[Fullback66]

Hey guys,
Is there any good videos or literature on how to replace rear main seal for a 1966 389, 4 speed GTO? With engine and 4 speed in the car?

I have a leak somewhere and though if might be the rear main seal. I check the oil all the time without it ever needing more oil. Could my tranny be leaking?
Where would a 4 speed leak from? I checked the fluids in the tranny and it seams fine. I am so lost.


Thanks
FB66

[dataway]

How much is it leaking? Using the old "Puddle size per day" method?

[stevep]

Pull the engine. It will make things a LOT easier.

[bill ryder]

DEFINITELY X2 on pull engine!!!!!!!!!!!

"Bill"!

[Cardo]

X 3 PULL THE ENGINE!

[Fullback66]

DANG! looks like it's time to pull the engine.
Thanks guys
FB66

[Fullback66]

DANG! looks like it's time to pull the engine.
Thanks guys
FB66

[gtospieg]

Since you need to pull the trans to pull the engine...check out the trans for leaks before you pull the engine. It's a lot easier to R&R the trans...

[Greg Reid]

Check the rear of the valve cover gaskets closely. Almost fooled me into thinking I needed a RM seal once.

[Fullback66]

THANKS GREG
i will do that

[Fullback66]

THANKS GREG
i will do that

[Kenth]

Also, rear of an old oil pan gasket has fooled more than one.
The rear oil pan reinforcements helps.

[Cammer-6]

also check distributor gasket
clean everything off real good then look for traces of fresh oil

[1967SC]

Just had mine done this summer. I used the one piece Viton form Butler.
I delivered the engine to him on a Friday morning and picked up that afternoon.
He was on the phone with Jim Butler as he was installing.

Also get the one piece oil pan gasket from Butler as well.

Good luck

[GTOh!]

Hate hijacking this thread but it’s exactly where I am. I’ve removed all but the WV code engine on my ‘67 so far and will be doing that as soon as my new engine stand arrives. I bought the Viton 2 piece seal because the folks at Butler said it’ll work for me. I hope they’re right. I will also be re-sealing and replacing all gaskets in my Muncie while it’s out.

My question is, does anyone have any tips or advice on how to best assure a good install of the rear main seal?

Thanks!
Don

[tom s]

FYI,im 50/50 on the 2pc viton,100% on the one pc viton and 100% on the Best Gasket Graftight rope seal.Tom

[mike202]

My question is, does anyone have any tips or advice on how to best assure a good install of the rear main seal?

I recently did a RMS on a 1969 428 in my Grand Prix. I pulled the engine and I went with the one piece BOP seal. Per Butler, this is what they use in their builds.

I had discussions with both Butler and Wade at BOP as far as getting some tips. As a matter of fact, I had Wade on the phone in real time as I was installing the seal. The instructions are clear and in this case I had to sand of the OD of the seal to get a proper fit. One deviation from the instructions was to locate the split line at 2 o'clock vs. 6 o'clock ( with 6 o'clock being the "top" of the block). This was suggested both by Butler and Wade. After putting it all back together, I ran the engine briefly on the stand and there was no leaks.

Unfortunately, after about 1k miles, the seal is leaking, so I am disappointed. It is not pouring out like the old rope seal, but it is leaking. I went back and forth on what seal to use (BOP vs. Best Gasket rope seal) and I went with BOP after talking to Butler. Reading many posts over the years here and elsewhere , it seems that some have good luck with the BOP seal and some have failures. This is also the case with the Best Gasket rope, too.

What I did notice is that folks seems to have better luck sealing up the 3" journal engines vs. the 3.25" journal engines, like my 428. Years ago when I built a 400 I used the rope seal from the gasket kit and it never leaked.

Hope this helps.