tylerdietzenbach

Okay so I just bought a 1998 Z28 Camaro. the car has a legitimate 27,000 ORIGINAL miles on it. My question is that when I'm coming up to a stop almost every time right before I come to a complete stop the car lunges/jerks forward. Its definitely noticeable. I have a hard time believing that its the transmission with the low miles but that's what it feels like. Its the only problem/complaint about the car I have found within the 1st month of owning it. This is my first rear-wheel drive car. Could it be the LSD (fluid?) or something? I have records of the oil changes but i don't see anything about a axle fluid change nor do i know much about them.

So i bought a 98 Z28 Camaro with 27,000-28,000 miles on it. when pulling up to a light or a sign, coming to a stop. right before a complete stop occurs it makes a jerk. Now after owning it for awhile now it still does it with no difference from my previous post about 8 months ago or so. But i do hear a knock at the same time as the jerk. the knock is not from the front of the car (everyone concluded transmission the first time i asked) However the knock i hear is from the rear of the car, i know this for a fact. Now could it be the differential? also sometimes when the car hits bumps or bounces there's a "ping" sound which is also from the rear. and I've also heard it just getting out of the car a few times. not sure if these are connected issues or separate. Thanks for reading and hopefully I can get some answers from the experts on here.

myk

iTrader: (4)

Are you hearing a clunking, or any other sort of noise? I don't think it's drive train related-nothing to do with the motor, tranny or 'diff, but rather engine control related. I'm not entirely familiar with how all of that stuff works, but I'm figuring something is going wrong as the car transitions from low cruise to idle. Let's see if anyone more familiar with this stuff steps in.

Which transmission are you running, btw?

RPM WS6

iTrader: (3)

What is happening with engine speed (rpms) when the condition occurs? Just before the complete stop, do you see/feel an excessive reduction in engine speed (sudden low rpm condition), possibily followed by a correction that may over compensate for a moment (rpm too high), thus causing a jerk/lunge?

In other words, do you see (gauges) or feel any indication that the engine is on the verge of stalling or idling rough just before the lunge is observed?

And have you scanned for any codes?

tylerdietzenbach

There is a slight knock sound about 1-2 full seconds before the jerk happens. I have the auto transmission, should have said that first my mistake. it does not run rough at any time either or come close to stalling. all gauges are consistent except RPMs. i have not scanned for codes. i know the check engine light is not on. no warning lights of any kind.

the rpms do actually move on the knock sound. they go from 900 to 1000 rpms. now this isnt at the stop its when i hear the knock which like i said previous is probably 1 full second before the jerk.

BoricuaHec01

Should've got the Carfax from the previous owner. **** blows man, sorry to hear.

mikey67

Carfax? You watch too much TV man.

To the op, can you give us more detailed info about the car? ...any mods etc. It would help with a possible diagnosis.

01ssreda4

iTrader: (96)

Sounds like a trans downshifting issue to me.

OP, understand this, mileage means nothing. Everything in these cars has age working against them, so anything can fail at anytime. Good luck.

tylerdietzenbach

i bought the car from a classic auto sales place in nebraska. the guy has tons of classics and some porsche 911s also. i got a free 1 owner carfax with nothing reported of any kind. everything is orginal on the car. not even a scratch. i guess it could be tranny related but it feels nothing like a car i had previous which had a downshift issue

zacht

iTrader: (18)

where at in nebraska are you???

myk

iTrader: (4)

Well if it's an auto and you're RPM's are fluxuating that's different. Looks like you'll have to find someone to diagnose your 'trans. As another poster said, mileage means nothing-the best machines will succumb to age at some point...

RPM WS6

iTrader: (3)

In my personal experience, transmissions don't usually fail from age alone. If they are low mileage and in excellent working order, they can sit around for a long time and still be just fine when you start using them. Of course, that assumes that nothing was wrong with them in the first place. Factory defects do exist, and low mileage failures do happen.

Having said that, I don't really see anything in this thread that points 100% to a transmission issue. The change in rpms is small enough that it could simply be the normal process of downshifting, which happens as the vehicle slows to a stop.

There are many suspension, chassis and drivetrain related parts that can cause clunks/jerks/knocks. If you are not familiar with inspecting these areas you may want to take it to someone who is.

LS6427

iTrader: (2)

There's only three ways an engines' rpm can increase.

You open the throttle blade

The IAC opens

Vacuum leak

I assume you're not doing it. So look into the IAC valve or a vacuum leak. Now it could be a fuel pressure issue, where it drops, then comes back up and jumps past a normal "off-throttle" idle position as you are slowing down. And an automatic tranny car will have an increased rpm as you are slowing down because the converter is unloaded.

If you can, get a scan while the engine is running and have them check everything before you go tearing into a tranny.

Your intake could be loose too, coming to a stop can torque everything and it can be getting a little gulp of air.

.

Tyler Z28

iTrader: (1)

+1 tranny downshift into first when your slowing is my guess. my elco did the same thing it was because of a dirty tranny cooler and a tired th350.

Gallstaff

iTrader: (1)

I've owned three LS1's and they've ALL done this. I wouldn't worry about it. I think this is pretty normal as the transmission downshifts to a stop. I mean **** dude, this is a 10ish year old sports car with a FOUR speed automatic transmission. You're going to feel it downshift like that. I'd say it's not much to worry about. My current 98 TA with 118k miles does it, my last TA with 89k miles did it, and my first 99 TA with 69k miles did it.

tylerdietzenbach

i bought the car in Omaha but i live 5 hours east of there in Iowa. there is a ping (spring?) in the suspension. i need to go through and change the tranny fluid and filter as well as the axle fluid anyways so a good time to do some inspection. sorry for the slow replies by the way. and i know the car sat every winter it has never seen snow and was always under a car cover. it was very well taken care of. the feeling is more of a lunge forward then a slip and jerk

ULTIMATEORANGESS

iTrader: (4)

id check your Ujoints and DS.

tylerdietzenbach

Thanks for the quick reply. I need to get around to that. I'm pretty unfamiliar with this type of car still. Only had a couple front wheel drive Olds before this haha. would these cause a pushing forward jerk feeling like i mentioned? I know they can cause some sounds

Anyone else with further ideas on 1 or both problems still would be appreciated. if you dont feel they are the same problem that is.

ULTIMATEORANGESS

iTrader: (4)

test your shocks also.

tylerdietzenbach

how do I go about testing/checking this 3 items? I have experience with working on minor things. Can do some body work and a little electrical. But still pretty unfamiliar with anything not involving struts, wheel bearings, cv joints stuff like that

SRTMario

I would get under the car and do an inspection. See if everything is connected, look at the shocks to see any evidence of fluid leaking from them. Look to see if any of your rubber bushings are bad. Grab onto things like the sway bar and torque arm to see if they have excessive movement.