wierd rattle

[moparvwfreak]

alright. i am not sure where this should go. MODS, if you think this should be in another section, please feel free to move it. :)

 

78 620, L20B, 4spd manual. i know i need to do the carrier bearing. That's being done tomorrow. but i have this weird rattle. it happens anywhere above idle. mainly at cruise RPM. but if i give it a touch more gas,or let off a touch, it seems to go away. so i am lost. here are my thoughts on it.

 

at first i thought timing chain, due to when i first ripped off the VC the timing chain has an assload of slack in it. today i pull it off to see the extent of the damage, adn there is NO slack in it what so ever. nice and tight, just like my L16. valve adjustment looks right, rockers have a touch of play, just like my L16.

 

so now could there be something loose in the trans?? i have been hearing a whine out of it recently. i have had the trans serviced as well as the rear diff. i'll have my mechanic look at it tomorrow when it goes in for some other work. stuff i dont have time to deal with ya know?? :D i do know that up until Friday, the trans was NOT bolted to the trans mount. that has since been solved.

 

clutch issue maybe?? thoughts???

 

thanks guys. if you want i will haul out the vid cam and see if it will pick up the rattle i am hearing. i would like to keep this truck on the road till i can get my 73 back into shape, literally. hell i have been enjoying the extra room a KC offers so i am alot more comfortable in it than my 73.

[datzenmike]

You can't have loose chain one time and fine the next. Define loose.

 

Get under and pull on the exhaust pipe along the whole length while looking for places it might rub against anything.

 

Check the alt. mount isn't loose or the alt mount to block bolts.

 

Check clutch fan/water pump.

 

Check the sheet metal that bolts to the exhaust manifold that provides warm

air to the carb... if it's there.

 

Check the air filter us clamped to the carb properly.

 

Question... does this happen in gear when driving or sitting still? Both? Can you localize the sound to the engine compartment, tranny... or unknown?

[moparvwfreak]

well thats how it was. as for loose, 12 inch of play on the non tentioner side. i may have turned the motor the wrong way when i got it trying to check the valves, hence the slack.

 

exhaust was just installed thursday and i noticed this before then.

 

as far as i can tell teh alt is tight. i had to adjust it the other day adn nothing seemed out of the ordinary.

 

fan clutch. seems tight and doesn't make noise when i spin it.

 

sheet metal for the warm air is GONE!

 

air filter is bolted down tight. made sure of that before i put the filter off my 73 on it.

 

mainly in gear BUT i can goose it with the clutch in and about 3k i hear it. hence why i was thinking chain. also i can feel it through the stick. which is why i was thinking trans.

[mike]

If it could be coming from the front of the motor and you had 1/2" of slack in the chain, pull your valve cover and look at the head on the side of the chain. The chain on my KC had damn near worn through the side. Quiet at idle and it would make noise at higher RPM.

[moparvwfreak]

I had the vc off today and the chain looked good. BUT I didn't look at the back of the chain. when I get it back from the shop I will take a look at that.

[Wharf Rat]

Do you hear this rattle when you rev the engine just a little bit and hold it there not in gear? Don't like to say it but rod bearings talk like that. If you don't have to be moving to hear it have somone hold the gas steady use a long screw driver and put one end on the timing cover and the other to your ear, then the side of the block ect. This works good for finding where those weird noises are coming from.

 

Good luck, hope it just a minor rattle

[moparvwfreak]

Do you hear this rattle when you rev the engine just a little bit and hold it there not in gear? Don't like to say it but rod bearings talk like that. If you don't have to be moving to hear it have somone hold the gas steady use a long screw driver and put one end on the timing cover and the other to your ear, then the side of the block ect. This works good for finding where those weird noises are coming from.

 

Good luck, hope it just a minor rattle

 

well I have had a rod bearing go and this is to light to be a rod. it almost sounds like a pinging but not quite. but I will try and see where its rattleing, if it'll start.

[Wharf Rat]

Ok, take a listen, when rod bearings are worn but not spun or gone so to speak, they will all rattle with the engine reved just a bit with no load on it.

 

If you catch them like that you can change them. Pull the pan down and one by one do them up. They look like there made mostly of copper when that worn and loose. On big diesels you "roll some bearings in" when doing a in truck rebuild :)

[moparvwfreak]

i will definatley look into that. who knows how many miles are on the beast, so it could be due for some bearings.

[Wharf Rat]

If they sound loose put the STP to it or lucus oil treatment with 40wt engine oil

 

Bearings in a bottle:)

 

The thick soup softens the rattle and buy you time :)

[moparvwfreak]

planning on an oil change and using a QUALITY Ford filter vs. that cheap ass pos Fram filter thats on it. defenatley Lucas in it. maybe 2 bottles.

[zed]

I had a wierd rattle on my Datsun Hardbody truck. Even the mechanics at Nissan couldn't find it - they were stuffing rags into the wheel arches at one point... A mate of mine found it - worn universals.

[moparvwfreak]

u-joints were done as of yesterday along with the carrier bearing. so that has been eliminated. thanks for the suggestion though :D

[mike]

Have you been able to tell if its in the motor/valve train/bottom end or running gear/tranny yet?

[moparvwfreak]

working on it now. i listened with a LONG extention, my stethoscope dissappeared again, and the bottom end sounds tight and the chains sound ok as well. oil pressure takes a while to build though so i think i might slam a new oil pump in it just ot be safe.

 

its begining to sound valve related. so i am going to readjust ALL the valves this afternoon since the motor is warm i should get a more accurate adjustment.