4.0/trans is knocking

skyhighZJ

skyhighZJ

Gov retirement < needs to live
Joined
May 31, 2012
Location
Aberdeen, NC.
Starting to get a rod knock in my 1997 XJ (243,000) Debating on a crate or to rebuild. Fully capable and have the facilities but wondering if anyone else has done it. Worth the $$ to do it yourself? What kit sis you use for internals? Did you change the cam profile? Any other tricks/ upgrades? TIA!!
 
IF you do it youself, do a budget 4.6 stroker. It'll only cost a couple hundred more than a basic rebuild.

That said, crate reman, drop in and wheel.

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Chris_M said:
IF you do it youself, do a budget 4.6 stroker. It'll only cost a couple hundred more than a basic rebuild.

That said, crate reman, drop in and wheel.

Are crates that reasonable compared to paying a machine shop for block work now a days. I mean I have researched long blocks and they seem fair but have also priced out the rebuild kits and they seem pretty damn cheap too ($$ not quality). Guess I'm just trying to balance experience against others personal experiences.
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Really just depends on how much you value your off time, or how much you enjoy the work.

When I had thus decision, I found a running 89 4.2, bored my 4.0 .040 over, and made a stroker.

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Yep...depending on what your into. When I built mine, I was planning to do the assembly myself. The shop informed me that if he put it together, it was $150 and added a 3 yr/36k warranty. I did everything but the crank, stopping just short of stroking it. Check out Titan Engines - Jeep Strokers Remanufactued Engines and Engine Kits. They concentrate on 4.0s and will build them all the way to a 300+ 4.9 beast...
 
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So the more I have listened to the knock it is right at the back of the engine. I'm wondering if anyone has heard of the trans (AW4) making a strong sharp clacking/knocking noise. I'm thinking maybe the pump is broke or???. FWIW when the jeep is cold it is barely audible. Once is warms up it gets Loud. It still engages R and Drive although I'm afraid to drive it for fear of a catastrophic melt down. The trans was out 2 years ago for a new torque converter and I had the pump replaced and all the seals. They said the rest of guts were good to go so they buttoned it up and I put it back in the XJ. I had driven it quite a bit after without issue. The Jeep then sat a while during the 1 ton swap. It seems this issue has all happened very quickly. Looking for thoughts.
 
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broncosbybart said:
Torque converter bolts tight?
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Yessir. Checked them yesterday and reapplied red loctite. I have been watching some YouTube videos of cracked flex plates and the noise is the identical but the rythm is different. Mine is very methodical and directly related to engine RPM's while most of the videos have more of a lope or irregular pattern to the knocking.
 
Had a Mustang break a flex plate, the knocking was directly related to engine rpm.

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Well I found a solid running low miles 4.0 for a decent price so I think I'm going to kill 2 birds with well, several hours and wrenches and a few beers lol. Just to verify if I use all my accessories (front assembly, intake/exhaust manifolds, dist.) will a 1987 XJ motor work? Guy as a grandpa owned XJ w/ a 53k miles motor for $400. Have videos of it running and driving. Seems clean but not sure of interchange.
 
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87 will work...intake/exhaust and sensors have to be swapped and such but the block and head will bolt right in and work...the intake gasket I forget which one you use...if it's the 97 or the 87 but I know you can use the motor from 87 to 01...I've done it many times
 
The only real issue is the fact the intake manifold ports on the HO intake will not match up with the openings on the 87-90 head.
It will run, but it won't be anywhere near as efficient as it could be.
It would be much more ideal to use a HO motor IMO.
 
After more research I learned that when a forum says all XJ 4.0 are interchangeable, it isn't quite the whole truth. So back to the hunt!
 
Is the short block the same? Could you just swap the head over?
 
Where'd you find a good motor? All the ones I've seen lately go something like this:

"Odometer showed 240k before I pulled it out. Ran great. Been sitting in the yard for six months, only has a couple of mouse nests in it. $1k OBO"
 
The short block is essentially the same and yes I could use my head but the renix jeep had a different cam profile and I would have to re-measure for pushrods cause the HO head has a different deck height than the renix.... In other words more hastle than it's worth. Going to wait it out to find a decent HO 4.0
 
shawn said:
Where'd you find a good motor? All the ones I've seen lately go something like this:

"Odometer showed 240k before I pulled it out. Ran great. Been sitting in the yard for six months, only has a couple of mouse nests in it. $1k OBO"
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In Louisiana where I'm stationed now but even down here it's exactly as you stated
 
skyhighZJ said:
After more research I learned that when a forum says all XJ 4.0 are interchangeable, it isn't quite the whole truth. So back to the hunt!
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despite what you might read on "forums", not to brag here, but I've done Jeep 4.0s for solid 15yrs now mostly on XJs and ZJs and THEY ARE INTERCHANGEABLE...as Jody pointed out thought, the renix head ports are different but you can use newer gasket/manifold which will cover the ports all the way and work just fine...I would know since I've done put many renix motors in 91-01 jeeps ...they might be little less power but WAY WAY STRONGER motor than any of the newer ones, just giving some pointers from personal experience. good luck in your search man
 
skyhighZJ said:
The short block is essentially the same and yes I could use my head but the renix jeep had a different cam profile and I would have to re-measure for pushrods cause the HO head has a different deck height than the renix.... In other words more hastle than it's worth. Going to wait it out to find a decent HO 4.0
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this is very interesting to me as I've done this many times and never had an issue...I've put the 00-01 heads with coil bolt holes on Renix blocks without issues and never changed the rods or such so unless the "tolerance" is very forgiving I'm not aware of this issue...you have me very intrigued myself with this info lol...
 
Jody Treadway said:
Doing it and doing it correctly are 2 different things.
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I'm really gonna have to look up spec and stuff cause I'm stumped now. I just always swapped anything within the 4.0 except the TJ and WJ and never had an issue or lack of power but now I'm really intrigued to find out the differences
 
The renix blocks are not stronger than the HO blocks. The 94-98 (not sure about the coil pack motors) blocks were higher nickel content and had better assembly for the main caps to include a girdle setup. The renix motors are reliable but less power and the blocks weren't cast as well as the HO motors
 
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@Chris_M @Jody Treadway @shawn @92_SquareEye

So @Blaze is getting me a great deal on a long block shopped down here. Yesterday I took my XJ over to the car shop here on post and pulled the motor. It was definitely the flex plate!! Only took a light tap with the hammer for it to fall into 2 pieces!!
 
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