some may have used them simply because it gave them the additional height they wanted without considering their angles, some may have used it because it gave them the angle they needed. the point is if you measure your angles then you will know what you need. hate to see you spend the money on those PMF blocks and do the work to install them only to find out you have a driveline vibration. measuring and figuring out your angles is a little bit of hassle but it is not that difficult to do.

from a practical stand point if the tapered 350blocks is being used without inducing vibration on other Excursions then it should work on yours but then again, measuring is your best bet.

fwiw, I have a 2 1/2" block with 2.5* of taper and my angles are within 2* of parallel and I have a very slight vibration. driveshaft is balanced. point being, every setup is going to be a bit different.

 

exactly my thought.

 

Thanks for the thoughts ill hold of on my parts ordering one more day and check the angles when the wife get home from work.

 

It's best to remove driveshaft to get measurements.
(Block wheels, e-brake etc so it dont roll when DS disconnected)

I will throw another hick up for you to consider. Pinion angle can change based on load applied and load in vehicle. Note the lower traction bars under your oem leaf springs to mitigate large rotations....mine were actually bent a little.

I assumed a 1 to 2 degree upward angle change due to rotational torque applied to rearend while driving.

So my static angle on flange on rear end was 2 degrees less/more ( depending on how u measure)than what the transfer case angle is. To make things right under loads. IE if transfer case flange is 84 degrees, I would be hoping for 85 to 86 degrees on rearend. (Note a 3 degree tapered block woud make the above static measurements 82 to 83 degrees, opposite of what would be needed). Around 80 degrees under load and why people have vibration issues even though a static 83 "looks" good. It may not be.

I don't even want to get into the issue of taller blocks causing more pinion angle change. 1 to 2 degrees seemed to work ok for me.....but I have a cv shaft and needed 4 degrees static. I only put 2 degree shims in.

 

Note the lower traction bars under your oem leaf springs to mitigate large rotations....mine were actually bent a little.
If your talking about the "slapper leaf" the rubber stops have been missing for the last 100k

Now we have gotten to technical I'm ordering a flat block if it vibrates ill go see the drive shaft people lol

 

Flat, is good....keeps things lined up the way it came.

Sorry for being too technical but there are always people complaining about vibrations and I tried to help best I could for anyone else reading.

Good luck.

 

No apology necessary I enjoy intelligent people having intelligent discussions .

My thoughts are the factory block is flat and I'm not changing any of the spring mounting points so we shall see.

 

OK, time for me to inject some more confusion (partially based on my often faulty memory). If I recall correctly the earlier pioneers who started swapping the truck spring under EXs went with the tapered blocks to match what the same wheelbase Super Duty trucks used, I think the longer trucks came with the flat blocks. Again this what I think I remember reading quit some time ago....

 

Intresting.... maybe those trucks had a cv type driveshaft. That would be my only guess as to why the blocks would be tapered.

 

I think what he is saying is they took the taller blocks out of the same f350's that they took the springs out of because that is what they had or were experimenting with. the f350 has the 2 piece drive shaft with the center carrier bearing discussed earlier.

 

Tapered F250 are what you want, based on previous history of this mod.

Left side 3.5" tapered block: Part #F81Z-5598-FA
Right side 3.5" tapered block Part #F81Z-5598-GA

Ford used the flat blocks on the long bed F-series trucks, tapered on the short beds, which works best for the Ex based on prior history of this mod since some users developed driveline vibration that was eliminated when they swapped in the correct tapered block.

I honestly don't know if the first guy to try this mod measured any pinion angles first, I just know which block has proven to work the best.

I know you know the technical aspects and the physics involved, Camo, so all I'm commenting on is what has historically worked for Ex owners who have previously done this mod.

Pretty much, yeah.

Also, I know for a fact that at least three times I can remember, someone used the flat blocks and had to swap in the tapered blocks to eliminate driveline vibration that appeared.

Stewart

 

I'd be willing to be just as many people put in a tapperd block and had to switch to a flat block. hence why taking a couple of simple measurements is a good way to determine what you need.

fwiw...the first pic I posted is measuring the drive shaft angle, to measure the pinion shaft and output shaft angle this picture more accurately depicts the method.

 

I can only comment on what I've read here, and over at TDS where I used to hang out back in '04, '05 and part of '06.

I've always urged people who were doing this mod to stay with the taper block so as to affect the pinion angle the least, because of what has "always worked" for those that posted on the boards.

I can't remember anyone ever chase a driveline vibration (after doing this mod) by switching from the F250 tapered block to the F250 flat block.

I'm not saying it didn't happen, I'm just saying if it did, I never read about it.

I know the proper way is to measure, so anybody that reads this, do it the correct way to make sure you're golden.

Just a quick side note, the OEM blocks on the 4x4 Excursions are also tapered (you have to look really close), but smaller than the F250 tapered blocks.

Stewart

 

Did not know oem 2" blocks are tapered. Going to measure my old ones and see how much.

Not sure how much oem 3.67" blocks are tapered but anything over 1 or 2 degrees would cause issues, and I personally would not use them unless flange measurements called for it.

 

Tom Woods is not only a cool cat but he has done a great job of passing on a lifetime of useful driveline info.

if you really want to geek out on the subject here it is.
Tom Wood's Custom Drive Shafts - Tom Woods Custom Drive Shafts Custom Driveshafts Specialist

the section on angles and slopes has some nifty ways to find your angles
driveline 101 covers the bases of what we are discussing here.
go to his tech page ( link in upper right corner )
Tom Wood's Custom Drive Shafts - Tom Woods Custom Drive Shafts Custom Driveshafts Specialist