Oil pan gasket replacement for 1972 GMC 402 engine

[jlampka]

How difficult is it to replace the oil pan gasket on a 1972 GMC 3500 series (1 ton) pickup? Thanks

[RustyPile]

Not very... First -- drain the oil and disconnect one or both battery cables at the battery. For clearance, remove the bolts holding the motor mount to the frame brackets, leaving the transmission attached to its crossmember.. Remove bolts that hold the fan shroud in place or remove the fan from the water pump.. Remove starter. Remove distributor cap and rotor. Attach a lifting device -- engine hoist, chain fall, come-along -- and lift the engine a few inches.. Remove all the pan bolts and whack the pan with a rubber hammer to break it loose....

I was a mechanic for over 30 years, and when I was full of piss and vinegar, I could have the pan on the floor in less than 1/2 hour...

Let me offer a serious piece of advice.. If you plan to do your own repairs to your truck, get your hands on the GM factory service manual - not Chilton's, or any of those "knock offs sold in the chain stores.. Motors Manuals are good if you can find one.. A few years ago. I found my GM manuals at a free download site.

[jlampka]

Thank you Rusty Pile!

[jlampka]

So the transmission stays attached to the engine?

[kwmech]

Originally Posted by jlampka

How difficult is it to replace the oil pan gasket on a 1972 GMC 3500 series (1 ton) pickup? Thanks

The big block in my truck has to be removed to do the pan. NO way will it come off the block, clear the flexplate, oil pick-up and the cross member just by lifting it up

[RustyPile]

Originally Posted by kwmech

The big block in my truck has to be removed to do the pan. NO way will it come off the block, clear the flexplate, oil pick-up and the cross member just by lifting it up

Not the case with mine.. I just changed a cracked and leaking pan on my BBC '71.. Process was exactly as I noted in my post...

[RustyPile]

Originally Posted by jlampka

So the transmission stays attached to the engine?

Stays attached to the engine and in the truck....

[EDIT] Depending on the type of exhaust you have -- duals, headers, crossover w/single pipe -- you may have to remove some of those components.. Also, you'll need to remove the flywheel/flex plate dust cover..

[72SB]

In lieu of using a engine hoist, you can use a floor jack with a flat block of wood under pan to lift motor up after doing pre hoist procedures Rusty notes. Then use pieces of 2x4 blocks between MM and stands to let motor sit on those. Motor wants to be about 4" higher so pan clears X member. I also remove dust/inspection pan for clutch/TC.

Pull pan off/out from rear. Confirm rails are flat before install. May need to use 1/4" thick bar stock & hammer to flatten out around pan bolt holes if they are deformed. I prefer the FelPro 1 piece pan gaskets. Use Permatex Black Utra on curved ends and where they meet flat part of pan front & rear

[jlampka]

My truck in an AC truck so will anything AC related (brackets, compressor, etc) need to be removed? Thank you

[RustyPile]

Originally Posted by jlampka

My truck in an AC truck so will anything AC related (brackets, compressor, etc) need to be removed? Thank you

None of that has to be removed. As I noted in my first post --- remove the fan clutch from the water pump or remove the screws holding the fan shroud.. If you remove the fan clutch, it remains inside the shroud as the engine is raised.. No need to even loosen any belts.. If you "un-mount" the shroud, it rises with the fan as the engine is raised.. Just watch as you raise the engine, don't let something get snagged or pulled..

[Joyridin]

I changed mine (no A/C) and it was relatively easy. I unbolted the exhaust, removed the shroud and fan, and jacked the engine up under the balancer. As stated, I put a 2 x 4 between the mounts to hold it up. No problems.

Here is another suggestion; Buy the Fel-Pro 1 piece pan gasket. After trying to replace the gasket with the 4 piece deal, you will thank yourself by going with the 1 piece gasket.

[jlampka]

Thank you everyone for your responses

[jeffahart]

Last time I did mine, on my K20, I didn't even drop the pan. I just let it sit on the crossmember. I jacked it up slightly, until the distributor ran out of runway. I was able to get the pan and block cleaned up and slid the gasket in from one side of the pan under the crank and dobbed some sealant on the four corners pressed the gasket up there and buttoned it up. I made pretty quick work of it. No leaks been probably close to 8-10 yeas now on this truck. Get a good fel-pro gasket.

Bottom line, not hard. With a little caveat: if you have not done an oil pan gasket before find a how to so you know where to place the sealant on your specified gasket, as that is needed for no leaks.

j

[72SB]

IMHO NEVER jack a motor up from balancer. I have personally seen one crack doing that. Use a carpet padded block of wood and floor jack under pan and jack up so you can then put 2x4 blocks between engine stands and block to hold it up

Agree on the 1 piece FelPro gasket. It comes with 4 plastic studs you use to hold gasket to block on the 4 corners. Then just slide pan over those studs, screw in side pan bolts them remove plastic ones and install the 4 corners. I use Permatex Black Ultra RTV. Better suited for high temp oil sealing vs other flavors

[weq92f]

Originally Posted by 72SB

IMHO NEVER jack a motor up from balancer. I have personally seen one crack doing that. Use a carpet padded block of wood and floor jack under pan and jack up so you can then put 2x4 blocks between engine stands and block to hold it up

Agree on the 1 piece FelPro gasket. It comes with 4 plastic studs you use to hold gasket to block on the 4 corners. Then just slide pan over those studs, screw in side pan bolts them remove plastic ones and install the 4 corners. I use Permatex Black Ultra RTV. Better suited for high temp oil sealing vs other flavors

.

Must be something new 'cause a few years ago when I did mine ( 396, one-piece fel-pro ), I didn't get the plastic studs. I improvised by attaching the gasket to the pan with very small gauge wire, got a few bolts in to snug the pan to the block and removed the wire. In my case I had a hoist to raise the engine and place the 2x4 blocks under the mounts. No leaks from the pan since.

-klb