Featured Technical 40-41 FORD PICKUP PARALLEL LEAFS

This is something that I had not contemplated prior to my telephone conversation with Dale the other day. Those raised shackles in the back (like we ran in HS) screw with the pinion angle of the diff. Effectively tilting the pinion up, how much is the question. I would guess that my 4.25" shackles (stock was 2" eye to eye), will raise the truck 1.125" (half the shackle raise). The spring is 48" long so the ce625nter point is halfway (24"), so I could be lifting the pinion .625"? If so, I would need to drop the *** end of my transmission the same and I don't recall building in any downward adjustment to the crossmember and mount. I guess I could raise the Hemi on its mounts?

I'll check it once it back together and on the ground. I may be overthinking it. That happens, regardless of what you hear from my wife and a few on here.

 

Wondering since you are basically putting back to where it was originally if the angle would be wrong.

But if it is off, there is no need to change mounts, instead use wedge shims on the spring pads.

 

Energy Suspension (I should get a commision) offers their GM style trans/crossmember mounts in two thicknesses, not sure what your current arrangement is but the shorter one could be a problem solver.

 

Yup I think if you are just putting it back to where you started that you are probably going to be pretty close to correct on the opinion regardless of method.

 

I bet you are correct. In fact, I mentioned to @Pist-n-Broke one day a couple of months back that the PU had developed a vibration. Smooth as silk until 40 PMH, then a harmonic brump, brump, brump, like you are running over the turtles (Bott's dots) in the lane divider. Gone by 50 MPH. That may be due to the rear end sagging and changing the pinion angle. Lifting it may fix the ride height and the vibration. Hmmm

Correct, I have some wedges around here somewhere if it necessary. Interesting.

 

I believe we touched on pinion angle at that time. The vibe wasn't there initially and slowly came on. You also hadn't mentioned the ride height was changing. I won't be surprised when you learn the two go hand in hand.

 

Just me thinking outside the circle, what about keeping the original (sagged) spring setup you have to locate/mount the diff, and run coil over shocks to get the ride height where you want it??
Leaves and coils working in harmony..
Or is that a bit of a Hmmmmmm suggestion.. Lol

 

That would make for a harsh ride.

 

It would only be harsh if you were running the total weight of the pickup rear on the sagged springs, plus the coils, my suggestion was to take the weight on the coil-overs (raising the rear 2''), and nothing/minimal on the leaf springs, they would only be locating everything, and taking the drive forces..

 

But if the leaf springs are still connected they will still be doing their share of carrying the vehicles m***. Any extra coilover springs fitted would need to have a very low spring rate because they would only need to bear the proportion of the m*** that is not already being dealt with by the leaf springs. There is no way for the coilovers to carry the entire vehicle m*** unless the leaf springs are completely disconnected from the system, at which point they would then no longer be able to locate the rearend.

 

This was my advice to B-B several days ago.

I firmly disagree. B-B was also confused with my explanation as to my opinion (I've only been doing this for 50 years so I'm no pro) and was going to do some follow-up with a spring manufacture. I haven't heard anything either way back from him. I'm no longer calling what's under his Truck, "springs" because if they were they'd be doing there job instead of letting the Axle rest on the Snubbers. Ther's NO Spring left in them.