Atdc94

So my rear main seal is bad. I have searched some but couldn't find anything. Is there any write ups on how to go about replacing this? Also is there any other modifications I would want to do while I am doing this? Thanks as always guys.

usdmholden

If your LS is older you should replace the oil bypass plug and the rear cover seal. The bypass plug changed sometime after 1998 or 1999 to keep it from pushing out and the engine losing oil pressure.

12639249 1 LS1 rear cover seal
12573460 1 LS1 barbell oil bypass plug
89060436 1 LS1 rear main seal

lizeec

iTrader: (57)

You can buy the rear cover assy. with a new seal already installed and it also comes with a new gasket and bolts for around $70.00 The rear seal and rear cover gasket runs you $60.00 I would get the complete assy. For only about $10 more

smws6ta

iTrader: (5)

If you are not aligning the seal properly then your going to have leak issues.

Link below has a tool kit that will help and is not expensive IMHO. I have it on my to order list.

https://ls1tech.com/forums/generatio...one-these.html

cmac06

iTrader: (16)

^^^yep, their whole set of alignment tools is cheaper than one "j" tool. For your rear main seal, you're looking at less than $40.

Burken01

iTrader: (88)

the engine will have to be pulled, flexplate/flywheel removed, then reassemble..

You should do the " drop the engine attached to the k member" method, you disconnect the brake lines to the master cylinder that go to the rear wheels, and a few wires, and unbolt the k-member and lift the car off of it..

only takes an hour to do it, then youll have easy access to everything..

theres a write up with pics on how to drop the engine/k member if you search for it..

usdmholden

I guess I don't see the point of the alignment tool. It looks nice and everything, but why not just put the rear main seal into the rear cover before positioning the cover onto the back of the block? That way the seal ensures the holes in the rear cover is concentric to the crank.

Roarin_8

iTrader: (5)

My motor wasn't pulled when the shop I used to go to changed the rear main seal, they did it when they dropped the trans to change the converter.

chrisfrost

iTrader: (8)

If it were Me I most likely would pull the trans to do the rear main seal and as long as apart probably the trans tq conv seal depending on how old it was and the trans dip-stick tube seal . Not sure where the prior poster was getting rear seal and cover gasket 4 $60 but I know at Advance auto parts the 2 together are like $30 and They are Federal Mogule which are the brand the factory gaskets and seals are at least some of the years of the LS based gen3 n 4's,,,at some point They changed gasket/seal vendors,,,,just not sure when and to what brand

Oh ya , as far as the alignment tool ,,,,,,,according to a repair manual You just measure the distance on each side of each of the covers to make them equal before tightening the bolts .

MyFirstLS1

iTrader: (8)

Engine does NOT need to be pulled.

Remove trans, clutch (if manual) and flywheel. Remove seal and using the tools linked above or a block or wood if you want to risk it use a rubber hammer and hammer it in.

I would recommend the rear cover with the seal as well since it comes with everything and a new cover gasket. But that tool with help you line the cover back up when reassembling

Burken01

iTrader: (88)

Let me rephrase, it's easier to replace if you "pull" the engine through the bottom using the drop the k member method..

I don't like the idea of pulling a tranny and doing everything under the car...

It's easier when you pull the k member, everything is easy access and you can do it alone with no help..

Tranny method requires 2 people

lemons12

iTrader: (71)

Trans takes one person.. I can do it by myself easily.

Drop the trans.

I recommend a converter if you don't have one yet along with a flex plate.

Clutch if you are a manual with a speed bleeder.

01 Vert ws6

iTrader: (18)

dorman makes a rear cover with rear main seal for 40.00

part number is dorman 635-518

Burken01

iTrader: (88)

Either way works, I could probably do the whole job in 1 1/2 hrs dropping the engine..

Whatever your comfy with...

lizeec

iTrader: (57)

The G.M. part # is 12639250 it comes with a new cover and a new seal already installed and it also comes with the rear cover gasket and new bolts, I just checked it online anywhere from $45.00 t0 $60.00 from G.M. dealers and even Jegs or Summit carry it. IMHO easier to drop the transmission and install the whole cover assy.