OK, I know this isnt blazer related, but I find so much help here that I figure Ill try my luck with you guys here cause Im sure I will get the good help I know I can rely on this forum for.

Wifes 1994 Explorer. 4.0V6, 4x4, A4LD transmission. Been parked a while cause its the rainy season and I didnt want to tackle this job and catch pnemonia so Ive had it parked for a couple months and been doing the car share thing. This truck is a gem and she really likes it... I hate it cause I cant scan the ABS in it without a special scanner and its a FORD, and friends dont let friends drive fords.

When starting it makes a horrible grind/screeching just like when the ring gear is worn out. I pulled the starter and looked in there, the ring gear and starter bendix are in great shape still. Sometimes it will start just fine, sometimes it will only grind until I manually rotate the engine a little. I pulled the starter when it was on a spot that it will only grind thinking I might be missing some teeth and nope, all the teeth are still there and none are chipped.

When running at idle the truck shakes like a cheap motel mechanical bed.

When revving it up the shaking gets horrible and at about 2000RPM it makes a metallic whirring noise and the vibration smooths out.

Anything about 2000RPM and that noise is so bad you almost need earplugs but there is no more vibration.

I have used my stethoscope to locate the noise to inside the bellhousing, I thought it might have spun a rear main berring to begin with. I have tried looking in behind the flexplate with a mirror to look for cracks, I cant seem to get a good veiw of this no matter how I bend the mirror and flashlight. I have removed the spark plugs and had someone rotate the crank by hand while I look in the starter hole. It seems to me that the flexplate is about 1/2cm egg shaped, as in I dont think its round anymore... This would explain why there is a 'dead spot' where the starter will only grind, and why it will start just fine other times. I can feel that all 3 bolts that join the flexplate to the TC are still there, well, the heads are there, cant tell if they are broken or not.

My question is this:

Am I retarded thinking that its possible for the flexplate to get out of round...? Is there something else I should be looking at before I go remove this driveline and exhaust to get at the flexplate? Is this something i can tell her that she caused? She likes to go from forward to reverse while still rolling slowly and hits the gas before the transmission engages sometimes resulting in a clunk into gear, it also has a trans fluid leak that she never tops up (I do when I fill her tank) and when the fluid is low she says she has to rev it up a little to get it in gear (I know I know she should get out and add fluid but she "got not time") This thing wont go into gear when its 1.5 litres underfull...

I have seem broken flexplates before, but not with these symptoms. All the ones I have seen broken before cracked around the 6 bolts and the flexplate grabbed onto the broken off part attached to the crank like a socket grabs a bolt... and those made a rattle like an impact wrench on very low speed does and made a "Clang" sound when going from reverse to drive and back... No vibrating and the vehicles were driveable. When taken apart the flexplate was in 2 separate peices with hammer marks where they used to be one peice.

Opinions please, I want to get cracking on this job this weekend so the wife will stop driving my blazer... Shes hard on cars and I would rather she be hard on her own car.

 

Sounds like you have a bad spot on the flex plate. It could be bent... Does it have a dust shield underneath?

Mark a spot on the flex plate and rotate it around while you check for any deviation in roundness and flatness. Measure from a fixed point on the block for both of these measurements.

 

I dont have a dust cover, but through the hole where the starter bolts up I held a bolt up crudely to see if there is a bend or deviation and there is no bend in it front to back, but it seems that its egg shaped... Like a camshaft lobe... Just a little bit. Front what I remember this flexplate should be straight and true...

So it is possible for this part to get all screwy on me. If its all busted up Ill get a photo.

Thanks Kyle, I guess Ill start pulling this truck apart once the rain stops where I live.

Good thing is a NEW flexplate is only $55 at the local NAPA center.

Its too bad that transmission is so large and going to be HEAVY as well... And I have to undo the exhaust where it goes 2 into 1 so the trans can get past the pipes, awesome. At least I can try and fix that fluid leak before she takes out the transmission one of these days too.