7 1/4 - 5 on 4.5 BC A body

[puregts]

Will the axles, and drums, interchange directly with the earlier 5 on 4" BC 7 1/4 or do you have to get the whole thing? I need to update two different A bodies for the larger circle, one I've put large BC disc brakes on already, so I need to make the rear wheels match. I'm about to do the same thing to another one so I'm looking for an easier/cheaper way out.

 

[cudamark]

No, I'm afraid not. The axle shafts are a slightly different length, the bearing outside diameter is different and the axle shaft/inner bearing diameter is different too.

 

[puregts]

No, I'm afraid not. The axle shafts are a slightly different length, the bearing outside diameter is different and the axle shaft/inner bearing diameter is different too.

Ain't that the way. Just when you thought you could put an end run on a problem the engineers get a clue and booger the whole thing. :banghead: Well, I guess I need the whole thing. *sigh*

 

[Charrlie_S]

I have not done it on a 7 1/4 so you would need to check the axle flange to see if there is enough metal. I have redrilled the small bolt pattern "A" body 8 3/4 axles and drums for the large bolt pattern.

 

[3404speed]

I was going to swap in later model a body 7 1/4 axles in my 69 Dart. Bought the axles, but found that the flange was 5 bolt on the newer axles, and 4 bolt on the 69. Spacing was different too, so I stopped there. Since then, I replaced the entire rear with an 8 1/4. Much happier. I could now check the 7 1/4 to see what is necessary to make the newer axles work...nothing to lose, except the time to do it.

 

[puregts]

Yeah, my Dart's 8 3/4 was a re-drill job also. But it was done by the owner of the donor car I got it from. He had it done by Currie Ent' out here. I called them about it, but they need to have one of the axles out of it and the bearing removed to see if it will chuck up in their machine. At that point it became kinda of a cost thing as I'd have to destroy a good bearing to find out. Then the cost of replacing it IF it didn't work and then if it did, I'd have to pay to get it done and then find the bearings and get them replaced. It came down to simple economics: I think it is cheaper to replace the whole thing than adapt. A recent check found the OE brake parts are drying up for the 7 1/4 and SBC front brakes too. Better off up dating across the board.

 

[2 Darts]

I went around on this with both cars. IMHO, it is easier and more cost effective to get a 7¼ BBP assembly than to try to convert an existing SBP to BBP. Avoid the 2.21 and 2.45 gear sets. They require a different housing. While Mopar made a number of different gear ratios for this axle, I haven't seen any aftermarket support for the 7¼ these days.

The 8¼ and 8.75 are good, too, just remember to get the spring plates and clips (u-bolts) with them. The tube diameter on the 7¼ is 2.75 inches, the others are 3 inches in diameter.

 

[zac_F71]

I have a BBP (big bolt pattern) 7 1/4 from a 73 dart I'd consider selling minus the drum backing plates...

if you want different gears later model dakotas had the 7 1/4 to- I scored a 3.55 R&P off ebay for $50 but just have the rear end work professionally done (I had a knowledgeable friend do in trade for a Ford 302 motor and he couldn't finish it)

 

[puregts]

I went around on this with both cars. IMHO, it is easier and more cost effective to get a 7¼ BBP assembly than to try to convert an existing SBP to BBP. Avoid the 2.21 and 2.45 gear sets. They require a different housing. While Mopar made a number of different gear ratios for this axle, I haven't seen any aftermarket support for the 7¼ these days.

The 8¼ and 8.75 are good, too, just remember to get the spring plates and clips (u-bolts) with them. The tube diameter on the 7¼ is 2.75 inches, the others are 3 inches in diameter.

I'm really trying to avoid the 8 3/4 as the Kids don't need it (yet) behind a /6. I have an A body, and the early B body, 8 3/4 housing and small circle axles laying about. But, knowing how kids are, I'd rather not have it in the car when it gets in it's first wreck. I'm trying to save it for the V8 swap later on down the road. But even then, it'll need the large circle axles. I know the /6, with a tow package, had it, but I heard the literal size took away some power from it. Not to mention the d-line issues 7 1/4 to 8 3/4. Minor, I know, and would have to with the 8 1/4 too, but yet another expense.

 

[puregts]

I have a BBP (big bolt pattern) 7 1/4 from a 73 dart I'd consider selling minus the drum backing plates...

if you want different gears later model dakotas had the 7 1/4 to- I scored a 3.55 R&P off ebay for $50 but just have the rear end work professionally done (I had a knowledgeable friend do in trade for a Ford 302 motor and he couldn't finish it)

You're a bit of a drive away from the Left coast. Would the backing plates from any B or late A body work in their place? I think even the early 8 3/4 P/U's rear brakes would bolt up. I'd have to measure the axle flange to housing flange to be sure but anything is possible I suppose...
How much and any ideas on shipping costs?