7.25 axle splines

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düler92

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Hello. I have a 7.25 axle from a 1972 Dodge Dart and a 7.25 axle from a 1973 Dodge Dart. Now the question: the axle from 1972 has a bolt circle of 4 inches. However, the axle from 1973 was 4.5 inches. could I remove the drive shaft from the smaller 4 inch axle and swap it for my 4.5 inch? or are there problems with the number of splines? does the differential carrier remain the same on both axles? does anyone have any experience with this? Thank you for your tips. A picture of the broken basket is attached

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Unbolt driveshaft and swap complete rear end, get large bolt pattern wheels, just compare location of brake flex line attachment. the 73 brakes are probably larger.
 
Thanks for the feedback. the brake lines and everything else fits. I planned to just remove the plugged axles of the 4 inch ones and replace them with the larger 4.5 inch ones. The large bolt circle is currently installed in the car. I currently have the 4.5 inch rims on it. Basically I want to make one out of 2 axes. Anchor plates should fit since the other axle is also 7.25 inches. best regards
 
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Backing plates are different between the small bolt pattern rear and the large bolt pattern rear. small BP backing plates have 4 mounting holes, and LBP backing plates have 5 mounting holes. Not positive if the LBP plates would fit using just 4 bolts, but you also need to check the offset. I don't know if that is the same. Also I think the center hole is different, as the bearing size is different. Brake size might be different, also. 9 inch as compared to 10 inch.
 
I would look into having the 4-inch pattern axles redrilled for 4 1/2-inch pattern, probably the cheapest route to convert to 4 1/2-inch pattern.
 
You can't change axles! only complete drum to drum assembly.
Now upgrade to 73 & up-front disk brake with 4.5 bolt pattern with the proper master cyl with Proportioning valve.
 
the current setup is at 4.5 inches on my Dart. In Germany I can't get a suitable differential basket for the 7.25 rear axle. My brother currently lives near Washington DC but can't find anything suitable either. I found a 7.25 rear axle in my area but with the 4 inch bolt circle. Normally I could take the differential cage out of this rear axle and install it in mine. Then add a new planetary gear and everything should be fine, right?
 
If I understand correctly. You should be able to take the good differential Carrier (cage) out of the one rear, and swap it into the rear that has the bad unit. Keep your original ring and pinion gears. Just swap the carrier unit. You might have to adjust the gear back lash, either by reseting the adjusters, or changing shims (depending on the rear). Then use your original axles and brakes.
 
Sorry my dyslexia kicked in and I thought the broken gears came from the 72-rear axle.
So basically, you need to change ring and pinion with the spider gear case from the 72 into the 73-rear axle, I have not done that yet, maybe someone here has, or
since you have both there maybe take them both apart test fit and let us know.
or what Charrlie S said.
 
I think he just needs to keep the same ring and pinion with the rear they are in now. Just swap out the ring gear carrier (cage). install the current ring gear on the good carrier.
 
Charrlie_S said:
I think he just needs to keep the same ring and pinion with the rear they are in now. Just swap out the ring gear carrier (cage). install the current ring gear on the good carrier.
Click to expand...
I've never tried to fix a broken 7 1/4. If just replacing carrier you just need to inspect ring & pinion gears for chips or cracking of teeth. I've always just replaced 7 1/4 assemblies with stronger diffs so not to worry about it anymore.
 
bcschief said:
I would look into having the 4-inch pattern axles redrilled for 4 1/2-inch pattern, probably the cheapest route to convert to 4 1/2-inch pattern.
Click to expand...
If I remember correctly re-drilling doesn't leave much materal between the outside of the studs and the od of the axle flange.
 
düler92 said:
the current setup is at 4.5 inches on my Dart. In Germany I can't get a suitable differential basket for the 7.25 rear axle. My brother currently lives near Washington DC but can't find anything suitable either. I found a 7.25 rear axle in my area but with the 4 inch bolt circle. Normally I could take the differential cage out of this rear axle and install it in mine. Then add a new planetary gear and everything should be fine, right?
Click to expand...
Yes, the cage/basket is commonly referred to as the differential carrier here. There is a bit of confusion as to what You proposed doing, but We've got it now, Charrlie_S is correct. It should interchange fine, good luck, & let Us know how it turns out for You.
 
I don't want to drill. there is too little material left. I think the only thing left for me is to swap the cage of the 4 inch axle into the 4.5 inch axle. then replace the inner gears of the cage with the setup from richmond, which fits my splines on the larger axle. I'll let you know if that worked. many thanks for your help. I'm always happy to receive further tips. If anyone knows where I can order a cage for the 7.25 axle with a 4.5 inch bolt circle in America, I would be very happy about a link. Nothing ventured nothing gained. sorry for my bad english.
 
Hey guys. I wanted to let you know that everything works. you can do it like I said. the 73 axle has screwable adjusters, the 72 has shims. the carrier and the bearings have the same dimensions. thank you for your help. ✌️
 
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