Highway Death Machine?

[Terrapin Flyer]

I just bought an '83 K5 with a 6.2L diesel, lifted (looks like 4" suspension, 2" body), 35x12.5x15 tires. Twice I had to hit the brakes hard at 70 or so on the highway, and both times I puckered up big time. The first time I was going straight and the Blazer dove to the right. The second time was on a gentle curve and the truck swerved back and forth (serpentine style) so bad I thought sure I was going to go over.

I'm totally new to lifted suspension, large tires, and 4WD. Was I a dumbass for driving that fast, or is there something wrong with my ride?

I looked around, and here's what I saw: stock front anti-sway bar, no obvious damage or loose/missing parts in the front suspension, no visible cracks around steering box, and steering parts all look stock. Keep in mind I'm am new to this, so I could easily be missing something.

I now keep it under 65 and allow lots of room in front of me.

 

[Chevy305]

I'm no expert, but that could be death wobble...

 

[imiceman44]

I'm no expert, but that could be death wobble...

I am no expert, but death wobble is completely different.
What most likely is hapening is either he has soft springs and the braking is making it dive and since it's on a curve it shifts weight from side to side back and forth.
The other possibility is the body lift could be lose.

maybe a few pictures of the suspension especially the front, maybe we'll see something you aren't seeing.

 

[sdavid]

Sticky or bad brake calipers could cause that; especially darting to one side. It basically locks up one front tire and pulls hard to that side when it happens. I have had several of these old GM 4x4s with those symptons/problems. Stock suspension does not help either, but lifted may make it worse.

 

[Terrapin Flyer]

Here's the front suspension.

 

[imiceman44]

I just bought an '83 K5 with a 6.2L diesel, lifted (looks like 4" suspension, 2" body), 35x12.5x15 tires. Twice I had to hit the brakes hard at 70 or so on the highway, and both times I puckered up big time. The first time I was going straight and the Blazer dove to the right. The second time was on a gentle curve and the truck swerved back and forth (serpentine style) so bad I thought sure I was going to go over.

I'm totally new to lifted suspension, large tires, and 4WD. Was I a dumbass for driving that fast, or is there something wrong with my ride?

I looked around, and here's what I saw: stock front anti-sway bar, no obvious damage or loose/missing parts in the front suspension, no visible cracks around steering box, and steering parts all look stock. Keep in mind I'm am new to this, so I could easily be missing something.

I now keep it under 65 and allow lots of room in front of me.

Well looking at the pics, I can say it's lifted 2 maybe 2.5 inches, and with this moderate lift nothing special is required for correction, and it looks like a clean install.
I don't see any marks on the spring showing a sheared pin, the only thing I can say could make what you had is what someone said:
Bad brakes.
Go over your brakes and see what happens, also check the shocks as one dead on one side could do that too.
Otherwise i still wouldn't do 70mph on a curve with a lifted truck, on a highway straight sections if brakes and suspension is good you should have no problem going 70mph, no more though and only if it's within the speed limits. (yeah right)

By the way, as a good driver you SHOULD allow for plenty of room in front of you, but these day s so many assholes want to jump in any gap you leave for yourself for safety margin.
Who is giving these people Drivers licences?

 

[BKinzey]

I'm going to say brakes as well. Go ahead and buy new shoes, springs & such for the drums as it's cheap to do. Pull your tires and take a look at the calipers & discs. While you are replacing the rear check the drums. Visually inspect the lines for pinched spots.

If you don't find anything obvious test your brakes on a long flat road where you can test panic stops to see if it is consistent.

The next step would be to look at the proportioning valve. Probably the most practical is to just replace it as well. I don't know if you can get those tested.

While you are doing that flush out the lines, calipers, resevoir etc. could be some crap in there clogging it up so you want all new fluid.

Let us know how it goes Oh, while the front tires are off the ground shake them to see if your bearings are loose.

If you've been driving a small car previously you will need to get used to controlling a heaver vehicle

 

[Desert Yeti]

My first guess would be brakes as well, given what you've already checked (my FIRST guess was cracked frame). It could also be bearings or ball joints... if they're sloppy a hard brake after an acceleration will shift them to the opposite extreme of thier play, possibly causing a dive to one side. What you said about braking on a curve supports this theory too.

Check the ball joints/hubs/bearings while you've got the wheels off

Some of it is just that even with everything working properly 24 year old stock suspension and brakes have a hard time with 70mph on 35's... drive carefully!

 

[rx7gslse]

my suburban did that... looking at the pictures It looks like there's a few leaks...

in my case the steering box was leaking and some of that got down into the brakes... fluid on brakes = grabby brakes.

See if any of those fluid leaks in the pictures gets to the brakes... if so.. clean the rotors real well with brake clean and replace the pads... (and oh yeah.. fix the leak!)

 

[imiceman44]

My first guess would be brakes as well, given what you've already checked (my FIRST guess was cracked frame). It could also be bearings or ball joints... if they're sloppy a hard brake after an acceleration will shift them to the opposite extreme of thier play, possibly causing a dive to one side. What you said about braking on a curve supports this theory too.

Check the ball joints/hubs/bearings while you've got the wheels off

Some of it is just that even with everything working properly 24 year old stock suspension and brakes have a hard time with 70mph on 35's... drive carefully!

Well I can't confirm from just looking at the pics, but I can really make an educated guess, I think his steering ball joints are tight, usually you can see a sign of them being sloppy right at the edge of the boot, same with the springs showing a sheared centering pin.
I still think it's brakes and maybe shocks.

 

[rockink5]

Check your calipers. I would almost bet that the left caliper is either froze or leaking on the pads. I had this happen before.

 

[Terrapin Flyer]

I dig this site

Beers are on me if y'all are passin' through Santa Barbara.

I think the brakes theory is the rigt track, but the rear, not the front. I was told that the front calipers are new and the brakes were serviced. I tried hard braking on pavement and dirt. On pavement I could hear the front chirping like it wanted to locl up, nothing from the back. In the dirt the front tires dug in deep equally but nothing at the rear. I think I'll try it in the dirt again going backwards. Granted the front would dig in, but the rear should still play a role, right? Someone mentioned an equalizer or something like that, so I'll look into replacing it.

There's nothing leaking on the front brakes, they're dry. I couldn't pull the rear tires off, I need a lug wrench that I'll pick up tomorrow. I'm still trying to find the source(s) of the leak(s) also.

Thanks again for the input.

 

[buefchris]

It's a good thing to your check brakes out, but remember your running 35's and a body lift ! If those shocks and springs are tired, raiseing the center of gravity and brakes that are too small for the tire size at 70 mph panic stops make for a bad como-plate Might wanna slow down MARIO.

 

[dsmd58]

id say if the rig pulled hard to either side while braking check out the calipers/rotors. one may be bad...

 

[Big Blzn]

At least you can even get your blazer to 70mph. I think we all probably have the same problem. Lifted, big tires, short wheel base, etc,etc. Check brakes and like you said slow down and give lots of room.
Be careful out there bro.
Hoby

 

[Chevy305]

Beers are on me

I'll take one...

 

[Hazy]

By the way, as a good driver you SHOULD allow for plenty of room in front of you, but these day s so many assholes want to jump in any gap you leave for yourself for safety margin.
Who is giving these people Drivers licences?

i love it when my lights are in the cab of the car in front of me

 

[Hazy]

Beers are on me if y'all are passin' through Santa Barbara.

I think the brakes theory is the rigt track, but the rear, not the front. I was told that the front calipers are new and the brakes were serviced. I tried hard braking on pavement and dirt. On pavement I could hear the front chirping like it wanted to locl up, nothing from the back. In the dirt the front tires dug in deep equally but nothing at the rear. I think I'll try it in the dirt again going backwards. Granted the front would dig in, but the rear should still play a role, right? Someone mentioned an equalizer or something like that, so I'll look into replacing it.

There's nothing leaking on the front brakes, they're dry. I couldn't pull the rear tires off, I need a lug wrench that I'll pick up tomorrow. I'm still trying to find the source(s) of the leak(s) also.

Thanks again for the input.

im no expert but i just got out of a brake class and you problem could be that the rear drum brakes aren't adjusted correctly, you should take off the tire and spin the drum (it should drag). about the "equalizer" they must be talking about a combination valve, but i don't think you would have a problem, but it is possible. within the combination valve there are up to 3 valves but you usually replace the whole thing a.k.a combination valve.


funny when you first buy a truck, everything is to clean then like 1 month later or less the real leaks come out. like my oil pan

 

[Terrapin Flyer]

Figured out the problem.

Now if I can just fix it. The proportioning valve has gone to front brake only mode. The rear fluid reservoir was empty. I can't get the valve to reset. I read here about a switch on the end, but if it's switch it won't depress.

This to me explains the squirrely behaviour and the excessive front brake dust.

 

[Goose]

If it's in front brake only mode your brake light should be on.
If the half of the master cylinder that supplies your rear brakes is empty, I would suspect a leak in the rear brake system, and not your proportioning valve.

Rear brake leaks are commonly from the wheel cylinders.
Also, the 'switch' on the proportioning valve is only on the part that controls flow to the front wheels. This part of the proportioning valve is the metering valve and it's supposed to keep equal pressure to both fronts. Lastly, I think you have to pull it out just a little to let fluid flow from side to side. Sometimes you have to do that to get the front brakes bled all the way.


If it were me, I would pull the rear brake drums and inspect the wheel cylinders. Probably replace cylinders and brake pads, turn the drums.
Bleed all four brakes good then see what it does.
I wouldn't be surprised if the master cylinder is bad also.
Running them dry is hard on them.