Hot Rods Well I got my 1930 model A running with t-5 and mercruiser them uh oh.

Stock radius rods split in two like a over ripe tomato. Pinion tipped up and then the carnage began. Would like to up grade to a late model rear end. Not prostock level

 

Yep, them radius don't work like that.
They hold or control the radius movement of the rear end. The stock torque tube controls the torque of the rear end. Soo where is your stock torque tube? What was in the car to control the torque?

Pete and jakes style ladder bars are really good at doing both

 

And post some pics, so we can give better advice

 

I assume it was stock radius rods with an open driveshaft [no torque tube]
If so, why not keep the stock radius rods but add a torque arm along side the driveshaft [3rd Gen Camaro style ]

 

Ok I used a kit from a gentelman in muncie ind. to convert the stock three speed trans to the t-5 fivespeed. it came with open driveline and pieces to convert the stock rear to an open drive line. had adapter plates on the trans to reattach the stock radius rods to the bottom of the trans. This set up worked great for like 5 years until I swapped engines

 

Hey I like that idea,simple and I dont have to reinvent the wheel, thanks Im going to research that still need a lot of repairing on the stock rearend first, or source another replacement unit, and driveshaft again.lol. These cars are going to kill me. I had a heart attack half way through the motor swap. But Im doing better these days.THanks again for your imput.yruhot.

 

Did you use the tin stock model a radius rods made out of 18 ga sheetmetal?

If so ... No 3rd torq arm will help those things , they just provide a little stability and a place for the mechanical brake to slide on

 

What?
The rear radius arms are there to control the rear axle from steering, they are normally attached to a torque tube..
If the OP had a torque arm and attached the radius arms to this it would operate as it was intended to.
[a single ladder bar with a fixed position front ball joint]
A torque arm is not a 3rd link, which is a common misconception

The reason the radius arms are collapsing is because of forward thrust from the axle centreline [drive torque], not just torque reaction.
All it takes is a little bit of torque reaction to bend the arms slightly, then the axle torque will put compression loads on them.
Axle torque [thrust] is greater than pinion torque reaction due to gear reduction.

 

Stock model A are TIN ..... As in sheet metal , you can step on them and bend them , they provide a little stability to the torque tube ... But NOT MUCH ... I wrote the way I wrote it like an exaggeration to create the point

28-34 radius rods are worthless unless combined with a torq tube