Rear Main Seal Leak

[chautauquasun]

84 Supra Rider
PCM 351w
1:1 velvet drive.

So I have had minor oil leak over the past 2 years. I would find oil in the bilge but very little and the dip stick would always show full. I thought maybe it was possible in the bilge from oil change. Or coming from a old oil drain tube. Started to notice it a lot more this year and today found that the bilge was full of oil after we skied. checked the dip stick and the oil was down to the add line. I filled the oil back up and checked the main seal while running in gear and noticed that I have a pretty good leak coming out of the main seal.

My question is, how hard is it to replace this? I am sure it isn't difficult but I am thinking that I am going to have to remove the engine and transmission to get at it. Is that correct? If so, I may try to get it through the summer and then look to have it replaced.

Any one know how difficult this is....and if the engine does have to come out...what kind of cost am I looking at if I have a marina or garage do this work?

thanks
Dan

[CJD]

Check you PCV valve and vent hose to make sure it's purging the pressure out of the crankcase. If it clogs and pressure builds, it'll blow oil out of the rear seal. If that doesn't fix it, then you are correct...you'll have to at least remove the tranny to get to the seal to replace it.

[michael hunter]

Its a 1 piece seal you will have to remove the trans,bell housing and flex plate to get to it.

[chautauquasun]

I haven't been on here in a while. Always good to see the forum is still up and thriving. This has been such an important tool for me with my old supra ownership. Thank you to all of you for all of your help over the years. She isnt the newest or fanciest boat on the lake but I still love her and everything this old boat can do. Pretty amazing that this old technology and styling still really holds well after all of these years.

So I limped through the rest of the year with what I believe is a bad main seal. It had been a slight leak for a few years but now if leaking pretty bad. Especially if we are using it hard like when weighted while surfing. So it looks like I will start this seal replacement in the next couple of months. A few questions:

1. I have never done this - is it difficult. I am guess the difficulty in breaking the prop shaft and transmission loose. Once out of the way I am guessing this is pretty simple. Any thoughts or things to watch out for?
2. Since I will have the transmission out...are there any parts that I should also consider replacing in the transmission? Flex plate? Should I have the trans looked at? Shaft bearings?
3. Any other thoughts? My neighbor had to replace his transmission last year and was able to block the back of the engine to support it while pulling the trans. Any thoughts on the best way to do this.

Thank you in advance.

Dan

[chris young]

Breaking the prop shaft coupling is a doddle, 4 bolts and a light tap and you're done. Personally if I had the tranny out, I'd rebuild it. According to Cusefan, and others, it is also a pretty easy job.

[lively]

Breaking the prop shaft coupling is a doddle, 4 bolts and a light tap and you're done. Personally if I had the tranny out, I'd rebuild it. According to Cusefan, and others, it is also a pretty easy job.

easy stuff , weights about 150 lbs , rebuild kit is about 150$ , and too easy not to skip ..

[lively]

also if the flex plate springs are rusted just get a new one , all parts are on ebay to compare to local stores ect . on the main seal is it the engine main or the trans main ?

[carlossa]

Could also be the camshaft welsh plug. Its been a while since I pulled a windsor apart, but chevs definately have them. They do tend to rust out and you will lose masses of oil.

[chautauquasun]

Lively,

thanks! I am a weekend mechanic so I may not be referring to the part correctly. It is the seal between the block and transmission. I can see the oil leak/stream on the bell housing where it meets the drive shaft. Is that the rear main seal? whatever it is called...that's where it is leaking. Is the rebuild kit for the transmission easy to do? I know the velvet drive is a simple transmission but I have never rebuilt one before. Again, I am not a mechanic but do all the work on my boat. Is the rebuild kit something a novice can tackle. The flex plate looks pretty simple.

thank you for the advice.

[wotan2525]

Are you losing transmission fluid or engine oil?

[chautauquasun]

engine oil. No issues with transmission fluid at all. Oil leaking from back of block where shaft meets the trans.

[lively]

engine oil. No issues with transmission fluid at all. Oil leaking from back of block where shaft meets the trans.
if it aint broke dont fix it , but if you just wanna freshen up the trans the velvet drive is very simple to rebuild or just change out the friction disc the kit does not come with reverse springs and you will need those if you decide to rebuild it .. service manual is online somewhere and i just followed the instructions .. rear main seal is the right term for engine and its really simple , just pop old one out with a screw or pick and clean and reinstall new .. run emory cloth around rear of crank where the lip of seal rides to smooth any high ridges .. cheers

[chautauquasun]

Thanks again Lively. I haven't had any issues with the trans but noticed last year the prop started to spin some when in neutral so I am thinking it is probably time for a rebuild. We have been weighting for surfing and wakeboarding and am sure that this is putting more strain on the transmission and it is starting to wear. Probably makes sense to do it now. DOes the kit include the the clutch pack? Would skidim carry the reverse springs? Anything else I would need parts wise to rebuild it? Also, do I need any special tools to rebuild it?

thanks
Dan

[Cooose]

This thread gives a good general idea of what you would be getting into on the rebuild.
https://www.mastercraft.com/teamtalk/showthread.php?t=53874

Lively also did a rebuild thread here but I believe the pictures may have died.

[lively]

Thanks again Lively. I haven't had any issues with the trans but noticed last year the prop started to spin some when in neutral so I am thinking it is probably time for a rebuild. We have been weighting for surfing and wakeboarding and am sure that this is putting more strain on the transmission and it is starting to wear. Probably makes sense to do it now. DOes the kit include the the clutch pack? Would skidim carry the reverse springs? Anything else I would need parts wise to rebuild it? Also, do I need any special tools to rebuild it?

thanks
Dan

No special tools , google 71c reverse spring for velvet drive , the prop is normal to spin in neutral , check selector where the cable mounts , it's probably tweaked and hanging pressure to slightly move prop . But either way it's normal .
I'll check my photobucket and look for pics .


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[lively]

https://sbo.sailboatowners.com/downloads/Hunter_gen_61323794.pdf


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