# changing the rear main seal in a 3.8



## northbay (May 7, 2005)

Just wondering if it would be good enough to drop the tanny to get to the rear main seal and how hard it will be to take it out the seal after wards.Ive only changed V 8 so I never tryed taking one out of a 3.8. Thanks for any im put


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## dameon (Dec 1, 2011)

a 3.8 buick/ olds block is a v-8 block missing 2 cylinders making it a v6. 350 olds are the same as 231 v6 just missing 2 pistons hope this helps


same for chevys 4.3 v6 there 350 v8 blocks missing 2 pistons


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## IMPALA863 (May 25, 2011)

dameon said:


> a 3.8 buick/ olds block is a v-8 block missing 2 cylinders making it a v6. 350 olds are the same as 231 v6 just missing 2 pistons hope this helps
> 
> 
> same for chevys 4.3 v6 there 350 v8 blocks missing 2 pistons


:nono: THERE NOT THE SAME CUZ THE CUBIC INCHS ARE WAY DIFERENT,,THATS WAT MAKES THEM RUN,SOUND,AND PERFORM DIFERENT,,A 350 PISTON IS GUNNA BE WAAAAAAYYYYYYY BIGGER THEN A 4.3,,,MATTERFACT IF U TAKE A HEADS OFF A 305 AND A 350 ULL NOTICE THE DIFERENCE IN THEM AND THERE BOT V8S,,,THEY MIT LOOK DA SAME ON THE OUTSIDE BUT THEN INSIDE IS DEFITENLY GUNNA BE DIFERENT,,SAME WIT THE REAR SEAL A NEWER 350 HAS A 2 PEICE AND THE OLD 1S ARE 1 PEICE


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## dameon (Dec 1, 2011)

i just figured cheap ass gm cut to piston out to save gas i looked at plenty of blocks they just look the same but shorter


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## northbay (May 7, 2005)

the rear main seal is part of the oil pan on a v 8 and on a 3.8 its not. its a circlure gasket about 2 inches above the pan. some body ssaid u need a dent puller to get it out cause its pressed in there pretty good.


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## dameon (Dec 1, 2011)

just go for shit worst case you have a mechanic come over and finsh the job thats how you learn. also check prices on the job might be a cheap mechanic out there


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## dameon (Dec 1, 2011)

this would have been helpful i the video was longer


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## pink63impala (Aug 5, 2004)

IMPALA863 said:


> :nono: THERE NOT THE SAME CUZ THE CUBIC INCHS ARE WAY DIFERENT,,THATS WAT MAKES THEM RUN,SOUND,AND PERFORM DIFERENT,,A 350 PISTON IS GUNNA BE WAAAAAAYYYYYYY BIGGER THEN A 4.3,,,MATTERFACT IF U TAKE A HEADS OFF A 305 AND A 350 ULL NOTICE THE DIFERENCE IN THEM AND THERE BOT V8S,,,THEY MIT LOOK DA SAME ON THE OUTSIDE BUT THEN INSIDE IS DEFITENLY GUNNA BE DIFERENT,,SAME WIT THE REAR SEAL A NEWER 350 HAS A 2 PEICE AND THE OLD 1S ARE 1 PEICE


350 and 4.3 have the same bore size.rods are different and stroke is different


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## IMPALA863 (May 25, 2011)

pink63impala said:


> 350 and 4.3 have the same bore size.rods are different and stroke is different


:nono:A 350 V8 engine (most common Chevy V8) has 43.75 per cylinder, and a 4.3L V6 has 43.67 per cylinder


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## orientalmontecarlo (Sep 17, 2007)

4.3 uses the same size piston as a 350, bore/stroke might be different obviously ....why you think 4.3 tbi have more torque and top end than 305s of the same era?


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## IMPALA863 (May 25, 2011)

orientalmontecarlo said:


> 4.3 uses the same size piston as a 350, bore/stroke might be different obviously ....why you think 4.3 tbi have more torque and top end than 305s of the same era?


IF DA BORE IS DIFERENT,,DA PISTON IS DIFERENT


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## orientalmontecarlo (Sep 17, 2007)

IMPALA863 said:


> IF DA BORE IS DIFERENT,,DA PISTON IS DIFERENT


correct and that is usually the case,but here we're talking about v6 262 4.3 liter engines and 350 v8 5.7 being the same all stock from gm no machining done to them.
The bore centers (4.400) and deck height (9.025) are also identical to a Mouse motor. The '85-up 4.3L V-6 has the same bore and stroke as a 350 V-8 (4.000x3.480), and takes the same pistons, cam bearings, main bearings, valvetrain parts, timing cover, oil pump, and front dress. Any V-8 trans will bolt right up to the 90-degree sixer. 


went through all types of shit while building a low-compression 4.3 turbo motor and ended up sitting in the corner.
​


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## orientalmontecarlo (Sep 17, 2007)

orientalmontecarlo said:


> correct and that is usually the case,but here we're talking about v6 262 4.3 liter engines and 350 v8 5.7 being the same all stock from gm no machining done to them.
> The bore centers (4.400) and deck height (9.025) are also identical to a Mouse motor. The '85-up 4.3L V-6 has the same bore and stroke as a 350 V-8 (4.000x3.480), and takes the same pistons, cam bearings, main bearings, valvetrain parts, timing cover, oil pump, and front dress. Any V-8 trans will bolt right up to the 90-degree sixer.
> 
> 
> ...


:drama::buttkick:


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## IMPALA863 (May 25, 2011)

orientalmontecarlo said:


> correct and that is usually the case,but here we're talking about v6 262 4.3 liter engines and 350 v8 5.7 being the same all stock from gm no machining done to them.
> The bore centers (4.400) and deck height (9.025) are also identical to a Mouse motor. The '85-up 4.3L V-6 has the same bore and stroke as a 350 V-8 (4.000x3.480), and takes the same pistons, cam bearings, main bearings, valvetrain parts, timing cover, oil pump, and front dress. Any V-8 trans will bolt right up to the 90-degree sixer.
> 
> 
> went through all types of shit while building a low-compression 4.3 turbo motor and ended up sitting in the corner.​


:nono: NOT EVEN THE 305 TAKE DA SAME CAM BEARINS,MAIN BEARINS,ROD BEARINS ...THE ONLY THING DA SAME ON A 305 ND 350 IS MOST OF DA OUTSIDE PARTS ARE INTERCHANGEABLE,,,SO WAT WOULD MAKE U THINK A 4.3 AND A 5.7 WILL BE THE SAME ON DA INSIDE IF NOT EVEN A 5.0 IS SAME AND THAT DAT ITS A V8 ALSO


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## orientalmontecarlo (Sep 17, 2007)

IMPALA863 said:


> :nono: NOT EVEN THE 305 TAKE DA SAME CAM BEARINS,MAIN BEARINS,ROD BEARINS ...THE ONLY THING DA SAME ON A 305 ND 350 IS MOST OF DA OUTSIDE PARTS ARE INTERCHANGEABLE,,,SO WAT WOULD MAKE U THINK A 4.3 AND A 5.7 WILL BE THE SAME ON DA INSIDE IF NOT EVEN A 5.0 IS SAME AND THAT DAT ITS A V8 ALSO



back in 97 i went through all there is to know about 4.3 gm engines inside and out so i wont argue with you anymore....if you like you can go ahead and read the article that might further your knowledge regarding 4.3s and 5.7s which is where i quoted in my response and you highlighted what i said with yours.

here you go.....i know its old but theres plenty of info for you there
http://www.hotrod.com/techarticles/engine/113_0208_chevy_43l_262ci_v6_engine_build/viewall.html


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## tmack6 (Aug 8, 2011)

Its pretty easy. If you have the original seal in there its a rope style seal. All you have to do is drop the trans inpection cover and the engine oil pan. Undo the rear main cap and pull the rope seal out with needle nose pliers. Clean the cap and any sealant residue off real good. The new seal will be a 2 piece neoprene style with small plugs. When you set the new seal in make sure that you clock them....put one side of the seal up around the crank and leave about 1/4" I believe hanging out on one end (read the instructions with new seal to verify), and on the cap leave a 1/4" hanging out on the oppositde side. There will be two little rubber plugs with nails in them that your suppose to jam into the cap somewhere. Most of us turbo guys dont even use those. You can but you can also Just inject rtv into that cavity. Then apply a small amount of rtv to the mating surface of the cap where it meets the block. Torque the cap back on, oil pan, inspection pan...let it chill for 24 hours and youre good.


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