Suspension Questions

[billyjo]

My first major suspension problem has to do with braking and deceleration. It feels as if the rear is moving around, like when I hit the brakes hard the back end kicks out . It does the same on deceleration but not to the same extent. I think it's done this ever since I had the 1 ton conversion done and when I first noticed it way back then I thought it was due to having the locker. Over the past couple of weeks I've been trying to trouble shoot this problem but I can't find anything that is loose or broken that would contribute to it.

Secondly I need to do something to help the ride out. I presently have a 4" suspension lift and it's a Sky Jacker soft ride. It's not that soft and I checked the part#s and they use the same springs on the K/5 as they do on the trucks. I've heard a lot about Alcans being the way to go. Anybody have any input or using them? I'm also open to entertaining other suspension options to try and soften the ride since I spend 95% of the time on the street.

Thanks,

Bill

 

[Yukon Jack]

Is the rear lift with springs or blocks? I have a Detroit in my 69 K20 and don't have any issues like you are having - I don't think it is Detroit related. Could it be a pinion angle problem? When you brake or decelerate, it may be causing the pinion to move just enough to bind the driveshaft? Or I guess your driveshaft could be bottoming out, kinda doubt that.

Maybe see if a friend can drive next to you and watch the rear axle when you brake to see if that helps solve the problem.

BTW - the pic of your rig in your sig is sweet!

 

[billyjo]

I have springs in the back with the zero rates but it did this prior to me installing the zero rates.

I never thought about the pinion angle being the problem. The springs came with shims to roll the pinion up but I don't think that it is near enough. I do have a CV joint from High Angle driveline where it attaches to the transfer case. So is your thinking that when it's binding causing it to push or pull on one side of the u joint thus cocking the axle? If this was happening I should be able to see where it was wearing on the u joint, correct? I'll check for that tonight. I don't think the driveshaft is bottoming out, it's been worked over several times so I know the length is right on it.

I also never thought of having someone drive next to me to see whats happenning.

Thanks for the input, I'm still open to any and all theories.

Bill

 

[Yukon Jack]

So is your thinking that when it's binding causing it to push or pull on one side of the u joint thus cocking the axle? If this was happening I should be able to see where it was wearing on the u joint, correct?

I would definitely think you would see some marking on the yoke if the pinion were moving enough to make contact with the u-joint. I think my front driveshaft might do this some when I hit the brakes hard when I have the hubs locked in and it makes the front axle feel like it is jerking/binding.

 

[2wdBlazer]

You probably already have done this but you did check your U-bolts right? Maybe spring bushings? Anything that could allow some slop.

 

[Burt4x4]

First thing that I thought of was axel wrap...your engine has the power for it. check the inside of your rear yoke at the diff and look for hit marks. If you see the hit marks then you have axle wrap.
My rear is wraping way hard now that I have that 454 in there I have gouges not hit marks hahahahaha

 

[billyjo]

I have checked the nuts on the u bolts several times and they are tight. I also went all over the rear yoke last night and couldn't find anything that looked like it had hit. I was all over everything last night trying to find something that looked like it was moving in a manner that it shouldn't have been but I came up empty. Maybe it is my spring eye bushings but they aren't that old.

I know I have axle wrap because when I spin the tires I get some bad wheel hop. I've thought and problably will go with some kind of anti hop bars when I figure out what I'm going to do with my suspension.

Burt, when you decel or get on the brakes does yours stop straight? The other day I was accelerating hard, there just happenned to be a Camaro next to me and @ about 85 I had to let off and hit the brakes and it was quite a ride so I've got to fix this problem.

Thanks,

Bill

 

[Burt4x4]

Well I haven't hit the brakes hard at higher speeds but I have hammerd on them simply testing, all seamed to stay fairly straight..not the wild ride you are having
Sure sounds like something is squishhy back there???
Having someone next to you watching may be the next step...but the person watching will know how to watch! if you know what I mean....
When you were looking at that rear yoke and the Ujoint did you look at the ujoint caps to see if it is spining? if it is spinning the retainer clip will scratch the cap and make it shinny were the clip touches the cap. If you see this then your caps are spining under heavy load..another axelwrap 'footprint'.
Duno man! sounds wierd....Axel gost

 

[billyjo]

Well I had one of my friends look it over last night and see if maybe there is or was something that I was missing. He came up with the same conclusion that everything looks good. Tomorrow I'll get someone to drive next to me to watch what's going on when I'm braking and maybe that will give me another clue. The only thing that it looks like it could be is the bushings in the spring eyes. I was able to get a little movement by prying the spring eye with a large screw driver and I'm thinking that driving is going to put way more pressure on it that I can with the screw driver.

If I'm going to change the bushings I'm thinking I'm going to change all of the springs and try and improve the ride quality. Right now I've got the 4" soft rides but nobody that rides with me thinks it's that soft. So what is the best set up to go with. I did a search about shackle flips, alcans and a bunch of other stuff but I'm looking for some input.

Thanks,

Bill

 

[Burt4x4]

Hmmmm..
Good luck!
I am not up to speed with the latest in suspension choices.
One piece of info that may still apply is the fact pre-made springpacks are set to pick-up weight specs so when you buy a 4" rear spring you only get about 2.5" of lift due to the fact balzers have a heavy butt compaire to a pick-up. I am running 4" Rancho spings in front and 5.5" Superlift springs in back...
Burt

 

[billyjo]

I had a friend drive next to me and he couldn't see anything that looked like it was out of place. Could my problem be bump steer? When I did the 1 ton conversion they removed my dropped pitman arm and substituted a straight one. And last time I had it aligned they told me I had some bump steer.

Bill

 

[Greg72]

How do you know that it's the REAR that's moving around? Could it possibly be the front?

I had a similar situation on my '72 when I first installed softer front springs. On braking the truck would always dart to the right....it turns out that the 1st Gen Blazers have a small metal tab mounted just behind the shackle on the drivers side front spring. This was a safety recall measure to hold the spring in place if a springbolt was to ever break.

When I looked at that bracket it had a shiny spot on it, indicating that my new springs were flattening out under braking and hitting that tab. Basically, the effect is that the driver side spring stops flattening out, but the passenger side one continues to flatten.....this moves the axle back slightly on the passenger side and causes the truck to turn (axle steer) to the right.

It's one explanation anyway...


Your factory push-pull steering could certainly be a culprit also. Under hard acceleration the steering wheel would pull LEFT and under braking the wheel will turn RIGHT. Crossover steering would be the ideal way to solve it, but you can experiment with different combinations of raised steering arms, dropped pitman arms and dropped draglinks to find a combination that works better. It's a little bit of trial-and-error but people have been successful in resolving steering issues by trying a few different combos.

 

[billyjo]

I originally thought that it was the front but since the steering wheel didn't jerk when hitting the brakes and the problem also happened when decelerating I figured it had to be the rear moving around. Couple that with the fact that I never really new what bump steer was led me to the rear.

With the new found knowledge of what bump steer is it makes much more sense now that this is my problem. Then when I consider the addition of the heavier parts from my motor and trans swap it makes sense that it is worse now then it was before.

My K/5 does have the angle bolted to behind the drivers side spring but it is about an inch back so it never makes contact. The front ALWAYS darts to the right with hard breaking or a quick dart with light decel. And it also moves to the left under acceleration but I thought that had something to do with the locker catching.

I want to thank everyone for the input as it looks like I've got the problem nailed down. Now I'm off to the ORD site to see what I need to buy to fix it.

Thanks,

Bill

 

[Greg72]

Yank that limiting plate!!!

Seriously, it's only 2 bolts. 1" away is still plenty close, with a soft enough spring you'll hit it.

Pull that bracket off and take it for a few test stops. If nothing changes.....fine, but I think you might be surprised to find that the bracket is your culprit. I was.