Will a 1956 3rd Member fit into a 1952 Axle Housing?

[Loren]

Okay so I made a very fast eBay transaction not knowing if it would work.

I found 3.54 gear ratio 3rd member from a 1956 Belvedere.

According to Andy's parts book it uses the same gasket so it must fit....right?

The price was right even with shipping.

Fingers crossed. What do you think?

 

I have three 3rd members with 3.73 gears so I might be marketing them if this works out.

I also got a call from the machine shop about my Chrysler IND-33 engine which is supposed to be ready in the next week or so.

It has only been there 9 months, thanks to COVID 19.

[Young Ed]

You might have to swap your side gears to use the original axles otherwise I believe it's a fit

[dpollo]

if you get the axles from 53 to 56 everything will fit.   (more splines). 

[Loren]

Okay I got the "pumpkin" today!

I had a loose housing from a '54 and it dropped right in.

I had the axles from the same '54 and they drop right in.

Years ago I bought a bunch of parts from a 1951-52. I still had the pumpkin from that shopping trip, so I tried the '54 axle in it.

It fits that one as well!

So I think it is safe to assume this 3.54 pumpkin will fit my Suburban.

 

Calculations:

6.70-15 Stock Tire size to modern equivalent  P215/70 R 15.....26.6 height

Using Spicer calculator with 3.54 ratio and 1 to 1 high gear.......3130 rpm @ 70 mph

3130 minus 30% Overdrive equals cruise speed of 2191 rpm

 

From the Chrysler Industrial Performance data Peak engine hp 120 @ 3600 rpm which yields 2880 rpm @ 80% of peak.

But wait a minute this engine has a "Continuous Service" spec. and that curve does not go up higher than 2800 rpm.

It seems the Chrysler Engineers figured it out for you. If you take them at their word that "Continuous Service" means just that, then a 70 mph cruise speed is very doable with a little reserve for brief passing.

Of course if you change the tire size that alters the whole equation. I used the modern size equivalent as a baseline.

Well I am excited!

[Sniper]

I don't think 80% of peak HP is the right parameter,  80% of peak torque, maybe.

 

80% of 2800 is 2240, which is close to your 2191 value which seems a better choice than 2880 using the HP value.

[Loren]

Well, we must remember this engine has a 4 3/4 inch stroke so peak torque is at 1,200 rpm.

It's very much like a Diesel in that sense.

I think 2800 rpm will be plenty for a cruise speed and 2200 rpm will be better.

Next we have to execute and see how it works for real.