Hot Rods ?s on installing 40 Ford Frt Axle in Mod A Frame

I'm installing a Welder Series frt crossmember (28"), a stock 40 frt axle, and looking at the Speedway/Posies frt spring #580-1009, 33-1/2" eye to eye, 1-3/4"W, I already have the Speedway perches #910-33047. catalogue says for 28-34.
will the perches work on the 40 axle?
is there another spring I should be looking at?
want to move the frt crossmember forward a bit, any problem with that? yes, I'll cut the frame for clearance.
any tips or suggestions so I don't **** this up?
thanks, mike roman

 

I can't answer to the special spring for the wider perches, but I can say that all the axles have the same diameter of perches. So a perch from 28 will fit in the hole all the way up to 48. The later wishbones had thicker (taller) bungs on the top and bottom so an early stock perch wouldn't have enough length to fit the nut, but most aftermarket perches are longer to allow a bolt-on lower shock mount, and should let you use any wishbone.

 

'40 front axle should be a bolt-in if you have all the axle parts; does require split or modified wishbone.

You raise an interesting question: If you're not running fenders and want just another inch or two for fan and firewall clearance, is it better to move the crossmember forward or the body backward?

 

are you doing this in a spring over setup? or spring in front like a stock 40 front end? are you using split wishbones? Hairpins? all this make a difference.

I ***ume you are doing a spring over set up. The rule of thumb is measure your perch bolt hole from the top center to center, then subtract 5 from that measurement. that will get you the correct width spring. I cant remember what the perch width is for a 40 axle, but a 32 to 36 axle is 36 and 3/8 inch, perch to perch. Subtract 5 and you have 31 3/8 inch for the spring, so a 31 inch spring will work just fine. With the further out location of the 37 to 40 perch locations, id say that 33 1/2 inch spring sounds just about right to me.

The thickness of the forged end of the wishbone is the vaarible in the perch length, those perches you listed should be fine, but you may not be able to get any kind of lower tube shock mount on the bottom of the perch if using a 35 to 40 wish bone.

 

We have a 40 axle on the Wife's daily 28,, we had to replace the front spring and the only one we could find was from Speedway, first clerk said no way, but got an 'old timer' and said 'why of course' and was sent out and has been in use for a year.

 

POSIES Rods and Customs – Super Slide Springs – Street Rod Parts – Hot Rod Parts – Truck Parts – Ford and Chevy Suspensions and Ch***is Parts » 28-34 Super Slide Springs

look at the online catalogue

 

thanks to all who responded. gonna call Posie to get the real lowdown, but looks like the 33-1/2" is the spring to use. I'll probably order from him direct, price is just a bit more. i'll post some pics as work progresses

 

NOTE: I found out when I tried that with my T bucket in the mid 50's that you don't want to spread split bones out to the frame rails with the 4o axle or you end up with a real big turning radius because the tires will hit the bones.

 

i thought about that & making a small wedge cut in them to tuck them in. thanks for the reminder

 

To get the real value out of running a 40 axle on a Model A you want to keep the spring-ahead bones and place a crossmember up ahead of the stock crossmember. This can be a piece of channel or box tube. Doing it this way is a great way to get down nice and low with or without dropping the axle. You may or may not need to kink the bones for steering clearance depending on where you connect the ends.

 

hmmm...I'm gonna have to think about that