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1990 zr1 problem

 
Old 02-13-2019, 09:44 AM
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ConcreteMan
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Default 1990 zr1 problem

Hi Tadge,
I have a 1990 ZR1 that fishtails in first and second gear in the "Power" mode. Just the other day, I was in 1st gear and shifted to 2nd gear and floored it. I almost lost control of the car, which fishtailed to the left. 1st gear is crazier. I don't think it's a tire thing - there is plenty of tread and the pressure is at 35lbs. Maybe the prostration? I have heard a clunk a couple of times in the rear when turning, and don't know if this has anything to do with the craziness. The Z has 40,000 miles on it and I keep it clean, garaged, and it looks like it has just come off the showroom floor. I take it to the Corvette mechanic every 5000 mile fpr an oil change and to check fluids, etc., etc. Please inform,
Sincerely,
Rob Galli
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Old 02-13-2019, 11:26 AM
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Sorry, this won't be sent to the Chief Engineer.
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Old 02-13-2019, 11:55 AM
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Originally Posted by ConcreteMan View Post
Hi Tadge,
I have a 1990 ZR1 that fishtails in first and second gear in the "Power" mode. Just the other day, I was in 1st gear and shifted to 2nd gear and floored it. I almost lost control of the car, which fishtailed to the left. 1st gear is crazier. I don't think it's a tire thing - there is plenty of tread and the pressure is at 35lbs. Maybe the prostration? I have heard a clunk a couple of times in the rear when turning, and don't know if this has anything to do with the craziness. The Z has 40,000 miles on it and I keep it clean, garaged, and it looks like it has just come off the showroom floor. I take it to the Corvette mechanic every 5000 mile fpr an oil change and to check fluids, etc., etc. Please inform,
Sincerely,
Rob Galli
Take off from a stop in 1st gear and lay down some burnout tracks. Take a look & see if you have 1 track or 2. If 2 tracks, how old are your tires? If tires are less than 5 years old, you may need to check the C-beam bolts for proper torque. DO NOT over-tighten.
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Old 02-13-2019, 03:38 PM
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Sounds like hard old tires
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Old 02-13-2019, 06:46 PM
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81c3
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Sounds like a healthy LT-5 to me....
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Old 02-13-2019, 09:49 PM
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Tread depth doesn't mean anything, Y and Z rated tires have a life expectancy of 5 to 7 years.
It doesn't matter if they're driven on or not.
A 7 year old tire with original tread depth will have no more traction than a bald tire with 30,000 miles on it.
That being said, very few rear tires on ZR1's make it to 30,000 miles.
Spirited driving eats tire rubber like crazy. So do burnouts. ;-)

'Crabs
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Old 02-14-2019, 07:50 AM
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Originally Posted by 81c3 View Post
Sounds like a healthy LT-5 to me....

....with old tires GC

Last edited by Goldcylon; 02-14-2019 at 07:50 AM.
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Old 02-14-2019, 11:02 AM
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Paul Workman
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...AND, that "clunk" in the rear, combined with the rear kicking to the left screams "C-beam" attachment to me. (Been there, done that!)
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Old 02-14-2019, 08:51 PM
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You need the ZFDoc's CBeam Plates.
http://zfdoc.com/c4beamplate.htm
These will help with keeping the car straight during excessive throttle input in the lower gears.
It won't cure it, physics being physics after all, = r x F = r F sin(), but they sure help.

TomC
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Old 02-15-2019, 05:20 AM
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what rear gear is in the car? many early zr1s had a "welded collar" sleeve on 4.10 gears that would fail and clunk like crazy as the front pinion bearing goes away in the diff. Ask me how I know
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Old 02-15-2019, 04:37 PM
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The power plant frame from the tail housing to the diff is likely loose and misaligned. Tires are probably cold, too much tire pressure, car possibly needs an alignment, and C4 beam plates can't hurt.

...All that being said, first and second gear in my car are useless on my new Nittos unless I warm them up first. Even then first is always wheelspin and a bit of pull to the right. I have 4.1 gears out back, a few extra ponies up front, and no beam plates though.
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Old 02-15-2019, 10:52 PM
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The car I bought this summer the owner bought new Goodyear F1's in 09. The rear ones have about 85 % of there tread and the front more. Now being this is one of Marc Haibeck's 510 packages it was not something to be driven hard on those tires. My buddy gave me a set of chrome A molds with a nice set of drag radials on the back and I bought a set of the BFG summer tires for the front. Made a big difference. On the street I'm running about 26 lbs. in the drag radials. Before the weather got so bad before Thanksgiving we took it out for a little cruise. Grip was pretty good in first but shifting at 7000 rpm in second she got a bit loose. Gears are currently stock 3.45's but I want to go with the 4.10's as I prefer how they feel. The beam plates and new tires are a must. Any tire more than 5 years old you might as well be on ice skates. They vulcanize with age ( rubber becomes hard ) and you just have no grip. Believe it! For 8.5 years I worked in the tire industry. Miss those days. Got some awesome discounts on tires.
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Old 02-16-2019, 04:48 PM
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ConcreteMan
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Thanks to all of you for your comments. Which tires would be the best to give me better traction?
Again thanks for all your replies!!
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Old 02-16-2019, 04:52 PM
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Thanks Crabs. Will check it out.
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Old 03-06-2019, 06:44 AM
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Paul Workman
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Originally Posted by ConcreteMan View Post
Thanks to all of you for your comments. Which tires would be the best to give me better traction?
Again thanks for all your replies!!
Mine is set up like yours, and I'm quite happy with the Nitto 555/555r combo, or the "G2" tires especially in the wet.
The GY F1-GS-D3s were excellent all-round, especially in the rain! But, on the drag strip...not so good - even at 20# pressure. The Nitto 555r was the ticket (that along with Bill Boudreau's C-beam plates). But, they are like ice skating above 45-50 mph on wet pavement, OR if temps drop below 20F! (I'm on my 3rd set of 555/555rs. Love um in summer, but I get "white knuckled" when it starts to rain...no kidding.)
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Old 03-06-2019, 07:14 AM
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Drag strip? Who the hell takes a ZR-1 to a drag strip?
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Old 03-06-2019, 10:20 AM
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Tom400CFI
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Why wouldn't you? I'd drag track the hell out of any car that I owned (in fact, I do!). ZR-1 would be no different.

There used to be a guy that frequented our track in SLC with a '90 ZR-1...he came down from Idaho. He was there every week. He ran the hell out of that car and I loved it. Rand very consistent 13.5's.


.

Last edited by Tom400CFI; 03-06-2019 at 07:14 PM.
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Old 03-06-2019, 06:00 PM
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Originally Posted by Tom400CFI View Post
Why wouldn't you? I'd drag track the hell out of any car that I owned. ZR-1 would be no different.

There used to be a guy that frequented our track in SLC...he came down from Idaho. He was there every week. He ran the hell out of that car and I loved it. Rand very consistent 13.5's.


.
Obviously, you dont know Dwight too well.....
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Old 03-06-2019, 07:15 PM
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I don't. He a drag track'er?
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Old 03-06-2019, 08:38 PM
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Dwight is hammer down for anything & everything.
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