drastic pinion angle after raising front trailing arms

[Custom 68]

Guys
I know this has been beat on regarding the pinion angle and maybe after all the reading I tried it got me confused again.
Anyway looking for some more info. I lowered the rear of my truck with some soft 5 inch drop springs. I also decided to flip my front mounts for my trailing arms understanding it was going to help my instant center. Well when I raised these mounts my pinion angle got pretty bad and now I need to fix it.
currently my engine is approximately 2.5 degrees with the tranny lower than the front. My pinion has the yolk (front) sticking up about 9.5 degrees. My drive shaft is basically zero degrees so it is level with the ground.
My understanding is that the pinion and engine/tranny should be parallel under load. That being the case I need to rotate the front of the rear end down. My choices are to relocate the front of the trailing arms back down to stock, make some shims for the rear to bring it down about 8 degrees or cut the saddles and rotate the entire thing that way. I really don't want to cut on my axles so I may take that off the table. Question is the moving my arm mounts up like I did is it worth leaving it and shim to get the angles correct? And is my understanding correct that the tranny should be down my 2.5 degrees and the front of the pinion should be up around 1.5 to 2 degrees static.
Thanks guys.
Dave

[PBFAB.COM]

Originally Posted by Custom 68

Guys
I know this has been beat on regarding the pinion angle and maybe after all the reading I tried it got me confused again.
Anyway looking for some more info. I lowered the rear of my truck with some soft 5 inch drop springs. I also decided to flip my front mounts for my trailing arms understanding it was going to help my instant center. Well when I raised these mounts my pinion angle got pretty bad and now I need to fix it.
currently my engine is approximately 2.5 degrees with the tranny lower than the front. My pinion has the yolk (front) sticking up about 9.5 degrees. My drive shaft is basically zero degrees so it is level with the ground.
My understanding is that the pinion and engine/tranny should be parallel under load. That being the case I need to rotate the front of the rear end down. My choices are to relocate the front of the trailing arms back down to stock, make some shims for the rear to bring it down about 8 degrees or cut the saddles and rotate the entire thing that way. I really don't want to cut on my axles so I may take that off the table. Question is the moving my arm mounts up like I did is it worth leaving it and shim to get the angles correct? And is my understanding correct that the tranny should be down my 2.5 degrees and the front of the pinion should be up around 1.5 to 2 degrees static.
Thanks guys.
Dave

Dave-

You just have to weigh the benefits of the raised front trailing arm pivot location with the work necessary to correct the pinion angle. Depending on your driving style you may never notice the difference.

On paper, it's a good mod. If you don't push your truck or drive it very hard you may never notice the benefits/difference.

With that said, your numbers behind what the pinion angles should be are sound. It's just finding the best way to modify the rear so it gets to that 1.5 to 2 degree angle you are looking for.

BEST way (also the most involved) would be to cut the perches off and re weld at the correct angle.

EASIEST way would be shims... but 8 degrees sounds like it would require a couple sets or one big one if anybody makes one that big... and it might look a bit odd.

Hope that helps.

Nate

[Custom 68]

Nate, thanks and yes it helps a ton. You are correct my best bet is to cut and reweld. I thought I might be able to make a shim that would work but again I will be better off to do it correct. I was also concerned about this big angle I didn't understand why mine was so far off I had understood the other benefit to raising the mounts was to help the pinion angle and mine seemed to have the opposite effect. I couldn't see that I had done anything wrong...
My main questions you answered I just wanted to make sure I understood and my reasoning was sound on the direction everything was pointing.
The cold weather is about here so I have some time I have built this truck to drive and to drive hard if I wanted to. I have tried to do any mods I can to enhance that.
Now for me to decide what to do since I can tear it out.
Again thanks
Dave

[Custom 68]

I think I better just cut these seats off and position them where they need to be.
Where can I get these spring seats? They seem to be tough to find in my usual spots?
Thanks
Dave

[PBFAB.COM]

Originally Posted by Custom 68

I think I better just cut these seats off and position them where they need to be.
Where can I get these spring seats? They seem to be tough to find in my usual spots?
Thanks
Dave

We build them. Shoot us an email and we will get back to ya if interested.

porterbuiltdirect@gmail.com

Nate

[Custom 68]

Thanks Nate, e-mail sent.

[_Ogre]

any trailer supply will have spring pads for about $5 each

[Robznob11]

Wow i have some what the same issue but i have 6" drop springs and the cpp x member that has the front mounts welded upside down permanatly. My pinion is still only at 4.5 up. Are you measuring at ride hight? Fully weighted on level ground? Can you drop the tranny any? 1/2" will gain you about 2.5 to 3* may not be good if you have a carb but you could check to see how level it sets after you drop it. If you have efi you can set it anywhere. I would remeasure tho caus i cant imagin how you got the pion up that much with your set up are you pulling the driveline and taking the measurement off the yoke face only other place is to pull the cover and take it off the machiened surface. Anywhere else yelds a false reading.

[Robznob11]

Originally Posted by Robznob11

Wow i have some what the same issue but i have 6" drop springs and the cpp x member that has the front mounts welded upside down permanatly. My pinion is still only at 4.5 up. Are you measuring at ride hight? Fully weighted on level ground? Can you drop the tranny any? 1/2" will gain you about 2.5 to 3* may not be good if you have a carb but you could check to see how level it sets after you drop it. If you have efi you can set it anywhere. I would remeasure tho caus i cant imagin how you got the pion up that much with your set up are you pulling the driveline and taking the measurement off the yoke face only other place is to pull the cover and take it off the machiened surface. Anywhere else yelds a false reading.

My soultion my tranny was 4* down and pinion 4.5 up. And rear end higher than tranny. Wich made the driveline run .5* up hilll yikes. So i put a 1/2 plate under tranny mount that made it 1* down and run 4* shims to set pinion at .5* up wich is actually .5* down as compared to front. So it can climb some. Re weld would have been better but like you i really did not want to do that. If you look up hotchkis antisquat kit it comes with 5* shims again leads me to believe you have a false mesurement caus people raise the brackets all the time. And from a preformance stand point it makes alot of sense in straight line or road corse. Every one knows trucks blow the tires off and in corners the rear tries to come see the front and the raising of the arms corrects the geomotry to prevent that.

[Custom 68]

Thanks for the reply and help. Yes I have measured this correctly. this is a static drop and I am loaded so to speak. I have a cover on the rear so it has lowered it a little more. It is pretty obvious of the upward point of the rear end (pinion) and when the drive shaft is installed you can see the angular difference between the two.
I really don't have much room to move the tranny around and I think the angle it is set at is correct. It is EFI. Also I understand what you are saying but moving the engine tranny combo will somewhat change the drive line angle but it will be minimal and it still wont get the two angles much closer. My best option is to remove the rear and do some cutting and re-welding. I have cut everything else up on the old girl so I might as well do this one too. I dont think any shimming will help to the extent I need to come down.
I did see the Hotchkis kit before and I agree I am not sure why my angles have gotten so extreme. That was in part what my post was also asking but regardless it is off and needs fixed.
I had went from using a drop spring and spacers to get my drop and now that I changed the springs it is worse. It was higher than i wanted before but not as bad.
Again any other thought will be great. I will get out there and remeasure but I know I am not off much if any.
again thanks
Dave