Hey everyone. Is there a time/mileage where the timing chain has to be replaced (obviously before it's breaking point)? I have heard of belts having to be replaced on the riceburners, but what about the chain on the 4.3Ls? Dare I say that word riceburner... I ALMOST considered a Subaru as my next car after seeing the videos about their AWD system (I am generally against AWD also). I might consider a newer car after I graduate and get a good job (but keeping the Jimmy). But considering the Toyota acceleration issue, my mother hounding me about her car and other massive recalls of riceburners, I won't buy a Japanese car.

 

Timing belts have a recomended replacement interval if it's an "interference engine". This means the pistons will contact the valves if the belt breaks, very expensive to repair. The 4.3L is not an interference engine so there is no recomended replacement interval. Timing chain & gears should be replaced when chain slack exceeds ~12 total degrees of crankshaft rotation, (6 degrees each direction). Timing chain problems on 4.3L engines are almost nonexistant. It's not uncommon for them to go 300K miles.

EDIT: Timing chains stretch, and the gears wear. At ~12 degrees slack, the chain can jump on the teeth of the gears, can't ever remember seeing a chain break.

 

having just done my mustang i looked at the timing chain on my old engine before i scrapped it. after 200k the chain was still on there pretty good...some wiggle but nothing that i would have been concerned with. i also cant think of any timing chain thread have ever been on here since i have joined.

 

WOW, lots of good news in this thread LOL! 300k out of one huh? This was the biggest worry I had buying this blazer with 190k. Runs really strong and is in great shape so glad to know the timing chain is not a big issue with these.

 

it kinda falls into the category of if you are going to take off your timing cover to inspect it you might as well replace it since youre in there. this is probably one part ive yet to break. when i tore apart my 73 400 engine the chain on one side moved like a half inch, thats the worst i ever seen.

 

I service a fleet of 4.3's and one of them has 387K miles, (original engine, trans & differential). It's driven every day, never been kept in a garage, and still runs strong.

 

^^^
hopefully one day my blaz and i will get there...well on our way

 

Ok thanks for the tips. I guess I won't be touching the timing chain anytime soon then. I just changed the oil today at 121,733 miles. Used Mobil1 High Mileage. Not quite to 300k, but I hope to get there. With some of the noise it is making when it is cold (not knocking) and the higher-than-usual metal particles on the drain plug, I hope so. Also did the front axle and transfer case fluids and when I took the fill plug off the transfer case, it was overfilled. I just had it checked a few months ago. Maybe it is because the fluid was hot, it was in 4HI and not because I had a leak somewhere?

 

Very difficult to overfill a transfer case due to the location of the fill plug. What usually causes it, is the transfer case vacuum switch leaking vacuum internally. It applies vacuum to the inside of the transfer case which causes transmission fluid to get pulled into the transfer case. It's a quick, easy, $20 fix, provided the fluid has not made its way into the vacuum system and components, (lines, reservoir, axle actuator, HVAC lines and actuators in the dash).

The switch: Dorman Help! 49315 - TRANSFER CASE SWITCH | O'Reilly Auto Parts is located on the driver side of the transfer case, inboard and slightly above the front output shaft:



15 minute job and no special tools needed.

 

There is no engine vacuum source to the transfer case on this truck. It is disconnected under the hood and capped. Been that way for a year and a half. No need for it anymore since I have the Posi-Lok to engage the front axle. When I replaced all of the other vac lines, I didn't bother with this one so I left it disconnected.

I thought I was doing some good by doing that to prevent the ATF getting into everything. Should I hook it up again or at least uncap it? How do I run new vac lines to the transfer case in that situation then? I was trying to find a vacuum leak causing HVAC problems and I replaced all the lines under the hood for that (except for the T/C), but that didn't help.