Recently had new booster installed 74 vette automatic with power brakes. Scare of my life, clevis came off rod and lost brakes. The clevis threads stripped off of rod causing complete loss of brakes. My question is do you think clevis and rod threads stripped do to over tightening or some sort of misalignment. Please advise it was a terrible experience .

 

Rookie guess: The new booster has Metric threads for some reason......Metric threads SEEM to engage correctly, but will strip out when force is applied.

 

Did YOU install the NEW booster???

I have installed the new booster and have yet to find one where the clevis would NOT swap over....but you never know...something may have changed.

I can SAY that I have seen some people swap out a brake booster and NOT remove the clevis PIN and clip...and they unthread the rod from the clevis and thread the new booster back onto it. BUT...in doing so...UNLESS they get it RIGHT....they can cross thread it and let it go out the door because they do not give a CRAP....and feel it is GOOD ENOUGH

Just 'saying'...I have SEEN this and had to go in and repair it after someone did NOT do it correctly in the first place. It is RARE that I have to do this...but it does happen.

DUB

 

Holy crap. How did you stop? Emergency brake? Downshift and turn engine off???
Good thing you're around to tell us about it.

 

50 mph on 3 lane highway in middle lane, readying to get in right hand lane to get to exit, apply breaks slightly to let car go by on right, bang to the floor nothing, got into drive two, then low got into breakdown lane in low, threw off cup holder on emergency brake ,applied gradually , stopped called installer on cell and swore at him for 20 minutes. If car in front of me was closer or whatever it would have been lights out. Clevis and booster rod threads were stripped. I think the only way that could happen is by over tightening or forced cross threading. The whole thing makes me sick!

 

Glad that you kept your head clear and though clearly and got it stopped.

YES...when I test drive a customers car and IF they have one of those dang cup holders slid onto the parking brake handle.,...the FIRST thing I do it get it off the handle and behind the seats. Because when your backside is beginning to suck up the bottom seat cover due to a problem...every second CAN COUNT!

I AGREE...THIS could have been AVOIDED. SIMPLY PUT....it makes me SICK when mechanics allow 'things' to go out the door when they KNOW it is not RIGHT.....BECAUSE that clevis CAN NOT spin when installed....so it means it was installed INCORRECTLY with very little attention to DETAIL.

A stripped out cigarette lighter housing is one thing...BUT the BRAKE BOOSTER... It just makes me SICK!

DUB

 

Thank god for this Forum to help peeps do it right.

 

I had the front brakes go out on my Truck (road debris hit my front brake line, and it blew out when I applied the brakes). I "almost split the difference" between a minivan on the left, a telephone pole amd embankment on the right and (luckily nobody in front of that.).

Brake pedal to the floor, I got as far right as I could without hitting the pole and just barely side-swiped the mini van, coming to a rest a little over a 1/4 mile down the road "standing on the emergency brake" (Which helped, but didn't do much on a 4x4 F-150).

Could have been a lot worse. There are usually a number of cyclists that use that shoulder / road down to the river.

I know how scary that can be. Glad to hear you (or anyone else) didn't get hurt..

 

I have worried the clip holding the clevis pin in would fall off, but never thought about the nut stripping and coming apart. Glad you are alright

 

I think GM did this as a standard practice but it's something I adopted a long time ago, and that's a jamb nut on BOTH the front and back of the clevis. Part of what leads to the thread failure is if the clevis is allowed to rotate slightly every time you use the pedal. To keep everything locked down tight, you use the jamb nuts. With the clevis tight and immobile, there will be far less wear on the threads which will greatly reduce the chances of failure. A couple jamb nuts are VERY cheap insurance.

 

You have a unique practice...which I know will work on a manual brake Corvette...I honesty do not think that it will work on a Corvette power brake booster.

The booster shaft does not have enough threads to allow using a jamb nut in conjunction with the clevis on a power brake booster. All you do it thread the clevis all the way and it stops and that's it.

Yes...the clevis does pivot on the pin..and should not rotate or twist if the spring washer is installed to keep any side to side play of the clevis with the brake pedal arm on certain years. The movement of the clevis is so minimal due to where it is attached towards the top of the brake pedal arm near the pivot for the arm.

Just so everyone does not get overly PARANOID about this mishap. This design has been working for countless years on thousands of cars.,....and there has been basically no reason to get worried. IF the parts are installed as they were DESIGNED to be installed...this design is bulletproof. This thread is dealing with a very specific scenario (even though it is not a good scenario)...it is not something that everyone needs to go in and change on their Corvette. It would be like getting a set of tires put on your car and the mechanic did not tighten the lugs on one wheel and it fell off going down the road...does not mean that we all have to worry about the lug nuts on our cars.

I still feel that the clevis was installed incorrectly or they installed the clevis in the wrong hole in the brake pedal arm ( if applicable)....because if the Corvette has the option of manual brakes...there is another hole in the brake pedal arm and if they put it in that...it changes the angle of the shaft coming out of the back of the booster and can cause it to get in a bind an thus allow a point for the shaft to break. Just my views on this.

DUB

 

OMG that's funny...

 

Dub, your right on again not enough thread on booster rod for nuts for an automatic. Should I go with the thought of just putting that clevis on( new one from Zip and new booster) like it's been for years, my mechanic is suggesting spot weld or locktite. I'm thinking just screw it like its been done for 40 yrs. Your opinion would be appreciated. Thanks

 

Yeah come to think of it, I've not done that with too many Corvettes, but them again, being fat and sort I also always thread the clevis out to the end against a jamb nut, and give myself as much pedal height as possible. One time was all it took for me to double up on the jamb nuts. A Sprint and I went head first into a wall because of clevis thread failure. If I didn't have harnesses in that car who know how bad it would have been.

 

Thanks..and YES...dealing with Corvette brake boosters is something that I have done numerous times...so I kinda know what is going on with them when being installed.

Take the clevis BEFORE you put it on the booster and slide it on the brake pedal arm and see how much 'side to side' play you have. I KNOW that GM used a spring washer between the clevis and arm to keep the side to side play in check....but I honestly can not remember when they stared it or stopped using the spring washer. I would have to look at my 1974 AIM and see....BUT I do KNOW that they were used.....and it is up to you if you care to use it if required .

Put the clevis on and get it tight and put it in the car. NO NEED to WELD anything.
Once it is installed...there is NO POSSIBLE WAY that the shaft will or can spin and un-thread....it JUST IS NOT going to happen.

Using a removable Loc-tite....that is up to you and I can 'say' that I don't do that. Once again...not needed. But do what you feel comfortable with.

JUST make sure that the clevis is going to the hole in the brake pedal arm that is correct for it to work and NOT put it in a bind.

DUB