95 Sport GT40 rear main leak

Unless your engine needs to be rebuilt which with only 850 hours would be unusual I would just replace the seal. Pretty sure you don't have to pull the engine just the transmission which isn't that hard to do.

Jordan,
I know you have mentioned it's engine oil but are you sure? Brownish would be engine and reddish would be trans fluid.

Like Gary said........listen to Dad but not to everything he said   

The thing that hasn't been mentioned is that you have a later 351W with a one piece rear main seal, and that's the reason it can be replaced without dropping the oil pan.

As mentioned you can jack up the rear of the engine a little and let it pivot around the front mounts which you loosen.

Then click on the links below, one has a post from somebody with the same name as me, giving a pretty good rundown on how to access and change the damper plate. The info is near the end of the thread. Being a GT40 you may have a few more things to remove but it's a good rundown of what's involved.

Once you're looking at the plate, you would remove that and then the six bolts holding the flywheel to the crankshaft and a rear main seal will be staring you right in the face.

You can use a pick to remove the old seal and then put in the new one. You'll be laying on the floor to do it, but it's not bad. Follow the instructions for whatever seal you decide to use especially if you decide to use a teflon rear main seal since they need to go in place clean and dry unlike a rubber seal that gets lubed up good before putting it in.

When it comes time to put the flywheel back on, make sure you've read the second link which talks about bolt hole spacing. It only goes on one way.

And then since you have a damper that's getting old and they just fail whenever they feel like it, I'd install a new damper.

if you don't put a new one in, the old one will crap out about a week later and leave you doing most of the job all over again.........or maybe it'll last 10 more years, you just never know

You could get the damper from Skidim as one place to shop. You need the damper for a PCM 1.23 to 1 transmission

As far as seals go, here are some part numbers from National Oil Seals, (they make FelPro's seals for them)

National 5278 is a Teflon seal that some will say is the latest and greatest technology

National 2377 is a rubber seal that works well too.

link

link

And while you're in there it would be a good idea to look at the front seal on the transmission to see if it leaks at all and decide if you want to replace it.

Been there done that
Sorry to hard to put them in order on my phone but you get the idea. Almost forgot the one with the seal

Jordanh wrote: checked propshaft run out .

Jordan,
Did you check the shaft aft of the strut? That's where most bends occur and where even a slight bend produces the most vibration. The max TIR is .003" anywhere on the shaft.

Jordanh wrote: I pulled the prop and checked the shaft directly aft of the strut, right before the prop, and on the prop mating surface.

That's were the bend in the shaft occurs so you probably didn't get a good reading You what to measure farther back on the taper. What reading did you get?

Jordanh wrote: between the strut and the prop nut.

Jordan,
This is a good spot. Wish you had mentioned it before. So, what did you get for the runout?

There was a video on this site of a gentleman aligning a coupling and checking runout that I followed when I did it. I did all this on my trailer. I have since learned that the coupling alignment is best done in the water as your trailer may not support your hull in the straightest fashion. I am going to recheck that coupling over the fourth

I will go through that lapping process next weekend as well as verifying my keyway fitment. That is a fantastic write up. I will report back with my results.    I'm not sure I will be able to get my dial indicator on the shaft next weekend. I won't have anywhere to mount it with the boat on the lift and I avoid the ramp like the plague on holiday weekends but will verify it when I get a chance.

8122pbrainard wrote: It can be done on the lift but you need to get wet.

That's the most profound statement I've heard all day, but the day is still young

So, anyways, thanks Pete, it'll make me chuckle on and off for a while   

And.........I'm not picking on ya, it's just funny

8122pbrainard wrote: The dial indicator base is clamped to the strut