The physics involved is exactly why a Vette would be less likely to roll while in gear than a 4 cylinder, if one takes the vehicle wieght out of the equation. It takes a lot more force to turn over an LSx than it does a typical 4 cyl.

I won't say "no way possible," but there certainly is no normal reason a C5 should roll in 1st or reverse. Hell, my GF's 2.3L Mazda won't roll in 1st on a normal grade.

Betcha it'll inch even faster in 6th. You use reverse or first because they have the highest ratios, therefore a relatively small revolution of the axle requires more revolution of the motor. Overdrive gears (5th and 6th) have the lowest ratios and give the opposite effect.

 

^^^ Disagree, but no time to argue the point.

To the OP, due to the p-brake design it seems to be more effective in the reverse direction, so if you are on a steep hill, park it nose-up.

 

Post up when you have a chance. I don't mind admitting when I'm wrong.

 

I was just about to post that... My money is on the Diff/Posi

 

As I said before.. I think the Posi is at fault..

Take a look at this post on another forum...you need to scroll to the top to see the pictures to understand the concept.

http://www.nastyz28.com/forum/showthread.php?p=1158892

Especially this response #4... This all makes sense... At no load...ie. Car off.. there is not enough preload on the Posi clutches... Hence the car rolls..

When driving... there is enough force on them to keep the car driveable..

Just my $.02 I could be wrong..

 

A busted diff might allow the car to roll with the clutch engaged, car in gear, and motor not turning over, but I don't see how the car would be otherwise driveable.

Nice avatar, BTW

 

Thanks, i'd love to meet her..


Look at the post above.. I think this is a pretty good explanation as to the slippage but staying drivable..

 

Well? Did you ever get it figured out?

 

No. Car seems to drive fine. Shifts fine. (needs a firm hand in first) No noise. Just rolls in gear. I am going right now to harbor frieght for a breaker bar and torque wrench (125 ft lbs!) to get the parking brake fixed.

After seeing that others have similar issues I am going to just leave it. Mine seems to be a little more pronouced though. My guess is that with 85k miles there are just slightly worn parts. Combo of trans, clutch, engine, rear end, etc.

If you see a post in the next couple of months about body damage you'll know I fogot to pull the magic handle!

 

Look guys .... and gals .... either the differential is so broken the car is undriveable .... or the OP is NOT GETTING THE CAR IN GEAR.

Study how a differential works .... I don't care what kind you look at ..... unless one drive shaft is COMPLETELY broken off the main pinion .... what the OP describes is IMPOSSIBLE if the car is in gear .... and you still could NOT drive the car .........

Let me help you morons figure this out .... you ever heard of a car (Corvette, Toyota, whatever) with an AUTOMATIC IN PARK that rolled down a hill ?????????

NO ........................


The differential is not the issue .......

Unless the OP jacked his car up so one rear wheel is off the road ... either he has a car that is doing "magical" things ... or as I said earlier .... he is not getting the car in gear.

Not possible .... he is NOT getting the car in a gear ......

 

Are you seriously incapable of posting without calling people names? You seem to have some good knowledge/info, but it really takes away from the points you make when they always include "idiot" or "moron." You need to

 

Fair complaint ... though they are two of my favorite words ..... it just gets me REALLY irritated when I see "information" posted that is so incorrect ......

Al Gore claimed to be the founder of the "Information Highway" ..... yeah ... right ..... what he forgot to point out is that there are a lot of garbage trucks out there that deliver ... well .... garbage information.

 

I agree that too much misinformation gets posted, and you seem to know you stuff, so I'm glad you're on the board. But sometimes people are just throwing out suggestions to try to address a mysterious issue, so don't be too hard on them.

 

Quote...
Let me help you morons figure this out .... you ever heard of a car (Corvette, Toyota, whatever) with an AUTOMATIC IN PARK that rolled down a hill ?????????

Ok, this moron has...

My wife and I were coupling in the front seat of our Toyota Corona. I forgot to set the hand brake. At a most inopportune time the parking pawls on the A/T could no longer hold back the weight of the rocking car. We were in the Tahoe area and parked facing a very big cliff. We managed to get the brakes before going off the cliff.

Further..

CONSUMER COMPLAINT: ODI Case Number: 10223692

Component: POWER TRAIN:AUTOMATIC TRANSMISSION

Details: TL*THE CONTACT OWNS A 1998 HONDA PRELUDE. THE CONTACT PARKED THE VEHICLE IN HER DRIVEWAY, REMOVED THE KEY FROM THE IGNITION, AND EXITED THE VEHICLE. WHEN SHE RETURNED TO ENTER THE VEHICLE, IT BEGAN TO ROLL OUT OF THE DRIVEWAY. THE CONTACT WAS DRAGGED BY THE VEHICLE, BUT SHE WAS ABLE TO LET GO AND ROLL ON THE PAVEMENT. THE VEHICLE STRUCK THE MAILBOX AND CAME TO A STOP WHEN IT STRUCK A POLE. THE VEHICLE WAS TAKEN TO THE DEALER ON JANUARY 30, 2006 FOR NHTSA CAMPAIGN ID NUMBER 05V025000 (ELECTRICAL SYSTEM:IGNITION:SWITCH). THE MANUFACTURER WANTS THE CONTACT'S INSURANCE COMPANY TO INVESTIGATE THE FAILURE AND NOTIFY THEIR LEGAL DEPARTMENT WITH THE RESULTS. THE CONTACT SUSTAIN INJURIES TO HER LEFT AND RIGHT SIDE. A POLICE REPORT WAS FILED. THE POWERTRAIN AND SPEED WERE UNKNOWN. THE CURRENT AND FAILURE MILEAGES WERE 115,320.

Occurrences: 1 Injuries: 1
Fail Date: 04/04/2008 Deaths: 0
Date added to datbase: 4/8/2008

Whatever dood...

 

Wrong and Wrong.... and nice name calling.. Make sure you have your facts straight before you do that or you will be doubley OWNED...

An Automatic transmission does not roll because it uses a Parking Pawl. It is a ratchet that locks the transmission gears.. Ever throw an automatic in park before a complete stop? BDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD...

And the car is going into gear.. Its a terrible assumption that the Original poster is so stupid that he cannot get his tranmission to accept ANY gear to park in..

Grow up...


Nobody bothered to look at my Post #25

http://forums.corvetteforum.com/show...6&postcount=25

By the way.. to the original poster.. I'd be curious if you can leave an EVEN Burnout stripe. If you dont want to be that drastic.. Jack up the rear of the car till the wheels are off the ground. Put the car in 1st gear.

The get 2 people and each of you grab a tire and at the same time turn them in the SAME direction... I'll lay you a Bet you can turn them. If so... The POSI is FECKED!

 

I've seen lots of posts about dirty clutch fluid causing the clutch pedal to stick. Could this be the cause? Maybe the clutch is slightly engaged, allowing the car to roll?

 

First, it's not a broken axle or differential. If either had failed so that car would roll, it couldn't be driven either as no power could be put to the ground (unless it's got something like a Detroit Locker in it).

I suspect a shifting collar on the tranny is worn and allowing the tranny to shift into neutral when sitting on a slope.

 

Some basic differential theory?

Most vehicles have an open diff that uses spider and side gears. You can spin just one wheel but that wheel goes 2X as fast as the speedo is reading. If you jack the car up in park or in gear and spin one wheel forward the other one goes backwards with no real resistance.

A posi diff is very similar to an open diff except it has clutches in between the side gears and the case. When the spider gears try to turn the side gears they get pushed out into the clutches and the clutches hold the side gears and case together making power go to both wheels. Most of the power goes through the spider and side gears and the clutches are just there to provide enough resistance to make both wheels turn together. If you have a weak posi or enough of a traction difference between the wheels you can still spin one wheel.

So, in either case, the diff will not allow the car to move without the pinion moving unless something is broken or one or more of the wheels is sliding.

If the car in question is driving right and seems to be making full power then there really can't be a drivetrain problem so just fix the emergency brake. A drivetrain problem that would let a car just coast while in gear would have to be a pretty major problem that would be noticeable when driving.

Peter

 

I agree that maybe I didn't put the car in gear the first time or possibly the second. But when I focus real hard and sit in the driveway for 20-30 min trying to park the car, I think I would have got in gear at least once. And then I used the search and backed the car out and tried each and every gear again focusing on reverse. So again maybe it's operator error, but I doubt it. I drove the car about 75 miles today, and I wasn't Sunday driving either. Absolutly no indication of any problem whatsoever


During my test drive from the brake work I may have let the clutch out a little too fast with the rpm's a little too high and squeeked the tires. (about 5ft!!) Felt like the diff was working fine.

Then I backed in and tried it with the nose facing downhill. The car was very very barely moving. And the same for reverse.

Good news is my new tools work great and now so does my parking brake!

 

And when I say i backed in and tried it again I was talking about the rolling in gear not the squeeking tires!