: transient powertrain "slack" when engaging??



mtflight
06-03-05, 12:32 PM
Do you know the slight "rolling" that occurs when you put the car in Park, then you release the brake? It rolls maybe two inches or so, as if there was a slack between "gear teeth" or something.

When I am not careful and step on the gas too hard--accelerating from a dead stop-- I feel a similar jolt as if there was "play" or slack in a chain or gear. It's certainly not major, and it can be avoided by gradually applying the gas upon intial acceleration from zero. I am assuming this is NORMAL.

When coasting, then stepping on the accelerator... I feel the same thing to a lesser extent... almost like the feeling you get when the AC compressor kicks on... except of course it's not slowing the car like the AC compressor, but rather doing the opposite (since you're accelerating).

So... is this all ok? or am I looking into transmission mounts, fly-wheel, engine mount issues?

Regards,

Alex

PS another interesting thing... is when I'm on "D" then I have to slow down for whatever reason, if I downshift into Third or Second gear manually... I feel a "hard" engagement. Almost like a "hard shift" or a slight kick.

I've asked before whether the car is designed for it to be ok to upshift for "engine brake"... received no replies... so I've since stopped doing that--I'd rather wear out pads than tranny (which shifts smooooothly and beautifully during everyday driving).

Spyder
06-03-05, 01:41 PM
you'd downshift for an engine brake...but no, I don't think that's normal...there shouldn't be any hesitation, as far as I know, when you take off at more than an idle or slight pedle.

jackc
06-03-05, 02:48 PM
You may have a front engine mount going bad.......

mtflight
06-03-05, 05:35 PM
you'd downshift for an engine brake...but no, I don't think that's normal...there shouldn't be any hesitation, as far as I know, when you take off at more than an idle or slight pedle.

Oops you're right I meant upshift.

Regarding the "hesitation" I'm not sure I would call it a hesitation. I may be exaggerating... it feels very minor. I guess it's kind of the same feeling when you are cruising with the A/C off, then you decide to turn it on. It feels just as light (except you get pushed back into the seat)...

One of my engine dog-bones is cracked (the rubber part in the center), so that could be it. I'm just surprised that's how it feels.

jackc
06-03-05, 06:32 PM
When my front mount went bad, you could definitely feel it "taking up the slack" until the dog bones took hold. Front mount failures are common due the torque lift put on that mount. If you say you've got cracked rubber in a dogbone, then both the mount and the dogbones are suspect to me. Check it out.

ps - this was my exact symptom: "When I am not careful and step on the gas too hard--accelerating from a dead stop-- I feel a similar jolt as if there was "play" or slack in a chain or gear. It's certainly not major, and it can be avoided by gradually applying the gas upon intial acceleration from zero."

mtflight
10-27-05, 04:26 PM
When my front mount went bad, you could definitely feel it "taking up the slack" until the dog bones took hold. Front mount failures are common due the torque lift put on that mount. If you say you've got cracked rubber in a dogbone, then both the mount and the dogbones are suspect to me. Check it out.

ps - this was my exact symptom: "When I am not careful and step on the gas too hard--accelerating from a dead stop-- I feel a similar jolt as if there was "play" or slack in a chain or gear. It's certainly not major, and it can be avoided by gradually applying the gas upon intial acceleration from zero."

Bingo.

Replaced both dogbones for cheap! No more slack/jerk.

weister42
11-04-05, 10:25 AM
Okay I went to gmpartsdirect.com and what exactly is the "dogbone" thing? How much does it cost and can I replace it myself? I have the same issue and would like to get rid of it.

mtflight
11-04-05, 11:04 AM
Okay I went to gmpartsdirect.com and what exactly is the "dogbone" thing? How much does it cost and can I replace it myself? I have the same issue and would like to get rid of it.

The GM part is probably close to $40 each. The aftermarket one is around 16 and 14. I chose aftermarket, because there's no technology behind it. Just a metal bone, with rubber and a pivot.

They are called torque struts, and they control the engine motion. They're holding on to the radiator support... and they look like bones that dogs eat. I got mine at Rockauto. You can certainly replace them yourself--piece of cake, maybe 30 mins for both.

weister42
11-04-05, 11:08 AM
I checked my torque struts and the rubber part definitely need to be replaced (I can move the dogbone just a little bit), do I replace the whole set or just buy the rubber inside it?

mtflight
11-04-05, 11:43 AM
I checked my torque struts and the rubber part definitely need to be replaced (I can move the dogbone just a little bit), do I replace the whole set or just buy the rubber inside it?

The rubber is what tears, the metal part is intact. I think they're only available as a whole (the whole "bone").

Ranger
11-04-05, 01:32 PM
I think a "little bit of play" is normal.