Jamie57

Got a line on a very nice (Really!) 2000 XJ with a supposed blown motor.
She says it's a rod gone but I've read so much about the flex plate making a similar noise. I've even heard it in person when I wanted to purchase a 98. They wanted way too much money for the jeep even if it was only a cracked flex plate and not a spun rod. I didn't tell them any different. It's still for sale last I heard.
Anyways what I thought was if I take off the inspection cover and take off the bolts holding the converter to the plate. Then push the converter back as far as I can into the transmission.
Now I want to start it up and listen.
Here's my question.
Do you think it will still make that horrible knock, now that there is no converter attached to it?
I'm thinking it shouldn't because there is no load on the flex plate anymore.
Basically it's just a spinning disc now. It no longer has that heavy mass of the converter to spin up and make the plate .... well, flex.
Am I on to something or will it still "Knock"?

cherokee-matt

Best thing to do is remove inspection cover and inspect the flexplate for any cracks. If you pull the convertor off the flexplate and something shifts and grabs you might make one heck of an ohh s**t. Could also isolate the noise with a mecanics ear. Check the oil for metal first before you waste your time if it is infact a rod spun.

Jamie57

Have read several threads where guys have not seen the cracks until the flex plate is off the vehicle. They're up near where the plate bolts to the crankshaft. Don't know how you'll be able to see that with the converter in the way. Which is why I'm trying to find a shortcut to actually removing the engine or transmission to diagnose this.
Also the amount of metal in the oil may not be enough to tell.

figure it this way.
If what I do works and it's the flex plate. it's only $100 bucks for parts and a few hours.
If it's the engine then I have to go about sourcing one and all that other stuff.
Time spent finding out the problem my way Maybe 20 minutes.
Pulling the trans or engine is several hours.

A_Jeepr

Cracked/ broken flexplate sounds like ringing with a knock to it.

Jamie57

Thats exactly the sound I heard on the 98.

What I want to know from someone who has fixed this problem is if I disconnect the converter will the sound go away.

That is a cheap and fast way to tell if it is indeed the flex plate and not a spun rod.

Then I can spend my time and efforts on fixing the problem instead of spending a lot of hours taking everything apart.

A_Jeepr

DO NOT remove the converter...simply replace the flexplate. only way to fix it. and make the sound go away. if you let it go too long it will fly apart, breaking a lot of things including you or some poor bystander.

Seen flexplates at the track come apart, go through the bell housing through the car, through a wood fence and lodge in the side of a car in the parking lot.

Jamie57

Maybe i'm not making myself understood.


I only want someone who has done this before to respond to my question.
If you have not changed a flex plate because it was cracked PLEASE follow this thread so we will both learn something.

I only want to DISCONNECT the converter for a couple of minutes to see (hear actually) if the banging goes away. THEN I will know if it's the flex plate or not.

BUT I don't know if that will work which is why I'm asking those WHO HAVE done this repair on their Jeep.

I'm assuming that if the load of turning the mass of the torque converter is removed the bang should stop.

BTW I'm going to do this ANYWAY. I was just hoping someone else had thought of it first and had tried it.

Jamie57

So riddle me this. How do you remove a torque converter without removing the transmission?

AND I'm trying to find out if it really is the flex plate and not a rod bearing.

A_Jeepr

the torque converter rides on a shaft, which pilots into the crank. you must remove the tranny to remove the converter.

furthermore, the torque converter and flex-plate act as a mass on the back of the engine so it will run correctly. Never done one on a Cherokee, but plenty of TH350s, 4L60s, ect. they are all smiler in design, and operate the same way, basic automotive physics.

Its easier to check rod bearings, remove the oil pan, use a plasti-gauge on each rod bearing cap, and make sure they are with in spec.

http://auto.howstuffworks.com/auto-p...-converter.htm

mopwrd340

dont run the motor with the torque converter un hooked u could damage the lugs on the front of it .remove the insp cover and look up in there you will see if its cracked . turn the motor over with a big screwdriver all the way around to see if its cracked ,

Jamie57

Too bad for the doom sayers. I did it.
There was at least an inch clearance from the plate to the converter attachment lugs.
Started right up and ran. Didn't explode and kill and maim the entire country side.
Trouble was, it really was a rod bearing.
Plus it had a big *** hole in the drivers side floor.
More work than I want to put into it. Other than that it really was a nice clean jeep. Black with black interior. Tinted windows and brand new tires.
Up in the Kwartha Lakes area if someone else needs one for the parts. Could probably get it for less now.

Jamie57

Did you even read my question? BTW it actually rides on 2 shafts one powers the internal fluid pump and the other the input shaft.
15 years as a Class A mechanic here in the great white north.

A_Jeepr

excuse me for wasting my time trying to help since you think you know is all having been a mechanic for "15 years" I have been working on stuff for 7 years (racing, Jeeps, and general repair of anything) and apparently I don't know what I am talking about.

Thanks for the test it was well appreciated.

Jamie57

I didn't say that. I said "Did you read the question?".
You gave helpful information but it wasn't pertinent to the question.

The 15 year thing was just to let everyone know I wasn't a complete noob. I do have my moments.

And I still can not believe I am the only one who has ever run an engine without the torque converter being bolted to the flex plate.

A_Jeepr

I have never heard of it personally. I do know that it along with the flex-plate helps the engine keep momentum when running.

eah well nevermind, got off topic a bit, no hard feelings