PDA

View Full Version : Rear main seal


Hunterb
11-17-2008, 05:39 PM
Hi all,

My engine was leaking a fair amount of oil into the bilge this summer. It's not coming from any of the easy to fix places (valve covers, timing cover etc.). It appears to be coming out at the rear of the motor and does not look like it's the pan gasket so I suspect it is the rear main seal.

The motor is a 1990 351 standard output. My question is what kind of a rear main seal is on that motor, a one piece or two piece, and is it possible to change it by removing the transmission and leaving the motor in place?

Would appreciate any suggestions or advice.

Thanks

Bruce

amber 6
11-17-2008, 06:09 PM
If you take the starter motor out is there oil lying at the bottom of the flywheel housing.
Mine had it was from the shaft seal from the gearbox which needed transmittion out to replace.

Hunterb
11-17-2008, 07:43 PM
Amber 6, Thanks for the reply. I gather yours was leaking transmission oil into the bell housing?

I'm really wondering about the rear main seal on the engine. I believe sometime in the late
80's that Ford switched to a one piece seal so it should be possible to change it by removing the transmission and the damper plate, flywheel etc. but it shouldn't be necessary to remove the oil pan ( I don't think anyway). If the oil pan has to come off then the motor has to come out. THe old 2 piece style seals required the loosening of the crankshaft to get the old seal out and the new one in whereas the one piece seals can be pulled out and pounded in without having to do that. What I'm trying to find out is 'in 1990 what kind of rear main seal is in there and can it be changed with the motor in place?'

Bruce

TRBenj
11-18-2008, 09:56 AM
Amber 6, Thanks for the reply. I gather yours was leaking transmission oil into the bell housing?

I'm really wondering about the rear main seal on the engine. I believe sometime in the late
80's that Ford switched to a one piece seal so it should be possible to change it by removing the transmission and the damper plate, flywheel etc. but it shouldn't be necessary to remove the oil pan ( I don't think anyway). If the oil pan has to come off then the motor has to come out. THe old 2 piece style seals required the loosening of the crankshaft to get the old seal out and the new one in whereas the one piece seals can be pulled out and pounded in without having to do that. What I'm trying to find out is 'in 1990 what kind of rear main seal is in there and can it be changed with the motor in place?'

Bruce
I *believe* Ford switched to the one piece rear main seal around 1980.

Bruce Carr
11-18-2008, 09:58 AM
Bruce,

I just went through this exact same problem with my '83 S&S. Mine definitely gets a little motor oil in the bilge (not ATF) and it is not coming from any of the easy to fix locations either.

You are in luck though. Starting with engines manufactured in 1983 (and newer) the 351W has a one piece seal which can be replaced by removing the trans and damper plate. There are some good instructions and pictures out on the web of this operation (do a search for 351W rear main seal replacement).

According to the folks at Skidim, 1983 and up engines got the one piece seal. Unfortuneately, the engine in my '83 was manufactured in '82 according to the serial number and most likely has the two piece seal. As you know, the engine has to come apart to replace this seal. It is going to have to get alot worse before I fix it.

Good Luck,

Bruce (also)

Hunterb
11-18-2008, 03:08 PM
Thanks guys,

That's good news for me. Before I get too excited I need to make absolutely certain it's not the pan gasket but I'm pretty sure it's not.

Pulling the transmission is not too bad of a job, I don't think. I need to check the damper plate as well because it's been making some funky sounds at idle so I can hopefully fix it all up at once.

Thanks again. Off to the parts store for me.

Bruce