how do i change front crank oil seal
Thread Starter
Junior Member
Joined: Feb 2009
Posts: 81
Likes: 0
From: uk
Car: IROC Z28
Engine: 5 litre 305
Transmission: 700r4
how do i change front crank oil seal
can someone run me through changing the oil seal that the harmonic balancer goes on on the crank
the engines a 1983 305 so im guessing u dont have to take the oil pan off, well thats what my book sais?
the engines a 1983 305 so im guessing u dont have to take the oil pan off, well thats what my book sais?
Last edited by IROCmatt; Mar 1, 2009 at 02:14 PM.
Supreme Member
Joined: Apr 2007
Posts: 1,087
Likes: 1
From: St. Petersburg, FL
Car: 88 Camaro
Engine: 305 TBI
Transmission: 700-R4
Axle/Gears: 2.73
Re: how do i change front crank oil seal
Think you gotta take that pan off, Well lift the engine enough to get the pan off, do you got a chilton or hayes manual ?
Thread Starter
Junior Member
Joined: Feb 2009
Posts: 81
Likes: 0
From: uk
Car: IROC Z28
Engine: 5 litre 305
Transmission: 700r4
Re: how do i change front crank oil seal
i got a haynes manual it sais 85 on the pan needs to come off so i take it i dont need to do that as its a very early one, hopefully someone knows, dont want to take pan off if i can help it
Supreme Member




Joined: Jan 2009
Posts: 2,313
Likes: 115
From: belle fourche,s.d.
Car: '82 z28
Engine: L83 5.7
Transmission: 700r4-1985
Axle/Gears: 3.42 posi
Re: how do i change front crank oil seal
No need to drop the pan on an '83(74-earlier i think
you do need to drop pan) when going back together,
make sure the 2 holes for the locating pins aren't
bent,that way the seal is centered properly.also make
sure the crank damper is fully seated against the
timing spocket when reasembled-use longer bolts or
threaded rod and nut to draw it onto the crank.
you do need to drop pan) when going back together,
make sure the 2 holes for the locating pins aren't
bent,that way the seal is centered properly.also make
sure the crank damper is fully seated against the
timing spocket when reasembled-use longer bolts or
threaded rod and nut to draw it onto the crank.
Supreme Member




Joined: Jan 2000
Posts: 3,178
Likes: 48
From: Tracy, CA
Car: '87 IROC
Engine: LB9
Transmission: TH700R4
Re: how do i change front crank oil seal
Pull off the accessory belts.
Remove water pump and crankshaft pulley(s).
Remove water pump (might want to drain the cooling system first).
Might have to remove the radiator to have access for the harmonic balancer removal tool.
Remove the timing chain cover. If you need to pry the bottom of the cover to separate it from the pan, you "might" have to lower the pan. The cover will come out without lowering the pan. Just don't distort the cover when prying. Pay attention to the alignment dowers for the cover.
Once the cover is out, pry out the seal. Install a new seal. Don't hammer directly on the seal. If it distorts, get a new one.
Check the condition of the timing chain while you're in there. If there's any slop, consider replacing the chain and sprockets.
Inspect the harmonic balancer where the seal rides. If there's a groove there, get a new balancer.
Replace the cover with new gaskets. To make fitting of the cover to the pan easier (if you didn't lower the pan) it helps to trim the corners of the lower gasket support that holds the little "smiley" cover-to-pan gasket. It allows the cover to slide into place while at the same time clearing the alignment dowels. Easier to see this during a test fit of the cover than to explain. Use some kind of gasket sealer to ensure you don't have to tear it apart again to re-seal.
If you lowered the pan, shoot some silicone sealer in between the block and pan rails after you clean off excess oil, etc. with brake cleaner. Then tighten the pan to the block. The idea is to put enough in there to re-seal what seal was broken when the pan was lowered. Use good judgment. You don't need the silicon inside the engine; just on the sealing surface.
Replace everything else in reverse order.
Remove water pump and crankshaft pulley(s).
Remove water pump (might want to drain the cooling system first).
Might have to remove the radiator to have access for the harmonic balancer removal tool.
Remove the timing chain cover. If you need to pry the bottom of the cover to separate it from the pan, you "might" have to lower the pan. The cover will come out without lowering the pan. Just don't distort the cover when prying. Pay attention to the alignment dowers for the cover.
Once the cover is out, pry out the seal. Install a new seal. Don't hammer directly on the seal. If it distorts, get a new one.
Check the condition of the timing chain while you're in there. If there's any slop, consider replacing the chain and sprockets.
Inspect the harmonic balancer where the seal rides. If there's a groove there, get a new balancer.
Replace the cover with new gaskets. To make fitting of the cover to the pan easier (if you didn't lower the pan) it helps to trim the corners of the lower gasket support that holds the little "smiley" cover-to-pan gasket. It allows the cover to slide into place while at the same time clearing the alignment dowels. Easier to see this during a test fit of the cover than to explain. Use some kind of gasket sealer to ensure you don't have to tear it apart again to re-seal.
If you lowered the pan, shoot some silicone sealer in between the block and pan rails after you clean off excess oil, etc. with brake cleaner. Then tighten the pan to the block. The idea is to put enough in there to re-seal what seal was broken when the pan was lowered. Use good judgment. You don't need the silicon inside the engine; just on the sealing surface.
Replace everything else in reverse order.
Last edited by paulo57509; Mar 1, 2009 at 05:50 PM.
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Supreme Member
iTrader: (3)
Joined: May 2005
Posts: 1,942
Likes: 0
From: Southern IL
Car: 88 GTA "Cocaine"
Engine: 350 tpi
Transmission: 700r4
Axle/Gears: 3.27
Re: how do i change front crank oil seal
if you shave the inside lip of the timing cover where the front oil pan seal sits - you wont have to drop the pan
sorry I dont have pics but you have to take off about an inch or so on each side
sorry I dont have pics but you have to take off about an inch or so on each side
Joined: May 2004
Posts: 5,338
Likes: 73
From: Lexington, SC
Car: 1987 SC/1985 TA
Engine: 350/vortec/fitech
Transmission: T56
Axle/Gears: 3.27 9-bolt
Re: how do i change front crank oil seal
You can get a timing cover seal 'kit' that includes a sleeve that fits over the seal surface on the harmonic balancer and a slightly oversized seal. Put one on my 85 last Summer rather than replace the balancer. 10+k miles later, still good.
Supreme Member




Joined: Jan 2000
Posts: 3,178
Likes: 48
From: Tracy, CA
Car: '87 IROC
Engine: LB9
Transmission: TH700R4
Re: how do i change front crank oil seal
Good call. I forgot about these repair kits.
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