Tranny Rattle
Question:
Hi Guys, I have a question for all of you GM guru’s. I have this 95 GMC Sierra, 4.3 Vortec, with a 5 speed tranny that rattles to beat all. I’ve heard of different additives & would like to hear some tips or advice. Hey,,,,,,Steve (Spence), are you out there ?? What’s your opinion of the "Lucas" additive in particular ??? Or does GM recommend something special for those rattling 5 speeds ??? Thanks & Regards Rich
Response:
Sounds like your anti-knock sensor is disconeccted and the computer isn’t retarding when it starts knocking. — Bob May Remember that computers do exactly what you tell them to do, not what you think that you told them! Bob May
Response:
Hi Bob Are you saying that the computer controls the 5 speed rattling ?? Geez,, what did I get myself into. I know if I downshift into 2nd turning a corner here in the neighborhood or anywhere (like rolling a stop sign) it won’t do it, but if I leave it in 3rd it rattles bad. Would that (sensor) cause the 5 speed tranny to rattle ??? My old truck didn’t do it. Can I use a bottle of that "lucas" tranny additive without messing anything up inside the trans ??? I’ve heard good stuff about it. What’s your opinion. Thanks Rich
Sounds like your anti-knock sensor is disconeccted and the computer isn’t retarding when it starts knocking. — Bob May Remember that computers do exactly what you tell them to do, not what you think that you told them! Bob May
Response:
Are you sure it’s the tranny rattling? If it is indeed the tranny rattling, you need to check the fluid for bubbles for a start. Then check the pressures when things are moving as you could be overpressurizing the tranny and causing some of the pressure limiters or the pump to cavitate and that’s bad news. — Bob May Remember that computers do exactly what you tell them to do, not what you think that you told them! Bob May
Response:
Well it sounds like the trans rattling. It does it when I accelerate around a corner while in 3rd gear. Say I slow down, turn the corner & then accelerate, all in 3rd gear. Where is this "anti-knock sensor" located ? I’m gonna go buy me a Chiltons tomorrow, for sure. The more I learn about this 95 GMC, the more I find out how much I don’t know, but thanks for the info, I really appreciate it. Rich
Are you sure it’s the tranny rattling? If it is indeed the tranny rattling, you need to check the fluid for bubbles for a start. Then check the pressures when things are moving as you could be overpressurizing the tranny and causing some of the pressure limiters or the pump to cavitate and that’s bad news.
Response:
The knock sensor controls ignition timing. I think Bob May assumed that you were hearing ’spark knock’. (The knock sensor does not have anything to do with the tranmission) There are a LOT of those trucks with the same noise. Chances are, the noise is gear lash. Not a serious thing, and any of the trucks that I used to see come in with that particular noise have never had a transmission failure. The noise I’m thinking of is annoying, but built right into it. TO BE SURE, drive down to your local GM dealership. Go to the service department and nicely ask if the shop foreman would mind driving the truck across the parking lot and listening to transmission ‘clatter’. Chances are he can verify that this is what you’re hearing and explain the reason for it far better than I could. If he’s been working there for awhile, it will not be the first time he hears it. If that’s what it is, learn to live with it. What’s the expression the engineers use…’design intent’..?
– Hide quoted text — Show quoted text -> Well it sounds like the trans rattling. It does it when I accelerate around > a corner while in 3rd gear. Say I slow down, turn the corner & then > accelerate, all in 3rd gear. Where is this "anti-knock sensor" located ? > I’m gonna go buy me a Chiltons tomorrow, for sure. The more I learn about > this 95 GMC, the more I find out how much I don’t know, but thanks for the > info, I really appreciate it. > Rich > Are you sure it’s the tranny rattling? If it is indeed the tranny > rattling, you need to check the fluid for bubbles for a start. Then > check the pressures when things are moving as you could be > overpressurizing the tranny and causing some of the pressure limiters > or the pump to cavitate and that’s bad news.
Response:
> Hi Guys, > I have a question for all of you GM guru’s. I have this 95 GMC Sierra, 4.3 > Vortec, with a 5 speed tranny that rattles to beat all. I’ve heard of > different additives & would like to hear some tips or advice. Hey,,,,,,Steve > (Spence), are you out there ?? What’s your opinion of the "Lucas" additive > in particular ??? Or does GM recommend something special for those rattling > 5 speeds ??? > Thanks & Regards > Rich
Hi Rich: Yes, I’m out here. My youngest daughter delivered another grand child for us this evening so, I’ve been away for just a little bit. Those 5 speed manual trannys rattle (the one in your 1/2 ton truck is an MG5) and they all tend to do it almost from brand new. There was an earlier post in this newsgroup from someone remarking about how much noise his tranny was making and was concerned about it until another truck similar to his passed him on the freeway and was making the same noise. If you search back through the posts, you’ll probably find it. You might try changing the fluid, but no guarantee that it will help. However, if you haven’t owned the vehicle since new, it’s possible that the previous owner changed the fluid and replaced it with something that shouldn’t be there. The correct fluid for that tranny is G.M. Part Number 12345349. It will take more than 2, but less than 3 to do a drain and refill. Suggested retail price is (I think) $9.20 per quart. The old fluid should drain out with about the same consistency as ATF or 30 weight motor oil. That tranny is made in the Hydra-Matic plant and looks more like an auto on the inside that most manual transmissions (in terms of clearances and oil passages). The wrong fluid could certainly cause havoc if it was too heavy. Outside of that, BG makes a product that was developed just for manual transmission noises (the name of which escapes me just now). Ask around at a local parts store or transmission rebuilder if they know whether BG products is in your area. I’ve never heard of the "Lucas" brand additive. I hope this tidbit helps. Take care, Steve Spence — G.M. Partsman since 1973 Chevy Olds Pont Buick Cad & Lt. Trucks Please remove the "-nospam" in my address to reach me I’m tired of getting unsolicited commercial mail
Response:
Well, first of all, Congratulations on that new grandbaby. Then back to this other stuff. I picked up a Chiltons last night & can’t find anything about an "anti-knock" sensor, it mentions it but doesn’t give any details on it. I also stopped by an old neighbors house, (he works at a major GM dealership), & he say’s to get used to it. Said it probably did it when it was new & will most likely do it for the rest of it’s life, without problems. I forgot to ask him about the anti-knock sensor though. I’ve gotta find out where it is on a 95 Vortec V6. I’m curious about it now, cause I do have a miss in it sometimes, & I put all new stuff like cap, rotor, & wires in it the same day I got it. So, keep your eyes open for any info on it that ya might run across for me, even a website. I’d appreciate it. Gotta run Thanks a heap, & again, congrats on the little one. Rich {{{{ 5 speed tranny that rattles }}}} Hi Rich: Yes, I’m out here. My youngest daughter delivered another grand child for us this evening so, I’ve been away for just a little bit. Those 5 speed manual trannys rattle (the one in your 1/2 ton truck is an MG5) and they all tend to do it almost from brand new. There was an earlier post in this newsgroup from someone remarking about how much noise his tranny was making and was concerned about it until another truck similar to his passed him on the freeway and was making the same noise. If you search back through the posts, you’ll probably find it. You might try changing the fluid, but no guarantee that it will help. However, if you haven’t owned the vehicle since new, it’s possible that the previous owner changed the fluid and replaced it with something that shouldn’t be there. The correct fluid for that tranny is G.M. Part Number 12345349. It will take more than 2, but less than 3 to do a drain and refill. Suggested retail price is (I think) $9.20 per quart. The old fluid should drain out with about the same consistency as ATF or 30 weight motor oil. That tranny is made in the Hydra-Matic plant and looks more like an auto on the inside that most manual transmissions (in terms of clearances and oil passages). The wrong fluid could certainly cause havoc if it was too heavy. Outside of that, BG makes a product that was developed just for manual transmission noises (the name of which escapes me just now). Ask around at a local parts store or transmission rebuilder if they know whether BG products is in your area. I’ve never heard of the "Lucas" brand additive. I hope this tidbit helps. Take care, Steve Spence
Response:
As Harv said, I considered that you probably aren’t having a tranny problem but an engine problem. The problem here is that I haven’t listened to the sound myself but have heard a lot of abnormal sounds in my life from cars and trucks and oftimes, the customer has no idea of where the sound really is coming from. Also, your description of the sound may or may not be a real representation of the sounds that are actually being emitted by the truck. I, and all others that respond over the web, are making educated guesses from experience and it’s quite probable that some of the guesses are way off. With today’s electronic controlled drivetrains, my desired general solution on intractable problems is to pull out my 9mm and give the engine the coup de gras between the headlights. Unfortunately, the owners of the cars generally frown on this fix for some silly reason. — Bob May Remember that computers do exactly what you tell them to do, not what you think that you told them! Bob May
