7-1/4 axle modification - SBP to BBP

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67CudaBob

67CudaBob

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I have a 67 Dart GT ragtop with 13 inch wheels and drums all around. It is a 273 - 2 bbl mated to a stock 904 with a 7-1/4 non sure grip with 2.94 gears.

I have already secured a disk brake setup with BBP for the front.

At this time, nor in the near future, will I be able to afford to swap the rear to 8-3/4, and I am wondering if anyone has successfully and safely drilled BBP holes into their 7-1/4 axles as a temporary fix to get to BBP wheels choices? This way I could buy one set of rims and tires and be good both before and after the 8-3/4 swap. The car will see little to no abuse until I can afford to mod the engine some and swap to 8-3/4.

I have seen 8-3/4 axles which are dual drilled, but I have not seen any 7-1/4.

Any thoughts or experience is appreciated.
Thank you
 
I'm currently running a 7&1/4 rear that has been redrilled for the big bolt pattern on my '67 Barracuda. In a few weeks I hope to have my Dana 60 ready to install. I can tell you that there isn't much meat left on those axle flanges after drilling them. At first we were going to install new wheel studs that would have required drilling bigger holes, but decided we better not. I wouldn't recommend it as a permanent modification, but it sounds like you're taking the same path that I did. - Bought new big bolt pattern wheels and changed over the front end to big bolt pattern discs. - And needed a way to get the car temporarily drivable while you put together another rear.
 
The 73 up A-bodies that had disc would have had bbp rear ends. The ones with /6 were mostly 7 1/4. This 7 1/4 rear end should be cheap (have one I couldn't give away) and would be a direct bolt in.
 
Ben Drinkin said:
Couldn't you just adapters for the interim?
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I would certainly consider them, but they seem to be a hard find for quality ones. I suspect if I could find some and use them for a year they would retain their value for the next guy in my shoes. If anyone knows where to locate a decent set, I would love to hear about them.
 
Oklacarcollecto said:
The 73 up A-bodies that had disc would have had bbp rear ends. The ones with /6 were mostly 7 1/4. This 7 1/4 rear end should be cheap (have one I couldn't give away) and would be a direct bolt in.
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Could I simple swap the axles without swapping the whole rear end?
 
Your best bet (safest) is to use 73 and up bb 7 1/4 axles. Second choice would be adapters (easiest and possibly cheapest). I have used both of these approaches in the past. IMHO, re-drilling the axles removes too much material for my comfort.

I have used Trans Dapt adapters.
 
67CudaBob said:
Could I simple swap the axles without swapping the whole rear end?
Click to expand...


That is the great unanswered question. As of now I have not ran across anyone that has actually done it to confirm either way. The housings show not to interchange according to Hollander.

If it would work you would also need to take the brake backing plates and everything on them plus the drums. From what I have read you have to pull the cover and some clips to get the axles out. I think it would be easier to swap the assembly.
 
lrazor said:
Your best bet (safest) is to use 73 and up bb 7 1/4 axles. Second choice would be adapters (easiest and possibly cheapest). I have used both of these approaches in the past. IMHO, re-drilling the axles removes too much material for my comfort.

I have used Trans Dapt adapters.
Click to expand...

Yeah, with Cuda's response about the lack of material that is left - even though it may work - leaves me with an uncomfortable feeling. Thanks for the heads up on TransDapt - looks like a quality product at about $85 per wheel, and will more than suffice for top-down cruising until I can spice it up a bit.

If I find some 73+ axles - as long as they are A body and NOT sure grip axles, they should plug and play, correct? Or, are axles just axles, and they do not care if the rear is sure grip or not?

I am new to this, and really appreciate the help
 
"Thanks for the heads up on TransDapt - looks like a quality product at about $85 per wheel"

My mistake - it is $85 per axle for the street duty ones.
 
67CudaBob said:
Yeah, with Cuda's response about the lack of material that is left - even though it may work - leaves me with an uncomfortable feeling. Thanks for the heads up on TransDapt - looks like a quality product at about $85 per wheel, and will more than suffice for top-down cruising until I can spice it up a bit.

If I find some 73+ axles - as long as they are A body and NOT sure grip axles, they should plug and play, correct? Or, are axles just axles, and they do not care if the rear is sure grip or not?

I am new to this, and really appreciate the help
Click to expand...

Sure-grip won't matter. If you do this please post the results here so we will have a confirmed answer.
 
Oklacarcollecto said:
That is the great unanswered question. As of now I have not ran across anyone that has actually done it to confirm either way. The housings show not to interchange according to Hollander.

If it would work you would also need to take the brake backing plates and everything on them plus the drums. From what I have read you have to pull the cover and some clips to get the axles out. I think it would be easier to swap the assembly.
Click to expand...

I suspect you are correct to do the whole thing - I was hoping to save on some shipping if I find something outstate by just taking the axles (and brake parts). But I suspect, like you, the safe bet is the whole axle & rear swap.
 
lrazor said:
Your best bet (safest) is to use 73 and up bb 7 1/4 axles. Second choice would be adapters (easiest and possibly cheapest). I have used both of these approaches in the past. IMHO, re-drilling the axles removes too much material for my comfort.

I have used Trans Dapt adapters.
Click to expand...


its a 7 1/4' rear end. the spider gears and ring gear are gonna blow up long before you hurt an axle flange.
 
67CudaBob said:
"Thanks for the heads up on TransDapt - looks like a quality product at about $85 per wheel"

My mistake - it is $85 per axle for the street duty ones.
Click to expand...


Check out these billet adapters that are made in the USA.

[ame="http://www.ebay.com/itm/Wheel-Adapter-5x4-5x4-5-Spacers-1-Made-In-USA-/390704899427?pt=Motors_Car_Truck_Parts_Accessories&hash=item5af7d3a563&vxp=mtr"]Wheel Adapter 5x4 5x4 5 Spacers 1 034 Made in USA | eBay[/ame]
 
67CudaBob said:
I suspect you are correct to do the whole thing - I was hoping to save on some shipping if I find something outstate by just taking the axles (and brake parts). But I suspect, like you, the safe bet is the whole axle & rear swap.
Click to expand...



Put up a wanted ad on this site. I would think you would be able to score something cheap and fairly close.
 
Oklacarcollecto said:
Put up a wanted ad on this site. I would think you would be able to score something cheap and fairly close.
Click to expand...

Does anyone know if I swap my 67 7-1/4 complete axle assembly with a post 73 7-1/4 axle assembly if my driveshaft will need to be modified, or should they be the exact same dims?
 
Woah woah woah.... Back the money spending train up.

Whats your plans for this 273? A 6-71 blower and a 250 shot of NOS?

Instead of spending $170 for adapters and down the road spending $900-$2,000 on an 8-3/4" just get a bbp 8-1/4" with 10" drums for $200-$400. You'll be hard pressed to break it with a 273.
 
/6 Matt said:
Woah woah woah.... Back the money spending train up.

Whats your plans for this 273? A 6-71 blower and a 250 shot of NOS?

Instead of spending $170 for adapters and down the road spending $900-$2,000 on an 8-3/4" just get a bbp 8-1/4" with 10" drums for $200-$400. You'll be hard pressed to break it with a 273.
Click to expand...

ROFL - No go on the blower and NOS - but I totally get your point. The adapters get me into wheels and tires in short order, (and looking at those 13" trailer tires is driving me nuts) and the adapters have value when I get out of them and install the disk fronts. I like your thought on the 8-1/4, as that is a cheap in and will be far better than my 7-1/4 with 139k miles. I won't need an 8-3/4 until I substantially increase my HP.

For now, the 273 will get some head work and 4 bbl manifold and carb. Anything more than that will probably involve a 360 crate, but that is years away.
 
/6 Matt said:
Woah woah woah.... Back the money spending train up.

Whats your plans for this 273? A 6-71 blower and a 250 shot of NOS?

Instead of spending $170 for adapters and down the road spending $900-$2,000 on an 8-3/4" just get a bbp 8-1/4" with 10" drums for $200-$400. You'll be hard pressed to break it with a 273.
Click to expand...

I've got to agree with /6 Matt. Before I'd spend that much on what's going to be a temporary solution, I'd reconsider going the 8&1/4 route instead of the 8&3/4. The reason I decided to go to a Dana 60 was cost. It was cheaper for me to find a good 9&3/4 and have it narrowed than spend what 8&3/4 posi's are going for. Either way I was going to have to remake the driveshaft. I re-drilled the 7&1/4 axles to get by until my new rear is done and to help facilitate in determining the actual rear end width I needed with my wheel/tire combo.
 

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67CudaBob said:
ROFL - No go on the blower and NOS - but I totally get your point. The adapters get me into wheels and tires in short order, (and looking at those 13" trailer tires is driving me nuts) and the adapters have value when I get out of them and install the disk fronts. I like your thought on the 8-1/4, as that is a cheap in and will be far better than my 7-1/4 with 139k miles. I won't need an 8-3/4 until I substantially increase my HP.

For now, the 273 will get some head work and 4 bbl manifold and carb. Anything more than that will probably involve a 360 crate, but that is years away.
Click to expand...

Your existing driveshaft, u bolts and shock plates will not work with the 8 1/4, so you would need those also. If you are going 8 3/4 then an 8 1/4 would be costly for a short time. You would still have to get another driveshaft modified to go from an 8 1/4 to an 8 3/4. If you want an 8 1/4 instead of an 8 3/4 at the end then go for it.
 
Keep in mind that if you do decide to use wheel adapters, that whatever thickness they are may screw with wheel clearance if you're planning on trying to fill up those rear wheel wells. The last set of adapters I bought were 1" thick.
 
Bob are you planning on running slicks? Ever? How about a manual trans? If the answer is no, seriously reconsider going 8-1/4" and calling it good. It'll live fine behind a modest 360 on street tires with an auto.

And btw, your 7-1/4 is fine for now, the original one in my slant car pictured below lived 170k miles behind my slant. And I was NOT easy on it. It spun a bearing somewhere, the gear set was fine.
 
Oklacarcollecto said:
Your existing driveshaft, u bolts and shock plates will not work with the 8 1/4, so you would need those also. If you are going 8 3/4 then an 8 1/4 would be costly for a short time. You would still have to get another driveshaft modified to go from an 8 1/4 to an 8 3/4. If you want an 8 1/4 instead of an 8 3/4 at the end then go for it.
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Well.....there is need and there is want....

My ego is getting in my way a little bit - as I am coming off a very strong 67 Cuda Fastback. But, if I step back an think about it, an 8-1/4 will give me more than I need in this car for as long as I let it. Gotta remember that I traded horsepower for a drop top - and my wallet can't afford both right now.
 
Well the thing is, your ego or your wallet will win. If your ego wins you get an 8-3/4" and if your wallet wins you'll get a good rear quicker so you can have fun sooner and delegate the saved money torwards that 360 youre talkin about.
 
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