Need little bag over axle advice

[kev2809]

I want to kind of re-do my upper brackets I did years ago. they are ugly and were made of scrap plate I had around at the time. my main issue is I feel I don't get the full stroke of the bag with these plates like this. when I removed the bag and jacked up the axle til the TA hit...I have a nearly 5 inch gap from the top plate and bottom plate. my dominator 2600s are 2.8" fully collapsed. if I'm adding this right, I'm losing just over 2 inches of lift. I'm thinking of cutting out the plates and welding 2x2 tubing with new plates. this would drop the new plates the 2" needed to get me more lift.

2nd option would be to keep the top mounts, but reweld them and beef them up..BUT, either add 2" spacer to make up the difference. or....switch to Firestone sleeve bags. they are 4.5" collapsed, with 13.8 max height with 5.5" diameter. ride height is suggested at 8.5". when jacking up my axle to where I would think the ride height should be..it's about 9" from top plate to bottom axle plate. which sounds like the sleeve bags are the way to go...then all I would need to do is just reweld those top mounts to beefed them up..no spacer needed.

my overall concern after reading some how to's is that the bottom axle plates should be 0 degrees at ride height when welded on. I don't know how I did these the first time....but when I set the axle at ride height, the angle is about 9 degrees on the axle brackets. when it's bottomed out (laid out) it was about 4 degrees. I mean, I never seen unevenness when the bag was deflated....but is this going to be a problem? the bottom plates are welded in pretty good and would hate to try to cut them out.

these pictures are the axle set to about ride height

[kev2809]

one picture is of "ride height", other is where it's laid out with the TA hitting the frame. I want to say it's about a 5" difference

[kev2809]

more

[SCOTI]

How are the front of the T/A's mounted? Original or was that changed?

[kev2809]

stock location. I did read in one of your posts about flipping the mounts on the TA crossmember 180 degrees but I have not done that.

[SCOTI]

Originally Posted by kev2809

stock location. I did read in one of your posts about flipping the mounts on the TA crossmember 180 degrees but I have not done that.

On aggressive drops such as yours, it's a good idea. There are shops making bolt-in brackets that offer some adjustability as well for some tuning range.

Might be worth getting the fronts closer to where they need to be first & then check the angle again.

[kev2809]

curious..what does flipping those brackets do? also, when you say get the front closer...are you saying flip the TA brackets and then check the angles of the axle brackets and go from there?

[kev2809]

ok I researched a little and seen that flipping those brackets brings my pinion angle back closer to stock..correct? so if those are flipped...it will turn the whole axle down which could straighten out the lower axle brackets I already have welded on....right?

[SCOTI]

Originally Posted by kev2809

curious..what does flipping those brackets do? also, when you say get the front closer...are you saying flip the TA brackets and then check the angles of the axle brackets and go from there?

Originally Posted by kev2809

ok I researched a little and seen that flipping those brackets brings my pinion angle back closer to stock..correct? so if those are flipped...it will turn the whole axle down which could straighten out the lower axle brackets I already have welded on....right?

Yes.
It will shift (rotate) the front mounting points higher which rotates the pinion up toward the bottom of the vehicle. You'll want to plan on things using the final angles. This is where the aftermarket multi-hole adjustable brackets would benefit you.

[kev2809]

1st pic is the truck laid out (axle jacked up until the TAs hit the frame). 2nd pic is the axle set at about ride height. 3rd pic is the angle finder set on driver side TA at ride height. passenger was very similar

[kev2809]

so....at ride height....that pinion angle should be as close to 0 as possible?

[kev2809]

went ahead and pulled the trailing arms out...Jesus that was a pain. they need to come out anyways since I bought new bushings for them...and will need to be painted.

however....how in the hell am I supposed to get the rivets on the brackets off? pulling the body off is an no go (it's a suburban)....and I can't get anything in there to cut them off. this looks like a nightmare....

[SCOTI]

Originally Posted by kev2809

went ahead and pulled the trailing arms out...Jesus that was a pain. they need to come out anyways since I bought new bushings for them...and will need to be painted.

however....how in the hell am I supposed to get the rivets on the brackets off? pulling the body off is an no go (it's a suburban)....and I can't get anything in there to cut them off. this looks like a nightmare....

This is another instance where the aftermarket parts are a benefit.

If re-using & flipping the original brackets, you're more than likely going to have to carefully drill & chisel them out. If going aftermarket? You can cut the majority of the bracket out of the way to have easier access for cutting & grinding out the rivets and/or what's left of the OG bracketry.

As for pinion angle, the working angle between the trans output u-joint & the rear differential u-joint needs to be between 0-1°.

[kev2809]

ok so this angle isn't going to work with the stock brackets it seems. I guess I will place this order and the re install everything and check again.

are there instances where going this low doesn't require any change in the stock arms or brackets? or does pretty much everyone that keeps the stock arms, and switch to an air bag in a spot other than the stock spring....have to do this?

[SCOTI]

Originally Posted by kev2809

ok so this angle isn't going to work with the stock brackets it seems. I guess I will place this order and the re install everything and check again.

are there instances where going this low doesn't require any change in the stock arms or brackets? or does pretty much everyone that keeps the stock arms, and switch to an air bag in a spot other than the stock spring....have to do this?

it's not a 'must-do'.

But the angles were set-up & designed by engineers @ certain heights. At 5-6" lowering, things aren't ideal but still work. When you start relocating the springs & the rear axle is now normally at or above where the top of the frame rail use to be, even the angles that would work @ 5-6" are now almost another 5-6" beyond that..... other things needs to be tweaked.

Could you still keep everything in the same location & it functions? Probably so. This is where planning pays off. You can try it as is & see what you get. If it doesn't work, it just means fixing the issue.

[kev2809]

well judging by what I found yesterday, the pinion is no where close to 0-1 degree when at ride height. so I'm guessing I'm gonna need the adjustable brackets. been working on this truck for 13 years, another few weeks and couple hundred dollars more doesn't hurt.

[SCOTI]

Originally Posted by kev2809

well judging by what I found yesterday, the pinion is no where close to 0-1 degree when at ride height. so I'm guessing I'm gonna need the adjustable brackets. been working on this truck for 13 years, another few weeks and couple hundred dollars more doesn't hurt.

It's not just the pinion angle as measured. It's the trans output shaft angle matching within 1° to the pinion.

The pinion angle could be @ 3°..... If the trans is within 1° of that it should function w/o vibrations that cause wear.

[kev2809]

ohhh I see so if I drop in the drivetrain....I would measure the output shaft degree....and it has to be within 1 degree of the axle yoke...right?

[SCOTI]

Originally Posted by kev2809

ohhh I see so if I drop in the drivetrain....I would measure the output shaft degree....and it has to be within 1 degree of the axle yoke...right?

Ideally, yes. Less than 1° difference but not equal/zero.

Manufacturers say the needle bearings in the joints need just a little difference to help them rotate.

[kev2809]

ok i guess i will hold off on the rear and get my motor and trans dropped in...been itching to do it for a while now anyways.

i have been flipping through the forums about pinion angles all day. from what i have read, the longer the truck the less pinion problems people seem to have. im hoping this is the case with me since mine is a suburban. if i can get away with just moving my bag mounts around i would be perfectly ok with that. or even using degree shims to help. its just weird though because i always flip through peoples builds and not too many seems to mention any of this stuff lol. especially the suburban ones.

what i dont get though, is if do use the adjustable TA brackets, the front mounting moves up. wouldnt that rotate the axle back, which would point the yoke even further up? i have a hard time understanding this...

[SCOTI]

Originally Posted by kev2809

ok i guess i will hold off on the rear and get my motor and trans dropped in...been itching to do it for a while now anyways.

i have been flipping through the forums about pinion angles all day. from what i have read, the longer the truck the less pinion problems people seem to have. im hoping this is the case with me since mine is a suburban. if i can get away with just moving my bag mounts around i would be perfectly ok with that. or even using degree shims to help. its just weird though because i always flip through peoples builds and not too many seems to mention any of this stuff lol. especially the suburban ones.

what i dont get though, is if do use the adjustable TA brackets, the front mounting moves up. wouldnt that rotate the axle back, which would point the yoke even further up? i have a hard time understanding this...

With the T/A set-up, the lower the front mounting point goes vs the rear axle/s height @ axle centerline, the more the pinion angle drops because of the fixed position of the housing on the arms.

[kev2809]

right, but doesn't the adjustable brackets move the mounting on the front arms up...not lower?

[SCOTI]

Originally Posted by kev2809

right, but doesn't the adjustable brackets move the mounting on the front arms up...not lower?

Yes, they move them up. But the reason for them is the chassis is going lower so it helps offset that change & put things closer to where they're supposed to be.

The adjustable ones let you tweak things more than just flipping the OE brackets.

[kev2809]

understood hopefully I can know more when I get the drivetrain in. I think either way I want to at least cut out the upper brackets. the more I look at them the more I hate them lol. thinking of even cutting off the axle bag mounts and buying a behind axle bracket and weld them on the front side.....like this setup

[kev2809]

ok, drivetrain installed, im ordering up the TA brackets now, so my rear end is up on jackstands and so is the frame. im assuming the truck has to be flat on the floor to measure angle of the output shaft and the also the rearend housing?

im also wondering if i should go ahead and get a drive shaft made, and bolt it up as normal with the TA's and then start messing with angles? i currently have the stock 2 piece but would actually like to have it a 1 piece if possible.