Ive been having trouble with my ETs being all over the place. C4, auto trans, stock converter 3.07 gears. I am running BFG G Force KDs and the car usually hooks good at the tree.1.85 60's. The problem comes when it shifts to 2nd. about half the time the back tires break loose. Not just a chirp but it feels like they are spinning free for maybe 6 feet. Hard to be real accurate on that part. Seems like it just unloads the rear tires just before it shifts. I am open to any ideas on this. If youve had this problem jump in and give me some suggestions.

 

Is the motor stock, & what kind of ET are you running... reason I ask, I had a 96... it was about the same Automatic, with 3.73 gear, and a 3200 converter... also 1.6 RR

With Drag Radials it 60' in 1.65 my 1/8 mile was 8.04 best 1/4 was 12.28 @ 112 but that was in KILLER AIR... normal Et was more like 12.45 @ 109 - 110 mph.

I find it odd you are hooking up off the line and spinning so HARD on the 1-2 shift.. my car even with street tires never spun on the 1-2 shift..

 

Is it possible that your getting out of the grove of the track?

 

 

ZZ4 motor 180 cc heads, headers, Miniram, usual stuff. 1/8 mile, 8.25-8.35 87 mph. 1/4 12.8 around 107. been a while since I ran 1/4 and my 1/8 has gotten a little better so the 1/4 should be also. . I did unhook one side of the sway bar and that helped traction off the line but not on the shift. Shifts at around 5900 rpm. It only does this about 1 time out of three maybe. Hard to dial in like that. Only 1 more week then the track closes for the season but I'm going to try and make it to Beech Bend after that but its a 120 mile drive.

 

I guess its possible, but Ive done a lot of racing and try to drive the same way every pass.

 

Thought I'd add that the car is tuned to be soft on the bottom end. Really weak the first 25 feet or so. Just to keep the Dana 36 together.

 

is it spinning both tires or could your posi be taking a dump

 

Both tires are spinning. I rebuilt the posi about 3 years ago. When I took it apart, I could not believe how worn out it was though.

 

Hmm, you're absolutely sure the tires are slipping? And at 5900 rpm, BEFORE the 1-2 shift? That just sounds odd. How do you know it's the tires slipping? Does the car kick sideways? I don't think it's just rare for tires to slip like that, I think it's unheard of. Typically, tires slip at launch, and immediately AFTER shifts. Velocity is change in location / time. Acceleration is change in velocity. Jerk is change in acceleration. Jerk causes wear, breakage, and wheelspin. If you graphed jerk on a typical 1/4 mile run, it would be highest at launch, and then fall off as the RPMs climb. Jerk spikes again, but not as high, when the transmission shifts to second and the engine suddenly drops back to lower RPMs to rev through the power band again. Jerk will spike again at the 2-3 shift, but not nearly has high as launch or 1-2 shift.

If the tires hook at launch and after the 1-2 shift, but something's giving way at 5900 rpm right before the 1-2 shift, I'd be suspicious of drivetrain issues. Torque converter slipping, transmission slipping, differential slipping? Could it be a suspension issue? Maybe the weight is coming off the back tires for some reason, causing them to slip? I have seen wheelie cars lose traction when the front wheels come back down and the car bounces. It's pretty scary. But given your problem description, I would need some hard evidence to convince me it was tires slipping.

 

Reoch99 it spins when it hits 2nd, not when its still in 1st. I think maybe the tires unload at that point.

 

Ok, I misunderstood. It still is odd to spin in 2nd and not 1st, but much more logical than what I thought was going on. Maybe you could borrow a pair of new-ish drag radials and see what happens? With my old worn out BFG drag radials, I was getting just a touch of spin at the line and again at the first shift, but with a new pair of ET street radials it's better. (low 1.7s 60')

 

It is odd that it spins at the 1-2 shift. Most hard hitting automatics will chirp the tires on the 1-2 but not spin. With most cars, the problem with traction is right at the start. Sounds like you need some better tires. BFG or MT Streets.

 

Was this on a single day at one track or more than one trip. Any other cars having problems?

If I hit it too hard off the line with the nitrous I will spin all the way down the track and have to let out of it. Like the others have said the 1-2 shift is usually just a chirp or small loss of traction.

 

Only one track. Actually seemed to be in the left lane. I was running Sportsman using the right lane with no issues. I made one pass down the left and felt the spin. A buddy was running my car in Trophy out of the left lane, and his ets were all over the place. I have had this problem on more than one occasion though. I think I have suspension problems, just dont know what to look at. I rarely go to other tracks because this one is 1 1/2 miles from home.

 

i would figure that the traction problem would be on a global standard rather than only a 1-2 shift. once under way i have never come across a traction problem in my vette. aside from using nitrous too late in the power band.

 

Sounds like a blown rear shock...,could cause what you describe..... have friend drive down bumpy road observe action of rear tires or disconnect shock and work by hand if bad either method you will know right away

 

I cant remember how old the shocks are. I know I replaced the fronts last year. I will check on the backs.
This week I will try less air in the tires, full tank of gas instead of 1/2, maybe even 100# of ballast. Maybe take out some timing. Only get 2 time trials, have to make the best of them.

 

If it was me I would try to recreate what happened first. Maybe make the 1st run without any adjustments and have someone watch closely from the outside to see what the tires and rear do. Possibly even video tape it. It may not even happen again or have been what you thought it was. Just a thought.

 

This has happened on more than one occasion. The car was apart most of this season so I did not get much track time. The BFG KDs are new this September and was hoping they would fix the problem. Definitely helped at the launch. If I clean them off good it hooks good. Just need to figure this thing out. Its raining today and does not look good for tomorrow. May have to head down to Beech Bend in the next couple weeks to try anything. Thats 120 miles each way.