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| What's needed to swap a '63 7.25 rear with a '75 8.25 rear? https://slantsix.org/forum/viewtopic.php?t=32026 |
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| Author: | retrorobot [ Sat Nov 01, 2008 5:14 pm ] |
| Post subject: | What's needed to swap a '63 7.25 rear with a '75 8.25 rear? |
I am planning on upgrading the 9" drums on my '63 Valiant to front disks, and due to the change in bolt pattern I'll need to change the rear end accordingly. I found a '75 Dart parts car...unfortunately somebody already got to the front end, but the 8.25 rear is still there. If I take the whole axle assembly (drum to drum), will it swap directly in to my '63 or does it need to be modded? If it needs mods, what needs to be done? Also, what other parts should I take? Driveshaft and yoke? Anything else? Thanks!!!! |
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| Author: | SlantSixDan [ Sat Nov 01, 2008 5:27 pm ] |
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The Dart's driveshaft will be way too long and have the wrong front end on it. The Valiant's driveshaft will need to be shortened a couple inches due to the longer 8¼" rear axle "nose". Don't guess at the measurement, measure the measurement. The rear axle assembly itself will drop right in, though unless the '75 was a stick-shift car, it probably has a 2.76 ratio. Your '63 would most likely have had a 3.23 or 2.93, depending on engine and transmission. If that difference does exist, not only will your acceleration grow slower, but you'll also need to use a different speedometer drive pinion. Note if you're going to larger wheels and tires, this difference will be amplified. The '63-type speedo drive pinions stop after '65, and are relatively hard to find. Other than that, drop in and go. |
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| Author: | retrorobot [ Sat Nov 01, 2008 5:57 pm ] |
| Post subject: | |
Thanks Dan! Is there a better (read: easier) option for converting the old 7.25 rear end to BBP? I'm not in a big rush, I have time to "shop" around for parts. Is a 73-76 7.25 rear a better choice in order to avoid the issues Dan mentioned? Is it possible to change the axles only rather than swapping the whole assembly? If so, what parts do I need? I'm not looking for high-performance...just a regular driver. |
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| Author: | sandy in BC [ Sat Nov 01, 2008 6:23 pm ] |
| Post subject: | |
You cant just swap axles........ |
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| Author: | SlantSixDan [ Sat Nov 01, 2008 6:29 pm ] |
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You could go to the aggravation of finding and installing a '73-'76 A-body large-bolt 7¼" rear, but the ratio difference would still be there. All you'd avoid is shortening your driveshaft. And you'd wind up with a much less robust rear axle. If you have easy access to the 8¼" assembly, go for it. |
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| Author: | DusterIdiot [ Sat Nov 01, 2008 6:36 pm ] |
| Post subject: | Worst Case Scenario.... |
Quote: though unless the '75 was a stick-shift car, it probably has a 2.76 ratio
Some 318 auto cars in the 74-76 range did get 2.45's too, not many, but some did... That would not help the situation anybetter either... -D.Idiot |
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| Author: | 66aCUDA [ Sat Nov 01, 2008 8:34 pm ] |
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If you want the 8 1/4 with a SG and higher ratio try a 90,s Dakota Pick-up You will have to have it narrowed and have the driveshaft shortened. But then you will have a pretty much bullit proof rear. Frank |
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| Author: | sandy in BC [ Sun Nov 02, 2008 6:48 am ] |
| Post subject: | |
You can get a LBP 7.25 rear axle and easily swap your early gears into it. I did that with my car. I swapped my 65 3.23 gears into a 75 housing in a couple of hours....after trying to swap axles. Eventually I swapped that out for a Ford Explorer with discs and 3.55 gears...... |
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| Author: | 2 Darts [ Fri Nov 21, 2008 8:03 pm ] |
| Post subject: | Re: What's needed to swap a '63 7.25 rear with a '75 8.25 re |
Quote: I am planning on upgrading the 9" drums on my '63 Valiant to front disks, and due to the change in bolt pattern I'll need to change the rear end accordingly. I found a '75 Dart parts car...unfortunately somebody already got to the front end, but the 8.25 rear is still there. If I take the whole axle assembly (drum to drum), will it swap directly in to my '63 or does it need to be modded? If it needs mods, what needs to be done? Also, what other parts should I take? Driveshaft and yoke? Anything else? Thanks!!!!
Whoa pardner. Where are the disks coming from? If it's from a 65-72 A-body, the bolt pattern stays the same. Find one and all the changing that needs to happen is the master cylinder, brake distribution and add a proportioning valve. You must go to 14 inch wheels if you change to disk brakes as the 13s will not clear the caliper. Parts are not hard to come by for the Kelsey-Hays calipers used on the 65-72 A-bodies. The main drawback to the suggestion is that the supply of 65-72 A-bodies with disk brakes is small. Until the Barracuda and Dart GTS with 383s of 67, the buying public didn't associate performance with the A-body. Installation rates are understandably low. Even so, they are out there in salvage yards. Good hunting. The information others have provided RE: axle swap has been fine. Didn't see anyone else mention it, but you'll need the mount for the shock to the spring assembly and the U-bolts. The 8¼ has a larger axle tube. |
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