New Clutch

[bobcostas]

Hey guys!

Good news! now i know what a slipping clutch feels like!
SO! I'm going to get a new one this weekend and try to replace it myself. i have a granny 4-speed and from what i've heard from some postings, they're a might heavy.

is there a "how to" posting somewhere in this msg board?

and I'm wondering of one of the OEM reproduction jobbies will do the trick
like this one

it seems pretty inexpensive.

thanks a lot y'all

[Heater63]

For regular use, sure, nothing wrong with Sachs.
Im using a Hays, pretty orange paint. LOL.

GM clutches come 10.4 (car), 11 (common truck), and 12" (big).
Check and see what you have before you order. Your spline count is probably 10.

[bobcostas]

Is there a trick to dropping the trans?

I'm going to attempt this tomorrow. was wondering if any of you cats had a tip or a "do not do!"

[sixfour4x4]

a clutch is a pretty big job...you haven't done this before? you'll really want to invest in an attachment for your floorjack to hold your tranny. 2wd or 4? a 4wd transfercase adds a lot of weight. you're going to run into snags. i see lots of swear words in your future. however if you want a step by step, here goes...

remove transmission tunnel cover.
remove bolts top the sm420 and pry off can shifter and trans top (stuff a towel around the gears as to not get them dirty!)
support motor and trans aside from crossmember
remove exhaust or anything else that could be in the way
disconnect speedo and e-brake
disconnect driveshafts (tape up your barrings so the needles don't fall out)
disconnect clutch mechanism (whether hydro or mechanical)
remove bolts from crossmember to tranny
remove crossmember (this aids in aiming the outputshaft back into the pilot barring)
support trans with floor jack
remove bolts from bellhousing to engine block
pull trans down and back
remove bolts from clutch pressure plate
remove clutch from flywheel
remove flywheel
********TAKE FLYWHEEL TO MACHINE SHOP!!!!!!!!!!***********######
also consider flipping your ring gear or replacing it...(theres a trick with an oven lol)
remove pilot bearing by any means possible(i have a trick with grease and a plug to hydrolically displace the barring hit me up when you get to this point)
bolt everything back down
now the fun part...you'll have to manuever the trans shaft back into the clutch and into the pilot barring. you can use the output to turn back and forth to work into the clutch. it's kind of like a space shuttle dock and it has to be just right....
bolt it all back up....

[bobcostas]

Dude. awesome. thank you.
I think i can handle this.
It will defiantly involve a few choice words and at least 2 bloody knuckles.

at least the 90 degree weather is already here.

[blackedoutharley]

Originally Posted by sixfour4x4

remove transmission tunnel cover. I.E. floor board that is bolted in.
remove bolts top the sm420 and pry off can shifter and trans top (stuff a towel around the gears as to not get them dirty!) Take a pair of slip joint plyers and grasp coupler at shifter base and turn courter clockwise while pressing collar down.. shifter will then come out easily... no bolts.
support motor and trans aside from crossmember There is no crossmember on a sm420 trans; the bellhousing is the support.
remove exhaust or anything else that could be in the way Yes
disconnect speedo and e-brake Speedo yes, e-brake maybe
disconnect driveshafts (tape up your barrings so the needles don't fall out) yes
disconnect clutch mechanism (whether hydro or mechanical) Yes, specifically the springs and linkage at the clutch fork.
remove bolts from crossmember to tranny N/A
remove crossmember (this aids in aiming the outputshaft back into the pilot barring) N/A
support trans with floor jack Yes and use a good jack preferrably with straps around trans !
remove bolts from bellhousing to engine block Depending on the size clutch you have currently this may not be required. The 12" clutch will not fit through the inspection opening at the bottom but the 10.5" does (or did on my '65 c-10 with the sm420 trans).
pull trans down and back yes
remove bolts from clutch pressure plate yes and buy new pressure plate bolts
remove clutch from flywheel
remove flywheel And replace the flywheel bolts as well.
********TAKE FLYWHEEL TO MACHINE SHOP!!!!!!!!!!***********######
This part will make or break a clean clutch installation. Have the flywheel turned!
also consider flipping your ring gear or replacing it...(theres a trick with an oven lol) As needed of course
remove pilot bearing by any means possible(i have a trick with grease and a plug to hydrolically displace the barring hit me up when you get to this point)
bolt everything back down
now the fun part...you'll have to manuever the trans shaft back into the clutch and into the pilot barring. you can use the output to turn back and forth to work into the clutch. it's kind of like a space shuttle dock and it has to be just right....
bolt it all back up....

The transmission is heavy be careful, take your time and it should go smooth.
For reference take a few photos prior to disassembly to use if you need a guide during reinstall.

[jonzcustomshop]

great play by play guys, if you do take off the bellhousing and crossmember, you will need to support the back of the motor somehow, an extra floorjack with a 2X4 ( so not to dent the oil pan) helps

[sixfour4x4]

Bob, i forgot to tell you, other than a standard set of sockets and wrenches you'll want to invest in a flywheel turning tool. you can use some other things, but it will make it a ton easier getting bolts off the pressure plate and flywheel. torque wrench is ideal so you can get flywheel around 65-70lb and the pressure plate to 35-40lb

Originally Posted by blackedoutharley

The transmission is heavy be careful, take your time and it should go smooth.
For reference take a few photos prior to disassembly to use if you need a guide during reinstall.

i didn't know about the trans support on the 2wd 420s.. good to know. also i could get my clutch out the inspection, but flywheel was a little big.

[sixfour4x4]

Originally Posted by jonzcustomshop

great play by play guys, if you do take off the bellhousing and crossmember, you will need to support the back of the motor somehow, an extra floorjack with a 2X4 ( so not to dent the oil pan) helps

on my 4x4 i could just put a board accross my leafs under my pan. on my wagoneer i have the trans off of right now i'm letting the 401 balance in hopes that those mounts will do their job

[Fred T]

I have always bought the clutch locally. With the 4 speed you need (at a minimum) a floor jack and someone to help. You shouldn't have to remove the shifter, just back up the tranny and lower it. You can also use an engine hoist by going in the driver's door.

The SM420 weighs about 135 lbs. Just heavy enough to cause problems.

A clutch alignment tool helps, as does two long bolts with the heads cut off. Put them in the top holes for alignment, makes stabbing the tranny back in a bunch easier.