changing the bolt pattern from 4" to4 1/2"

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deputybob2004

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Im wanting to change the bolt pattern on my 70 dart swinger from 4" to 4 1/2".
It has disk brakes on the front and drums on the back. where is the best place to find the parts i need to do this? Can a guy buy new rotors with 4 1/2 inch bolt pattern, and can I also get new axles with the same 41/2 inch bolt pattern and just have the drums re- drilled?
any help would be great.
bob
70 dart 340
71 demon
75 duster
 
Your 70 Dart should have Kelsy Hays 4 piston calipers. I know everything for that system is expensive. I think your best bet would be to change to 73-76 single piston factory brakes. I cant really help you, as I have only converted 9" drums to the 73-76 disks.

I don't know what rear you have, but it is a 7 1\4, no you cant change just the axles. Something about the bearing sizes being different. I don't know about 8 1\4 axles. As far as 8 3\4 axles, Mopar never made one with a LBP for an A body, so axles would be after market only.

Not all the answers you were looking for but I hope it at least gives you a start.

good luck

TopHat
 
thanks for the insight. I see new kits in the mopar mags. they are around 500 bucks so that might be the way to go. as for the rear it is a 8 3/4" so I guess i'll get some axles from strange or mosier. thanks for the help.
 
For the front you need upper control arms, spindles, calipers and rotors from any 73-76 disk equipped A-Body. If you have an original 340 car, the rear axle is an 8 3/4". As stated already, there were no production big bolt pattern axle shafts in the A-Body width. You can either try to score C-Body axle shafts and have them resplined, order aftermarket shafts (best bet) or have you current shafts redrilled (not the best way to go). If you do the C-Body or aftermarket shafts, you will need drums and backing plates from a 4 1/2" bolt pattern car. The axle flange was thinner on the 4" shafts, and they used an oddball brake drum. It will be far easier to find the correct rear brakes than modify your originals, as just about every other RWD Mopar used them including Dakota pickups.

For $500 you should end up with new rotors, calipers, lines, bearings, drums, shoes, master cylinder a pizza and a 12 pack. People are charging way too much for the factory stuff on eBay, so start scrounging junkyards. $200 for all 4 corners is about the most anybody should pay for used brake parts.
 
I like to use the factory 73-76 parts because when something wears out you can go to the parts store and you don't have to wait on the UPS truck.

TopHat
 
For the front you can use early Mustang rotors but would need to machine the back step to match the spindle and find the right outer seal. See other threads on this site about using Mustang rotors. This way you keep your stock spindles and calipers and pad type.

For the rear Moser or others can drill the stock axles and drum brakes.

This is likely your cheapest route and you can easily go back to stock if you ever want to. Just keep your old front rotors and rear axle lugs.
 
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