Is my tranny so special?

I have a 1990 XJ with automatic tranny and 4WD, it has been making a terrible nock and and sounds like it is going to come apart if the RPM's are increased.
Yes the knock has been checked out, motor replaced, twice
(dont ask), and still the same knock exists!
Now with all the knowledge of a replaced motor, it seems fair to say, "It's the tranny making that noise", so now it's time to find a replacement.
After the ugliness of replacing a motor too many times, I want to find a reliable replacement, rebuilding estimates are in the range of $2000.00, I found a "new" factory replacement on E-Bay for $895.00 plus shipping!!
When I ask "why is it soo expensive", I'm told that my jeep has a limited amount of years that can go in it.
I'm hoping to get some guidance from you folks here at as this is the place where most of my real tough questions have been answered in the past.
So is it true, is my tranny so special, or are there other year tranny's that will work?
Does anyone out there know what other options I have at this point?
I miss my jeep and want to get back in it.
Thanks in advance for any and all input!!

What makes you think it's not the flex plate or the torque converter?
All 4 speed auto's are expensive to replace or repair.

Open the inspection cover and make sure all four bolts holding the torque converter are tight (I don't have the torque values handy right now). Buy an AW-4 from most any 87-01 XJ but be aware that the output shaft can have either 21- or 23-spline...earlie ones had the 21 and I don't have info on when that was changed. See my post in Mod Tech from 4-5 days ago with 21 and 23 spline in the title if there's any more info on that.

It sounds like your describing the noise I had when the bolts holding the fly wheel backed out a little. Or that maybe what Yucca-man's talking about too. Because his instructions are the same as what I was going to tell you to check.

DAryl

Just a thought, if the motor had been replaced (twice?) he would have had to loosen and tighten the flex plate bolts........Hans

Oatmeal said:

Just a thought, if the motor had been replaced (twice?) he would have had to loosen and tighten the flex plate bolts........Hans

Click to expand...

X2.

what about trany mount? the AW4 in your 90 should be compatible with 87-91 at least. not sure when the trany computer was intergated into the ECM. the AW4 isnt a "special" item at all. Toyota used them for several years in the V6 Supras. $895 for a good one is pretty reasonable by my standards.
you said "don't ask", but i really have to question why the engine was replaced without some real in-depth troubleshooting. alot of things "move" under your rig and sounds transmit to different areas than where they originate.
describe your "knock" as detailed as you can get. when it happens, how frequent, anything you can think of.

it could very well be a bad trany but the AW4 has a very good track record regarding failures. lets get to the bottom of this.

busted up catalytic converter insides make horrible noise too. Use a stethoscope to determine where it'$ coming from.

I've not looked at the flex plate bolts but is it possible the wrong ones were installed? Maybe too long?

JoBo

Wow, thanks everyone, I'm allways impressed with the kind of response I get from this web site.
I will try to explain a little further about why my engine was replaced too many times, I originaly had a motor go bad and replaced it with one from a national engine re-builder (bought the warranty).
I had the replacement installed by a mechanic (too busy with my five kids), I drove the jeep for about 9 months
untill I started hearing a knock,(sounded like a rod hitting the block) slight at first, then louder as time (about 3 weeks) went on. The noise would be there when I first started it or after it was hot, it increased with RPM, and sounded like it was comming from the right front portion of the block.
I know noises can be transmitted through the engine and tranny , but the mechanics were useing stethescopes to try to locate the noise.

Since the motor was under warranty, I took it to a shop(not the same one that put it in as they were out of business)
to have them check it out, they told me it was the motor and we started the warranty process.

The engine re-builder sent two replacement motors to the shop which were both "bad"(knocking rods) according to the mechanics, I personally heard both replacement motors run and it sounded like they were about to come apart(rods knocking), so after the third motor was installed I was left with my original "knock".
Sorry this is taking so long but you asked.

Still, present at all times, increases with rpm, sounds like it's comming from right front, and at 2000 rpm, your afraid something might fly off the thing and hurt you!
Yes, now I'm leary of the shop I had the work done at and I want to handle this myself, I will check the bolts on the flywheel if I can access through the bell housing and check for length issues or lose bolts, but, I'm at the point now where I just want the best fix possible that I dont have to worry about leaving me dead on the trail!
This jeep had about 200,000 miles on it when all this started so I'm thinking it might be best to just junk this tranny and and get a new one, I just want to do it right and stop all this messing around and get out there and break something the right way, on the trail !!!!
Again, thank you all and I still would appreciate any input on this matter.

Well the tyranny and the torque converter are sold as two separate parts. If you have the knock in park then it can’t be the transmission. That would leave the flex plate or the torque converter.

As you can probably tell by my post's, I'm only somewhat
mechanically inclined, but I'm willing to try anything.
Tell me how to check the flex plate, do I have to drop the tranny to get at it?