I'm also wondering if it's a weak starter solenoid. Maybe if the gear teeth don't mesh when the starter gear hits the flywheel, the gear just spins against the flywheel and never hooks up. Trying a new starter is a lot easier / cheaper than pulling the tranny and replacing the flywheel. And if the new starter doesn't fix the problem, you can just tuck it away until you do need a new starter.

 

On my 06 Expedition I am getting a grinding noise intermittently during cranking. After several attempts the starter would correctly engage, and the vehicle would crank. Inspection of the flexplate (flywheel) reveals damaged teeth on the flexplate, not causing the starter to slip on the flexplate, but rather, allowing on that one spot on the flexplate, the starter the achieve cranking speed before engaging the flexplate. Vehicle requires new flexplate to solve this problem. This problem seems unique to these model vehicles so i'd presume its created by mis-engineering by the manufacturer. Hope this helps. - Jon

 

While swapping out transmission on my '98 w/5.4L, I installed a new flywheel.

I had the intermittent grinding while starting as well and upon removal of flywheel, I found that there were 6 teeth ground up on the flywheel in one spot. NAPA had a new one in stock for like $60 or so. Swapped that out and also replaced the power supply cable to the starter as the original had rotted severely on the starter end.

 

Somebody correct me if I am wrong, I am working from memory from about 20 years ago.
The flex plate on a V8 engine will have 4 wear spots. The engine will stop on one of the same 4 places. If just 1 or 2 of the teeth on one of those 4 spots is bad, and the starter just happens to try to engage in one of those bad teeth it will do this. The starter will grind along the outside of the flexplate instead of engaging.
The sarter selenoid on these, again if my memory is correct, has a plunger that goes in the selenoid. When power is applied it acts line an electro magnet pulling the plunger in, which actuates an arm that pushes the drive gear out. We used to re-build starters but the last time I went into a parts store to buy parts to rebuild a starter they looked at me like I was crazy. I was told "you don't rebuild those, you buy a new or rebuilt one". The same with alternators.
Instead of replacing the starter you could replace the drive gear and the selenoid, but I haven't had good luck finding parts for starters anymore in our throw away society.
If you suspect the flexplate as the problem, you can check it without pulling anything.
Pull the cover off the lower part of the bell housing to expose the gear and the torque converter nuts. Visually inspect each tooth on the gear, and feel each one too. Look for them to be worn or to be deformed from wear. The wear will be on the front side of the tooth, not on the pointy end of the tooth. Inspect every tooth on the gear, then turn the gear. It works best to have an assistant turn the engine with a socket and breaker bar while you look. Might even want to mark the gears as you check them with a grease pencil or a soap stone. Be sure to disconnect power when turning the engine just in case something happens and it tries to start, and keep your booger hooks out of the bell housing when the assistant is turning the engine.
If replacement is required you can pull the engine or move the transmission back. You only need enough room to get a ratchet and socket in to remove the bolts, 4 to 6 inches should do. So, it is a lot easier to slide the transmission back!
If the gear teeth look good, of course inspect the starter gear. If that is good, it is probably something in the wiring not getting full power to the selenoid, or the selenoid sticking for some reason.
If it is the flex plate ring gear, it could be just 2 or 3 teeth. The engine just happens to only stop on those 2 or 3 teeth every once in a while.

 

deputydog - MY FIL (former Ford mechanic) told me the same thing (they only stop in 1 of 4 spots). I never knew that before.

 

The engine will always stop with one cylinder on a compression stroke. When you cut the power to the plugs, the engine will turn itself to a stop. Of course, if you have 0 compression it will just wind down until friction stops the engine from turning. With compression it will stop when a piston is on the compression stroke.
Next time you have a V8 apart, watch the pistons as you turn the crank. There will be 2 pistons somewhere in the engine that will always be very near, or at TDC. So, the compression will always stop the engine with the gear ring at 1 of 4 spots. Those spots will be seen in older engines as a 3 inch or so strip on the gear ring that shows more signs of wear than any other place.
I may be wrong, but 6 cylinders should always stop in the same 3? places. It may be 2, I don't remember exactly.
So, when you check your ring gear you won't have to check the entire gear, you will see the wear on 4 spots. 1 or 2 teeth on one of the spots can give you a problem on occasion, on the 1 time in 100 that the engine stops with that exact worn gear where the starter will hit.
In the past machine shops could pop those gears off and press a new gear on, but I am sure it is way cheaper to just by a new flexplate. I doubt you could even buy the new gear in todays throw away world!

 

Yeah, I don't think you'll find a machine shop or garage that will replace a ring gear for the $60 price tag that NAPA gets for a complete, new flexplate.

Plus, the original ring gear was welded on to the flexplate, and the replacement was the same way.

 

I might be mistaken about replacing the ring gear too, it has been a long time since I have worked on one. Back then, whenever the flex plate needed replaced I just went to the junk yard and picked up a used one.

 

Well after two new starters and lots of thinking about replacing the flexplate my starter was still grinding. Yes at lest once a week sometimes twice I would try starting it and hear a loud screeching sound, that would be the starter grinding on the flexplate. After a couple of trys it would start. Then I found a post about a maybe a bad ground on the starter. I checked all the wires on the starter and up to the battery, no
problems there. Then I found two smaller wires coming off the battery wire harness both ground wires. One was grounded to the firewall the other next to the radiator. Make sure and clean all rust and corrosion from these grounding points. After removing and cleaning both ground wires, no more grinding!
Its been over two month and not one time!!! The dealership and another shop (which replaced the starter) both suggested replacing the flexplate.
Crazy right?

 

i tested my battery with a volt meter with it hooked to the battery and when i would start the truck the volts were going down to 8 volts. So i went and got a new one and with the cranking amps up where they belong it has not happened to me seems to be that older batteries are the problem. not enough cranking amps may be the cause.

 

Mine does it all the time I can wiggle gear shift and will start is wiggleing shifter just coincidence someone told me to do that

 

A cracked flex plate and or a ballooned torque converter should be the problem . Age can crack the flex plate at the crank mounting bolts . A ballooned torque converter can also crack the flex plate . The only fix is replacing both items .

 

A cracked flex plate and or a ballooned torque converter should be the problem . Age can crack the flex plate at the crank mounting bolts . A ballooned torque converter can also crack the flex plate . The only fix is replacing both items .

 

I had that problem. Replaced the battery cables running to the starter with 2 gauge and it hasn't done it since.

 

Fixed - Two red wires where they join just before connecting to the battery. Cut the tape off that covers the connection and clean the wires
thoroughly. You may even have to pry them out of the factory connection and install a new terminal end.

Rule of Thumb: If it happens intermittently the problem is Electrical. Still doing it(screeching). Check the ground wire connections(4) to firewall and clean oxidation.