Loose Flexplate bolts

Figured out the rattling coming from my 4.0 Removed the inspection cover and I could actually turn the flexplate bolt that I could get to with my bare hands. A couple of questions: 1) what size bolts are these (2) I can tighten the one on the bottom easily enough but what about the others (3) how many bolts are there. Should I just hit the starter until the next bolt is reachable?

Dragline said:

Figured out the rattling coming from my 4.0 Removed the inspection cover and I could actually turn the flexplate bolt that I could get to with my bare hands. A couple of questions: 1) what size bolts are these (2) I can tighten the one on the bottom easily enough but what about the others (3) how many bolts are there. Should I just hit the starter until the next bolt is reachable?

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I would take the fan and the belt off and turn the motor with a socket while the tranny is in neutral. You are lucky if your flexplate didn't strip out or crack.

If it were my vehicle I would pull the tranny ( a friend or tranny jack might be helpful) and take the flexplate off and inspect it. Better to be safe than sorry.

Oh yeah, I think there are six 1/2 or 13mm bolts, but I'm not quite sure. Its been four years since I have taken my tranny off.

The hub bolts are 1/2"-20x.500 - ARP has a Pontiac flexplate bolt kit that works for those.

The outer bolts are M10x1.5(? not sure about the pitch offhand) "place" bolts that should be replaced with OEM. There are four of those.

Use LocTite 242 or better on all bolts when reinstalling.

You would be wise to check the flexplate and see if it wants replacing, since you're down there anyhow.

As far as turning the engine proper, just put a 3/4" socket on a long-handle ratchet and stick that on the crank nose bolt. Should be no trouble.

5-90

Sorry to jack the topic, but what's the big deal with the flex plate? What's it's purpose? What kinda noises does it make? I never understood and maybe that will solve some of my noise problems. Thanks

Mine made so much noise that ppl turned to see where it was coming from driving down the street. We though it was the TC, but upon removing the tranny and TC we found the noise was the flexplate.
If it breaks altogether you won't have anything for your Bendix to turn to start your engine. Not that expensive and is a common prob. on auto. XJ's

dizzymac said:

Mine made so much noise that ppl turned to see where it was coming from driving down the street.

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Ditto on the noise, it was downright embarrassing. Tightened them all up and it's now as quiet as ever. Once I got one tight, I could actually turn the engine from underneath using a wrench on the bolt to get to the next one.

Dragline said:

Once I got one tight, I could actually turn the engine from underneath using a wrench on the bolt to get to the next one.

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That's how I did it too; there's enough room that you can just get 90* worth of the flexplate/converter showing and can tighten or loosen the bolts and turn the assembly to the next bolt.

I have an 89 5 speed...
So no flexplate like an auto...
But I have an odd intermittent rattling kind of noise at idle. Sounds like it's coming from the lower back engine/trans area.
It sounds like a wooden spoon banging on a metal bowl
Might my flywheel also have this issue?

dont mean to sound dumb, but does anyone have a picture of the bolts that need tightening? if its a relatively easy procedure, I wouldn't mind checking mine for tightness as well. thanks,

Nav

53guy said:

Sorry to jack the topic, but what's the big deal with the flex plate? What's it's purpose? What kinda noises does it make? I never understood and maybe that will solve some of my noise problems. Thanks

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The flex plate is a thinnish (1/8" or so) metal plate that serves as the mechanical coupling between the engine and the torque converter. The torque converter itself has enough mass to serve as a flywheel - and the flexplate/torque converter assembly answers the purpose of a clutch in a manual transmission (but the clutch is a mechanical 1:1 coupling, while the torque converter is a hydraulic coupling that allows slip - unless it's "locked," the torque converter is never 1:1)

A cracked flexplate can sound like rod knock - instructions for checking it out have been posted here numerous times before - at least twice by me.

Note that the torque converter screws and flexplate screws are not "standard" hex head screws - they are, as I mentioned, "place bolts" - they're designed to clamp with the outside portion of the screw head, and to distribute the shear load on the screw over a greater area of the screw (not really what's going on, but that's the easy way to explain it.) I wouldn't use replacement hex head screws from the hardware store for this job...