Clutch Problem, Help???

[Steve]

Folks, I've got a restored 67/350 HP/4speed (M-21). I can't keep a throw-out bearing in it since losing the first one several months ago.

I've completely replaced the pressure and clutch plates, bearings (both the throw-out and pilot) twice. In addition, I've repaced three throw-out bearings alone Put a new fork in it the last time (just in case it was bent and I couldn't see it) and I still can't keep a bearing from failing.

The bearings are lasting only about a 100 miles before failing. When they fail the pedal adjustment goes to the floor.

Beats me as well as the mechanic, any ideas what's wrong? Any ideas will be greatly appreciated. Thanks in advance!

[Joe L.]

Re: Clutch Problem, Help???

Steve----

First off, are you sure that you are using the correct clutch release("throw-out")bearing? Basically, there are 2 different release bearings used in GM manual trans cars of the 60s-70s period. Often times, the wrong one is used. Your car should use bearing GM #908244, or the CONFIRMED EXACT EQUIVALENT THEREOF, which is 1-1/4" long. It DOES NOT USE GM #908092, or the equivalent thereof, which is 1-7/8" long. Make sure of this first, before we go on to other possibilities.

[Joe L.]

Re: Clutch Problem, Help???

Steve----

First off, are you sure that you are using the correct clutch release("throw-out")bearing? Basically, there are 2 different release bearings used in GM manual trans cars of the 60s-70s period. Often times, the wrong one is used. Your car should use bearing GM #908244, or the CONFIRMED EXACT EQUIVALENT THEREOF, which is 1-1/4" long. It DOES NOT USE GM #908092, or the equivalent thereof, which is 1-7/8" long. Make sure of this first, before we go on to other possibilities.

[John H.]

Re: Clutch Problem, Help???

I've only seen two things that cause throwout bearing failures in my 40 years of digging into them: a) improper free play adjustment (1/2"-3/4" at the pedal) and/or no return spring to keep the pedal on its bumper - these cause the finger contact surface of the bearing to ride on the clutch release fingers all the time and will fry the bearing in fairly short order. b) Engaging the little hooks and spring fingers on the clutch fork on the flange at the rear end of the throwout bearing instead of in the groove just forward of the rear flange; this, in effect, makes a LONG throwout bearing out of the short one, results in inability to achieve correct free play, and also fries the bearing in short order. These assume that you're using the correct (short) throwout bearing to begin with.

[John H.]

Re: Clutch Problem, Help???

I've only seen two things that cause throwout bearing failures in my 40 years of digging into them: a) improper free play adjustment (1/2"-3/4" at the pedal) and/or no return spring to keep the pedal on its bumper - these cause the finger contact surface of the bearing to ride on the clutch release fingers all the time and will fry the bearing in fairly short order. b) Engaging the little hooks and spring fingers on the clutch fork on the flange at the rear end of the throwout bearing instead of in the groove just forward of the rear flange; this, in effect, makes a LONG throwout bearing out of the short one, results in inability to achieve correct free play, and also fries the bearing in short order. These assume that you're using the correct (short) throwout bearing to begin with.

[Steve]

Re: Clutch Problem, Help???

John & Joe,

Thank you guys for your helpful tips. John, you are discribing my problem. I've sensed that we are not properly adjusting the free play. Regarding the fork, we are inserting it into the bearing grove and not onto the flange. However, I'll check again.

Joe, thanks for the part numbers. We are using the short bearing but I'll check to ensure it's the correct one.

I'll let you guys know how it turns out. We'll be taking the unit out this week and going over it with a fine tooth comb. Third time's the charm. Thanks again!

Steve

[Steve]

Re: Clutch Problem, Help???

John & Joe,

Thank you guys for your helpful tips. John, you are discribing my problem. I've sensed that we are not properly adjusting the free play. Regarding the fork, we are inserting it into the bearing grove and not onto the flange. However, I'll check again.

Joe, thanks for the part numbers. We are using the short bearing but I'll check to ensure it's the correct one.

I'll let you guys know how it turns out. We'll be taking the unit out this week and going over it with a fine tooth comb. Third time's the charm. Thanks again!

Steve

[Steve]

Re: Clutch Problem, Help???

John & Joe,

Thank you guys for your helpful tips. John, you are discribing my problem. I've sensed that we are not properly adjusting the free play. Regarding the fork, we are inserting it into the bearing grove and not onto the flange. However, I'll check again.

Joe, thanks for the part numbers. We are using the short bearing but I'll check to ensure it's the correct one.

I'll let you guys know how it turns out. We'll be taking the unit out this week and going over it with a fine tooth comb. Third time's the charm.

Thanks again!

Steve

[Steve]

Re: Clutch Problem, Help???

John & Joe,

Thank you guys for your helpful tips. John, you are discribing my problem. I've sensed that we are not properly adjusting the free play. Regarding the fork, we are inserting it into the bearing grove and not onto the flange. However, I'll check again.

Joe, thanks for the part numbers. We are using the short bearing but I'll check to ensure it's the correct one.

I'll let you guys know how it turns out. We'll be taking the unit out this week and going over it with a fine tooth comb. Third time's the charm.

Thanks again!

Steve