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Torque converter/flex plate possible noise?

C

canadianwheeler

NAXJA Forum User
Location
canada
My setup is a 92 xj, 4.0 L, AW4, 31's, 5 " lift, 4.10s

Anyways... About a year ago i was getting this rattle comming from my torque converter quick check of the flex plate bolts told me they were loose. Tightened them up. NO more noise.

The other day i started to hear the same noise again but only at about 60-65km an hour. Not any other time. I figured it was the flex plate bolts again so i pulled the inspection plate and to my surprise they were all still torqued down perfect.

Anyone have an idea what it is? It sounds like a metal on metal rubbing sound. Like the flywheel is rubbing on the housing. When i speed up over 65/kmh or low down under 60/kmh is goes away.
 
I just gave someone else tips on checking for flexplate cracks - in the last day or so.

The flexplate will usually crack around the hub, where it bolts to the crankshaft flange. Remove the inspection plate, take a bright flashlight and a stout screwdriver, and GENTLY pry the flexplate back and forth (toward and away from the engine) while you watch the hub.

Flexplate cracks on XJ's are just common enough that everyone should know how to do this - and it's my first thought with the symptoms you describe.

If you need new bolts, and OEMR ones cost bux, ARP has a set of Pontiac flexplate bolts that work neatly - they're threaded 1/2"-20 x .500" Don't use "regular" bolts for this, the flexplate bolts are designed a bit differently.

The torque converter bolts are, natch, metric. I think they're M10x1.5-15 or M10x1.5x20m/m. They're also "place bolts," and I have yet to find an acceptable substitute for OEMR.

5-90
 
Parts are not expensive but you need to pull either the engine or the transmission to install it.
So your looking at $400.00+ parts so around $600.00 in a shop.
 
Flexplate was $40-50, last time I got one. You can't cross - if you've got a RENIX rig, you need a RENIX flexplate.

Bolts, if you need them, I don't know. I had a set of ARP's around that worked neatly. They were for a Pontiac with A/T - 1/2"-20x.500" "place" bolts.

Pull the transmission, pull the torque converter, and an impact wrench comes in REALLY handy to break the flexplate bolts loose. Replace flexplate, secure bolts to torque spec with LocTite #242. Reassemble.

I've been able to do it in an afternoon, without power tools. I do have a transmission jack, and that comes in VERY handy! You'll only need to pull the transmission back far enough to let you work - you don't have to pull it all the way out.

5-90
 
This sucks... i guess it needs to be the flex plate. I cant think it would be anything else. Its just like when my bolts were loose before but it really shakes below my feet now.
 
Like I'd said, you can probably do the job yourself. It can even be done without impact tools (I have done so.)

You'll need the flexplate (natch,) but you should also get a front pump seal for your transmission (since you're going to have it out anyhow,) and you might want to do your CPS, if you've got 100-150K or better. I'd think about doing the transfer case rear output seal as well, since you'll also be there.

ARP #200-2904 will work for replacement bolts - they're listed for a Pontiac, but have six of the correct size bolts. It's the kit I use.

I'd also replace the upper bellhousing bolts - you'll need an E12 socket to get them out, and they can be readily replaced with 3/8"-16 bolts (I'm thinking they're about 1-1/2" or 1-3/4" long, but take one out to make sure. Hex heads are just fine.)

5-90
 
UPDATE:

So before diving in and pulling back the tranny i wanted to take it to a shop to get there opinion. The owner of the tranny shop took it for a test driver with myself riding shot gun. Like it has been doing to me at about 65 km/h the truck started getting a vibration and a ticking noise. So the mechanic tried doing the same thing with the transmission in 3rd and 1-2 gear. In all gears at 65 km/h the same thing. Which makes me think that is has nothing to do with the RPM's only speed related! ?

Then he tried somthing i never thought about. He brought the jeep up to 80 km/h with then just the engine off and cruised. When the jeep slowed down under its own power the noise came back (around 65/kmh).

The mechanic says since the noise was happening with the engine off that should rule out the flex plate and tourque converter? Sound right? Does the flexplate stop turning when the engine is shut off?
 
with the auto trans in neutral and the engine off the flexplate should not be moving, seeing as your problem is speed sensitive..........your gonna have one hell of a time finding it, i had a similiar problem last year, couldn't track it down but sounded like my torque converter bolts again, checked they were fine, spent a few hours under my rig, just throwing wrenchs on any and very bolt/nut i could find.............don't know what one it was but the sound went away. Do you have any driveline vibes?? Just another thought, my exhaust hanger on my t-case mount was broken before too and gave me a knocking sound at times
 
I'd take a look at drive train components. Inspect your u-joints closely. You may even try removing the drive shafts one at a time to see if the sound goes away. Check the u-joints on your front axle. Pull the wheels off and check brakes, bearings, etc. Have the tires balanced.... You get the idea. Get under there and start nosing around.
 
heeperman said:
with the auto trans in neutral and the engine off the flexplate should not be moving, seeing as your problem is speed sensitive..........your gonna have one hell of a time finding it, i had a similiar problem last year, couldn't track it down but sounded like my torque converter bolts again, checked they were fine, spent a few hours under my rig, just throwing wrenchs on any and very bolt/nut i could find.............don't know what one it was but the sound went away. Do you have any driveline vibes?? Just another thought, my exhaust hanger on my t-case mount was broken before too and gave me a knocking sound at times
Click to expand...


Thanks for the response. The jeep was in "D" when he turned it off then threw it into "n" to start it again.

So for sure when the engine is off even though we are crusing a decent speed the flex plate should not turn??? I need to know for sure so i can rule this out.
 
I dont have any drive line vibes. Been running the same lift/tires for about a year now. It defently feels like its comming from the front end. I really hope this does not turn into one of those "Name that sound threads".
 
BrettM said:
pull the front driveline first, that's the easiest place to start
Click to expand...

I am driving around right now with out a front drive shaft. Since i am waiting to install my front gears. (running 2 different gear ratios)
 
ABN146 said:
Any luck on finding out what was going on?
Click to expand...

I still never found out what it is. I checked the flex plate and it has no cracks. My thoughts are now leaning towards the rear drive shaft..... At the moment i just craked the music a little louder
 
Two more things to help eliminate the source. Put the xfer case in neutral and run through the gears. If noisy, then it's between the xfer case and engine. Put the rear end on jack stands and if noise is present to eliminate anything in the front. If you're daring, you can crawl under and track the noise down in either case. Of course, not hearing the hearing the noise isn't conclusive.
 
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