8.75 Not centered?!?!

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DGrace

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Hello. I recently purchased a Moser fabricated 8.75 and am in the process of installing it in my '73 Dart. I had it made to optimize the wheeler space with a 15x8.3 Weld S71 and 255 60 ET Drag Radials. I got everything mocked up - spring perches @ 42" and u-bolts snugged up, offset shackles, I haven't gotten My Dr. Diff offset front hangers yet (trying to determine everything will fit) but I have the original front hangers in place and against the frame. The wheels are bolted to the axles and slid into the housing (no carrier yet) and against the snap ring. My problem is the passenger side is about 1/2 - 3/4" closer to the outside fender. Was planning on Dr. Diff rear Cobra disc brakes but now it will hit. The spring perches must be set equal distance from the housing ends correct? Is there any other way to center the rear? Can't really move it to the driver side because it's already very close to the springs. Stuck and not sure what to do. I'm planning on SS springs with poly bushings but am just using the stockers for mocking. As always, any advice, experience, knowledge, and prayers is greatly appreciated! Been a while since I've messed with this stuff but I don't remember it being this tough?

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just for fun, measure from the outer fender to the frame rails and see if you are off there

it could be your front hanger bushings are making it not sit right, with the offset shackles in place, but i would guess your just seeing slop in the build

production and assembly tolerances are a lot tighter then they used to be, and what your describing isnt unusual
 
diymirage said:
just for fun, measure from the outer fender to the frame rails and see if you are off there

it could be your front hanger bushings are making it not sit right, with the offset shackles in place, but i would guess your just seeing slop in the build

production and assembly tolerances are a lot tighter then they used to be, and what your describing isnt unusual
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Both sides measure 14 1/2" from frame to wheel well lip.
 
It doesn't look that far off in the pics but with brakes installed, that's an extra 1/4 - 1/2" further out depending on the brakes.
 
Not a surprise that the axle isn't centered up perfect in the car. These cars were built with sloppy tolerances all around.

Now it's time to massage stuff to get it spot on. Verify the perch locations.
 
crackedback said:
Not a surprise that the axle isn't centered up perfect in the car. These cars were built with sloppy tolerances all around.

Now it's time to massage stuff to get it spot on. Verify the perch locations.
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Perches are supposed to be equal distance from the housing ends correct? Dr. Diff informs 42" apart using his offset front hangers. In the pics, it's 41.5". Will see when I get the hangers & it's bolted up tight. Just trying to get as much info as possible before perches are welded. Thank you.
 
My 69 has the same problem, one side is closer to the right fender. As stated the cars are not equal and have at up to at least 1/2" tolerance in them.
 
Steven190 said:
My 69 has the same problem, one side is closer to the right fender. As stated the cars are not equal and have at up to at least 1/2" tolerance in them.
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Mine too. Centered to the frame rails & inner fenders, but the outer fenders themselves differ by 1/2". It is just the way these cars were slapped together!
 
69_340_GTS said:
Mine too. Centered to the frame rails & inner fenders, but the outer fenders themselves differ by 1/2". It is just the way these cars were slapped together!
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Even though the measurement from the frame to the wheel lip is equal? I'm just not seeing where the difference is in the body/frame.
 
No, no. The rear end is centered relative to the frame rails. But the fenders (i.e. "fender lip") themselves are different side-to-side. Basically one side has about 3/4" to 1" more room for a tire than the other side does. This is not unusual!
 
now that you got pictures up, it almost looks like the spring perches are the same on both sides (relative to the wheels, as we would expect)
but the springs on one side run level, while on the drivers side it moves inward, away from the tire

id say, install the offset front hangers and see where you're at
 
Hang on boyz
This won't work without the spacer installed and the endplay set. Currently there is no way of telling which axle will end up where. That's why it's best to not have the perches installed until the very last.
Unless you're using Green bearings, then just put me on ignore.
On the inside edges if you have 1/8 from the sidewall to the spring with weight on the tires, then you have enough room. To the inner tub-walls you need a minimum of 1/4 inch for straight line work, and at least 3/8 for bombing around town. I usually narrow the rear a little too much and then pound in the offending areas.
To the outside 1/2 inch is good at the fender lip.
Almost nobody ever sees both sides at the same time unless the car is on a hoist. And almost nobody can remember 3/8inch difference when wandering around the car. And it won't affect the handling. If it bothers you, install a spacer on the one side to even it up.
I prefer Timkins cuz I can move the axles around with spacer thickness and fabricated backing plate shims, as may be required.
I don't like the Greens; just personal preference. Timkins last forever.
 
diymirage said:
now that you got pictures up, it almost looks like the spring perches are the same on both sides (relative to the wheels, as we would expect)
but the springs on one side run level, while on the drivers side it moves inward, away from the tire

id say, install the offset front hangers and see where you're at
Click to expand...
Thank you, that's my plan at this point. Ordered my offset front hangers from Dr. Diff but they won't be in for a bit - site says he's at SEMA. Also have my SS springs coming too. The "funny" thing is, when I got the housing and axles from Moser, it was a touch short. I was planning on using Wilwood low profile disc brake setup but when I mocked it up, the left side looked too close to the spring and Dr. Diff informed me that his 10.7 Cobra kit would push it out a little more..... so I had the axle registers cut to fit them (Mopar specs). Now the right side seems too close to the fender and the Cobra kit will push that side out too far. I'll get it all bolted in and snugged up and see where I'm at. Perches welded and brakes ordered when I figure it out. The only thickness the Wilwood kit adds is the .18 rotor thickness. That difference on the right side is a head scratcher. I measure and measure and can't seem to see where the difference is? I noticed the 7.25 rear was off on the right also but thought it may be worn springs and bushings? Thank you for your input.
 
Since the spring perches are not welded yet, loosen up the u bolts and center the axle using the fender. That should center your tires. Where does that put the perches and springs at?
 
Jadaharabi said:
Since the spring perches are not welded yet, loosen up the u bolts and center the axle using the fender. That should center your tires. Where does that put the perches and springs at?
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I figured the axle/housing measurement by centering the wheel/tire combo in the wheel wells. Without the springs, the wheels are right on. When the springs are clamped at 41.5", the difference from side to side occurs.
 
With the axle and tires centered you tighten the the u bolts an the axle shifts sideway?
 
Jadaharabi said:
With the axle and tires centered you tighten the the u bolts an the axle shifts sideway?
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When the springs and perches are snugged equal distance from the housing ends, and positioned close (no offset hangers yet) to where they will bolt, the wheels shift to the right. It's as if there's not as much room on the passenger side but I can't see a measurement discrepancy?
 
DGrace said:
When the springs and perches are snugged equal distance from the housing ends, and positioned close (no offset hangers yet) to where they will bolt, the wheels shift to the right. It's as if there's not as much room on the passenger side but I can't see a measurement discrepancy?
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If you're using the stock spring mounts shouldn't you be at 43 inches instead of 41 and a half.
 
Jadaharabi said:
If you're using the stock spring mounts shouldn't you be at 43 inches instead of 41 and a half.
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No, you're a couple posts behind. Going to use Dr. Diff's offset hangers. Tried a little narrower to see if it would help.
 
If you Center your rear axle with the tires at the outside body line with the springs Hanging basically loose and your u-bolts loose. Where does the spring come to on the rear end forgetting about 43 in or 41 and a half just with the spring hanging loose on each side where are they on the axle housing?
 
mycuda said:
Are those pics with the car on ground totally?
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No. The center section isn't installed and the bearings are against the snap rings. Wheels are hand tightened with a couple lug nuts. Frame is suspended up a bit so I can get under it and the housing is supported with a jack letting the tires contact the floor with light pressure. I know it's not the most accurate but I figured it would give me a good indication from side to side.
 
Jadaharabi said:
If you Center your rear axle with the tires at the outside body line with the springs Hanging basically loose and your u-bolts loose. Where does the spring come to on the rear end forgetting about 43 in or 41 and a half just with the spring hanging loose on each side where are they on the axle housing?
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Without the springs installed and the wheels centered in the wells, there's not enough room to fit the right side spring. The second picture is the right side spring against the frame with only about 1/4" of clearance from the tire and maybe a fingers width to the lip. The brakes will shift it out + or - a 1/4" also. I realize from all the posts I've read (even some of the Chevy sites) that there's an issue with the right side and when you push the limits as far as space is concerned, those issues are more noticeable. I know quite a few have dealt with this and I'm just looking for advice. I figured that's part of the purpose of this site. Thank you for you help. I'm waiting for some parts to get a more accurate picture of what's going on. I'll post when they're installed.
 
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