Moparts

Centering rear end in chassis, anyone done this

Posted By: MileHighDart

Centering rear end in chassis, anyone done this - 03/19/11 09:55 PM

Not sure if this was actually planned by chrysler, or if its just manufacturing tollerances back then.

On my 68 Dart the 8-3/4 rear seems to be off center somewhat. Just judgeing from the clearance between the tire and the fender lip on both sides. I have about 1" clearance on the pass side, and about 1/4" on the drivers side.

Anybody try to fix this, either by elongating the locating hole on the spring perch, or buy cutting the perches off the housing and welding on new ones ?

I'd just like to get it shifted to the right about 3/8" to make my clearance on both sides a little more even.

Thanks for any input !
Posted By: Four40mopar

Re: Centering rear end in chassis, anyone done this - 03/19/11 10:17 PM

Are you sure this is an A body 8 3/4? Sometimes B body 8 3/4's get shoehorned into A bodies.
Posted By: MileHighDart

Re: Centering rear end in chassis, anyone done this - 03/19/11 10:18 PM

I removed this 8-3/4 from a 71 Scamp I used to have and installed it into my Dart.
Pretty sure it was stock in the Scamp.
Posted By: ahy

Re: Centering rear end in chassis, anyone done this - 03/19/11 10:38 PM

If you loosen everything up - front hanger to frame bolts and U bolts and give it a good shove, you may get some movement. I doubt you'll get 3/8" but worth a try.

Uneven spacing isn't all that unusual. Tolerences weren't held very tight.
Posted By: 1_WILD_RT

Re: Centering rear end in chassis, anyone done this - 03/19/11 10:55 PM

In the past I've loosened everything up, attached a come along to force everything to one side then tightened everything up... On a current project I've got the spring pads cut off & it's definitely a better approach, things will center perfectly & won't be in a bind...
Posted By: Stanton

Re: Centering rear end in chassis, anyone done this - 03/20/11 02:52 AM

b-body Plymouths are slightly off center.
Posted By: autoxcuda

Re: Centering rear end in chassis, anyone done this - 03/20/11 07:45 AM

My 68 Dart is off center compared to the rear body.

BUT REALIZE, you are just centering the rear end to the body. The body is just along for the ride. The position of all four tires relative to each other is what matters for the car to go down the road straight.

That being said it's probably not going to be down to 1/16" or something. Alignments alone change wheelbase and track width some. The service manual has some guidelines, but you'll have to look at your last alignment sheet.
Posted By: 1_WILD_RT

Re: Centering rear end in chassis, anyone done this - 03/20/11 07:55 AM

Quote:

My 68 Dart is off center compared to the rear body.

BUT REALIZE, you are just centering the rear end to the body. The body is just along for the ride. The position of all four tires relative to each other is what matters for the car to go down the road straight.

That being said it's probably not going to be down to 1/16" or something. Alignments alone change wheelbase and track width some.




Alignments change track width in the front.. The reason I've chased centering the wheel in the wheel well side to side is for max tire clearance.. & I'm sure thats what the O/P is looking for as well..... My current project isn't a Mopar but the same ideas apply so I've cut the perches & I'm also likely gonna order rear springs with the center pin moved 1.5" rearward from stock.... There are other ways of moving the axle rearward but since I'm planning the replace the springs & ESPO will do it why fight it...

Attached picture 6539406-sideveiw.jpg
Posted By: screamindriver

Re: Centering rear end in chassis, anyone done this - 03/20/11 10:59 PM

I've swapped out many rears...Different body styles,narrowed or simply correcting angles...And I've always centered the rear to the wheelwells when welding in new perches... I never ran into any problems with an alignment afterwards....I just figured I was correcting the bad tolerances...
Posted By: RodStRace

Re: Centering rear end in chassis, anyone done this - 03/20/11 11:08 PM

I'd measure the unibody too, it may be just a fender skin off or the whole thing off.
Posted By: MileHighDart

Re: Centering rear end in chassis, anyone done this - 03/21/11 12:05 AM

Quote:

I'd measure the unibody too, it may be just a fender skin off or the whole thing off.



I did do a little measureing this way. Like from the outside of the framerail out to the edge of the fender.
Its different on the two sides of the car.
Its great, the precision with which our cars were built.

Doing some more measureing right now with the new wheels/tires on. I'll probably just try to move it to the right about 1/4" just to center it within the wheel wells a little better.

Heres what I'm looking at.
This is the passenger side, measured with a tape measure I have 1" clearance.

Attached picture 6540545-pass.JPG
Posted By: MileHighDart

Re: Centering rear end in chassis, anyone done this - 03/21/11 12:13 AM

Heres the Drivers side, Measures 3/8" clearance.

Attached picture 6540558-drivers.JPG
Posted By: Mopar_Country

Re: Centering rear end in chassis, anyone done this - 03/21/11 03:29 AM

Is it an optical illusion or is the lip on the driver side a little wider than the other?
Posted By: DirectSubjection

Re: Centering rear end in chassis, anyone done this - 03/21/11 03:53 AM

70s Mach1's have the same issue - really annoyed my buddy.
Posted By: moparpollack

Re: Centering rear end in chassis, anyone done this - 03/21/11 04:08 AM

My buddy's 71 Barracuda was the same way. Just poor sheet metal alignment. Hammer as needed and move on.
Posted By: MileHighDart

Re: Centering rear end in chassis, anyone done this - 03/21/11 04:44 AM

Quote:

Is it an optical illusion or is the lip on the driver side a little wider than the other?



You must have really good eyes, cause I just went out an measured that. The pass side lip is slightly narrower, but just my maybe 1/16" depending on where exactly you measure it. Both lips are between 7/8" and 1". I could trim them both a little bit just for more clearance.
Posted By: Mopar_Country

Re: Centering rear end in chassis, anyone done this - 03/21/11 04:54 AM

Another thing you might check is the distance from the top of the wheel to the lip. If the driver side is a tad lower it would be into the bulge more, reducing the distance.
Posted By: ghostrider

Re: Centering rear end in chassis, anyone done this - 03/21/11 05:33 AM

The entire driveline is supposed to be just slightly off center by design. Shouldn't cause you any problems to center it, the u-joints just work at the slightly different angle.
Posted By: lokalik

Re: Centering rear end in chassis, anyone done this - 03/21/11 12:34 PM

Quote:

Is it an optical illusion or is the lip on the driver side a little wider than the other?

sure looks like one is wider than the other. you could use masking tape and transfer the pass side to the drivers side to see how much you need to remove.
Posted By: NachoRT74

Re: Centering rear end in chassis, anyone done this - 03/21/11 03:14 PM

ok... I have same "issue" on my Charger... IN FRONT AND REAR...

rear is small diff but in front I have around 1" difference being passenger side deeper into the fender

( and is not the only 73/74 charger I have noticed this )
Posted By: BradD

Re: Centering rear end in chassis, anyone done this *DELETED* - 03/21/11 03:54 PM

Post deleted by BradD
Posted By: RodStRace

Re: Centering rear end in chassis, anyone done this - 03/21/11 04:06 PM

Quote:

Your whole drive line is off center to the right!! They were built this way. It was so the car would be better balanced with a driver behind the wheel.
Brad



That would make sense if the right side is tight.
This one is tight on the left rear.
They just didn't have tight tolerances back then.
Posted By: JohnRR

Re: Centering rear end in chassis, anyone done this - 03/21/11 05:17 PM

How is your alignment of the trans yoke centerline to the pinion yoke centerline , are they in line or is the rear shifted to the left?

The reason the driveline is off center is to give the driver a little more room in the passenger compartment I would think.
Posted By: ghostrider

Re: Centering rear end in chassis, anyone done this - 03/21/11 05:46 PM

Quote:

How is your alignment of the trans yoke centerline to the pinion yoke centerline , are they in line or is the rear shifted to the left?

The reason the driveline is off center is to give the driver a little more room in the passenger compartment I would think.



They are offcenter to the passenger side for clearance around the steering gearbox that is on the leftside.
Posted By: Pntastar69

Re: Centering rear end in chassis, anyone done this - 03/21/11 07:49 PM

Quote:

Heres the Drivers side, Measures 3/8" clearance.



Was that 1/4 replaced recently? If so, perhaps the lip wasn't shortened. They do require trimming, specially the 1/4 skins.
Posted By: MileHighDart

Re: Centering rear end in chassis, anyone done this - 03/21/11 07:59 PM

Quote:

Quote:

Heres the Drivers side, Measures 3/8" clearance.



Was that 1/4 replaced recently? If so, perhaps the lip wasn't shortened. They do require trimming, specially the 1/4 skins.



No, the car is all original, no new sheet metal
Posted By: 69fish

Re: Centering rear end in chassis, anyone done this - 03/26/11 04:50 AM

I don't have anything to add to the discussion-I just wanted to say those wheels really "woke" your car up. It looks like a different car-looks great!
Posted By: Mopar_Country

Re: Centering rear end in chassis, anyone done this - 03/26/11 05:22 AM

Did you come to a conclusion on the spacing?
Posted By: 68HemiB

Re: Centering rear end in chassis, anyone done this - 03/26/11 05:38 AM

I'm sure glad you didn't get any paint on Elvira when you stabbed that rattle can to death.

I have nothing else to add.
Posted By: MileHighDart

Re: Centering rear end in chassis, anyone done this - 03/26/11 06:20 AM

Quote:

Did you come to a conclusion on the spacing?



Not a conclusion really, But I do think its more of an issue of the body panels being a little different from one side to the other rather than the rearend being offset in relation to the frame rails.

I just got the new green bearings for my new bbp axles yesterday and finally have it assembled so I can really see where the wheels are going to set.
I also trimmed the width of the fender lip on both sides by a little over 1/8". Laid it out with masking tape, and ground off a little with a disk sander and a 50grit disk.

I think I can live with the clearance I have now, although it is still different from one side to the other.
I have about 1" clearance on pass side, and now have about 1/2" on the drivers side. So I guess I'm not going to worry about moving the rear for now.

This is how the drivers side looks with the lip trimmed back a little.

Attached picture 6550173-S5002754.JPG
Posted By: MileHighDart

Re: Centering rear end in chassis, anyone done this - 03/26/11 06:24 AM

Quote:

I don't have anything to add to the discussion-I just wanted to say those wheels really "woke" your car up. It looks like a different car-looks great!



Thanks !

Actually it really does look different now, since its about 1/2 primered, getting it ready for new paint. But I agree with you, the wheels really look sweet, better than the rallys I took off.

Attached picture 6550176-S5002759.JPG
Posted By: MileHighDart

Re: Centering rear end in chassis, anyone done this - 03/26/11 06:26 AM

another pic just to show off a little.

Attached picture 6550179-S5002745.JPG
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