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'99 Z28 - rear end slipping in reverse?

This is a discussion on '99 Z28 - rear end slipping in reverse? within the Drivetrain forums, part of the LSx Technical Help Section category; I've got a '99 Z28, 6 speed, bone stock except for a Ram clutch kit a few years ago. I've ...

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    '99 Z28 - rear end slipping in reverse?

    I've got a '99 Z28, 6 speed, bone stock except for a Ram clutch kit a few years ago.

    I've got a couple of racing karts that I tow with a little ~ 300lb utility trailer. A while back I noticed slipping and what smells like burnt rubber when trying to back the trailer up even gentle inclines. There's no problem going forward, the car happily spins the tires, or chirps into 2nd if I want.

    Now I even get the slipping noise and burnt rubber smell when I'm just backing the car uphill a bit with the wheels turned.

    Is it possible that the differential is slipping when under load in reverse? The noise seems to come from the rear, and the smell is definitely not like burnt brake or clutch lining.

    thanks,

    Gn

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    Quote Originally Posted by Gnobility View Post
    I've got a '99 Z28, 6 speed, bone stock except for a Ram clutch kit a few years ago.

    I've got a couple of racing karts that I tow with a little ~ 300lb utility trailer. A while back I noticed slipping and what smells like burnt rubber when trying to back the trailer up even gentle inclines. There's no problem going forward, the car happily spins the tires, or chirps into 2nd if I want.

    Now I even get the slipping noise and burnt rubber smell when I'm just backing the car uphill a bit with the wheels turned.

    Is it possible that the differential is slipping when under load in reverse? The noise seems to come from the rear, and the smell is definitely not like burnt brake or clutch lining.

    thanks,

    Gn
    keep in mind that usually when backing up you are feathering the clutch which is actually slipping it. could be clutch you smell.

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    Quote Originally Posted by dklowrider View Post
    keep in mind that usually when backing up you are feathering the clutch which is actually slipping it. could be clutch you smell.
    Yeah, I know. Would a clutch slip in reverse waaay before spinning the tires? Could the replacement Ram clutch somehow only have ~1/4 the grip in reverse?

    I never rev the engine and side-step the clutch, but I do occasionally launch pretty hard with some tire spin. The clutch never makes the moaning noise I hear in first gear, and I never smell the odor that I do when I'm backing uphill.

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    Quote Originally Posted by Gnobility View Post
    Yeah, I know. Would a clutch slip in reverse waaay before spinning the tires? Could the replacement Ram clutch somehow only have ~1/4 the grip in reverse?

    I never rev the engine and side-step the clutch, but I do occasionally launch pretty hard with some tire spin. The clutch never makes the moaning noise I hear in first gear, and I never smell the odor that I do when I'm backing uphill.
    i never ran that particular clutch but i believe they are pretty heavy, as in either in or out, not a lot of play in between. when you are backing up you would usually slip the clutch as you are backing cuz you would be going pretty fast to try and back up with a trailer and have the clutch the whole way engaged[as in your foot off the pedal totally] so you would be slipping it on purpose in a way you never would by regular driving, plus the weight of the trailer working against you. i think youre smelling the clutch, unless you are completely engaging it and its slipping by itself. but the clutch grabs the same either way you are going, its the output shaft of the transmission that will change the direction of the car, the clutch is on the input side always going the same direction. the only difference is i believe reverse gear is a higher ratio than 1st, backing would sort of be like pulling out in 2nd gear.

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    You're right...the clutch assy, flywheel & input shaft are always going the same direction as the engine. DOH!!!

    I'm still suspecting the differential...maybe the limited slip clutches or something are shot. It's doing it now even without the trailer...just reversing out of a parking spot on a slight grade, and it never happens going forward

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    Quote Originally Posted by Gnobility View Post
    You're right...the clutch assy, flywheel & input shaft are always going the same direction as the engine. DOH!!!

    I'm still suspecting the differential...maybe the limited slip clutches or something are shot. It's doing it now even without the trailer...just reversing out of a parking spot on a slight grade, and it never happens going forward
    Impossible. The differential can't slip. Its a constant mesh ring and pinion, if its not putting down power its blown up

    Same goes for the transmission, its either in gear or not in gear. Can't "slip".

    Sounds like your clutch is burning up. What kind of RPM's are you at when you are backing the trailer up?? Performance clutches aren't meant for towing or extended slippage, that sounds like your issue.

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    Quote Originally Posted by Wesman View Post
    Impossible. The differential can't slip. Its a constant mesh ring and pinion, if its not putting down power its blown up

    Same goes for the transmission, its either in gear or not in gear. Can't "slip".

    Sounds like your clutch is burning up. What kind of RPM's are you at when you are backing the trailer up?? Performance clutches aren't meant for towing or extended slippage, that sounds like your issue.
    im trying to show everything thats going on with the clutch but we keep going back to the rearend for some reason.

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    Quote Originally Posted by Gnobility View Post
    You're right...the clutch assy, flywheel & input shaft are always going the same direction as the engine. DOH!!!

    I'm still suspecting the differential...maybe the limited slip clutches or something are shot. It's doing it now even without the trailer...just reversing out of a parking spot on a slight grade, and it never happens going forward
    the limited slip clutches are designed to slip so that your outside wheel can go faster than the inside one when youre turning, while allowing them to stay locked together in straight running or reduced traction situations.

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    Quote Originally Posted by dklowrider View Post
    im trying to show everything thats going on with the clutch but we keep going back to the rearend for some reason.
    Sorry to be a PITA, but I kept after the diff as the source of the problem because

    - it sounds like it's coming more from the rear of the car
    - it smells more like rubber than burnt clutch linings I've smelled in the past
    - the clutch hooks up with no problem in first, even when starting on a steep incline. Backing up (even without the trailer now) on a much slightler grade causes the strench and the slipping noises, and I never hear it or smell it in first

    I thought there was a possibility that a worn limited slip clutch-pack unit might be able to somehow slip only while backing up. Sounds like that isn't possible.

    Now I'm wondering if the tranny or ring & pinion might be binding a bit in reverse only. Reverse & the fwd gears really do behave that differently.

    Gn

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    Quote Originally Posted by Gnobility View Post
    Sorry to be a PITA, but I kept after the diff as the source of the problem because

    - it sounds like it's coming more from the rear of the car
    - it smells more like rubber than burnt clutch linings I've smelled in the past
    - the clutch hooks up with no problem in first, even when starting on a steep incline. Backing up (even without the trailer now) on a much slightler grade causes the strench and the slipping noises, and I never hear it or smell it in first

    I thought there was a possibility that a worn limited slip clutch-pack unit might be able to somehow slip only while backing up. Sounds like that isn't possible.

    Now I'm wondering if the tranny or ring & pinion might be binding a bit in reverse only. Reverse & the fwd gears really do behave that differently.

    Gn
    im not trying to tell you something is wrong with your clutch! im simply saying that what you are doing[backing a trailer up a hill] could be causing you to smell clutch cuz you have to slip it to do that. its not "normal" driving so you might have an "abnormal" smell. it doesnt mean anything is wrong especially if it only does it backing a trailer up a hill! turning makes it worse. try pushing your car with the wheels straight, then try pushing it with the wheels turned and a trailer hooked to it.

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    you know what the bad part is? you may actually have something wrong with your car. but other than the obvious type of problem, its hard to tell everything sitting at a computer. i saw you didnt say that you were turning and backing the trailer up a hill, but my example still has some merit. hope it all works out good for you.

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    If I try and back a trailer up a driveway apron I get major slippage & burnt rubber odor.

    Now even backing up out of a downhill facing parking space with no trailer and an empty car causes the slipping sound and some burnt smell.

    The clutch is solid as a rock going forward though.

    Beats the hell out of me. fwiw, I'm 49, and having been driving manual trans cars and motorcycles since I was 13. The original clutch in the Z28 lasted 140K miles, and I only replaced it then because the clutch slave cylinder crapped out.

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    Quote Originally Posted by Gnobility View Post
    If I try and back a trailer up a driveway apron I get major slippage & burnt rubber odor.

    Now even backing up out of a downhill facing parking space with no trailer and an empty car causes the slipping sound and some burnt smell.

    The clutch is solid as a rock going forward though.

    Beats the hell out of me. fwiw, I'm 49, and having been driving manual trans cars and motorcycles since I was 13. The original clutch in the Z28 lasted 140K miles, and I only replaced it then because the clutch slave cylinder crapped out.
    this could be a tough one. maybe you ought to get it up on a lift so you can look it over real good underneath, all suspension parts, phr etc.

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    I think your tires are rubbing on something, especially in reverse. What size tire are you running?

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    I would check the inner edges of the front tires. You first said backing uphill and turning, you're transfering weight forward and with the wheels turned the edge is closest to the wheel well. Did you recently put tires/rims on it? Is it lowerd, or worn original parts?

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    Quote Originally Posted by Ten5TireRacer View Post
    I would check the inner edges of the front tires. You first said backing uphill and turning, you're transfering weight forward and with the wheels turned the edge is closest to the wheel well. Did you recently put tires/rims on it? Is it lowerd, or worn original parts?
    I think you & Cutlass have it...10 year old springs & suspension bushings are causing rubs at weird suspension loadings - full-lock turns backing uphill, and worse with a loaded trailer. I haven't seen any surfaces rubbed clean just looking into the wheelwells, or cuts on the tire corner (stock 235/55 x16", btw), but I expect I'll find some when I pull the wheels.

    Gn

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    Quote Originally Posted by Gnobility View Post
    I think you & Cutlass have it...10 year old springs & suspension bushings are causing rubs at weird suspension loadings - full-lock turns backing uphill, and worse with a loaded trailer. I haven't seen any surfaces rubbed clean just looking into the wheelwells, or cuts on the tire corner (stock 235/55 x16", btw), but I expect I'll find some when I pull the wheels.

    Gn
    that sounds like another good place to look. only problem is when youre backing up are the tires going around fast enough to actually produce a burnt rubber smell?

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    Quote Originally Posted by Gnobility View Post
    I think you & Cutlass have it...10 year old springs & suspension bushings are causing rubs at weird suspension loadings - full-lock turns backing uphill, and worse with a loaded trailer. I haven't seen any surfaces rubbed clean just looking into the wheelwells, or cuts on the tire corner (stock 235/55 x16", btw), but I expect I'll find some when I pull the wheels.

    Gn
    just catching up to see if you found anything.

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    Quote Originally Posted by Cutlass View Post
    I think your tires are rubbing on something, especially in reverse. What size tire are you running?
    The title and things said the thread don't make sense to me. You are pulling a trailer with a Z28?

    If you are smelling rubber, then the tires are being pushed or spun. Such as stated above. That is my best guess.

    How would you know that a diff is slipping in reverse? That is what I don't understand. That would require heavy throttle going backwards and turning.

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    I know whats wrong...............YOUR TOWING A TRAILER WITH A CAMARO!! But seriously why would you tow a trailer and hope you figured it out.

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