Changing the rear end over

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Muad'Dib15

Muad'Dib15

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So, I'm in the middle of literally doing a 3/4 drive train swap on my barracuda. the wheels are being replaced, the rear end (7.25) is being replaced with a 489 8.75, and the engine is being rebuilt. Literally the only thing staying the same is the transmission. So I"m sticking a 489 housing out of a 68 Charger in the rear end to replace the 7.25 and I have a few questions.
1. how far do I need to narrow it. new wheels are 17x8 with a 4.75 back spacing.
2. is the body being off 3/4 of an inch normal. like one side with 245/60 15s in back clears by that much and the other drags?
3. what do I need to set the new pinion angle at?
4. What is that castlated nut on one axle? Does that set the bearing preload or something?
5. Can I use sealed outer bearings on it?

I'm trying to get this all done asap so if someone could help me soon I would greatly appreciate it.
 
Muad'Dib15 said:
So, I'm in the middle of literally doing a 3/4 drive train swap on my barracuda. the wheels are being replaced, the rear end (7.25) is being replaced with a 489 8.75, and the engine is being rebuilt. Literally the only thing staying the same is the transmission. So I"m sticking a 489 housing out of a 68 Charger in the rear end to replace the 7.25 and I have a few questions.
1. how far do I need to narrow it. new wheels are 17x8 with a 4.75 back spacing.
2. is the body being off 3/4 of an inch normal. like one side with 245/60 15s in back clears by that much and the other drags?
3. what do I need to set the new pinion angle at?
4. What is that castlated nut on one axle? Does that set the bearing preload or something?
5. Can I use sealed outer bearings on it?

I'm trying to get this all done asap so if someone could help me soon I would greatly appreciate it.
Click to expand...

I will try my best.

1) The stock A body width flange to flange is 52 5/8" I believe. A body spring perches are also 43" apart center hole to center hole, if I remember correctly.

2) Yeah. Body variations were pretty common across the board....although you might have previous repair.

3) Probably about 4-5* nose down.

4) That is the axle bearing adjuster. It is used to adjust axle end play.

5) Yes. The Mopar Green Bearing kit is a nice upgrade.
 
Muad'Dib15 said:
So, I'm in the middle of literally doing a 3/4 drive train swap on my barracuda. the wheels are being replaced, the rear end (7.25) is being replaced with a 489 8.75, and the engine is being rebuilt. Literally the only thing staying the same is the transmission. So I"m sticking a 489 housing out of a 68 Charger in the rear end to replace the 7.25 and I have a few questions.

1. how far do I need to narrow it. new wheels are 17x8 with a 4.75 back spacing.

As far as narrowing, I would suggest securing the car on stands, place the wheels/tires in the wheel wells where you want them and measure the distance between the two wheels where they mount.

2. is the body being off 3/4 of an inch normal. like one side with 245/60 15s in back clears by that much and the other drags?

The drivetrain is usually set to the right of the vehicle slightly to compensate for the engine being set to the right due to steering clearances.

3. what do I need to set the new pinion angle at?

I replaced my 7 1/4 in my 74 Sport with an early B rear, I maintained the same pinion angle.

4. What is that castlated nut on one axle? Does that set the bearing preload or something?

It is for setting axle end play.

5. Can I use sealed outer bearings on it?

If you're referring to green bearings, then yes. If it's a suregrip you may have to remove the thrust buttons or block from the center section depending on which unit you have.

I'm trying to get this all done asap so if someone could help me soon I would greatly appreciate it.
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If you shorten the rear you will more than likely need new axles, as the ones in there I don't believe can be shortened and made to work. Someone else can confirm or deny that.

I believe you can use C body axles shortened or just order new ones.

Someone else will chime in here and correct me if I'm wrong.

Also if you use the green bearings, the axle end play adjustment will no longer be needed.
 
1) The stock A body width flange to flange is 52 5/8" I believe. A body spring perches are also 43" apart center hole to center hole, if I remember correctly.
Click to expand...

I believe you are correct on the measurements there Rob.
 
Thanks guys, Muad's dad here. Where do I get this green kit for the rear bearings.
the rearend looks like it has a lot of pinion angle, pointing up..w.whats the correct angle.
also on the axle ends does this green kit come with the plate to secure axles in housing, taking place of that castlated nut, which is only one one axle. I understand why it's there but on one side only.???weird DODGE...nuff said Thanks D
 
Call Cass at http://www.doctordiff.com/ he can fix you up with everything you need. He is the differential guru.

I understand why it's there but on one side only.???
Click to expand...

There is really no need for one on each side if you think about it. Inside of the diff/suregrip the is what is known as thrust buttons (clutch type suregrip) and thrust block (auburn suregrip or cone type) the axles come to rest on these buttons or block (sandwiched in between if you will) and the adjuster tightens everything together.


The rearend looks like it has a lot of pinion angle, pointing up..w.whats the correct angle.
Click to expand...

Are you looking at it with the suspension hanging or loaded? 4*to 6* nose down. When I did mine I used a straight edge and carried some marks along the tube from the perches before I cut them off and moved them. I just used that same mark to align them to and welded them back on. I ended up with around 6*.

weird DODGE...nuff said
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Hey, hey, hey..........LOL.

Hope this helps.

Is there a sure grip in there now? If so the thrust buttons or block should be removed with the green bearings, I would suggest you ask Cass if you talk to him. Although some say they have put them together with them in there. I prefer the Timken roller bearings my self so it's a moot point.
 
Thanks , The third member appears to be just a standard diff, spider gears in the middle. He got himself a pretty tight rear. almost no backlash. So it wasn't abused. The guy gave him a pair of Srange axles too. A lot bigger around. If we have the rear narrowed the original axles , at the splined end become smaller as you move to the outer bearing. So I'm curious as to how they're going to re spline the axle if it is smaller in diameter. The stange axles are almost an eighth of an inch bigger in diameter. that would be doable I think.
 
How I set pinion angls.

http://www.rosslertrans.com/Pinion Angle.htm

It's one of the last thjngs that I do on a car. It's best done loaded on the suspension and at weight. Angle will depend on suspension style and use. Street car, try not to exceed 4* down.

On an A body rear, when installing the perches, factory set the angle of pinion is up 5* when perches are parallel to the ground. I NEVER install them there on my stuff. Most of the time I take most of that 5* angle out.
 
Just so you know too, "nose down" does not mean pointing down at the ground. It means nose down in relation to the drive shaft angle. So it could actually be point UP when you're done....
 
StrokerScamp said:
Just so you know too, "nose down" does not mean pointing down at the ground. It means nose down in relation to the drive shaft angle. So it could actually be point UP when you're done....
Click to expand...

That's a good point, when I did mine I used the factory angle and after I got it in the car it was sort of pointing up. I thought for sure I screwed it up., but it works like a charm.

I guess a better term would be negative pinion angle.
 
noooo, I'm taking it to a guy who does this professionally. I just want to know what is needed to this so I know what to tell him and if anything that doesn't involve cutting it can be done at my house I'll do it there.
 
Muad'Dib15 said:
2. is the body being off 3/4 of an inch normal. like one side with 245/60 15s in back clears by that much and the other drags?
Click to expand...

I believe the main reason the wheels aren't exactly centered is because of the style of the stock adjustable bearings. The passenger side bearing has an adjuster on it to adjust the bearing preload and when it's properly preloaded it pushes the drivers side axle out a little while it's in a little. 3/4" is more than I normally see. My Cuda is off by 1/2" and is what I generally see but if the thrust pin in the center section is worn it makes the offset more. If you do away with the stock type bearings and adjuster setup and use green bearings the axles will be centered.
 
74DartSwinger360 said:
the green bearings arent good for the street only a straight line the orange bearings are better for the street
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I have read this on forums too and also read where several guys rebutted saying they have ran them on the street for a long time with no problems, so who you gonna believe? Come to think of it I know a guy that has had a set of green bearings on his street driven big block 70 Cuda for several yrs. with no trouble. I do agree that the original tapered wheel bearings are a better design for a street car but also remember that a lot of Ford truck rearends used roller type wheel bearings and lasted a long time.

Oh yeah, what the heck are orange bearings?
 
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