Childeric

Kind of embarassed to ask this question... but, I'm doing an engine swap cuz some "nice old man" lied thru his teeth at me, but I'm seeing something odd here and would really appreciate some feedback. I'm using the original TC that came in my 99XJ and I have two flexplates which are identical (original and from the donor motor). The FP bolt holes line up with TC pattern correctly on both, but what I have here is the holes in the FP (both) are bigger than the bolt shaft which secures the TC. The holes in the FP are the perfect size for the crank bolts and the TC bolts are like a whole size smaller-WTH? Is this normal? I can't hardly believe it is, but if so that might explain countless noisy/destroyed FP's. These holes are not oblong/worn, they are just BIG. Also I'm pretty sure I don't have the wrong TC in the jeep but at this point nothing would shock me. I may have to look up some sort of sleeve to take up this slack... ridiculous!

SG Mason

I have a brand new, unused flex plate waiting to be installed. I will measure the hole size when I get out to the garage today and post the measurements when I take a break from working on the Jeep.

I also have a donor transmission waiting to go in my 98 that has a torque converter on it so I will take a look at the bolt size on that too.

SG Mason

OK I just measured the bolt holes in my new flex plate and they are all roughly 0.52". I say roughly because it is a little hard to get accurate measurements when your hands are shaking It isn't too cold here, 46°F, I just have hand and arm issues and the dampness is playing havoc with them today.

Childeric

Thank's SG, I will measure, bet they are the same as mine. If they really are commonly larger than the bolts, that's the most nutso thing I've ever heard, pun intended.

Childeric

This from the JeepForum; "The flexplate should take 1/2"-20x.590 place screws, and the torque converter wants M10-1.5x15m/m place screws".

SG Mason

I got my torque converter bolts out and measured them at 0.385" or 9.78mm.

Childeric

Yeah, they are a 10x1.5x15 in a half inch hole I have a fix I'm going to try, should work.

cruiser54

LocTite.

SG Mason

I think the reason for the larger holes is because it is a "flex" plate. It needs to be able to flex and if the holes were the exact size as the bolts it wouldn't be able to flex as easy and put more stress on the plate itself.

LocTite and proper torque should be fine, but the bolts and threaded holes must be clean for the LocTite to work properly.

Childeric

Hmm, ok I suppose that could be true about the "flex" but not sure what oversized holes would do for that exactly, not completely convinced yet. I'm def using the loctite red, but I seriously doubt it's strong enough to increase surface bond so much that it could keep the bolt head from sliding around because of 2mm of bolt play, under 200hp. I dunno I really think this may be why these rigs are prone to problems with the flexplate banging around and then cracking.. maybe Lee Iacocca will chime in here and set me straight.

Childeric

Oh well, this is what I did, will keep an eye on it.

steelybill

Kinda seems to me that if there is any movement of the bolts in the plate, they will never remain torqued up tight.
That's either a strange set up, or the wrong parts, or.......

It may be worth the effort to locate some bushings that could be cut to sit in the holes, just a bit shorter that the plate thickness.

Another way would be shoulder bolts.....??

Childeric

It's a strange set up, i'll watch them.

CCKen

If anything, use Blue Loctite, not Red.

Here's some data concerning new flexplate bolts.



These 6504383 bolts are PT Cruiser Clutch/Flywheel bolts, and replace the original Jeep drive plate/TC bolts. If you were to order the orignal bolts at the dealer they would sell you these replacement bolts.

You can buy them from your Chrysler dealer or here:

http://stores.revolutionparts.com/mo...ch_str=6504383

Note that these bolts have a larger head surface area, and a larger hex head size.

I installed these bolts on my new flexplate installation and had no problems installing or torquing them.

Childeric

Yeah those bolts do make more sense, thanks. I am curious tho to see if my cone head bolts work though... Do all AT flexplates use over sized bolt holes inherent in the design? Already used red loctite, going to take something going WRONG for me to change them now ;-)