rear main seal? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

franko72 · 01-14-2005, 06:30 PM

I have been noticing motor oil on the floor of my garage located directly under the area between the bell housing and the rear of the oil pan. I changed the valve cover gaskets. changed the intake gaskets . The problem is still there.I guess that I am in denial but have to face the facts. How hard is it to change out a rear main seal on my 72 402 Big Block?Do I need to pull the motor or seperate the Transmission to get to it?Where else could the oil be leaking from or what is a good way of being sure that it is the rear main seal.

Perchjerker · 01-14-2005, 06:37 PM

What kind of Tranny is it? My 3 speed is leaking gear oil and it looks like the rear main is leaking.

franko72 · 01-14-2005, 07:12 PM

automatic 400 turbo . It is definitly motor oil. I guess i'll try the chiltons if no one replys

franko72 · 01-14-2005, 09:05 PM

any help out there?

PMS · 01-14-2005, 09:52 PM

If it is like a small block you would put a block of wood - chunk of 2x4 between the motor mounts to raise the engine up so you can pull the pan then you can get to the rear seal. Watch the dist. as you jack the motor up. Not to bad....

72402 · 01-15-2005, 12:17 AM

I pulled the pan off mine once with it in the truck. The pickup tube came out of the oil pump. It's been so long ago, I really don't remember what I had to do to get it off. Must not have been too hard though, I was on a camping trip. Fixed it at the lake. Had to have it to pull my boat back home. Now that I think about it, that was almost 30 years ago. I don't think she's ever failed me since. The top half of those seals can be hard to get out sometimes, but have patience. Frank

**kwmech** · 01-15-2005, 01:38 AM

Be sure it is the main seal first, possible it could be just the rear arch seal of the pan.

jimfulco · 01-15-2005, 04:52 AM

Check the oil pressure sender too.

Super Duck · 01-15-2005, 06:12 AM

if the truck is a 4x4 the pan will come down with no problems. if it is 2wd you have to jack up the motor and put blocks behind the mounts. then the pan will come off. after that pull the pump and rear main cap. one half will be in the cap and the other you will need to push out with a small swrew driver (be careful not to gouge the crank) or the provided tool with the new seal. then put it back together. torque the bolts and put the pan back on.

dwaite72lnghrn · 01-15-2005, 09:24 AM

I have changed the rear seal on my 1 ton with it still in the truck. It is a tight fit but the oil pan can come off. The big problem is the rear seal trying to push the old seal out them buggers are really stuck in there. The only other issue is getting the pan gasket to seal good with all of the movement to get it back on, PATIENCE>>>Patience take your time.

ABHaulR · 01-15-2005, 11:23 AM

you should try to stager the seal sections so the main cap and the seal is not in the same place. when you put the new seal in the top half make sure you push it in approx a 1/4 to 3/8 of an inch past the smooth surface of the block. also put a small dab of silicone on the ends of the seal.
Dwayne

franko72 · 01-15-2005, 12:45 PM

Thanks for the info!

neonlarry · 01-15-2005, 03:59 PM

I wouldnt try to change the oil pan on a 2wd with the engine in the truck. I had to replace the timing chain on mine, and I have not been able to get the oil pan back on. Now I have to wait until I make some space in the garage so I can pull the engine and do it that way. I wish I had know to begin with that I needed to pull the engine, becasue I have been trying to get it put back together since august now. lol

JayDubBlazer · 01-15-2005, 04:02 PM

Quote:

Originally Posted by franko72

I have been noticing motor oil on the floor of my garage located directly under the area between the bell housing and the rear of the oil pan. I changed the valve cover gaskets. changed the intake gaskets . The problem is still there.I guess that I am in denial but have to face the facts. How hard is it to change out a rear main seal on my 72 402 Big Block?Do I need to pull the motor or seperate the Transmission to get to it?Where else could the oil be leaking from or what is a good way of being sure that it is the rear main seal.

I think I might have the same problem with my 350, don't want to admit it but I think I need to replace that seal. So thanks for asking the question, I really was not looking forward to it if I had to pull the engine.

01-14-2005, 06:30 PM	#1
franko72 Franko72 Join Date: May 2004 Location: Cincinnati,Ohio Posts: 471	rear main seal?motorheads needed I have been noticing motor oil on the floor of my garage located directly under the area between the bell housing and the rear of the oil pan. I changed the valve cover gaskets. changed the intake gaskets . The problem is still there.I guess that I am in denial but have to face the facts. How hard is it to change out a rear main seal on my 72 402 Big Block?Do I need to pull the motor or seperate the Transmission to get to it?Where else could the oil be leaking from or what is a good way of being sure that it is the rear main seal. __________________ 1972 C20 cheyenne Super 402 BB/400 turbo LWB A/C Tilt, Cruise Control, Saddle tanks, Tach My Home Page Better to burn out than it is to rust Last edited by franko72; 01-14-2005 at 09:20 PM.

01-14-2005, 06:37 PM	#2
Perchjerker Beer Power!!!!!!!!!! Join Date: Nov 2003 Location: Nacogdoches, TX Posts: 280	What kind of Tranny is it? My 3 speed is leaking gear oil and it looks like the rear main is leaking. __________________ Rather be fishin'

01-14-2005, 07:12 PM	#3
franko72 Franko72 Join Date: May 2004 Location: Cincinnati,Ohio Posts: 471	automatic 400 turbo . It is definitly motor oil. I guess i'll try the chiltons if no one replys __________________ 1972 C20 cheyenne Super 402 BB/400 turbo LWB A/C Tilt, Cruise Control, Saddle tanks, Tach My Home Page Better to burn out than it is to rust

01-14-2005, 09:05 PM	#4
franko72 Franko72 Join Date: May 2004 Location: Cincinnati,Ohio Posts: 471	any help out there? __________________ 1972 C20 cheyenne Super 402 BB/400 turbo LWB A/C Tilt, Cruise Control, Saddle tanks, Tach My Home Page Better to burn out than it is to rust

01-15-2005, 06:12 AM	#9
Super Duck Chevy Nuttttt Join Date: Sep 2004 Location: Santa Maria Ca. Posts: 568	if the truck is a 4x4 the pan will come down with no problems. if it is 2wd you have to jack up the motor and put blocks behind the mounts. then the pan will come off. after that pull the pump and rear main cap. one half will be in the cap and the other you will need to push out with a small swrew driver (be careful not to gouge the crank) or the provided tool with the new seal. then put it back together. torque the bolts and put the pan back on. __________________ 67' Chev swb step side 69' SS elky 03' Chev ext cab 4X4 hey who lernt me to spell is there anything else?

01-14-2005, 09:52 PM	#5
PMS Registered User Join Date: Aug 2004 Location: Overland Park, KS Posts: 79	If it is like a small block you would put a block of wood - chunk of 2x4 between the motor mounts to raise the engine up so you can pull the pan then you can get to the rear seal. Watch the dist. as you jack the motor up. Not to bad....

01-15-2005, 12:17 AM	#6
72402 Registered User Join Date: Nov 2004 Location: Cameron, Oklahoma Posts: 199	I pulled the pan off mine once with it in the truck. The pickup tube came out of the oil pump. It's been so long ago, I really don't remember what I had to do to get it off. Must not have been too hard though, I was on a camping trip. Fixed it at the lake. Had to have it to pull my boat back home. Now that I think about it, that was almost 30 years ago. I don't think she's ever failed me since. The top half of those seals can be hard to get out sometimes, but have patience. Frank

01-15-2005, 01:38 AM	#7
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,599	Be sure it is the main seal first, possible it could be just the rear arch seal of the pan.

01-15-2005, 04:52 AM	#8
jimfulco Registered User Join Date: May 2003 Location: Shreveport LA Posts: 3,170	Check the oil pressure sender too.

01-15-2005, 09:24 AM	#10
dwaite72lnghrn Registered User Join Date: Jun 2002 Location: central pa Posts: 1,525	I have changed the rear seal on my 1 ton with it still in the truck. It is a tight fit but the oil pan can come off. The big problem is the rear seal trying to push the old seal out them buggers are really stuck in there. The only other issue is getting the pan gasket to seal good with all of the movement to get it back on, PATIENCE>>>Patience take your time. __________________ 72 longhorn c30 502BB/th400/fact air/4.11rear/ custom camper 72 bug(the better half's) under reconstruction 2009 HHR aqua blue 71 GMC k20 350/sm465 2009 Chevy hd3500 6.6 Victory Red crew cab dually Dave & Jeanne

01-15-2005, 11:23 AM	#11
ABHaulR Registered User Join Date: Jun 2003 Location: West Valley City, Ut Posts: 311	seal you should try to stager the seal sections so the main cap and the seal is not in the same place. when you put the new seal in the top half make sure you push it in approx a 1/4 to 3/8 of an inch past the smooth surface of the block. also put a small dab of silicone on the ends of the seal. Dwayne __________________ 72' GMC Suburban 10 1/2" of Lift, 40" Tires! Waiting for restoration 67' Chevy, What to do??? And Bad Ass American Bulldogs!

01-15-2005, 12:45 PM	#12
franko72 Franko72 Join Date: May 2004 Location: Cincinnati,Ohio Posts: 471	Thanks for the info! __________________ 1972 C20 cheyenne Super 402 BB/400 turbo LWB A/C Tilt, Cruise Control, Saddle tanks, Tach My Home Page Better to burn out than it is to rust

01-15-2005, 03:59 PM	#13
neonlarry Registered User Join Date: Feb 2002 Location: Vacaville, CA Posts: 2,746	I wouldnt try to change the oil pan on a 2wd with the engine in the truck. I had to replace the timing chain on mine, and I have not been able to get the oil pan back on. Now I have to wait until I make some space in the garage so I can pull the engine and do it that way. I wish I had know to begin with that I needed to pull the engine, becasue I have been trying to get it put back together since august now. lol __________________ 70 C/10 Light Red 350/TH350, HEI, Duals w/40 series Flows, 91 seat, LED taillights 99 Pontiac S/C GTP, SLP Ram Air hood, GMPP Konis & springs 95 Neon ACR, MP PCM, AFX UDP, 3.0 CAI



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