40 Ford rear in a 32 chassis

[32phil]

When installing a 1940 rear in a 32 chassis using the stock 1940 spring (straight), I understand the rear does not quite fall exactly in the same spot as the original 32 spring (curved).
Does anyone know if the rear lands closer to the front of the car or more rearward ? If so, how much ?
I have to repair a 32 rear crossmember so I'm thinking I may just add an inch or so in the right direction and correct any bias one way or the other. I have to shorten the torque tube anyway so might as well do it to match the new location.
As always, I defer to the experts on The Barn.
After all....I'm just the Lock and Key Guy...……. what do I know.....
Thanks in advance, Phil

[Cool Kat with Hot Car]

The distance from the centerline of the rear axle to the center of the rear spring bolt is the same for a 40 and a 32. The problem is interference between the 40 spring and the walls of the crossmember. This can be taken care of by grinding the edge of the spring to fit. The second hurdle is torque tube length. There are many ways to overcome this. The way that seems the best is to use a 32 or 34 drive shaft with a torque tube/pinion coupler turned down to fit the cut off end of the drive shaft which is then welded together. 46 wishbones can be used as they are short. The boss for attaching the wishbones to the shortened torque tube will need to be repositioned.

[32phil]

Thank You for the quick response

[rotorwrench]

Some folks modify the cross member. Some replace the cross member with one more accommodating of the later type springs. Modification of the springs has already been mentioned.

[Andy]

I changed the axle. I made a weld jig off the 32 axle and cut the spring hangers off the 40 axle. I used the weld jig to reposition them to the 32 position and welded them back on. This let me keep the stock spring and unmodified rear crossmember. The jig is available for the shipping cost if anyone wants to do it.

[bobH]

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Originally Posted by Cool Kat with Hot Car

The distance from the centerline of the rear axle to the center of the rear spring bolt is the same for a 40 and a 32. .

Huh? My measurements beg to differ. JMHO

[TomT/Williamsburg]

My avatar has a .40 rear spring installed. Just needed a bit of grinding to get it to slide down into the crissmember. Not to much of a big deal to do. But, the 40 rear spring is a heavier ujit than what the 32 needs imho - mine rides pretty hard. Perhaps an aftermarket Posies 40 reaR spring might prove to be a better choice. I am looking into swapping mine out for one at the moment .....

[Fortunateson]

How about '40 rear bones? OK or too long?

[TomT/Williamsburg]

More than likely you will have to cut them down once the torque tube is shortened since they connect to it.

[RalphM]

I found it easier to install a 1940 rear crossmember in the 32 frame. Of course I flattened it so it wouldn’t sit so high.

[TJ]

Why not a model A rear crossmember in the '32 frame?

[glennpm]

Re.

Originally Posted by Fortunateson

How about '40 rear bones? OK or too long?

The wish bones for the 40 do not have to be shortened. Both the torque tube and driveshaft must be shortened and the lug for the torque tube relocated on the torque tube. The dimensions I used are attached.

I removed two leaves from my 40 spring and have polyethylene between the remaining. I now have an eight leaf spring and the ride is good. If anything, I would remove another leaf not add one. The two leaves that I removed are shown in the attached. You may also be able to see the front center grinding and two notches on the rear, to clear the 32 curved cross-member. The spring is centered in the cross-member by the square head spring pack center bolt.

[RalphM]

“The wish bones for the 40 do not have to be shortened. Both the torque tube and driveshaft must be shortened and the lug for the torque tube relocated on the torque tube. The dimensions I used are attached.”

After shortening my torque tube my 37 radius rods were too long. They would have mounted forward of where the T-tube begins to taper down. I cut about 6” off them, heated and bent them in at the backing plate mount, and had to move the anchor mount on tube as well.
Of course if I had to do it again, a pair of 46-48 bones would fit the bill and save some work.

Also during the test drive( after removing some spring leaves ) I found that the longer bones were hitting the frame. Had to add leaves back in there. The shorter bones would not have done this.

[glennpm]

Yes the 40 wishbones also don't require shortening.


Ralph, do you know what you have for spring leaves now and is it a good combo?


Thanks,
Glenn

[RalphM]

My spring is a posies reversed eye super slide for a 1940. It works really good .

[glennpm]

Thanks Ralph,


I have a Posies on the front of mine and very happy with it too!

[Tim Ayers]

If looking to lower the rear, ‘26/‘27 T crossmember and corresponding spring. Lowers the rear by about 3” and looks totally stock if unaware.