Off the wall question

[Frogman]

I jacked up the rear of my 98, (turned off Air Ride), and started the car. Turned off the traction control, and slowly started accelerating in Drive. Once the speedo got to about 40MPH, the motor started acting funny, and would not easily go past 45, IIRc.

Is this normal, aka: the computer is trying to figure out why the rear wheels are turning, and the fronts are not, so it derates the motor, or did I forget to turn something else off?

I did this little experiment in an attempt to find the elusive shudder I'm dealing with.

 

[JC1994]

dunno'...

 

[MrWilson]

i would think that wouldnt be a problem, or else how would you be able to use a dyno? just make sure ur not just jacking it up, get some stands under there too.

 

[Frogman]

Yeah. Thank you for that safety advice, Mr. Wilson. I had two midgets holding the rear end of the car up.

 

[94m5]

I'm not really sure man.




Could it be the awkward angles of the CV joints in the rear? Like wilson said.....they run these cars on dynos all the time, so this IS wierd.


Mike

 

[Psychostang]

I saw on the MKVIII message board, that a shudder during initial acceleration is due to a defective 1-2 shift accumulator piston.

Here is a link: http://www.markviii.org/LOD2/part_numbers.htm#Spring

 

[MrWilson]

just makin sure, lol.

 

[Joeychgo]

Yeah. Thank you for that safety advice, Mr. Wilson. I had two midgets holding the rear end of the car up.

ROFL!!!!!!

 

[Frogman]

I saw on the MKVIII message board, that a shudder during initial acceleration is due to a defective 1-2 shift accumulator piston.

Here is a link: http://www.markviii.org/LOD2/part_numbers.htm#Spring

Yes sir. I have a 98, and I have the J-Mod done.

Come on people! The person who gets this right gets a one year membership donation to LvC!

 

[MarkOfDeath]

when you do it, keep the car in first till 30 then upshift in to 2nd, turn off overdrive as well

 

[MrScalia]

can't rember why .... but what you did is not good for the rear-end or trany.
I just rember being yelled at from shop teacher for doing the same thing.
something about no presure on the rear-end.

 

[MarkOfDeath]

WARNING: IF ONLY ONE DRIVE WHEEL IS ALLOWED TO ROTATE, THE SPEED MUST BE LIMITED TO A MAXIMUM SPEEDOMETER READING OF 55 KM/H (34 MPH) SINCE THE ACTUAL WHEEL SPEED WILL BE TWICE THAT INDICATED ON THE SPEEDOMETER. EXCEEDING A SPEED OF 55 KM/H (34 MPH) OR ALLOWING THE DRIVE WHEEL TO HANG UNSUPPORTED CAN RESULT IN TIRE DISINTEGRATION/DIFFERENTIAL FAILURE, WHICH CAN CAUSE SERIOUS PERSONAL INJURY/EXTENSIVE VEHICLE DAMAGE.

After a road test, it is sometimes useful to do a similar test on a hoist. (Use an axle hoist, not a frame hoist. An axle hoist will not change the driveline angles. If only a frame hoist is available, axle stands must be used.)



Elevate the rear wheels slightly. Check to make sure both wheels will turn. WARNING: THE ELECTRICAL POWER TO THE AIR SUSPENSION SYSTEM MUST BE SHUT OFF PRIOR TO HOISTING, JACKING OR TOWING AN AIR SUSPENSION VEHICLE. THIS CAN BE ACCOMPLISHED BY TURNING OFF THE AIR SUSPENSION SWITCH. FAILURE TO DO SO CAN RESULT IN UNEXPECTED INFLATION OR DEFLATION OF THE AIR SPRINGS, WHICH CAN RESULT IN SHIFTING OF THE VEHICLE DURING THESE OPERATIONS. CAUTION: The suspension must not be allowed to hang free. When the Constant Velocity (CV) joint is at a high angle, extra vibrations as well as damage to seals and joints can occur.
Start the engine and place the transmission selector lever in DRIVE (D). Explore the speed range of interest using the drive/cruise/float tests.
A coast down in NEUTRAL must also be conducted. If the vehicle is free of vibration when operating at a steady indicated speed and behaves very differently in DRIVE and coast, an axle concern is likely.

 

[MarkOfDeath]

so by u letting the suspension hang you might of caused damage hope this helps

 

[JC1994]

I guess he let it all hang out! LOL!

 

[MarkOfDeath]

man your silly, hey did your headers make that much of an improvement, you should get a 3500 stall, it wakes these cars up

 

[JC1994]

I know! a little. yeah a stall would be cool.

 

[Frogman]

I don't understand the whole "Only one wheel rotating" bit.

I ran the car for max of 10 seconds. As soon as I noticed the motor acting up, I shut it down. Granted, I did use the brakes, I did not slam them, but gradually applied them.

Thanks MOD. Will update as soon as I get home, and get a chance to look around some more.

 

[mespock]

I'm going with the Midgets

 

[MarkOfDeath]

if only one wheel is moving, the speed is doubled, i guess

 

[Frogman]

That'd be hard to do on a posi unit, me thinks.

 

[MarkOfDeath]

well i dont know what mods you have, im just saying what needs to be done, or checked

 

[Frogman]

Aye. 3.73's with Trak-loc.

 

[MarkOfDeath]

let me know if leveling the suspension works, so i can look into other possible problems

 

[phreakness]

has your chip been programed with the 3.73 gear set? How extream was the angle of the car when you started the car?

 

[Frogman]

MOD, I reset the suspension height to stock. Haven't had a chance to test it out though. Will know Thursday. Thank you sir.

phreak = What Chip?

What was the Angle of the car? umm.. I think the midgets had the rear raised to about 1.4degrees off center. I dont know what the angle was... enough for the tires to clear the cement.