Help with a knock - stumped...

RacerX

RacerX

Professional Knucklehead; aka Jeffncs / RacerX
2A Bourbon Hound OG
Charter Member
Supporting Member
Joined
Dec 17, 2016
Messages
3,440
Location
Wake County
Rating - 100%
73   0   0
I recently installed a new Luk clutch kit into my 82 CJ7. It’s a straight 6 and a T5 manual trans.

Scenario:
I have maybe 50 miles on the new clutch and it’s been perfect...until this afternoon. After flushing my cooling system, I took it for a test drive to help drain the water from the floors (washed it and rinsed out some dirt/mud from interior).

I came to a complete stop at a stop sign on a slight hill. I accelerated moderately from the stop as I turned left and heard a pop and subsequent knocking in time with the engine rpm. I immediately thought driveshaft as I “felt” the noise in the shifter.

Some additional details / observations:
Knock is present while trans is in N
Knock is present while clutch pedal is released
Knock is NOT present while clutch pedal depressed
Knock stays in tune with the engine rpm (speeds up/slows with engine speed)
Trans seems to function with shifts with no impact on the knock
T-case works fine too with no impact on knock

My initial fear after confirming the driveshafts weren’t the source was engine failure, but the oil pressure is good and engine runs at usual temp with no oil in the coolant. The intermittent sound with clutch engagement rules the engine out in my opinion.

Clearly there’s something going on with the rotating assembly... I just have no ideas yet and really don’t want to pull the trans until I know if I should also be looking for a replacement engine (current engine has 185k and I have a line on a running, low mileage 4.0 with EFI).

I torqued everything and double checked! I also used blue loctite on the flywheel and pressure plate bolts.

Trying to get this thing going as I was hoping for a fall beach trip and URE. This is a major curve that I’ve never run into with a seemingly successful clutch job?!?!?!

Thoughts? Throw-out bearing? I know I’m likely pulling the darn trans again, but I’m so frustrated by this unexpected development!

I’ll ask for advice on the 4.2->4.0 swap in a separate thread...after some add’l reading.

Thanks in advance!!
 
Last edited:
i would think clutch fork, throw out bearing.

it would be great if it just was an issue with the clutch pedal assembly and fork.

all that junk is manual on yours right? i’d check all of that first

nothing hydraulic until YJs i thought.
 
Just a bunch of rods, springs and levers... all manual. Unfortunately, this rhythmic knock seems to be coming from the bell housing itself. I’ve read input bearings at the front of the trans could cause it too. Throw out bearings usually just make noise when they’re pressed into the pressure plate.

I’m dreading the reality ahead of me. I know I’m pulling a trans again and hate it.

I’m thinking I may try finding a shop (any luck @SDIVER2006?) to throw a rebuild at it and the T-case.
 
Last edited:
Jeffncs said:
Just a bunch of rods, springs and levers... all manual. Unfortunately, this rhythmic knock seems to be coming from the bell housing itself. I’ve read input bearings at the front of the trans could cause it too. Throw out bearings usually just make noise when they’re pressed into the pressure plate.

I’m dreading the reality ahead of me. I know I’m pulling a trans again and hate it.

I’m thinking I may try finding a shop (any luck @SDIVER2006?) to throw a rebuild at it and the T-case.
Click to expand...

bummer

i had one make a noise/rattle that was rhythmic with the rpms when the clutch fork boot was worn...
 
vp9c said:
bummer

i had one make a noise/rattle that was rhythmic with the rpms when the clutch fork boot was worn...
Click to expand...

I wish it would be something simple and easily corrected. Unfortunately, this is a legit knock... to the point that I thought I threw a rod! It’s loud and very noticeable.
 
Last edited:
sounds like you will be pulling the transmission again...

wonder if the pilot bushing failed or front input bearing
 
Two guesses would be throwout bearing or potentially clutch spring came out some how and bumping something.
 
When reading my first instinct was throwing bearing or something with the pressure plate. Did you replace the pilot bearing while you were in there? When taking it apart, take your time to inspect for unusual wear on any parts, may lead you to a clue as to the causation. Too many of your clues lead to a rotating part in the flywheel, clutch disk, pressure plate family and their supporting parts interfering with another part or itself
 
Thanks to all... I’m going to enjoy the weekend and try not to futz around with it. I’d love to go to the range and possibly fishing instead. I’ll mess with it after I get some down time.
 
Missing a 10mm socket (or any socket) by chance?

I left one in transmission that bounced around for a year making a ticking noise lol.
 
Having someone push the clutch in and out slowly and then aggressively with the engine not running. You watch the harmonic balancer/crank pulley. Is it moving with the clutch depressions.

Had a truck doing something very similar to what you describe. It was a thrust/main bearing, allowing the crank to move just enough to cause a “knock” type sound.
 
Mike Overlay said:
Having someone push the clutch in and out slowly and then aggressively with the engine not running. You watch the harmonic balancer/crank pulley. Is it moving with the clutch depressions.

Had a truck doing something very similar to what you describe. It was a thrust/main bearing, allowing the crank to move just enough to cause a “knock” type sound.
Click to expand...


I had my wife operate the clutch while under the Jeep and sure enough I see the HB shift forward with the first clutch press and maybe with the second then it stops. If I manually turn the crank with the HB bolt, I’ll see it shift again.

What did you do to correct the thrust/main bearing issue in that truck?

Another new issue is that the screaming starter is back and just as loud as before.

Theorizing a bit here... if the crank is shifted forward 1/16” or so, would that also create the screaming starter along with the engine-timed knock?

I pulled the inspection plate, shift fork boot and starter. Using a mirror and a bright light, I can’t see anything out of place. The pressure plate appears to be clearing the bell housing and the input shaft and all parts appear to be where they belong....

I’m debating a 4.0 swap with fuel injection with pulling this trans again.... I may as well go all in to maybe avoid doing it again this winter (was already planning to do it eventually).
 
Jeffncs said:
I had my wife operate the clutch while under the Jeep and sure enough I see the HB shift forward with the first clutch press and maybe with the second then it stops. If I manually turn the crank with the HB bolt, I’ll see it shift again.

What did you do to correct the thrust/main bearing issue in that truck?

Another new issue is that the screaming starter is back and just as loud as before.

Theorizing a bit here... if the crank is shifted forward 1/16” or so, would that also create the screaming starter along with the engine-timed knock?

I pulled the inspection plate, shift fork boot and starter. Using a mirror and a bright light, I can’t see anything out of place. The pressure plate appears to be clearing the bell housing and the input shaft and all parts appear to be where they belong....

I’m debating a 4.0 swap with fuel injection with pulling this trans again.... I may as well go all in to maybe avoid doing it again this winter (was already planning to do it eventually).
Click to expand...

I bet the crank movement is the problem. I would look at dropping the oil pan and see if you have a way of removing a main bearing cap, try and walk the old bearing out of the block. Oil up new bearing and slide, gently tap new bearing back in the block. Loosing all the other main caps while completely removing one at a time.

Replace all the main bearings. One of which I believe has the “thrust bearing” shoulders
 
Last edited:
Mike Overlay said:
Having someone push the clutch in and out slowly and then aggressively with the engine not running. You watch the harmonic balancer/crank pulley. Is it moving with the clutch depressions.

Had a truck doing something very similar to what you describe. It was a thrust/main bearing, allowing the crank to move just enough to cause a “knock” type sound.
Click to expand...

I love to turn my own wrenches when I can, but this is a reminder of why it is good to know a pro or two and support them every now and then.
 
Mike Overlay said:
Having someone push the clutch in and out slowly and then aggressively with the engine not running. You watch the harmonic balancer/crank pulley. Is it moving with the clutch depressions.

Had a truck doing something very similar to what you describe. It was a thrust/main bearing, allowing the crank to move just enough to cause a “knock” type sound.
Click to expand...
Jeffncs said:
I had my wife operate the clutch while under the Jeep and sure enough I see the HB shift forward with the first clutch press and maybe with the second then it stops. If I manually turn the crank with the HB bolt, I’ll see it shift again.

What did you do to correct the thrust/main bearing issue in that truck?

Another new issue is that the screaming starter is back and just as loud as before.

Theorizing a bit here... if the crank is shifted forward 1/16” or so, would that also create the screaming starter along with the engine-timed knock?

I pulled the inspection plate, shift fork boot and starter. Using a mirror and a bright light, I can’t see anything out of place. The pressure plate appears to be clearing the bell housing and the input shaft and all parts appear to be where they belong....

I’m debating a 4.0 swap with fuel injection with pulling this trans again.... I may as well go all in to maybe avoid doing it again this winter (was already planning to do it eventually).
Click to expand...
@Mike Overlay is da man!
 
lowcountry said:
I love to turn my own wrenches when I can, but this is a reminder of why it is good to know a pro or two and support them every now and then.
Click to expand...


I agree, but I’ve been supporting the local gun shops with my discretionary funds...

I think this is going to be the kick in the back side that drives the engine swap. The current engine is just tired and power is lacking after 187k miles on the odometer.

While I don’t really want to lose the fall driving time, the engine swap may be the smart call for the long game. I was already considering pulling it over the winter.

I have to do some reading for installing a FI engine into my carb’d Jeep. I already know I have to install a Crank Position Sensor, a fuel return line, fuel pump and the harness. The engine and full harness is $400 (~60k miles).
 
Last edited:
Jeffncs said:
I agree, but I’ve been supporting the local gun shops with my discretionary funds...

I think this is going to be the kick in the back side that drives the engine swap. The current engine is just tired and power is lacking after 187k miles on the odometer.

While I don’t really want to lose the fall driving time, the engine swap may be the smart call for the long game. I was already considering pulling it over the winter.

I have to do some reading for installing a FI engine into my carb’d Jeep. I already know I have to install a Crank Position Sensor, a fuel return line, fuel pump and the harness. The engine and full harness is $400 (~60k miles).
Click to expand...

That was definitely not a shot at you, just complimenting @Mike Overlay willingness to share.

I know where a running 258 out of an 83 is sitting and taking up room if there is any interest. He just dropped a sbc in his Jeep.

Eventually I want to do the 4.0 liter head swap on my 4.2 and us FI. I have to get mine looking as good as yours first.
 
Last edited:
Jeffncs said:
I have to do some reading for installing a FI engine into my carb’d Jeep. I already know I have to install a Crank Position Sensor, a fuel return line, fuel pump and the harness. The engine and full harness is $400 (~60k miles).
Click to expand...

It might be cheaper to buy the whole donor jeep. PCM/ECM along with the wiring harness plus other non thought of items such a brackets, air box, etc will be headache to chase one at at time as you discover they will make life easier and the install cleaner, user friendly.

For the time being, main bearing set is cheap, your labor is free
 
Before I pulled the trans, I'd check and make sure the starter is tight. Then pull the starter and check out the nose to see if it's hitting anything. I would also take a pry bar and make sure the flywheel isn't moving.
 
John said:
Before I pulled the trans, I'd check and make sure the starter is tight. Then pull the starter and check out the nose to see if it's hitting anything. I would also take a pry bar and make sure the flywheel isn't moving.
Click to expand...

My wife ran the clutch pedal while I stared at the harmonic balancer... sure enough there’s a visible shift forward as she pressed the pedal down. I could probably work through replacing the main bearings, but I think I’m going to upgrade the engine with a low cost 4.0 with EFI.
 
Pull the pan, replace the thrush bearing and always place the shifter in neutral without depressing the clutch before cranking. Deactivate the clutch override if the Jeep has one. Good luck.
 
We had a horrid rattling after a transmission rebuild. I pulled the inspection plate and discovered the numbnutz rebuilder didn’t tighten down a bell housing bolt. It. Would sling around as soon as the rpm’s went up.
 
Pink_Vapor said:
We had a horrid rattling after a transmission rebuild. I pulled the inspection plate and discovered the numbnutz rebuilder didn’t tighten down a bell housing bolt. It. Would sling around as soon as the rpm’s went up.
Click to expand...

Huh?!? All bell housing bolts I know of are all accessed from the outside. How would it get inside?

Was it a pressure plate bolt?
 
Jeffncs said:
My wife ran the clutch pedal while I stared at the harmonic balancer... sure enough there’s a visible shift forward as she pressed the pedal down. I could probably work through replacing the main bearings, but I think I’m going to upgrade the engine with a low cost 4.0 with EFI.
Click to expand...
I forgot you said the noise stopped when you depressed the clutch so ignore my thoughts about replacing the thrush bearing. My bet it is transmission related, depressing the clutch stops the rotation of the transmission parts and when released the noise begins, has to be coming from that area. I have seen the shifter cause a busted synchronizer from being installed incorrectly, good luck.
 
Last edited:
I wonder if a tooth could have let go on a cluster gear inside the transmission? I busted a tooth off in an ‘88 Montero one time by sticking it in reverse while my foot slipped off the clutch.

Knocked like crazy until I replaced the transmission.
 
Here’s where things stand right now....

I’m going to pull the trans this weekend after lining up a trans jack (buying) and an engine hoist (borrowing). Once the trans is out, I’m going to run the engine with no trans in place to see if the knock is there or absent.


If the knock is gone... Ill continue the disassembly while inspecting the rotating parts for signs of scraping/wear. If nothing on the exterior rotating assembly, I’ll check the trans internals for teeth and play in the input shaft. I’ll rebuild / replace the trans or clutch parts as necessary.

If the knock is present, I’m pulling the engine in favor for an EFI 4.0. I may do this anyway since it’s all part and I hate doing trans drops all the time! I’m not going to invest anything into an engine with 185k on it. I’ll send it along to the next owner for a rebuild / core exchange.
 
Last edited:
I was able to get the knock to stop... well - it’s not actually fixed yet! I took the trans out again... The input shaft and spline look fine and don’t have any unusual movement - minimal wiggle, which is typical.

Sadly, I have to get a new starter - 3rd one to die. Thank you lifetime warranty!

I’ll get the starter in tomorrow and run the engine without the trans but with the clutch and bell housing to isolate the noise to trans or engine/clutch.

That replacement engine is getting more attractive the longer I stare at the trans sitting on the floor and the engine only held in place with 4 bolts, 5 wires and 4 coolant hoses....
 
Jeffncs said:
I was able to get the knock to stop... well - it’s not actually fixed yet! I took the trans out again... The input shaft and spline look fine and don’t have any unusual movement - minimal wiggle, which is typical.

Sadly, I have to get a new starter - 3rd one to die. Thank you lifetime warranty!

I’ll get the starter in tomorrow and run the engine without the trans but with the clutch and bell housing to isolate the noise to trans or engine/clutch.

That replacement engine is getting more attractive the longer I stare at the trans sitting on the floor and the engine only held in place with 4 bolts, 5 wires and 4 coolant hoses....
Click to expand...

The knock before, was it able to duplicate with or without a load on the engine?
 
@Mike Overlay

Knock stayed in time to the engine RPM. Didn’t get louder or change otherwise

I’m going to stick the new starter in tomorrow morning to see if the knock is there or not and to see if I can observe anything while running with the trans out.
 
Last edited:
Jeffncs said:
@Mike Overlay

Knock stayed in time to the engine RPM. Didn’t get louder or change otherwise

I’m going to stick the new starter in tomorrow morning to see if the knock is there or not and to see if I can observe anything while running with the trans out.
Click to expand...

Was as it while driving, (load on engine with the weight of the vehicle with the “torque” required to put in foward motion) or just sitting still and reving the engine, or both?
 
@Mike Overlay
I was stopped at a stop sign. I accelerated harder than usual from the stop and heard a bang. From that point, the knock was rhythmic to the RPM of the engine. It knocks while driving and while sitting at idle in my garage. Load and no load - no difference
 
Jeffncs said:
@Mike Overlay
I was stopped at a stop sign. I accelerated harder than usual from the stop and heard a bang. From that point, the knock was rhythmic to the RPM of the engine. It knocks while driving and while sitting at idle in my garage. Load and no load - no difference
Click to expand...

Just thought of this but have you checked the engine mounts? Yeah, it's a WAG...

Hard acceleration + bang = broken mount
 
Last edited:
rdinatal said:
Just thought of this but have you checked the engine mounts? Yeah, it's a WAG...

Hard acceleration + bang = broken mount
Click to expand...

Thanks for the suggestion and it’s a good thought but that would only create a bang upon acceleration when the torque twists the engine away from the mount then drops back into place.

My knock is mechanical... I’d love for it to be something simpler (and cheaper!!!) to fix!
 
Jeffncs said:
Thanks for the suggestion and it’s a good thought but that would only create a bang upon acceleration when the torque twists the engine away from the mount then drops back into place.

My knock is mechanical... I’d love for it to be something simpler (and cheaper!!!) to fix!
Click to expand...

It all depends on how the mount breaks. I've seen some where there was a gap or light touch on metal to metal contact. The engine could be moving slightly and making the sound.

Lift the engine slightly one each side and see if it changes.
 
rdinatal said:
It all depends on how the mount breaks. I've seen some where there was a gap or light touch on metal to metal contact. The engine could be moving slightly and making the sound.

Lift the engine slightly one each side and see if it changes.
Click to expand...

I didn’t think about it that way. I’ll take a look today, Thanks for the suggestion!
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom