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rear wheel locking up


kaybyrd's Avatar
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04-26-02, 06:30 AM   #1  
rear wheel locking up

I have a 79 Chev Blazer, 4wd, full sized truck and the other day the left rear wheel seemed to bind up while making a right hand turn. The noise was sort of a popping sound, not a metallic sound or gind either. I could feel the "hop". We moved it to the side of the road in case it was the rear-end.

It did it a couple of times after we got it home, and we determined that it wasn't both sides locking up and us not noticing that since I was turning right (causing the right hand tire to "pivot" as opposed to the outside tire). I took it to the shop (lovely rain again here and no garage/carport for me to work under) to have the brakes checked and they said they were fine. It hasn't done it again since the brakes were checked. I checked the grease in the rear end and it's fine. I also had the rear end serviced about 9 months ago. They pulled the cover off, checked the gears, installed a new gasket and fluid. The shop (at the time) said that the rear end was in great shape. I haven't been off road, or done any major towing since and there appears to be no fluid leaks.

Could it have been a rock, or something binding the left wheel? What other possibilities am I overlooking? Am hoping to get some sunshine soon so that I can pull the wheels off and check bearings, etc. I know that I have to find a full service shop around here. The one I took it to doesn't do anything beyond brakes, alignments and tires.

Kay

 
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04-26-02, 07:53 AM   #2  
Joe_F
Does it do it upon braking or just driving?

It could be a hung up wheel cylinder or a clog in the brake line, or an issue with the proportion valve sending fluid to the rear wheels.

How's the condition of the wheel cylinders and lines going to the rear wheels? If the cylinders are original, pitch them. They get stuck after a few years of use.

You might also change your brake hardware in the rear as this will also cause trouble as well.

Barring that, something wrong in the rear end, but we need a better description to go there first.

 
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04-26-02, 08:36 AM   #3  
I replaced the wheel cylinders 3 years ago when I purchased the truck. One was leaking, so I replaced both sides. As soon as the rain slacks up I'll get out there and check the lines, etc. Not sure what I'm looking for, though. Obvious things would be wear and binding of the lines?

As far as braking and driving, driving seems to be fine, however, when I brake it pulls to the right, and hard. This I am hoping is caused by the fact that I desperately need to replace the outer tie rod before it gives and does major major damage to axle, etc. I didn't pay attention when I installed the last one and didn't install it correctly (didn't tighten the nut far enough, and corrected it after driving it for a week). I also had asked the shop that performed the alignment immediately after I installed the tie rods to check my work, said they did. My brother in law rechecked it and discovered my error. Not having good shocks on the front doesn't help matters either.

My husband thought that maybe the emergency brake might be binding up. When he went to get the truck from where I left it he said that it was binding until he put it in reverse, rolled backwards, and then went forward again. It didn't bind again until he got it almost home. It bound again and released as he was making a right hand turn into the drive way. I'm thinking along the lines of the hardware binding since after backing up, it released the bind.

Kay

 
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04-26-02, 08:59 AM   #4  
Joe_F
If it pulls to one side when you brake, you likely have:

1) A bad brake hose going to the caliper,
2) A sticky caliper

or a combination of both. New hoses are cheap insurance. They rot from the inside out and act as check valves. Dump them for new ones. Any parts store will have them in stock.

Try that first. Replace the hoses, bleed the system and tell us what you have after that.

 
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04-26-02, 01:06 PM   #5  
Charles E.
One other thought although remote. If it is equiped with positraction ocasionally they build up a residue on the clutches and when you try to turn they drag one wheel or pop and sound like they are breaking off teeth, usually only when hot. After it cools off everything works fine. Only solution I know is to change the gear oil and add a couple of tubes of positraction additive. Although Joe is probably right in which case don't play with it a brake problem can be very dangerous. Good luck! Charles

 
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04-26-02, 03:33 PM   #6  
My son just informed me that I don't have positraction, but "live". Don't ask, I don't know. What is the difference between the two?

Kay

Ps. I will do the brake work. The front brake hoses in this little town are special order. They'll be here tomorrow. Hopefully I can get on this asap. Wouldn't you know, the minute I sold the "backup" car, this truck would need major work...LOL.

K.

 
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04-26-02, 06:18 PM   #7  
Joe_F
Posi traction will provide more power to the wheel that is not slipping. It is also called "Limited Slip" and "Safe-T-Track" (Pontiac term) depending on the marketing term. They are all the same G80 option on the books in GM.

 
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04-26-02, 06:54 PM   #8  
PosiTrack?

Joe_F:
I have always thought that "posi-track" was a system of clutches that continuosly made contact to allow both rear wheels to spin and only release when the traction differential became greater than the clutch presure, like turning a corner.
"Limited slip" on the other hand, is a system that is used on 3/4 ton and up trucks that use a cam arrangement to force the clutches closed when one wheel spins. I have this type on a '79 3/4 ton crew cab. The rear wheel has to make a half revolution before the other wheel will grab.


GregH.........HVAC/R Tech

 
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04-26-02, 07:25 PM   #9  
knuckles
Differential types

Greg H,

GM has marketed several differential designs as "posi-traction".

Off the top of my head I can think of 4.

1. Original "clutch pack" type differential w/ coil springs providing preload. (1960s)

2. Cone type differential with "s"-shaped spring providing preload.(1970s & 80s)

3. Gleason "Tor-Sen" torque sensing differential. (A few years only & limited to 3rd gen F-body in the mid 1980s). The smoothest limited slip ever built, but suffered from poor reliability.

4. Governor style differential. This was used on many cars & light trucks in the mid 1980s and up.

Posi-traction is a GM marketing term. In reality, all "posi-traction" differentials are limited slip differentials. Other types of diffs are:

1. Open differential. Provides max torque to the wheel w/ the least amount of traction. Often referred to as a "one legger".

2. Locking differential. Uses dog clutches to provide positive engagement of both axles when travelling in a straight line. Balky operation (clunks & jerks on moderate/hard turns) limit its use to 3/4 ton & larger trucks.

3. ARB Air locker. Strictly an aftermarket piece. Acts as an open diff when "off". Uses compressed air to actuate a sliding clutch & fully lock both axles to the ring gear when engaged. Popular w/ the street/strip crowd & the off-road set.

 
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04-27-02, 07:42 AM   #10  
Joe_F
Greg:

Any of these for GM will show up as the "G80" option on their buildsheets, sales sheets, etc.

As Knuckles mentioned, they have used various marketing terms over the years. Pontiac had a few names.

All still G80

 
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04-27-02, 07:14 PM   #11  
knuckles & Joe_F:

Thanks for the info.


GregH.........HVAC/R Tech

 
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