Hey all,
Before you say it, yes, I did do a search on this topic first. I searched on "rattle", "trans", "transmission", "AW4", "noise", "sound", "start", and even "weird" and "strange". I read through mountains of threads, but nothing that addressed what I'm experiencing, so here goes.
1989 XJ Laredo, 175k on the original 4.0 engine, AW4 auto trans, NP231, D30/35, pretty much bone stock. We recently replaced the cat and muffler (plates were broken inside, muffler was just old), and once that rattle was fixed, we found another one that it had been hiding.
It only happens upon startup, within the first minute or so, whether the engine is hot or cold. The engine starts, and after a few seconds you hear (and can feel through the floor) a rattle, almost a clunking grind. As the engine accelerates to 2k RPM (regardless of gear, even in park), it accelerates in its own frequency until it suddenly goes away.
I checked the torque converter bolts, all are quite tight (as tight as I can get them, I'm guesstimating over 100 lb-ft). The check for cracks in the flex plate comes up negative, it's very tight, doesn't flex at all. Trans fluid level is... weird. When checked with the engine cold in park (idle around 800-1000 RPM), it read low this morning. I put in about 3/4 of a quart, and after having run it a bit, the idle in park was now up to 1500 RPM, and the fluid level was OVER full.
The creeping idle is a different issue altogether (I'm guessing it's either a bad TPS or a vacuum leak), but this rattle-clunk is really concerning me, especially when the trans reads low one time, and high another. Oh- fluid is fresh, not burned or dark, as I just replaced the filter about 6-8k miles ago.
So - any suggestions?
Before you say it, yes, I did do a search on this topic first. I searched on "rattle", "trans", "transmission", "AW4", "noise", "sound", "start", and even "weird" and "strange". I read through mountains of threads, but nothing that addressed what I'm experiencing, so here goes.
1989 XJ Laredo, 175k on the original 4.0 engine, AW4 auto trans, NP231, D30/35, pretty much bone stock. We recently replaced the cat and muffler (plates were broken inside, muffler was just old), and once that rattle was fixed, we found another one that it had been hiding.
It only happens upon startup, within the first minute or so, whether the engine is hot or cold. The engine starts, and after a few seconds you hear (and can feel through the floor) a rattle, almost a clunking grind. As the engine accelerates to 2k RPM (regardless of gear, even in park), it accelerates in its own frequency until it suddenly goes away.
I checked the torque converter bolts, all are quite tight (as tight as I can get them, I'm guesstimating over 100 lb-ft). The check for cracks in the flex plate comes up negative, it's very tight, doesn't flex at all. Trans fluid level is... weird. When checked with the engine cold in park (idle around 800-1000 RPM), it read low this morning. I put in about 3/4 of a quart, and after having run it a bit, the idle in park was now up to 1500 RPM, and the fluid level was OVER full.
The creeping idle is a different issue altogether (I'm guessing it's either a bad TPS or a vacuum leak), but this rattle-clunk is really concerning me, especially when the trans reads low one time, and high another. Oh- fluid is fresh, not burned or dark, as I just replaced the filter about 6-8k miles ago.
So - any suggestions?