Rear axle question

[1booga]

Hello everyone,

I am new ot the forum, and to this era of automobiles. Hoever I now own a 1949 Meadowbrook that I have begun to work on. I plan to (gasp) put a magnum v8 and 5 speed out of a ram 1500, which i understand is a somewhat common swap. My question is in regards to the rear axle. It seems that most people replace it when doing a drivetrain swap. My question is, is that necessary, or would the stock rear hold up? I not looking for a million-dollar ride, just something that i can learn with. Or is it worth it to take the Chrysler 9.25 out of the truck and narrow it/ put really backspaced tires?

Happy to hear input.

[Plymouthy Adams]

the 5 speed, be it auto or standard will have an approx. .70 or .72 OD so we will call it .71 for GP and do the math and should put you at 2.77 final ratio when in OD....you should be fine and if you do not hot dog it everyday, the rear gear should be ample...however...most rear gears are changed for the upgrade to the brakes.....and without the e-brake on the rear of the original tranny, you are going to be without an e-brake...so...all in all do the rear gear...stock late model Dodge 8.25's with 3.55 will be very nice...

Edited July 2, 2018 by Plymouthy Adams

[1booga]

Understood. Its not a strength or gearing issue as much as brakes it seems

[48ply1stcar]

Also more top end with fewer RPM.  With a newer rear axle and brakes, cheaper and greater access to replacement parts.

 

[dpollo]

I doubt if you would break the original rear but there is some good advice given above, especially about the parking brake.  Also, the axles in the 49 are one year only

so if you do break one a replacement may be hard to find.

[Plymouthy Adams]

  On 7/2/2018 at 9:02 PM, 1booga said:

Understood. Its not a strength or gearing issue as much as brakes it seems

Expand  

well, you got to look at this twofold.....first is in your case where you are upgrading and going to modern OD tranny...the rear gear at the stock ratio of 3.9 is not going to be that bad on fuel and performance but as you going to also undergo the cost to a driveshaft, the smarter money is on the rear upgrade for ratio, e-brake and rear brake be they disc or floating shoes.

 

second is the guy who does not have access to the OD that is commonly installed (R10 unit) and wants better ratio for economy and will trade off the stock brakes to get where he needs to be even given the expense of the driveshaft mods yet retain his tranny mounted e-brake

 

by far ratio is to me one of the most driving factors in the upgrade....highways have improved to the point that the ratios that are stock are just a bit out of date for economy and are expensive for high speed operations not that many here will run their engines at the speed it is designed for fear it is running too fast and sounding way to busy....

 

 

[greg g]

Consider old jeep Cherokee. They fit with not a lot of mods. Are about 3.55 to 1 if you can find a two wheel drive unit they are usually limited slip.  They are Dana units so parts are easy to find. Bolt pattern will take stock whee.