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intelligence on drive plate / flex plates

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Old 11-27-2018, 01:08 PM
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Default intelligence on drive plate / flex plates

Unlike many other transmissions, the Discovery has a two plate system to connect power from the engine to the transmission.

Starting from the block and working towards the rear of the car...
1. The drive plate with reluctor tabs for the crank sensor and the starting ring gear on the outer edge. This is attached to the main output shaft of engine (#1 in the diagram)
2. a spacer
3. a flex plate which bolts to the torque converter (#7 in the diagram)






These items are bolted together and form the 'drive plate assembly' The second disc, aka the flex plate (#7), allows for longitudinal movement (front to back) of the torque converter.

Over thanksgiving my truck ruined the starter...


I have also heard, intermittently, what sounds like a very light bottom end knock. I thought I might be looking at replacing journals but now I'm putting 2 and 2 together and am suspicious that my drive plate is cracked or faulty in some way.

Talk to me fellas. What am I looking at? How deep is the water? Anybody with a lift want to help drop a transmission?

So, I'm looking for your educated thoughts, experiences, and information.
 
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Old 11-28-2018, 09:50 AM
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That's not what I expected to see. Are you sure that the two bolts securing the starter were bolted up tight. It almost looks like the starter rotated when you tried to turn over the motor. I was expecting chewed up pinion gears. Is there any damage to the ring gear?
 
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Old 11-28-2018, 10:01 AM
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Third time trying to post to this ****ty website.

Did the broken parts of the starter come out when you removed it? If not have you removed the bell housing inspection plate (round plate on the bottom) and the lower front cover? That was you can inspect the ring gear for damage.
 
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Old 11-28-2018, 10:50 AM
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That is my next move. Get it parked in a spot where I can leave it and remove the inspection plate and hopefully get a clear idea of what is going on. What types of things/sounds/symptoms should I be looking for? I doubt I'll be able to see a crack in the flex plate since it will be behind the drive plate.

I was stranded in NJ and an indy shop did the work. He said he made sure to fish out all pieces that were in there.

That said, I don't really trust the guy and he charged me like a dealer would, maybe a bit more. That story is for another time.

My bottom end sounds similar to this, but not nearly as loud.


Assuming I do proceed with the project, what else should I be doing while the trans and engine are separated? Rear crank seal?
 

Last edited by WaltNYC; 11-28-2018 at 12:09 PM.
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Old 11-28-2018, 03:41 PM
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Sadly, you're not really going to know what's wrong or how bad it is until you get the engine and transmission separated. I don't know what damage may have been caused by the remains of the starter banging around in the bell housing. That rattle towards the end of the video sounded similar to the rattle I had before the reluctor rings sheared off the drive plate on one of my DI almost 20 years ago. If it's a flex plate, they're cheap enough new. If, and I really doubt it, you need a drive plate I have them, as we've discussed. Get it apart and post up pictures. We can go from there.
Cheers,
Paul
 
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Old 11-29-2018, 12:50 PM
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Originally Posted by Paul Grant
Sadly, you're not really going to know what's wrong or how bad it is until you get the engine and transmission separated. I don't know what damage may have been caused by the remains of the starter banging around in the bell housing. That rattle towards the end of the video sounded similar to the rattle I had before the reluctor rings sheared off the drive plate on one of my DI almost 20 years ago. If it's a flex plate, they're cheap enough new. If, and I really doubt it, you need a drive plate I have them, as we've discussed. Get it apart and post up pictures. We can go from there.
Cheers,
Paul
I'm gonna grab a boroscope and give it a shot. It may not be definitive, but it might.

If not, I'll post a video of the sound and let everyone else guess along with me.
Could be a week or two before the garage where I'll park it and potentially do the work is ready.
Thanks for your thoughts. I'll reach out if I need the drive plate.
 
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Old 11-29-2018, 05:05 PM
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Everytime I see a flex plate thread I always wonder how many engines have been condemned by folks that had bad cam bearings or a jacked up flex plate
 
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Old 11-30-2018, 06:26 AM
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On the basis that I will go forward and replace the flex plate... I'm playing with the idea of pulling the engine (rather than dropping the trans), putting it on a stand, and doing the head gasket which is the original. I generally take the position of "if it ain't broken, don't break it", but this seems like an opportunity that I won't have again.

Is this mushrooming too far? I'll be working on this on weekends. No real time constraints, but it is my only 'permanent' vehicle (I can rent, borrow, and zip car as needed) so I want to have it back on the road in 3-4 weeks. I can get some help lifting and replacing the engine, but the rest of the work will be solo.

Is this a crazy idea?
 
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Old 11-30-2018, 07:44 AM
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No it's not crazy and with a bit of planning easily done.

​​​​​​Make sure to order all the bits you want to replace and have them on hand. Look over the engine bay for old hoses, belts and cracked hard lines order those to. Also a good time to do plugs and wires.
 
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