The Stovebolt Site Forums The Shop Area Driveline clutch

so i'm installing a new clutch on my 1957 235, with a sm 420. its going in a 1951 3100 panel and as far as i can tell, the entire drive train is a miss match. the motor is a 1957, the rear is 1955 and the sm 420 is a "late model"

my question is should the pressure plate sit flat against the flywheel when the clutch plate is installed and the bolts are snugged down?

when i bolt it together, there is about a 1/8" space between the pressure plate bolt flanges and the flywheel.

i have a new clutch that came with the truck but not sure if its the correct one although when i run the number, it comes up correct.

any ideas or is this normal?

All I can say that is not normal. Something is mismatched or backwards.

In very basic terms, the raised hub of the clutch plate faces the pressure plate and the flat side of the clutch plate faces the flywheel. Did yours install like this?

yes. i've tried 6 clutches and can't seem to find the correct one. can i replace a 9 1/4" with a 10"?

Let's go back to the beginning. New pressure plate? New clutch plate? Which make and what size? What size flywheel? Do you know anything about the flywheel?

Lets define snugged down.
Just snugged down in my mind is not torqued down.
Snugged down will not compress the pressure plate springs.
Torqued down should bring the pressure plate tight against the flywheel.

"bolts snugged down", do you mean just a tad more than finger tight, or tightened down to the proper torque? If "snugged down" means just a bit more than finger tight, yes, that is normal. As you tighten them down to the proper torque, it collapses the springs on the pressure plate and squeezes the clutch disk tight. The pressure plate should fit tight against the flywheel when the bolts are tightened to the proper torque.

Usually if a clutch disc if inserted backwards, the coil springs inside the disc rub and prevent proper insertion.

Ed

ok, so first, thanks for the info.

the one i have now, which came with the truck, new in a box is a LUK 1042. the PP and disc are the same size as the old one, 9 1/4"

i can't tell you all the other ones i've tried but i do have2 other #s. PTQ K1872-01 and PTQ K1874-06. neither worked.
i can't tell you anything about the flywheel but if you tell me what would help, i can see it and count the teeth etc. pretty sure from memory it's held in place by 5 center bolts.
the problem started when i put the 1042 in and noticed when the bolts were more than hand tight but not near torque, that the PP didn't sit on the flywheel. but from what i'm hearing here, i just didn't make it tight enough? if thats the case, well i'm feelin kinda stupid...and also happy.

i started looking for a clutch that matched the old one because it looks so much differant than the new 1042. so please let me know, should i just reinstal the 1042, torque the PP down and that should be that?

The metal cover of the pressure plate will be close to 1/4" away from the flywheel until you tighten the bolts down all the way. That's what compresses the spring and sandwiches the clutch disc tight against the flywheel. If the gap didn't exist, the clutch would slip and wouldn't drive the transmission. When you depress the clutch pedal, the diaphragm spring is compressed further and the pressure plate is drawn away from the disc to allow gear shifting. To avoid distorting the cover, turn all the bolts down evenly, maybe 1/2 turn at a time, until they bottom out. It the bolts are 3/8" (9/16" bolt head) torque them to about 35 ft/lbs.
Jerry

Just asking, but what is the casting number on the flywheel. The 57 passenger and most 57 truck flywheels should have a clutch face that is about 10 inches, and when new, used a 9 1/2 clutch plate. You can use a 10 inch plate with a corresponding 10 inch pressure plate but its really not necessary. So if its a real 57 flywheel, consider a slightly larger 9 1/2 clutch. Some 57 truck flywheels accommodated an 11 inch clutch plate and flywheel. I have never actually had one of those but I understand, and hopefully someone will come along and either correct me or confirm my understanding, is that those flywheels used a somewhat specific and maybe even rare pressure plate.

If you are using a 51 flywheel, that might explain the smaller 9 1/4 clutch plate.

Make sure the raised hub on the clutch plate faces the pressure plate, and that the hub fits into the pressure plate. If it does, then install them and tighten the pressure plate bolts down completely (using a centering tool of course) and see where you are at.

A really great resource for clutches and pressure plates, and the rebuilding of OEM GM cores (better then the offshore Chinese junk that is sold today) is HR Clutch in Bensalem, PA. Old school company. They were the source for Schieffer clutches and pressure plates back in the day when the Hurst Company was located in Glendside Pa. They are a wealth of knowledge and can build or rebuild anything. A couple of years ago they rebuilt a scheiffer pressure plate, and one of their own clutches that I originally purchased in 1981. The work was spot on.

http://www.hrclutch.com/

thank you guys for all the great info.

in addition to making myself both crazy and a great installer and remover of clutches, i've also managed to drive the guys at the local auto zone nuts.

i'm gonna go install the first clutch and torque the bolts down now....

ok so... thanks to all the folks on this forum because after many problems and countless questions, i've just driven the old panel out of the shop and around the block. although the thing was running with open hedders and i didn't have the floor pan installed over the trans, it was the best ride i've had in a very long time!

i'm not finished yet and i don't want this to sound like an acceptance speech. i just wanted to say thanks to all the folks who helped.

so, thanks.

just for the record, dragsix nailed it. the flywheel is a '51!

thanks again