Hello guys.
I think I may have figured this out yesterday, but I felt too sick to my stomach to put it to words.
I need to bounce this off of some people who know what I am talking about.

I just finished my spring upgrade this weekend on my 76.
Rebuilt the steering column (Jim Shea is my hero), new steering box, new flex coupling (ecklers sold me a counterfeit part, spines are 180* off) new front wheel bearings, new SSBC Big Bite cross drilled slotted rotors, New chrome break booster/master cylinder combo, new proportioning block, new AGF power steering pump, and a B&M launch control solenoid.

I installed the line lock at the rear of the proportioning block, as I want to lock out the rear breaks, not hold the front ones on. I installed the B&M backwards, with the out port plumed in to the rear of the proportioning block, and the in port to the rear of the car. My logic was that I am concerned that the valve may have been designed to only hold pressure one way, and all the instructions and examples are for drag applications.

I think that the B&M solenoid is also a check valve of sorts and is keeping some pressure in the rear calipers.

I went for an hour drive yesterday and after a while I could smell hot something, and assumed it was crap burning off the hedders. Then I noticed bad road vibrations at about 65mph, like a wheel out of balance, but it would come and go. When I got home I got under the car and the rear rims were hot and the calipers were quote hot (150*F or more). The Diff was soo hot oil was leaking out of the plug and when I touched the front yoke I burnt my hand, to hot to touch, about 200-210*F or so. The front calipers were also quote warm, but I assume that is normal, not where near as hot as the rear..


I think it was good that I drove home in the rain :-)

So I think that the rear breaks were constantly on a little bit and causing great stress on the rear end.
I am going to remove the Line lock and run without it for a while to see what the difference is, the try it again the other way around.

What do you think?
Should I change the oil in the rear end?

Could the vibrations be caused by the breaks binding when they got hot and the fluid had no where to expand?


Comments and Ideas are welcome,

thanks,

-->Darcy

 

Sorry to hear about your problems. Regarding the line lock (I have the Hurst one in my car - on the front brakes): The solenoid valve is not a check valve. It is either full open or full closed.
Why would you install it on the rear brakes?

 

You are lucky if you didn't break anything major.. It's definetely a good idea to change rear end fluid.. The linelock should always be installed on the front brake lines. It is actually not legal at NHRA tracks to have the linelock operate on the non-drive wheels (rear wheels in a Corvette's case)

 

Not sure on this one myself, but as parking brake maybe?????

Not sure I would have gone down this path myself, but is seems to me that whatever you did was causing the rear brakes to remain engaged as you drove, thus the heating of the rims and calipers. I would pull both rear wheel and inspect the caliper pads and rotors for heat related damages, wheel bearing too for good measure. as to why the diff got hot, if was the result of heat transfer through the half shafts ( which i doubt) then you must have been really cooking those brakes. more likely the increased load on the diff from the posi not being able to work like it supposed to because of the braking is more likely the case. i would change out the fluids and observe, but a closer inspection may be in order

 

Line locks are very simple. Off or on!

Here is mine. all I had to buy was TCI roll control selenoid, short green Male to male pipe, 90 degree brass block Female /male out, and bend the pipe 90 degrees.

See it is hooked into the front brake bowl.

 

Why was it installed on the rear brakes???? The whole world wants to know!!!

 

I know it is backasswards to block fluid from the rear and hold the petal down to hold the front. He accomplished driving with the rear brakes on

The whole idea is to have the front brakes hold without your foot on the brake petal. Your right foot needs to be on the gas petal

 

What he said......., why ??

 

Thanks for the feedback.

I will replace the oil in the diff, and see how everything works with out the B&N.
Thank you for the tip on the NHRA rules. If I ever find myself considering competing there I will be sure to take it in to consideration.

The half shafts were cold. I tried to wiggle them to see if one of my new U-joints were the source of the vibration. All the fluid is new Ford Heavy Duty DOT 3. I bought a power bleeder and flushed 2L though the system last weekend.

I installed the solenoid on the rear lines because I wanted to disable the Rear bakes.
I have an Automatic and this setup offered me a unique opportunity to mess around in interesting ways, and it works quite well, and is a lot of fun :-). One foot on the Accelerator and the other to feather the front brakes as required. I didn’t think I would be the first to think of this application….

I will take a picture of the setup this weekend before I remove it, and post it for your amusement.

I will be really disappointed if this is not the source of my issue.

For the rear end, do I just go to GM and ask for POSI or Limited Slip Differential oil?

 

If you can get the rear tires spinning fast enough with the typical line lock setup. Once you hit the release the car hardly moves and you have all the steering without any brakes on all four tires.

You can buy differential oil anywhere. The tube of Posi additive is more of a dealer item.

 

[ It is actually not legal at NHRA tracks to have the linelock operate on the non-drive wheels (rear wheels in a Corvette's case)[/QUOTE]

I didn,t know corvettes where front wheel drive

 

I SEE! You want a little drifting action, so you can use the front brakes and keep the back wheels cranking without burning up the rear pads Sound like fun but you need to understand that valve blocks brake fluid come in or out when engaged and this is very dangerous on the street!!! I am very concerned about your Differential. They don't heat up like that (even under a heavy load) unless something is wrong and changing the oil is not going to fix it

 

I am not familiar with the "drifting" thing but don't most use their parking brake for this???

 

hugie82: Yeah, I had to drive a ways to find a safe place where no one was around. I only got to use it twice, and it was a blast. Wish I would have got it on camera. But definitly not for street use.

I have an autocorss on saturday, so I will remove the solenoid on friday and change the oil, then see how it works on the track.
If there is no difference, I will be quite dissapointed.

On the bright side, my suspension is nice to work on as every bolt is new and kopper coated :-)
The rear end is only 3 yrs old has less than 8000 miles on it.

I will let you all know how it goes.

-->Darcy

 

You are right but instead of using the E-brake to break the rear end lose, you use the gas and some front break to get the back wheels to come lose. SWEEET

 

Your problems with the differential all depends on how hot the unit got...and for how long. If the fluid is still a liquid, the metal components may still be OK. You can check out the condition of the lube when you change it out. Gear lube smell pretty bad when it's new....'cooked' gear lube should stink to high Heaven. But if you don't find any clotted clumps/chunks in the lube when you remove it, you should put fresh lube and posi-additive in it and hope for the best. Believe me, you'll know if it isn't working properly. If it is damaged, the friction plates are most likely damaged and/or warped.

 

If your rotors were not glowing red hot and you didn't notice any drag from the rear end of the car while you were driving it, there was not enough friction from the rear brakes to cause much of a problem. Full throttle racing use will apply much more torque than what you've done.

I wouldn't worry about the diff.

 

I agree, I'd worry more about the pads and rotors than the diff.

And put the line lock in the right way!

 

I'd like to try it....In someone elses car!!!!

 

Update:

I was wrong, which is good.
The diff and everything is Ok, but I did change the oil just to be safe.
Removed the line lock and put it all back together, then went to the Autocross on Saturday.

The car worked awesome, and the rice rockets kicked my ***. But I had a blast, as one of 4 American cars out of 50+, and the only vette.

At the end of the day the rims were hot, same as before.(not anywhere near glowing)
So I figure that the SSBC Big Bite rotors are grabbing the pads and causing this excess heat. Once the pads wear a bit it will probably go away.

The brakes do work amazing though. The rotors bite hard. I was able to go wide open in to a turn, brake hard, then punch it again.

Now I need better tires, something sticky...

Thanks for all the help and suggestions.

-->Darcy