OregonXJ91

I have a 91 cherokee automatic and i have narrowed my knocking sound to a cracked flexplate.

How do i go about replacing it and what do i need parts wise? and do i have to drop the tranny to replace it? All feedback helps thanks.

ThatPurpleXJ

It would probably be easier to drop the tranny then the engine but that really is the only way. I do have an extra flex plate off a 96 that I put in my engine. If you need it let me know I'll sell it to you

5-90

Four screws secure the torque converter to the flexplate, remove these. (15m/m wrench, I believe.)

The transmission and transfer case may be set back as a unit - remove the bolts & nuts that secure the lower inspection plate, then the four screws that secure the transmission to the engine. You will need an E12 "external Torx" socket to remove the upper screws, these may be replaced with standard hex head screws. They are threaded 3/8"-16, although I do not recall the length. www.kelleyswip.com/tech.html and follow the links, or match the lengths at the hardware store.

Six screws secure the flexplate to the crankshaft, they should take 11/16" or 3/4" sockets. They're torqued to ~105lb-ft, so you'll need some effort to remove them. You may either hold the flexplate or the crank pully - if you hold the crank pully, remove the belt, use a strip of belt to cover the ribs on the pully, and use a chain wrench to hold it (it's the best way I've found so far - I have known cases where the crank nose screw has ruptured when using it.) A similar method may be used to torque the screws back down - just reverse the handle on the chain wrench.

Consider the use of LocTite #242 (or equivalent) on the flexplate-to-crank and torque converter-to-flexplate screws to be mandatory! Replacement of the screws is cheap insurance, but don't get them at the hardware store. ARP makes a kit for Pontiacs that will work for the flexplate screws (1/2"-20UNFx.590", 6pcs,) and some digging may turn up an equivalent for the torque converter screws (M10-1.5x15m/m, as I recall. Four pieces.) Both of these applications use "place bolts," which you won't find at the local hardware store. You won't find the proper lengths anyhow (and common hex head capscrews will fail in this application - they're not made for it.)

Note that the flexplate is "keyed" through having one screw out of the six located slightly "off-pattern" - if you can't get all of the screws started, you need to spin the flexplate on the crank flange until you can (this is because the base timing signals are derived from the flexplate and the trigger notches on it - if it's in the wrong place, the engine won't run! That's why I tend to suggest "painting" one of the screw holes as a timesaver, when you have to remove the thing and reinstall it later.) The torque converter is not similarly keyed - once you get one screw started, the rest will mate up.

It is recommended that the torque converter be installed in the transmission before the transmission is pushed back into place - there are only two positions that will allow it to fit, vice four for the flexplate screw alignment (there are drive notches in the TC snout for the transmission oil pump. You do not want to break the drive tangs for the oil pump!)

I would suggest inspection of the TC snout (use a fingernail to feel for a ridge) and replacement of the front pump seal while you're in there. Disturbing that seal will likely lead to failure, and you'll kick yourself in the head if it starts leaking next week. You'll need a seal puller to remove it (cheap tool,) and a small mallet to install it (I use a brass hammer - denser than steel, smaller head, and it can be filed smooth more readily later.) Smear some RTV black around the seal shell before installation, and grease the snout of the torque converter prior to assembly (the former to assist sealing around the perimeter, the latter to help prevent scuffing the lip and premature failure.)

Torque specs should be on my site - www.kelleyswip.com/tech.html and follow the links. If I don't have your year listed, I should have something close to it, use that. (Torque specs for subassemblies didn't change much over the years, so far as I've seen.)

djgrayxj

Note from DJ
Here is some information I have from some previous post.

External Torx bolt info on tranny bell housing
There are two bolts at roughly 1:00 and 11:00 looking forward. Heads (if OEM) are an E-12 "External Torx" using proper sockets is highly recommended (Lisle makes a good low-buck set of E-Torx sockets - check Sears or your local parts house that carries Lisle.)

Note that those bolts are 3/8"-16 (SAE), so they can be replaced with a hex head cap screw of the same length and thread. I highly suggest that you do so it will save you headaches.

These two bolts are best removed first before any of the lower easier bolts with the proper socket. The reason being you don’t want to round of their heads [which will only create more problems]. And by removing them first you prevent the possibility that the transmission bell housing and the engine will start to separate at the bottom first, which will greatly increase the difficulty in removal of the two bolts because of increased friction regardless of their head configuration.

djgrayxj

Question to OP Oregion91XJ from DJ
What information are you basing your decision on that you have a cracked flex plate?
If you share that information with the rest of us someone might come up with easier and cheaper fix.

OregonXJ91

What do i paint to keep everything lined up?

5-90

Remove the first screw.

Apply paint such that it will show on both parts (I usually give it a quick blast of some bright colour from a small rattle can - typically something like Safety Orange or Safety Yellow.)

Go grab a sammich, give the paint some time to set up.

Resume job.

I do the same thing with driveshaft yokes when I take them apart, or any other rotating assembly. Theoretically, it's not necessary. Practically? It's a good idea, just in case the theory is off...

Firestorm500

Are you sure there's not some magic stuff in a bottle that can be bought at Autozone that will fix this?