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7/20/2014 3:36 PM  #1


8" Rear End 2.79

1967 Coupe, 289, C4, 8" 2.79 Gears

I went to a car show Last night, about 15 miles away. Had no problems getting there, everything was great. After the show, on the way home I was smelling something strange, like burned peanuts. Car was driving fine. As I near the house the smell got worse and I could see a little smoke coming from the back of the car and it seemed like the car was having a little trouble getting going. Being so close, I went on home.

Upon inspection, the smoke was coming from both rear wheels, around the drums. When I felt the wheels, near the center hub, it was exceedingly hot, very hot. Both sides were smoking. I check the center hub of the rear end. Surprisingly it wasn't that hot, but is was pretty hot. So I checked to make sure i didn't have the emergency brake on or something, it wasn't engaged.

Question. What are the sympotms of a bad rear end? How can I verify if it is the rear end? I believe it is the original, I changed the oil in 2007 when I restored the car. I haven't had any trouble before now. I have actually cleaned the wheels at car shows and don't remember any excess heat near the hubs before, so why would it be so hot all the way out by the hubs?

Is there a good rear end guy in the Dallas area that can rebuild or help my fix mine, or maybe has one for slae to swap?

Thanks Again, I know somebody has had to have dealt with this issue before.


A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty.
 

7/20/2014 4:24 PM  #2


Re: 8" Rear End 2.79

Could  it have been your parking or rear brake dragging??
 IF both drums were smoking, I would suspect brakes before the rear end itself.

Tubo


If it ain't broke, I haven't modified it Yet
 

7/20/2014 5:10 PM  #3


Re: 8" Rear End 2.79

Thanks Tubo, I did check andthe parking brakes were not engaged. It is a mystery to me why the outsides of the rear end was so hot and the pumpkin area was hot but I could hold my hand on it.

I'll just ahve to remove the drums and see if I see brake problems. Not sure how to check the rear end itself.

Thanks

 


A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty.
     Thread Starter
 

7/20/2014 5:30 PM  #4


Re: 8" Rear End 2.79

Jeff, just a couple of suggestions before you start pulling things apart.  First, jack up the rear end and see if you can turn the rear wheels by hand.  Second, after you've put jackstands under the axle, back out the bleed valve on one side, just a half turn.  If brake fluid squirts out with a little force, you have a problem, maybe with the proportioning valve.  You really want to see the brake fluid barely drip.  At least you'll know what you are up against.  Also, the emergency brake cables on these cars have been know to bind up, but usually after you have engaged the emergency brake.  Either way, you will probably need to re-do the brakes on the rear - shoes, pistons, etc.
The reason the pumpkin did not get hot is because it is not the problem.

 

7/20/2014 5:35 PM  #5


Re: 8" Rear End 2.79

How far did you drive?  If the lube is very low the axle bearing will run dry and the carrier will start getting hot because it isn't getting enough lube.  I think.

BB


"you get what you pay for, good work isn't cheap, and there are NO free lunches...PERIOD!"
 

7/20/2014 7:19 PM  #6


Re: 8" Rear End 2.79

Thanks all, here is my plan.

I will place jackstands under the axle and check the wheels to make sure the turn freely. While it is up I will take off the wheel and do a visual inspection, and also check the parking brake cable. Ill try the brakes and the parking brake to see if they are still functioning properly. I'll check for any fluid residue at that time.

If everything checks out, I will have to pull the drums off and inspect the brakes. If all that checks out I have to assume there is something wrong with the rear. I can do those things myself, but an a little unsure about the 8". Now might be my time to have to learn, LOL.

Can someone tell my how to check the grease level, and how to tell if it is bad?

I will make sure I post the results back here, but not for a couple of weeks. I'ts vacation time, and I leave tomorrow to Pentwater, Michigan, to a cottage on the lake for a week! YAY!

Thanks again for all the replies!


 


A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty.
     Thread Starter
 

7/20/2014 8:19 PM  #7


Re: 8" Rear End 2.79

You seem to have convinced yourself that there is a problem with the rear.  All fingers point to the brakes but you will need to be thorough in your inspection.  Don't assume anything is correct as found until you can verify.  Below is a list of what I would check but I am sure that I will miss a few things.

1.  Brakes are set too tight - not something that can occur spontaneously but may not be observed until a long trip.  This can be compounded if the e-brakes have not been properly adjusted.
2.  Incorrect parking brake setup - If brakes are adjusted too loose, some will attempt to correct by tightening the e-brake cable.  The brakes need to be fully retracted and properly adjusted before the e-brakes can be properly set.  Loosen the cable fully and ensure that the brakes fully retract.  Backplate wear and wear of the retainers, springs, etc., can hang the shoes up so that they do not return to rest.
3.  E-brake cable is hanghin up  - Over time one of the three brake cables can hang up due to corrosion or lack of lubrication.  Even through the handle is fully released the cable may still apply pressure.  Since both brakes were affected, it is likely that the front cable could be the culprit.
4.  Master cylinder issue - If the master cylinder does not retract either due to debris inside or incorrect actuation rod length, it can hold pressure and since the rear drums are self-actuating this can lead to a significant  drag - the suggestion to check bleeders for residual line pressure is good but also consider loosening the master cylinder attachment nuts a few turns to see if this reduces residual pressure.  If your master cylinder has residual pressure valves, these may be clogged or damaged.  Think of any service work that may have been performed recently as it may have had an uintended consequence.
5.  Wheel cylinders - if these have not been maintained and there is moisture in the system they may have jammed when operated.  Unlikely that both would be affected at the same time but never say never.
6.  Rear brake hose deterioratiton - If the rear flex line is decaying or if there is an obstruction due to exhaust work or just age there may be a kink in the line or actual debris or delamination that is holding pressure.
7.  Distribution block issues with proportioning valve (or whatever the term is this month) - Debris or corrosion may be causing the system to retain pressure in the rear circuit

I'm sure others can add to this list or add clarity.

I agree with the suggestion above that after extreme heat, you should replace everything in back and start over with new shoes, wheel cylinders, flex hose and maybe hard lines if there is evidence of corrosion even the hard lines.  Have the drums inspected and make sure they are within spec. These are all pretty low-cost items and with an undiagnosed fault this is not the time to save a buck or two.  If you are not familar with the correct servicing of drum brakes try to find a competent local shop (not a big box store) in your area but don't drive it again until you have eliminated the drag condition.

The oil level in the rear is easy to check and some google searches will come in handy to find pictures, etc., so you can see where the fill plug is located.

The good news is, you now know what burning brakes smell like so that the next time you know to stop.

 

7/21/2014 9:50 AM  #8


Re: 8" Rear End 2.79

I had the same situation happen to me once.  It turned out to be a bad rear brake hose that was colapsing internally and not letting the pressure off the brakes.

 

7/21/2014 10:37 AM  #9


Re: 8" Rear End 2.79

Thanks guys, I'll answer Bullet Bobs question first: About 15 miles is all.

I am thinking more and more that is must be a brake problem, Thanks GPatrick! I don't have back brake hoses, they are solid all the way to the wheel cylinders. When I get back, I'll go through the entire brake system and check everything out and get back to yall.

Thanks!!


A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty.
     Thread Starter
 

7/21/2014 10:55 AM  #10


Re: 8" Rear End 2.79

fgsjeff wrote:

 I don't have back brake hoses, they are solid all the way to the wheel cylinders. When I get back, I'll go through the entire brake system and check everything out and get back to yall.

Thanks!!

Yes you do.  You have to have one between the body  and the  rear axle...like all cars.  That is the hose the other guys  are  referring to and it WILL cause the trouble you are having.

BB


"you get what you pay for, good work isn't cheap, and there are NO free lunches...PERIOD!"
 

7/21/2014 2:50 PM  #11


Re: 8" Rear End 2.79

You're right! the one from the body to the rear end. My Bad, thanks!
 


A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty.
     Thread Starter
 

7/22/2014 3:07 PM  #12


Re: 8" Rear End 2.79

fgsjeff wrote:

You're right! the one from the body to the rear end. My Bad, thanks!
 

Yep... that's the one that caused my problems.

 

7/23/2014 4:48 PM  #13


Re: 8" Rear End 2.79

Axle bearings on an 8" do not run dry even if there is no lube in the differential.  They are sealed bearings with their own lube.  I think you can safely eliminate BOTH bearings failing at the same time.

You have something holding the brakes applied.  Typical cause is the center hose or a frozen wheel cylinder.  Since it is affecting BOTH sides, I am betting it is the hose.

One test I woulod perform before removing anything...

Put car on jackstands, tranny in neutral, ebrake NOT applied.
Undo the brake line from the master cylinder front port (the port that goes to the rear brakes) and see if that frees up the wheels so they will rotate.  If so, there is something holding pressure in the master cylinder, like a booster rod adjusted too long or something mechanical keeping the mc from being able to get to normal static position.

Once you do that test and you determine it is not MC, then (after pumping the brakes back up so they drag) go to rear wheel cylinder (one or other, does not matter) and do the pablo test.  If releasing pressure at that point releases both wheels, you have determined the blockage is in the hose or the steel line from the hose to the distribution block. or in the proportioning valve.  Since you have the hose undone, replace it if it is more than a few years old.  They do not cost much.  If that does not cure it, then go to the prop valve.


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
 

8/09/2014 3:20 PM  #14


Re: 8" Rear End 2.79

Update: I placed the rear end on jack stands today. Pumped the brakes up real good and got out and both wheels were locked up, but after another quick pump, they released all of a sudden. Since both wheels would not turn, I figured you guys were right about the center hose. Found the right one at the local Pep Boys, put it on and tried to bleed it. I was not able to bleed it, not sure why but I didn't get any air out of the upper connection, just brake fluid. There has to be air in there somewhere?

Anyways, after the frustration of not being able to bleed them I was checking to see if the brakes would stop the rear wheels when applied. To my delight they were stopping well enough that I could not turn either rear wheel as hard as I tried. I pumped them up several times, got out and the rears turned perfectly. So after checking for leaks, I put her on the ground and went for a test drive. The brakes feel different than before, better actually. Got her up to 35 and they stopped really well. They also seem a little spungy - ier than before. The seemed really hard to push before the hose change.

I am delighted that it seems to have fixed the problem. BTW that is the only component I didn't change 8 years ago when I went through the barking system. Go Figure. LOL

Anyway I tried blowing through the new line before installation(with my mouth), it was sort of hard, but I was getting air through it. On the one I removed, I could not seem to get any air through at all.

I can't help but worry as to why after an hour of attempts and half a bottle of fluid I didn't seem to get any air out. but for now I am satisfied.

Thanks guys, another problem solved! This site rocks!!!!

 


A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty.
     Thread Starter
 

8/09/2014 6:06 PM  #15


Re: 8" Rear End 2.79

Since that hose is so close to the end of the brake system, it may have "gravity bled" itself before you got to the bleeders.  Try bleeding again later after driving a while.


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
 

8/11/2014 8:15 AM  #16


Re: 8" Rear End 2.79

fgsjeff wrote:

I was not able to bleed it, not sure why but I didn't get any air out of the upper connection, just brake fluid. There has to be air in there somewhere?
 

This statement strikes me as odd... you are bleeding the rear brakes at the wheel cylinders, right? ... not trying to somehow bleed it at the brake hose (which doesn't bleed everything)

fgsjeff wrote:

The brakes feel different than before... seem a little spungy - ier than before. The seemed really hard to push before the hose change.
 

The fact that they feel spongier makes me concerned that you still have some air in the line.


I'm hoping that I just misunderstood your wording... but just in case I didn't...you need to bleed your rear brakes at the wheel cylinders (right side, then left).

 

8/11/2014 9:15 AM  #17


Re: 8" Rear End 2.79

I blead the rear brakes from all three places, the wheel cylinders first. I never seemed to get much air out. I did more bleeding at wheel cylinders than anything. I only tried to bleed it at the upper hose connection because I didn't get much air out of the cylinders. It was incredibly hard to bleed at the hose connection but i was thinking the bubble of air was staying at the highest point, near the hose.

The bottom line is that there is still air in there, and I wanted to take the car somewhere that day, which I did. It stopped fine all night, but as you say I need to get any other air out of the system. I will definately bleed them some more this coming weekend.

Thanks

 


A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty.
     Thread Starter
 

Board footera


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