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Is it possible to replace a Two-Piece Rear Main crankshaft seal on a '79 C3 SBC without pulling the engine? Manual tranny, bell-housing, clutch and flywheel have been removed. Can the oil pan be dropped without pulling the engine?
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 22759
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Yes. The oil pan can be dropped by disconnecting the steering idler arm, and pitman arm, and let the steeering linkage drop down. To replace the main seal you will need to loosen (but NOT remove!) all of the main cap bolts to allow the crank to drop just a bit to give some clearance to remove and replace the main seal pieces. Be sure to retorque the main caps bolts properly, and make sure the ends of the main seal are NOT lined up with the split at the rear main cap...the seal needs to be off-set a little to keep it from leaking there.
Joel Adams
C3VR Lifetime Member #56 
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Had to do that job on "BLKBRRD" (twice!). Dropping the crank a touch made the task a lot easier. Good luck...!!!
Jim Olson 
"The Toys"...!!! Save the Wave! 
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Honestly, I just removed the rear main cap and was able to pull the old seal out and push the new upper half in.
You can also get a seal that has a slightly offset lip in case your old seal has worn a groove in the crank.
Dropping the crank though sounds like a better way to do it.
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Thanks for the replies! Many years ago, I had replaced a 2-piece seal on a 1985 GMC Jimmy 4wd, 305 V8; it had more space under the oil pan. So my actual concern: if it was even do-able on my 1979 C3, by moving steering linkage out of the way only. On the 305, It did not require loosening all the main caps.
While under there though, with my L48 having 100,000 miles, it would not hurt to take a look at anything else while i am that far into it.
I do appreciate anybody's suggestions based on their hands-on experience!
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 22759
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
As far as "dropping the crank", it's not really moving it that much. However...it does help slide the new upper seal in WITHOUT scraping the outer edge of the seal as it goes into the engine block. It is not totally necessary, but it do make it easier, imho. Done many like that. Hell of a lot easier than doing them damn ol rope seals, fer sher! 😁 One thing to look out for, is to make sure you have the new seal pointed in the right orientation...don't wanna put it in backwards....it'll leak....🤭
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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in Forum: C3 Engines, Driveline and Handling
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