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Rear End Alignment HELP!

 
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jdub45
Bfix "What's a Bronco?"
Bfix


Joined: 22 Mar 2015
Posts: 2
Location: St. Louis, MO

PostPosted: Sun Mar 22, 2015 5:49 pm    Post subject: Rear End Alignment HELP! Reply with quote

First time post, not a first time user of this site. I've used the information from this site in rebuilding my 1969 Bronco. 302, with manual 3 speed, stock front and rear axles, stock drive shafts, and stock transfer case. Did a search on this topic and need some help…

I've done a frame-off refresh of my Bronco (yes a refresh, it's definitely nor a restoration because I've done it all in my garage.) When I started, I pulled the body and all of the components off the frame. The frame was wire wheeled, grinded in spots, and patched where where spots rusted through.

Specifically with the rear end: I replaced both rear leaf spring mounts (the ones closest to the rear bumper) and both rear shock mounts. Installed a lift kit from TBP or Bronco Graveyard (at this point I can't remember which I've purchased lift kits, wiring harness, roll cage, glass, brake lines, disc conversion, seats, the list goes ones…) that had new leaf springs, shocks, and bushings (for the rear) and springs, shocks, bushing and adjustable track bar (for the front). Everything appeared to bolt together correctly to the original 9" rear end.

My Bronco is assembled and I put 31" Goodyear Wrangler DuraTracs on new AR 15X8 alloy eight hole wheels. Had the tire place do an alignment and they were able to align the front end, BUT they reported that the rear end has a mis alignment and they obviously couldn't do anything with it.

Here's the specs:
Left Front Right Front
Camber .7 deg Camber .6 deg
Caster -.9 deg Caster -1.4 deg
Toe .11 deg Toe .10 deg
Total Toe .21 deg
Steer Ahead .01 deg

Left rear: Right Rear
Camber -.3 deg Camber -.2
Toe .18 deg Toe -.34

Total Toe: -.16 deg
Thrust Angle: .26 deg

Here's are the symptom of the above alignment. When I let off at relatively high rpm's (3,000) the Bronco wants to veer right. It's not uncontrollable, but it's definitely not how I want it to drive given the investment thus far. I also don't want to rip up these new tires. I'm guessing the rear end alignment is pushing the truck to the left and when I shift of let off the gas (and the thrust of the rear end lowers) the truck wants to follow the correction I'm making in the steering to make it go straight under power.

So, I'm not sure what to do now. I'm guessing a couple issues:
1. The frame is bent. I didn't notice and signifigant deviations from the stock measurements or any visible bends when I tore it down to the frame. I don't think this is it.
2. I screwed up the rear leaf spring mounts. This is a real possibility. I can already tell the drivers side mount is about a 1/2 lower that the passenger mount, creating a visible rear body lean to the drivers side.
3. The new products are defective. I don't think this is it either.

So, what do you think?

I'm thinking I've got to correct the rear shock mounts, but before I start hacking and whacking on all of my newly done hard work I'd like some input. I'd also like to only do it once; so if this is the next course of action…how do I ensure I don't f'it up again.

I know this is a long post, hope I gave the group everything I can. I appreciate any input!



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DirtDonk
BFix Locked and Loaded
BFix Locked and Loaded


Joined: 27 Jul 2003
Posts: 2749
Location: San Jose, CA

PostPosted: Wed May 27, 2015 8:08 pm    Post subject: Reply with quote

Well hey jdub. Sorry for the lack of responses for so long!
I've actually tried unsuccessfully to get on this site several times over the last few months and just kind of temporarily gave up. Looks like most of us took at least a two month vacation.

Nice rig! So did you get any of your answers anywhere? Or at least have someone to discuss it with?
Anyway, I'll tackle a few of the items here even if you did.

What about your steering angles? Your symptoms of pulling left and right are very common to this type of suspension. And your alignment specs are way out. I like your camber (both less than 1 degree positive) but hate your caster (both negative when they should be positive). Do you know how much lift you got? if not, can you measure between the bottom of the frame rails and the top of the axle tubes at both ends? The front should be 7" stock, and the rear 6" stock. So anything above that is your lift.

I would think the shock mount locations would be the least cause of any ill moves. Spring hangers, yes, but even then, those rear specs didn't look horrible. Maybe I'm not remembering correctly though. Did the alignment shop give you a printout with the recommended settings?

What, if anything did you do with the steering. Looks like you did a bang-up job on the whole chassis, but it's the little things that can mess with a lifted EB.

Here's to hoping you've got all your issues ironed out, but if there are any more details, let us know. Especially pics of the front steering linkage from straight on.

Thanks. If you've been talking over on Classic, I might have seen you there and just not remembered.
have fun!

Paul

_________________
'71 Bronco - 302 4v
3.5" WH/Skyjacker Lift
33 x 11.50 x15 Thornbirds on 15x7 Enkei's
Kayline soft top
Hanson bumpers
Dual batteries, Large 1G alt.

WWW.WILDHORSES4X4.COM Mr. Green
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jdub45
Bfix "What's a Bronco?"
Bfix


Joined: 22 Mar 2015
Posts: 2
Location: St. Louis, MO

PostPosted: Fri May 29, 2015 12:37 pm    Post subject: Reply with quote

Hey Paul,

Thanks for the response! I haven't had much luck in solving the handling issues. To answer your questions; I put a 2 1/2" lift on it and didn't receive any other specs from the tire shop on the alignment. In fact, I'm not sure they had done an alignment on a vehicle this old.

The lift kit included new c bushings, track bar bushings, and radius arm bushings. I also added an adjustable track bar, although I'm not sure I've got it adjusted correctly. I didn't change the tracking bar drop, pitman arm, or steering linkage.

I'm wondering if the track bar isn't adjusted correctly, if that's part of my problem? Traveling this week and plan on adjusting the track bar next week. It's drive able and fun, just want to dial it in a bit more.

Justin
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DirtDonk
BFix Locked and Loaded
BFix Locked and Loaded


Joined: 27 Jul 2003
Posts: 2749
Location: San Jose, CA

PostPosted: Sat May 30, 2015 9:25 am    Post subject: Reply with quote

Do you remember if the C-bushings were 2, 4, or 6.5/7 degree types?
Do you have manual steering still, or have you converted to power?

If you have power steering, with a '69 I would just go straight to 7° bushings no matter what is recommended and no matter what height lift kit.
Reason is that back then Ford did not spec out much caster and Dana/Spicer obliged by being inconsistent as well. While more positive caster is better for road manners usually, it's also harder to steer. With power steering that's not an issue and you can go wild up to a point.

Caster:
Regarding your caster numbers, if those are indeed negative numbers you might even have your C-bushings in bass-ackwards. Even professionals have done that, even after reading the directions, so it's VERY possible no matter who's doing the install.
One easy way to check is to look at them closely from the side and see which way the offset is pushing the axle. You can see the little "humps" just inboard of the side flanges. You are looking for the humps to be at the lower edge of the front bushing halves, and upper edge of the rear bushing halves. If they're not, it's time to re-orient them and maybe even replace them with some that have more offset.
Another way to see how they are is to look at your pinion and u-joint. If the pinion is pointed roughly straight up into the driveshaft centerline or above, they're in wrong. If the pinion is pointed below the centerline of the shaft, the C-bushings are in correctly, but are just not doing enough.

Most shops these days seem to not even want to give you a printout of your caster and camber because they think that both are non-adjustable. That's incorrect and you should always get a reading of both. Luckily at least your guy did that.
Just make sure that those negative numbers are not in fact positives, and I think you're on to at least one of your issues. Getting out of the negative range and into the positive range to at least 2.5° or so will make a world of difference. Getting it to at least 4 degrees if you have power steering would be great.

Rear springs:
Did you wait until the rig was back on the ground before you torgued the rear spring bolts? If not, loosen them up a bit, jump up and down on the rear and then re-tighten.
With aftermarket bushings you do not always use factory torque settings either. That's something like 100 to 150 lbs depending on the bolt. With our poly bushings you might need much less.
The way to tell is by how much sooner the ears of the mounts contact the inner steel sleeves of the bushings. If the ears touch the bushing flanges first, then only put as much compression on them as you need to contact the inner sleeves tightly. What you don't want to do is compress and expand the bushings to the point they're obviously distorted. Since you have locking nuts on those bolts, you can simply torque them down to what's needed (often less than 40) and leave them. If your old hardware is worn it won't hold that torque for long, so it's good to use new locking nuts when installing poly bushings.
On the flip side, if the inner sleeve is contacted well before the bushings, you can use factory torque value. It would still be a good idea to make sure your locking nuts are still in good shape. Eventually any of them can loosen if the locking nut is no longer good.

Re-torque your main axle-to-spring u-bolts after a few hundred miles.

Tire pressures:
Don't inflate to maximum values on most tires. Most of us find a sweet spot for the front between 28 and 30 psi. With some liking 32. But rarely more.
The rears are usually either the same, or less. Mine is always happiest with less. Every tire and wheel combo can be different on every different Bronco. So as always "your results may vary" is a phrase to live by with EB's!
If yours are already in that range, good. But it never hurts to experiment. My Roadhandlers and TrueTracs liked 32, my Swampers like 20!

Toe-in:
Even though it's adjusted, it's easy to readjust in your driveway with normal hand tools. So if you ever get a wild hair, mark where it is right now and give the adjuster a twist just a tiny bit at a time. Maybe an 1/16 of a turn at a time? See how you like by driving it for a while, and try again. If you just can't find a better spot, go back to the original position you marked. You DID mark it, right?

Trackbar adjustment:
To check your trackbar adjustment, leave the vehicle with it's full weight on the ground (normal ride height) measure to a point in the center of your frame crossmember just under the engine and mark it on the back edge. Hang a plumb-bob from it (I used string and a bolt) and find the center point of the axle. Mark that point with some tape and a marker and see how far off the string hangs from that mark.
If you need to adjust the trackbar shorter or longer, remove just the top bolt, drop the upper eye out of the bracket and adjust accordingly. Rinse dry and repeat until you get it right.
With the trackbar, it's best to make sure that each time you twist it you orient the eye in such a way so that it is at the right angle to slide up into the bracket again. This just keeps any twist loads while driving to a minimum, but really us mainly to make it easier to install.
And speaking of which, no matter which way you have to adjust the bar, you can VERY EASILY get it lined back up to the bolt hole by turning the steering wheel. Yep, turning the wheel while the bar is disconnected has the very disconcerting effect of moving the body and frame left or right over the axles! Weird the first time, but a huge help when you don't have to muscle things around just to line the bar up again. Seems these things never want to line up once you've pulled them anyway, so that's a good trick to know anytime you're servicing things up front.

"The Test":
Once that's done, the best thing you can do for yourself is to have a helper sit in the truck and rack the steering wheel back and forth continuously while you watch all the goings-on up front. They only need to go about a 1/4 to 1/2 turn in each direction for this to work. While they do that you simply sit under the front and make sure everything is doing it's job with no excess rotation or sideways movement. When it comes to steering components such as tie-rod and draglink ends, ANY movement that does not push the next component (free play) is bad. These things are supposed to be very tight, so any play means that they're worn out. Maybe not to the point of failure of course, but in need of replacing to reclaim the best road performance.

If you do need to replace the steering linkage, only go back to stock if you have small tires, don't plan to ever take it off road, and don't want full adjustability. At the very least, you want an adjustable draglink to keep your steering box in it's "on-center" position.
If you are going to use larger than 32" tires, or plan to go off the highway with your Bronco, a beefier and fully adjustable linkage like the venders sell is a good upgrade. It's stronger and is less expensive to change the rod ends the next time they wear out. Yes, it's more expensive up front (about 100 bucks more if I remember?) but well worth it if your budget permits.

And speaking of on-center. Don't ever re-orient the steering wheel to make it look centered. Best to re-orient the box by moving the pitman arm over one spline or so. I'm guessing your steering wheel was slightly off center after the lift (most are) and the steering box being off it's center can also lead to more vague feeling issues on the road. Best to keep it centered then, with the steering wheel as your visual clue.

Of Pitman Arms and Trackbar Brackets:
Another issue possibly, is the lack of a dropped pitman arm and trackbar bracket. Yes, they're not specifically "required" for a 2.5" lift, but some Broncos, mine included, end up needing them anyway for proper road manners. Since that's more money, you can at least wait until you've done all the other stuff first. If you still feel it needs something else, then I'd do that.
What these two items together can do is improve the angles of your trackbar and draglink, but also help to re-center the steering wheel and box after a lift. Same thing an adjustable draglink does in fact, but the adjustable draglink does it more precisely (for any given amount of lift) and is something to consider even if you do go with the arm and bracket.

That's about it for now. Hope that wasn't too much to absorb, but since you've been cruising the site for awhile, I figure you're soaking all this stuff up anyway.

Good luck.

Paul

_________________
'71 Bronco - 302 4v
3.5" WH/Skyjacker Lift
33 x 11.50 x15 Thornbirds on 15x7 Enkei's
Kayline soft top
Hanson bumpers
Dual batteries, Large 1G alt.

WWW.WILDHORSES4X4.COM Mr. Green
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