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  1. #1
    Join Date
    Sep 2008
    Location
    Parkersburg, WV
    Posts
    1,863

    Default Fiy damper plate replacement

    There seems to be a lot of you on the forum that are looking at damper plate (also know as a flex plate) replacement this spring so I thought I would share my experience since I have some extra time right now. First of all, the signs that a damper plate is going bad will be a "knocking" noise coming from the bell housing of the transmission. The plate in question is bolted to the flywheel and transfers power to the input shaft of the transmission via a splined coupling. The coupling is an integral part of the flex plate that is mounted to a set of springs that "soften" or "dampen" the jolt that you get when shifting from neutral to forward or reverse. The flex plate is there to protect the transmission, and PCM will not warrant a new transmission that is installed without also installing a new flex plate!

    So if you are having this knocking sound coming from the bell housing, and it's there at idle and then tends to become faint or go away after engaging the transmission and throttling up, then chances are you will be needing to replace the flex plate soon. A flex plate is either going to work, or it's not going to work - there's no in-between. A failure will be catastrophic and leave you stranded - as it did me!

    So you need to order a flex plate from a reputable supplier. There are differing opinions on this, but my experience is that you get what you pay for so I ordered mine from www.skidim.com. Regardless of where you buy it, just be sure that it is made for a marine application. The disassembly and replacement is relatively easy and can be done in an afternoon, or mere hours for some. The transmission weighs only about 90lbs (small block Ford) and maybe 120lbs with the bell housing.

    Procedure: Romove the drive shaft coupling bolts and slide the shaft toward the aft of the boat. You may need to remove your prop to have clearance to do this since your prop may hit your rudder. After draining the transmission, remove the transmission and bell housing as a single unit - on the PCM 351 you will need to unbolt the rear mounts as well as disconnect transmission hoses and shift cable. Remove the starter as well. As soon as you remove the bell housing you will see the flex plate. Unbolt it from the flywheel . . .

    Now is a good time to inspect your flywheel to be sure all the teeth are there! Mine was missing teeth (good place for a West Virginia joke) so I also removed the flywheel and took it to a local machine shop to be re-ringed. Also I went ahead and replaced the rear main oil seal at this time since it had a slight drip.

    Re-assembly is very simple, but be sure to use a torque wrench when fastening the damper plate to the flywheel (and the flywheel to the crank if removed). Hook everything back up, put in some new transmission fluid, and away you go. Good as new!

    Some pics:


    Old flex plate.

    Last edited by csuggs; 03-14-2012 at 12:20 PM.
    Clint
    Wake the World - West Virginia
    www.waketheworldwv.com

  2. #2
    Join Date
    Sep 2008
    Location
    Parkersburg, WV
    Posts
    1,863

    Default

    New rear main oil seal installed.



    New flex plate installed.

    Clint
    Wake the World - West Virginia
    www.waketheworldwv.com

  3. #3
    Join Date
    Mar 2011
    Location
    Charlotte, NC
    Posts
    311

    Default

    Good write up Clint. One question for ya. When reinstalling did you have to use a shaft aligning tool? Similar to the way you install a manual transmission into an automobile application. If so, where can this alignment tool be procurred? btw, mine is a 454 not a 351.
    "Where There's a Will, there's a way!"

    Check out my 1987 rebuild thread here
    http://www.supraboats.com/bbs/showth...-Resto-begins.

  4. #4
    Join Date
    Sep 2008
    Location
    Parkersburg, WV
    Posts
    1,863

    Default

    Quote Originally Posted by wspeedin View Post
    Good write up Clint. One question for ya. When reinstalling did you have to use a shaft aligning tool? Similar to the way you install a manual transmission into an automobile application. If so, where can this alignment tool be procurred? btw, mine is a 454 not a 351.
    Will - no alignment tool needed!
    Clint
    Wake the World - West Virginia
    www.waketheworldwv.com

  5. #5
    Join Date
    Mar 2011
    Location
    Charlotte, NC
    Posts
    311

    Default

    really? this is good news! thanks!
    "Where There's a Will, there's a way!"

    Check out my 1987 rebuild thread here
    http://www.supraboats.com/bbs/showth...-Resto-begins.

  6. #6
    Join Date
    Feb 2010
    Location
    Oklahoma
    Posts
    101

    Default

    good info - mine eggshelled last year on 4th of July @ about 9pm doing 25 MPH - replaced it and back on the water next day - with alot of help from the good folks on here!
    and the point about the noises and knocking is soooo correct... too bad for me I had no idea what the heck was about to happen...I'm so much smarter now...LOL
    and it's a relatively simple task - simpler if you have a forklift!
    05' Launch 22SSV
    Saepe Expertus - Semper Fidelis - Fratres Aeterni

  7. #7
    Join Date
    May 2006
    Location
    Nashville
    Posts
    2,104

    Default

    Nice write up Clint. Thanks!

  8. #8
    Join Date
    Jun 2010
    Location
    Oregon
    Posts
    204

    Default

    Yes great ride up Clint. From what Iíve heard you never know how long a flex plate last. I replace the one in my comp at about 1200 hours. When I inspected the old flex plate it was just starting to crack in a few spots.
    We should all complement Clint on how clean he keeps his bilge.

  9. #9
    Join Date
    May 2006
    Location
    Nashville
    Posts
    2,104

    Default

    Okay, well I did my damper plate replacement this past weekend. Some things to cover before hand.

    1) Clint your bilge will now make mine look like sewage, thanks. Now I have to clean it.
    2) As he stated a SBF tranny weighs about 90. However, the 454's does not. It weighs right at 135lbs. I know because I weighed the heavy bastard.


    Here are the steps and some tips. Pictures will be added for visual clarity.

    1) WD-40 is your friend, have a fresh bottle ready. The night before you do this, hose down everything with WD-40. The bolts, the mounts, the mounts mechanism, everything. This will make the following steps easier.

    2) Make sure there is no power on, you will be removing the starter. Remove the starter, and anything else bolted on the bellhousing. This will make it easier, trust me.

    3) I did not remove the tranny fluid lines going to the cooler from the tranny. But I did remove all water hoses from the cooler.

    4) Begin unbolting transmission. There will be 5 bolts on the top side of the bellhousing. Make sure you pay attention as they are all different lengths. It's easy to figure out where they go, but don't get left or right confused. I've seen bolts not go back into a hole they haven't been in for 20 years, and damage can occur to threads.

    5) Now on the 454 there is a backing plate behind the flywheel bolted to the bellhousing. And since the flywheel stays, and the bellhousing does not, this cover plate must come off. Or you will feel like a complete dumbass moron when you realize you've been pulling on a transmission for an hour and can't figure out why it won't move. There are 6 small bolts (size 11mm) that will hold that plate on. 3 on each side, and if it's still from factory, will have silicone all over it.

    6) Now that the tranny is unbolted, and free to move, the mounting brackets are next. Now if you aren't familiar with these brackets, they can be tricky. On the parts that bolt to the transmission, there will be three bolts. Two to the tranny, and one vertical bolt that doesn't look like it goes anywhere. That vertical bolt is a wedge bolt to hold that square bracket in place on the round arm. Loosen the nut on the vertical bolt until it gets all the way flush with the top of the bolt. DO NOT REMOVE COMPLETELY. Then with the nut still on, tap it with a hammer until the bolt drops. The nut must stay on so you don't damage the threads. You may have to tap hard, but this is where more WD-40 can come in. Once you get it to drop, then remove the nut completely. This wedge bolt keeps the whole tranny from moving side to side on those round arms of the mounts.



    7) Now remove the bolts from the side mounts holding the tranny in place, on the side of the tranny. You don't want to move the mount or the bolts holding the mount in place as you might not get them back into place. So by removing the mounts from the tranny, it's easy to line them back up.




    8.) NOW BE CAREFUL HERE. This is where the tranny is now free to drop. So watch your toes and fingers. The tranny is held in place by two guide dowels, so it can't just drop. But if it slides back it can drop off. Once the mounts are free, you can wrestle them to the sides by loosening them and sliding them towards the stringers and fold back. Again, WD-40 will help if they won't move.

    9) Once they are out of the way, time to break out the muscles. WITH A FRIEND, slide the tranny back, and on the floor. With this engine and tranny, you don't have enough room to put on the new plate with the tranny in the bilge. So put down a bunch of big thick shop towels, and lift it onto the floor next to you.

    10) Once out, you can choose to drain the tranny of old fluid (which I did).

    11) Now you should be able to see the damper plate. Hose down the bolts with WD-40, and take a break. Give them about 10 minutes to work in. I don't know how hard they would be if I hadn't, but I didn't care to find out. Loosen the bolts on the damper plate and remove. It's very easy.





    12) Now check to make sure you have the right part by checking the sizes of the old vs. new, and also make sure the new slides onto the shaft of the transmission.




    13) Bolt up the new damper plate with a torque wrench. And time to put it back together.

    14) Do everything in the exact opposite.


    HELPFUL TIPS:
    1) Lower the trailer jack so that the engine is more level. This will keep the tranny from sliding off the dowels when you don't want it to when removing. And also when you're trying to bolt it back up.
    2) When putting the transmission on, you will have to line up the shaft with the damper plate. But something you may not know. The tranny will still free spin even when it slides on the plate. So don't expect the tranny to stop wiggling once on properly. It can be deceiving.
    3) A hoist. A hoist is extremely handy to use. While my shop can do a lot, a hoist that high is what I don't have. So I improvised by using my tower to put the tranny back on. I put ratchet straps around the tower to help take the load off, while I lined it up. Took me 4 minutes to do it. 2.5 of those were to remove the tranny since it was free spinning, and I thought I had done it wrong. See Tip #2.
    4) Put a piece of wood under the back of the motor to prevent tipping that could damage the engine mounts, and make lining it up difficult.
    5) If you can't get the mounts lined up, use a wrench to turn the square headed bolts on the tranny mounts to move the mounts up and down. Loosen the lock nut holding the spindle in place in the middle first. Once aligned and mounted, adjust so the coupler bolts up flush to the tranny. IMPORTANT: MAKE SURE COUPLER AND TRANNY ARE ALMOST DEAD FLUSH FOR ALIGNMENT!

  10. #10
    Join Date
    May 2006
    Location
    Nashville
    Posts
    2,104

    Default

    Here is my hoist device. The tower can lift up my 280lb friends, under a heavy load. So I'm pretty sure it can hold 130lbs for 5 minutes.




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