same height and adjust the shim for any thickness difference)

What ratio gear are you going to? Most of the low ratios I've built use a main shim in the .082 to .095 range, the 4.88 I recently built used a .086 thick shim.
DD


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PostPosted: Fri May 03, 2002 3:50 pm 
(User Above) wrote:
: Rick,
: That pinion depth number is the key you need to
: select the correct shim. If I remember
: correct, that number is the distance between
: the ring gear carrier centerline (capfaces)
: and the top of the pinion head. (2.750 inch
: range?) There are some special tools which
: makes shim selection real easy, (bolt this
: tool in and use the shims like a feeler
: gage, just find the one that fits snug
: inbetween the tool) or you need a depth
: micrometer and a calculator. You may want to
: call around to rearend / tranny shops in
: your area and see if they have that tool you
: could borrow or rent. Randy's sells that
: tool at a reasonable cost. (may-be we can
: split the cost, I need one!)
:
: Trouble with setting-up rear end gears is that
: you have to make your "best guess"
: on the main pinion shim thickness, assemble
: everything, set the preloads and backlash,
: then take a contact impression off the gear
: teeth. If it is off center, you take
: everything apart, (including pressing off
: the main pinion bearing) and select a
: different shim based of what the contact
: pattern looked like. ( the shop manual shows
: these contact patterns and how to adjust)
:
: If you are good, (or lucky) you get it right in
: 2 or 3 trys. I have had to do so many trial
: assemblies on these that I have a main
: pinion bearing that has the ID honed-out to
: a slip fit. I use that bearing to do trial
: assemblies and find the correct shim / gear
: pattern, then swap (press-on) the new
: bearing. (I measure both bearings to see if
: they have the same height and adjust the
: shim for any thickness difference)
:
: What ratio gear are you going to? Most of the
: low ratios I've built use a main shim in the
: .082 to .095 range, the 4.88 I recently
: built used a .086 thick shim.
: DD


The gears I am installing are 4.30 ratio. I'm sure I will be installing some more of these in the future, so I may check into purchasing the tool from Randy's. Do you remember roughly how much they were?
Even with the proper tool, do you still have to install the bearing and new pinion into the housing to get a reading? Then adjust from there? Would starting with whatever shim is in the original be a good starting place?

Thanks,

Rick

rcovalt@innernet.net


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PostPosted: Sat May 04, 2002 9:25 pm 
(User Above) wrote:
: The gears I am installing are 4.30 ratio. I'm
: sure I will be installing some more of these
: in the future, so I may check into
: purchasing the tool from Randy's. Do you
: remember roughly how much they were?
: Even with the proper tool, do you still have to
: install the bearing and new pinion into the
: housing to get a reading? Then adjust from
: there? Would starting with whatever shim is
: in the original be a good starting place?
: Thanks, : Rick


What is that spacing number on your gears?
I have done a bunch of these by starting with the spacer out of the stock rear but take a close look at the factory gears first, there is a number painted right on the pinion head, starts with a + or a - sign, this is a referance to how far off "perfect" that gearset is. ( -0, sometimes + 0 but the - was faster to write so that's what you see to indicate "perfect" centerline) If I see a big number, like + 24 that means the shim will be way to thick for a "perfect" (- 0) gearset, so I will try a thinner shim from the start.

Once I take my best guess, assemble and check the contact pattern, then try again, and again . . .
I think Randy's checking tool is a bit over $100.00, it just sets up a small slot space to slide the shims through. The shim that slides through "snugly" is the one that gets you pretty darn close if not "spot-on", on the first try.
DD


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PostPosted: Fri May 10, 2002 5:48 pm 
(User Above) wrote:
: What is that spacing number on your gears?
: I have done a bunch of these by starting with
: the spacer out of the stock rear but take a
: close look at the factory gears first, there
: is a number painted right on the pinion
: head, starts with a + or a - sign, this is a
: referance to how far off "perfect"
: that gearset is. ( -0, sometimes + 0 but the
: - was faster to write so that's what you see
: to indicate "perfect" centerline)
: If I see a big number, like + 24 that means
: the shim will be way to thick for a
: "perfect" (- 0) gearset, so I will
: try a thinner shim from the start.
:
: Once I take my best guess, assemble and check
: the contact pattern, then try again, and
: again . . .
: I think Randy's checking tool is a bit over
: $100.00, it just sets up a small slot space
: to slide the shims through. The shim that
: slides through "snugly" is the one
: that gets you pretty darn close if not
: "spot-on", on the first try.
: DD


The pinion depth # is 2.767 and the backlash is to be .008. I haven't pulled the original punkin out yet to see what the factory markings are on that pinion.

I just re-read the installation instructions from Richmond, and it states that if you don't have a Pinion Depth gauge to try the old shim first. If that isn't available they say to try a .090 shim as a starting point.That's right in the ballpark of what you said.

When I try it I'll let you know how things went.

Thanks, Rick



rcovalt@innernet.net


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