how to fix brake/bump steer in 88 suburban that had 2.5 inch lift springs installed

highdesertranger

Adventurer
wow that's a lot of panels for only 10 amps. that looks like it should be at least 400 watts which would work out to 30+ amps. what controller are you using? highdesertranger
 

Larry

Bigassgas Explorer
Here is my .02 cents….

First, does your Suburban have height sensing proportioning valve near the rear axle with an arm that attaches to a bracket on the rear axle cover? Being an ’88 it should. If so, that could be your problem. When the ride height is changed on vehicles equipped with a height sensing proportioning valves the braking power is biased towards the front axle as the truck thinks it is under hard braking where the rear end of the truck is lifted up in a nose dive panic stop. This was an early attempt at ABS to prevent the rear wheels from locking up. If your Burb has that height sensing proportioning valve you can bypass it by moving the brake line directly that currently screws into the height sensing proportioning valve directly to the main brake hose that feeds both rear wheel cylinders. It doesn’t matter how perfect your alignment is if the majority of the braking power is going to the front axle it will pull one way or another under a hard stab. They usually pull right due to the crown of the road.

Second, do not use a drop pitman arm. Drop pitman arms are flat out dangerous and shouldn’t even be sold in my opinion. On two occasions I’ve seen where drop pitman arms have broken the steering gear output shaft due to the leverage the drop pitman arms puts on it. Ask Mosesburb with the sweet orange ’72 Cummins powered Suburban. That exact thing happened to him at the Overland Expo 2013 when we were doing a photoshoot for a mag under moderate flex. We heard huge CRACK… We looked around and didn’t see anything obvious then driving home he noticed it didn’t see to steer very well. When he got home and started looking around at the steering gear he found the output shaft was cracked ¼ through. Scary thought to drive from Flag to Phoenix like that. I’ve seen the same thing happen to an old Dodge that also uses the Saginaw steering gear and push/pull steering rod like a GM. For whatever geometric reason a raised steering arm works so much better with less forces being put on the steering box and frame. Sure, there are probably tens of thousands of old lifted GM trucks running around with drop pitman arms that have never had an issue but my thought is, I don’t want to be the one in a 10K guy that breaks a steering output shaft plus not every body really uses their fullsize 4x4's that way I do.

You can practically hear the loud CRACK in the picture from that moment.
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YES! The problem is the steering arm is more difficult to replace so most people take the easy route and use the drop pitman
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NO! BTW, I have a brand new drop pitman in a box that you can have if you really want one. Just PM me and pay the freight.
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FWIW, some wandering and bump steer will never completely go away on a lifted Burb. My 4" lifted K10 goes down the road straight as an arrow with no wandering or bump steer meanwhile, my 4” lifted Suburban wanders constantly. I mean you have to keep your eyes on road all the time! The interesting thing is the front axle and springs came out of my K10 before the K10 got a D60 swap with heavier springs. The K10 never wandered with this axle or springs but the Suburban does. Everything on the Suburban is new including the steering box. I've had more damn caster wedges in and out of this thing trying to fix the issue it isn't funny and it has gotten 75% better. I might be able to add a bit more caster to it to help out a bit more but I am going to hold off until after the 8.1L swap and the installation of the front winch bumper where the front end will gain a lot of weight.

Adding weight may help my particular problem but yours is a bit different. Go check that height sensing prop valve and take it off if you have one and stay away from a drop pitman if you really wheel your Burb.
 
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dwh

Tail-End Charlie
Agree with what Larry just said - raised steering arm is better than dropped pitman arm. (If for no other reason than it keeps the stuff up higher away from rocks.)

Also agree with what cyclic said - good bloody luck finding one with less than 4" of rise.

Also agree with what Larry said - height sensing proportioning valve is the likely culprit.


"Bump steer" means it will turn itself when you hit a bump and the suspension compresses. If you go over a speed bump a little too fast - does it try to rip the wheel out of your hand? If it doesn't, and it's only doing it under braking, then it's not bump steer.

Dropped pitman arm is a compromise used when the suspension lift is so high that the raised steering arm is not enough. That adjustable "connector rod" between the pitman arm and the steering arm is a "drag link". There are also offset drag links. If you want a 12" lift, you might end up needing all three.

For a 2.5" lift you really shouldn't need anything, which is why they don't make 2" raised steering arms - don't need 'em.


If you go to the Skyjacker site and look up lift kits, they show 3 2.5" kits for that truck. Two of the three say that the dropped pitman arm (part #CA50) is required (and I ask - if it's required...then why isn't it included?), but the third kit does not say the dropped pitman arm is required.


I don't see the dropped pitman arm as a problem with the truck in the OP - 1/2 ton, not running 40" tires, doesn't have a 6" lift, probably doesn't have a big block or other 700 lb. engine. It's mild, not wild. Broken steering box output shaft is a very rare failure. With those Chevys it's much more common to just rip the steering box off the frame - which is why they make support brackets and weld-in frame reinforcment/repair plates for those trucks.



I wouldn't do the dropped pitman arm until after I determined if it's the proportioning valve.

I can't recall offhand - do those trucks have the normal proportioning valve (usually right under the master cylinder somewhere) AND the height-sensing valve back over the rear axle? If so, then yea, I'd bypass the extra valve. I think that valve is primarily intended for trailer towing anyway, if there is a lot of tongue weight.

If not, then I'd get rid of the height-sensing valve after I installed a normal proportioning valve.
 
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dwh

Tail-End Charlie
Or, if you're going to tow a trailer with a lot of tongue weight - just cut and extend the lever arm to the height-sensing valve by 2.5".
 

Rockhounder

Explorer
My 88 1500 does not have any proportioning valve or other unidentifiable hardware on or near the rear axle, and the brake master cylinder looks like the totally old school type with one pipe going out to the front axle, and the other pipe going to the rear axle (see pics)

I did buy the Skyjacker 2.5" arm got a pretty good deal from summit for $70 with discount. It looks totally robust and three times the metal mass of the factory arm. I did check the steering box for any signs of cracking and fatigue, none seen now, but will put a brace on the box, just for insurance. The tires are 33's (33x12.5 r15) and I do not rock crawl (if I can help it), and do not do aggressive crazy driving or yanking of the steering wheel side to side, so we should be pretty safe with this arrangement. Hope to install it tomorrow, will keep you all posted on what it does to the steering while braking. To the previous poster, who mentioned bump steer.. yes, I do not notice it much on bumps, only on real hard stops where the weight transference makes the nose dip aggressively. Then if I keep my hands straight on the steering wheel, it wants to go to the right. If I hard brake with my hands off of the steering wheel, it brakes pretty much straight, but the steering wheel spins counterclockwise about 40 degrees, then returns to level on its own as I let off the brakes.

I will let you all know what ends up happening with the brake steer issue after installation.

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Rockhounder

Explorer
wow that's a lot of panels for only 10 amps. that looks like it should be at least 400 watts which would work out to 30+ amps. what controller are you using? highdesertranger

to be technically accurate, I have seen it go to 11.5 amps, but the panels are 15 watt panels, x9 panels total, amorphous elements, with long horizontal cell structure if seen from the underside. I am using a basic 30 amp charge controller, which also has a built in outlet for acc power. The only thing I do not like is the low voltage buzzer..... thinking ofcutting that out as it does no real purpose other than to irritate me when I know that I am low power.... The panels are the harbor freight cheapo specials ($150 for 3 panels with the discount coupons I get the set for $150 (promptly toss the unnecessary stuff like the included battery charge center box, and the useless 20 gauge wiring... save the 12v flourescent lights though, they are useful, and put out about as much light as a 60 watt regular 115v flourescent bulb.

I liked the size and shape of the panels as I was able to use them to follow the roofline profile I designed (with the underside venting which keeps the roof noticeably cooler.)
 

Rockhounder

Explorer
hey rockhounder what kind of rocks do you hound. highdesertranger

our favorite areas are basically everywhere east of barstow, along either side of the 40 fwy, Northern Cadies, Calico north side, etc. My personal favorite is the paul bunyon agate, tons of beautiful jaspers, jaspagates, and of course the thin hollow agatized veins that break apart to reveal beautiful sugar frosted druzy in the most beautiful browns and blues. We also like to go south to Julian area, and go tourmaline hunting, up in Montana we have friends we go gold prospecting with as well.
 

1stDeuce

Explorer
Rockhounder, you're on one of the right paths! My K10 did the exact same thing after I changed from Uber-stiff springs to factory rate soft springs, with a 2" lift. It had no problem with the stiff springs that were in it before that, but only because the suspension never moved! Once the nose could dive under braking, I got good at steering to the left quickly if I braked hard. The axle would also self steer some when articulated.

Because I was not excited about the extra leverage that the drop pitman arm places on the steering box mainshaft and on the frame, I went a different route... The steering arms that you can buy are all for 4" lifted trucks, which is too much... But I found that the steering arm off an older solid axle Dodge Ram (Like 70's/80's vintage) was a direct bolt on to the GM knuckle, and was designed for the drag link to mount from the bottom and result in the same positioning as the GM arm with the drag link mounted from the top. I reamed the taper into the dodge arm from the top, mounted the drag link chevy style, and found it to provide about a 2" gain in height, which leveled my drag link perfectly. No further problems, no extra stress on the steering box and frame.

Here's a picture that I found on Four Wheeler's website of a dodge steering arm with a spacer. (I didn't do this!!) You can see that the arm bends up slightly compared to your GM arm, and you can also see the drag link mounted to the bottom. Funny that someone would use the spacer, when they could swap to a GM arm and flip the drag link and get almost the same thing...
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Honestly, the drop pitman you got should be fine, especially if you plate or brace the frame where the steering box mounts. :)
Chris
 
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Rockhounder

Explorer
Ok, Here is the latest news, got the new pittman arm installed. Just had to play with the rotation of the turnbuckle, tightened that connecting rod by about a half inch, in order to get the steering wheel back to level.

Suburban now stops directly straight ahead, no pulling, even at full skid stop (only did that once, just for a split second, as it would really suck to grind some flat spots on my new tires)

No pulling to either left or right, literally solid straight.

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dwh

Tail-End Charlie
Beauty!

That Dodge steering arm on the Chevy knuckle is a neat trick too. Gotta file that one under future reference.
 

Larry

Bigassgas Explorer
Glad it worked out Rockhounder
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I'm surprised it doesn't have a height sensing prop valve. Maybe that was a 3/4 ton only thing
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Keep an eye on the steering gear output shaft if you do any hard wheeling. The lowered pitman arms are hard on steering gears. Most of the low height lift springs don’t have much flex in them so you should be alright.

The Dodge block is a good alternative for a D44 or Corp 10 bolt. The hard part is finding that block and studs strong and long enough. Pretty much the same method as the D60 block from ORD to raise the steering arm on my K10.
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