Rear Main Seal

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nobull1

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OK time for the next project on my 763. I had the main belt cover off the other day and seen some fresh oil down on the bottom of the cover. this doesn't surprise me because there is a lot of caked on crud all around, under, and behind the flywheel. The only thing that makes sense is the rear main seal leaking. So after looking at my book it appears that you can take a half dozen bolts out of the flywheel and pop it off. Then you take another few bolts out and take the bearing case cover off. I assume that the seal is in this cover and should be easy to replace? I will also assume that you don't have to take the shroud behind the flywheel off to get the bearing case cover off....that would not be good This seems like an easy job..ha..ha, but you know how things have a way of going, especially for me. Has anyone done this repair and offer any advise or tricks. The seal will be in in a couple of days so I just want to be prepared. Just don't say there isn't enough room and the motor has to come out.
 

Fishfiles

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Your preping seems good , sounds like you know what your up against , one thing I can say that could help you is to mark the seal carrier plate and the flywheel as the bolts don't seem to line up in any position , and you can get almost all in and then have to remove them and rotate it to line up --------- check the play in the crankshaft bearing as I have changed that seal before a couple of times and found it leaked again in minutes , once it was the blowby tube pinched and clogged up causng excessive back pressure and another time it was the crankshaft moving up and down ---------the hardest part of that job is scraping the gasket off the carrier plate , if it don't tear upon removing it I would leave it alone and just put some good sealant on it , I don't know what they put on it but it is really hard to cut off
 

Tazza

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I would suspect the hole in the housing will be large enough for you to remove the rear main seal and housing. Make sure if there are any shims there that they go back in. It should be a straight forward job but access may make it a little harder. At least you don't need to pull the engine down to replace the seal.
I see no reason why you would have any problems with the repair. When you re-insall the plate ensure the rear main bearing carrier is the rite way up!!!! if its not, the oil passage will not line up and you will spin the bearing. From memory its not easy to do as the bolt holes are drilled so you can't. Mark the top of the aloy cover you remove so you know what way is up, this way you can't go wrong. There is a symbol on there, i just can't remember what way around it was.....
Good luck with it!
OOH i do assume the oil is black engine oil? if so, it has to be the rear main. If its fresh it could be the pump.
 
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nobull1

nobull1

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I would suspect the hole in the housing will be large enough for you to remove the rear main seal and housing. Make sure if there are any shims there that they go back in. It should be a straight forward job but access may make it a little harder. At least you don't need to pull the engine down to replace the seal.
I see no reason why you would have any problems with the repair. When you re-insall the plate ensure the rear main bearing carrier is the rite way up!!!! if its not, the oil passage will not line up and you will spin the bearing. From memory its not easy to do as the bolt holes are drilled so you can't. Mark the top of the aloy cover you remove so you know what way is up, this way you can't go wrong. There is a symbol on there, i just can't remember what way around it was.....
Good luck with it!
OOH i do assume the oil is black engine oil? if so, it has to be the rear main. If its fresh it could be the pump.
Supposedly the carrier plate and flywheel have marks/pin to make installation idiot prove...ha ha. When checking the bearing for play do you mean the main bearings or is there a bearing in the bearing case cover?
 

Tazza

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Supposedly the carrier plate and flywheel have marks/pin to make installation idiot prove...ha ha. When checking the bearing for play do you mean the main bearings or is there a bearing in the bearing case cover?
The end of the crank does have a pin for the flywheel, but from memory there is no pin that goes from the block through the seal carrier.
There are thrust washers in the rear centre main bearing carrier that the seal carrier bolts to. This limits the amount the crank will move back and forth (limit is .015" i believe but don't quote me). This can only be checked with the seal still in place. If the crank moves up and down or side to side your centre main bearings are worn but if its that bad you should have low oil pressure. Replacing the centre mains means pulling the whole engine down. The head has to come off, timing cover off to get the crank and centre main bearing carriers out. Its not like a regular car that you can simply remove the sump to get access to the centre mains or replace the crank. Still not a hard job but just takes a lot longer!
 
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nobull1

nobull1

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The end of the crank does have a pin for the flywheel, but from memory there is no pin that goes from the block through the seal carrier.
There are thrust washers in the rear centre main bearing carrier that the seal carrier bolts to. This limits the amount the crank will move back and forth (limit is .015" i believe but don't quote me). This can only be checked with the seal still in place. If the crank moves up and down or side to side your centre main bearings are worn but if its that bad you should have low oil pressure. Replacing the centre mains means pulling the whole engine down. The head has to come off, timing cover off to get the crank and centre main bearing carriers out. Its not like a regular car that you can simply remove the sump to get access to the centre mains or replace the crank. Still not a hard job but just takes a lot longer!
Tazza
Thanks for the all the info. I hate not being prepared when I start a job, the more knowledge the better. Maybe I will take a couple of pic's along the way and post.
 

Tazza

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Tazza
Thanks for the all the info. I hate not being prepared when I start a job, the more knowledge the better. Maybe I will take a couple of pic's along the way and post.
I totally agree! Its better to have an idea of what to expect and to know springs or other pieces will not be flying out at you when you remove a plate! There is nothing there to jump out and bite you in the a$$. The hardest part will be gaining access and then installing the new seal in the carrier. Seating the seal for me was the hardest part! i had nothing that big to use to push it in with.
 

Fishfiles

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I totally agree! Its better to have an idea of what to expect and to know springs or other pieces will not be flying out at you when you remove a plate! There is nothing there to jump out and bite you in the a$$. The hardest part will be gaining access and then installing the new seal in the carrier. Seating the seal for me was the hardest part! i had nothing that big to use to push it in with.
I think only the old machines had line up pins on the crank for the flywheel , the 853 series I did last didn't have them and the bolts seem to only line up one way , maybe it had been removed along it's way , and I don't remember the 763 having them either
 
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