78 C20 4 speed granny trans

[4onthefloor]

Hi I'm new to forums and this is my first post ever, at present I have a 1978 Chevy C20 Scottsdale with a 4 speed granny trans. it currently has a oil leak at the rear main and I would like to install a new clutch. an anyone tell Me what is involved in fixing the oil leak and how I find out what size clutch kit I need. I've never worked under a truck with a manual trans before, although I had 8 Chevy trucks in my life the oldest a 61 the newest a 2000 and 5 between 73-87. thanks for the help in advance Ned aka 4onthefloor.

[roundhouse]

I'm not sure about the rear main.  As I've never fixed one

Regarding the clutch
Pull one bell housing bolt and go to the hardware store and get two long long bolts with the same threads

Cut the head off and saw a slot in he end where the head used to be

Replace two of the bolts with these new long headless ones

Then  Remove the rest

This supports the weight of the trans so the weight is not hanging on the input shaft and clutch when you're removing and re installing the trans

I thought our rear main was leaking but inside the bell housing was clean and dry

All the oil was coming from the intake manifold

As for the size.   It could be a 10" or an 11"

No way to know till you remove it

You will also want to have the flywheel resurfaced since you're gonna have it out anyway


Remember , the first thing to do when working on a car is remove the neg battery cable

[4onthefloor]

        Thanks roundhouse for posting this information, It'll be a big help as I have never done a clutch. Now to learn about rear main seals...

[Engineer]

Odds are since you have a 3/4 ton, and the 465 trans you'll have a 12" clutch with a Borg&Beck pressure plate. This is the best clutch GM put in our trucks.

A new one (no core) is about $110.00 at AutoZone. P/N: NU1862. It comes with a new pressure plate, disc, throwout bearing, pilot bearing, and alignment tool. It also has a lifetime warranty. You will have to have your flywheel resurfaced to maximize clutch life, and avoid chatter.

http://m.autozone.com/autozone-mobile/en/parts/Duralast-Clutch-Set/_/N-6o243?id=5690

[FlatBlack77]

here is a brand new flywheel for $75. it might be cheaper than having the one in the truck resurfaced. i know around here you are lucky to get one redone for less than $50 and you may be waiting awhile depending on the work load of the machine shop.
http://www.autozone.com/drivetrain/flywheel-manual-transmission/brute-power-flywheel-manual-transmission/chevrolet/c20-3-4-ton-p-u-2wd/1978/8-cylinders-l-5-7l-4bl-ohv/628815_77100_0/

[4onthefloor]

Thank you Engineer and Flat Black 77, for the info. and the links, Your help is more then appreciated

[roundhouse]

Google for tips on removing  the pilot bushing in the back of the crankshaft

Lots of creative ways and most autoparts stores rent a special puller designed just for that job

When you reinstall the clutch
Pay attn to how the disc is sitting when you take it out of the box
And use a marker to label engine side
And trans side

It's offset a little on one side

When you bolt the clutch onto the flywheel
Start all the bolts and tighten them down one turn at a time going around

You can twist or warp the clutch if you tighten one  bolt down too much at once

Also while you're tightening the bolts wiggle the alignment tool

It will help make sure the disc is in the center

Also when you stab the trans back on
It should slide on all the way
You may have to turn the output shaft on he back of the trans a little to get the splines to line up

Pay attn to make sure you get the throwout bearing on the fork properly

And if the trans won't slide all the way on
Do NOT use the bolts to try and force it
You will break the mounting ears on the trans or damage the clutch disc

I have used a ratchet strap hooked to the trans and the front bumper r something    That's ok.  A ratchet strap isn't strong enough to break anything

Hook a strap on each side of the trans and to the front bumper or frame crossmember

If a ratchet strap and Tuning the output shaft a little won't get it lined up
Your disc is in a little off center
You will have to pull the bell housing and loosen the bolts holding the clutch to the flywheel and re align it



On some trucks you may need to tilt the engine back to reach the top bolts on the bell housing

This is easy when the trans is hooked on
But after the trans is out you may need to place a jack under the front crankshaft pulley

Use a block o f wood  between the jack and the pulley

Having a transmission jack also makes this job much safer
I wouldn't attempt it without one
THe trans is just too heavy
I'd guess it's 150 -  175 lbs

The shifter stick is pretty easy to remove
There is a metal cup holding the stick in
Put the trans in N and push down on the cup and turn it 1/4 turn CCW and it will spring up
You will need a cloth or rag to get enough traction to turn it and if it won't press down use a wood block and gently tap it with a hammer a time or two till you see it go down and spring back up

I wouldn't take the top off the trans
But if you do want to
Put the trans stick all the way over to the right and  halfway back into reverse

Then when you put it back on its a lot easier of you tilt the trans about 45* forward and slide the top back on

[Engineer]

Also when installing the pilot bushing in the crankshaft there is a taper to the hole on one side. That taper faces out. Putting it in backwards will make installing the transmission difficult for that last inch.

[4onthefloor]

Thank you guy's for all your help, the information will make this job much easier for me I can't thank you enough...