Hello all, I am in search of the oem rear leaf blocks from the early 2000s superduty trucks. Looking specifically for the 3.5” block, and am wondering if any of them are tapered for use on our excursions which are a 137” wheelbase, as the f250 blocks for the 137”WB truck are flat. I assume that is a 2wd model with a longer driveline so no need for a taper to prevent vibes. Has anyone found the correct ones and do you know which wheelbase truck they were from? I have rear B code springs that I’m looking to supplement with an additional 1.5” with these blocks.

Thanks!

Thanks, I am familiar; can’t recall if the excursion shaft is single or double cardan shaft? With our relatively short driveline length I’m just worried about vibes if it starts getting too steep. Really it’s only about 3.5” over stock so should be ok.

My EX does not have the double cardan joints, just the simple single U joint on each end.
A few years back I found these blocks that are for a 137" wheelbase F-350 4X4, Right 7C3Z5598C and Left 7C3Z5598B. But check which shafts you have first as that may affect the application.

To answer my own question and hopefully help out the next guy looking for this info...

99-01 F350 156”/158”/172” WB
3-5/8” Block Non-Tapered
F81Z-5598-DA

99-01 F350 137”/142” WB (What the Ex Needs)
3-5/8” Block with Taper (roughly 1/2” over 4” span)
F81Z-5598-GA (Left)
F81Z-5598-FA (Right)

the operating angle at 3.5” over stock will be fine but that is not what the taper is changes, the taper is to adjust the pinion shaft angle so it is parallel with the output shaft and the way to determine that is measure both and then select the correct shim. the correct shim is based on the springs arch since they vary the mounting surfact angle, most springs require a 2* shim. but without measuring you will not know.

cv type drive shaft requires the driveline to be straight inline with the pinion shaft so thst would be a diffrent taper.

Yes my excursion has a single cardan shaft with both outputs at the same angle currently, actually the pinion is about 1.5 degrees less to account for rise upon acceleration. The flat blocks should in theory keep this the same and shouldn’t induce any vibrations. They are only 1.5” taller than what I currently have in there.

at static ride height parallel is ideal but within 1/2* is typically no noticable vibration, any more the 1* most of the time you can detect the vibration.