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Mopar A-body 8-and-three-quarter (8.75 or 8¾) inch axles
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Feb 4, 2025
A full dive into Plymouth and Dodge A-Body (Valiant, Duster, Demon, Dart, Swinger, Barracuda) 8 ¾ inch axles — what they were used on, changes from year to year, adapting to fit your car (or new brakes), SureGrip, and so forth! Presented by CudaPete. #mopar #axle #dodge #plymouth #dart #valiant
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hello welcome to today's edition of
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motels I'm your host Cuda Pete and today
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we'll be talking about the 8 and 3/4 in
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or 8.75 in Mopar re axle as found in the
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a bodies from 1968 to
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1972 so why have we specified those
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years those are the ones that are most
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common and the most applications exist
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the 8 3/4 was available in the earlier a
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bodies but it was a different axle it
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had taper shafts that changed in ' 66
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but the axle is still a little different
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and it really became more common in 1968
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so that's what we're going to be talking
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about today and we're going to be
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talking specifically about a body
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applications because those tend to be
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the most confusing to everybody so as a
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definition of a body this will be a
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Dodge Dart a Plymouth Valiant a Plymouth
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Duster Barracuda and so forth however
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the 8 and 3/4 8 and 3/4 could be found
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other other cars and even truck
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and vans as it was used for heavy duty
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service so in 6869 a bodies that could
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have the 8 and 3/4 is V8s the 273 the
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318 the 340 the 383 and
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440 these would all be either with the
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727 automatic or three four-speed manual
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transmissions starting in 70 and 72 it
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was only the 318 and the 34 40 that this
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was available with and again it was with
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the
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727 or a 304 speed however you could
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also find this as part of the towing
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package with the slant 6 up front or for
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a heavyduty application again in this
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case it would be the manual transmission
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or it would be the 727 automatic the
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83/4 was never found before the 904 I'll
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qualify that and not say never because
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as we all know M par is Infamous for
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making specials and unique one of the
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kinds so I know there's probably
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somebody out there who has a 73 dodge.
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four door with the 426 Hemi and the 904
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and the 83/4 inst all Factory stock if
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you have that car we'd like to hear from
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you the housing itself The Design This
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is called the hotkiss design or banjo
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design and the reason for that is this
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Center section is removable with these
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bolts here you can unbolt this take the
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whole Center section with the gears out
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so in that case it's very similar to the
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Ford 9 in now where do we get 8 and 3/4
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or 8.75 and 9 in that's the diameter of
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the Ring GE Ford's had a 9 in diameter
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ring gear Mopars have an 8 and 3/4 in
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diameter ring gear so there's a/ qu inch
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difference this is also known as the
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banro type because some people think it
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looks like a banjo when this is removed
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um this was in service up until in a
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bodies up until
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1972 as they said and they're unique for
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the a bodies they're different than the
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B's so in the case of the a body from
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end to end flange to flange you're going
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to find this is 52 and 58 in wide and
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then spring perch to Spring perch is 43
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in Center to center now in the case of a
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b body this is going to be wider the
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spring purch by approximately half inch
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on either side so an inch difference
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because it's a bigger
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car and even among that there's sub
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subset differences between the two
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between 68 69 and 70 to 72 this axle
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housing shown here this is a 70 to 72
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variant and that's we can tell because
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the vent for the axle tube is located on
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the driver's side sort of maybe a
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quarter the way down the axle tube if
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this was 68 or 69 the vent tube would be
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located more towards the center section
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so it's a little different when you're
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looking at these um designs
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so the center section though is the same
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regardless if it's an a body B body C
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body all the center section interchange
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but there are three different variations
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of the center section the first one
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which this one is is a 741 and you can
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tell that the numbers are here cast into
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the side you can see
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741 and this is also known as the small
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type it has a 1 and 38 inch stem pinion
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this is the stem pinion here so it's 1
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and 38 the next one up would be the 742
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case that has a little bigger stem
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pinion as 1 and
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3/4 and then the biggest one the 489 has
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a 1 and 78 in taper stem pinion these
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are cylindrical stem pinions whereas the
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49 is a tapered design and the
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741 fine for most Street back
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applications same for drag races
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um the 489 is considered the most robust
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so for a real high horse applications
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you'd probably want to use the um 49
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gear ratios that were available uh since
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this could be found in trailer towing
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packages trucks vans cars they vary 2.76
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2.93 323 this is 323 3.31 3.55 373 391
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and 410 so those would be available from
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the
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factory these are also available with
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the short grip which is Chrysler's word
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for py traction um so there were two
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types of short grips there's the earlier
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version which is called the clutch type
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and then there's a later version called
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The Cone type this has the con type in
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it and one way you can tell if a rear
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axle has positraction or Su grip I
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should say is by turning the axle and if
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both sides go in the same direction when
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you do this that means it's a short grip
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if they go in opposite directions that
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means it's an open rear
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rent so this one is a 323 with a short
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grip uh cone type uh unit on it as far
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as U joints go there's two types of U
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joints there's the small 760 7260 which
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this is the
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7260 and then there's the larger type uh
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7290 which would be here so in opinion
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you can have a small or a large Type U
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joint and then of course the drive shaft
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would be unique for 8 and 3/4 in
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applications a lot of cars came with the
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725 7 and a/4 inch actual this housing
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is actually two and a/4 in longer than
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the 7 and a/4 so that means the drive
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shaft has to be 2 and 1/4 in
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shorter to fit in the car properly so if
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you're making that conversion uh you
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should still measure it but
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approximately you'll have to shorten the
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drive shaft by 2 and 1/4 in as far as
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axles
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go they're the same length on both sides
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and all a body 8 and 3/4 in rear ends
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are small bolt pattern meaning five on
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four lug nut
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configuration with right hand threads on
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the passenger side or right side and
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left-handed lug nuts threads on the
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driver's side or left side side of the
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car so that's the standard application
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for an a body these never came um of
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course qualify that these never did come
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from the factory with the big wheel bolt
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pattern and they never did come with the
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right-handed lug nuts on the driver's
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side so they're all small wheel bolt
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pattern and they are all configured
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right hand thread left hand thread stock
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bearings in these axles are a tapered
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roller bearing but there's also you can
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put in a sealed bearing most commonly
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known as the green bearing this axle has
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been retrofitted with the green bearing
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uh the big benefit with that is there's
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no endplay adjustment with the tapered
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bearings you have to have an endplay
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adjustment on one side not a big deal to
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do but with the sealed bearings you just
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put them in tighten it down and you're
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good to go um there are some differences
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on these cars depending on years like I
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was saying if you're going to do that
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version for the 7 and A4 these have 3
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tubes
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on a small wheel BT pattern 7 and A4 has
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22
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in so that means you
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need 3
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in to put on
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here going that on the bottom mounting
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plates for your shocks you'll need 3in
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drill Val special
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your shs go with that now if you have
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ler 74 in rear they did from a car that
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had post 73 Disc Brakes Tower disc
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brakes I should say and a 10in rear
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drums then that seven and a quar would
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beig and have Tu on it so if you have
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that then you can use the parts from
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that so there are a lot of specialized
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Parts on this this rear axle that are
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unique
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bodies and that transfers down to the to
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the to the brakes themselves so we have
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1 and 3/4 in TRS on
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here break shoes and to go along with
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that we have a
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special it has flare or on it and that's
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to fit in the space that this has to fit
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into so this is a special drum it's
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Unique to the bodies
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and this is the correct one for the
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application going along with the brakes
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because this two wased in different
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positions these lines so there's
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actually three sets of lines available
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and three different keys this key here
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is the 1470 and 71 if you had 68
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69 this would be the the only difference
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it looks the same from the top the way
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it's round off turn match the profile of
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the housing over this location here and
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this would be for 6869 this is going to
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be 70 and 71 and in 72 they changed it
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has a completely different block T which
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I don't I don't have but each has its
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own unique set of brake lines so the
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brake lines for the
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6869 would end here and the driver's
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side would be shorter this would be 70
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to 72 or 71 excuse me and 72 will be
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different
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72 the driver the passenger side is the
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same but the driver side is different
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because this block is different so you
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have to be careful with that if you have
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a setup that you're doing for
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72 it's the same as 73 for the 8 and A4
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inch so I guess maybe Chrysler was
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trying to economize using similar Parts
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at that time but just be aware that
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there are three different types brake
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line setups on the back and three
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different types of
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T's
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so with that um there's also a different
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brake hose for the connection to the to
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the main brake line where the
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6869 is approximately 1 inch longer than
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the 70 or um 71 so you have to make sure
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that you get the right correct rubber
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brake hose to connect the system
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up but in any case this was just a
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general overview
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of what is involved with the 8 and 3/4
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for the a bodies from 68 to
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72 there's a lot of questions out there
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about what parts fit which years what
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interchanges what doesn't interchange a
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lot of people try to
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modify uh bigger housings bbody or uh
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cbody or whatever to make them narrower
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to fit within the a body confines but if
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you can find one of these uh they're
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getting harder to find but it's usually
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the best if you can get what's correct
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for the application so like I said I
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hope this helps clear everything up and
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if you have any questions or comments
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please let leave them below thank you
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[Music]
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