Wheel Hop

[acammer]

Originally Posted by George-CZ

Man... if I hadn't seen it with my own eyes, I wouldn't have believed it.
Start with manual transmission on the drag strip at 5500 rpm

If you had told me, when I started racing this car 6 years ago, that it would need that kind of RPM, wide open, on a 2-step, I wouldn't have believed you. It's been a learning curve to get here.

And shifts at 7000 RPM with an LS3 engine, so I'll say it's impossible.

Actually, the target shift RPM is 7,700rpm - I bring a "soft" rev limiter in at that point, and have the "hard" limiter at 7,800rpm. It's actually built safe to turn 8,000rpm or a little more, but the curve suggests 7,700rpm is about the sweet spot.

It's very "not stock" - it has our (where I work) GPI Max Package 2.0 - which is essentially aftermarket LS7 cylinder heads that we finish specifically for use on an LS3, a very carefully thought out valve-train (Johnson short-travel link bar lifters, PSI 1513 springs, Comp Max-Lift BSR shaft rockers), and a cam and intake system that works well with everything else. It's still surprisingly streetable. I have some great video's on my Youtube regarding the details on what the Max Package is, dyno results, street driving it, etc - so please do check that stuff out if you're interested.

4.63 gears..? I have to study that. I wanted a shorter gears. But I was afraid that number one would be practically unusable.

Yea - for sure that's a very not-stock option as well. I have a G-Force "9 inch" in the car, which consists of a Strange 9 inch Pro Iron center section with their 35 spine S-Trac differential, 4.63 gears, and that lives in a G-Force fabricated housing that fits the factory differential location, using G-Force Renegade axles, and a 1 piece aluminum 3.5" driveshaft.

I ended up with the 9 inch setup because I grew tired of trying to make the OEM differential and axles live up to the rigors of stick shift drag racing, and I wanted to fit more gear ratio than the factory rear end would support. The factory rear end is just very marginally sized for the car - in an automatic car which is far less abusive, they do pretty well, and are a nice, efficient, light weight unit. In a stick shift car, they are one of the more common failure points - the aluminum case is subject to distortion under extreme load, the ring and pinion is undersized, etc. My failure mode was always ring gear teeth, I would either pull a few right off, or one time I even managed to crack one, but not break it. Sounded awful!

The 9 inch is heavy, and undoubtedly one of the least efficient rear end setups you could run with it's substantially more aggressive hypoid offset - but that is all a trade off worth making for incredible strength and reliability. It was costly to purchase, but I'm hoping it should be the last rear end I ever buy, and only need to come out if I want to make gear changes.

I have a good read on our website about more conventional rear gear options for these cars. The bottom line is simple, there really isn't much of a reason to NOT go 4.10s. They are more likely to be noisy than a factory gear ratio, even when properly setup - simply put they move the audible resonant frequency down to a speed where you can more easily hear it. Your stock 3.45s might be noisy, but at a speed higher than you typically drive at. Aggressive differential and rear subframe bushings also can help transfer noise into the cabin more easily.

This is hard for a lot of people to wrap their head around, but the shorter first gear actually makes it easier to use at the drag strip, as it requires less clutch slip. Stock cars with 3.45s, especially once they have a tire with good traction, require a big clutch slip on the launch, or they will bog. They also need more RPM on the launch to better overcome that smaller ratio. 4.10s (or more in my case) really help shorten up the length of the clutch slip. Now, it's true, on street tires, if the car has enough power to overwhelm the tires with the factory ratio, it's going to be even easier to do so with 4.10s. I don't blame the gear ratio for that, I blame the tire, because with good traction a 4.10 can hook well on the street. It ultimately depends on what you want from the car, but 4.10s were one of my favorite mods on my car - they were great with bolt ons, and cammed setups. The 4.63s are more fun still!

Sorry, information overload! I have had some slow mornings this week - as evidenced by all this posting.

[George-CZ]

Originally Posted by acammer

If you had told me, when I started racing this car 6 years ago, that it would need that kind of RPM, wide open, on a 2-step, I wouldn't have believed you. It's been a learning curve to get here.



Actually, the target shift RPM is 7,700rpm - I bring a "soft" rev limiter in at that point, and have the "hard" limiter at 7,800rpm. It's actually built safe to turn 8,000rpm or a little more, but the curve suggests 7,700rpm is about the sweet spot.

It's very "not stock" - it has our (where I work) GPI Max Package 2.0 - which is essentially aftermarket LS7 cylinder heads that we finish specifically for use on an LS3, a very carefully thought out valve-train (Johnson short-travel link bar lifters, PSI 1513 springs, Comp Max-Lift BSR shaft rockers), and a cam and intake system that works well with everything else. It's still surprisingly streetable. I have some great video's on my Youtube regarding the details on what the Max Package is, dyno results, street driving it, etc - so please do check that stuff out if you're interested.



Yea - for sure that's a very not-stock option as well. I have a G-Force "9 inch" in the car, which consists of a Strange 9 inch Pro Iron center section with their 35 spine S-Trac differential, 4.63 gears, and that lives in a G-Force fabricated housing that fits the factory differential location, using G-Force Renegade axles, and a 1 piece aluminum 3.5" driveshaft.

I ended up with the 9 inch setup because I grew tired of trying to make the OEM differential and axles live up to the rigors of stick shift drag racing, and I wanted to fit more gear ratio than the factory rear end would support. The factory rear end is just very marginally sized for the car - in an automatic car which is far less abusive, they do pretty well, and are a nice, efficient, light weight unit. In a stick shift car, they are one of the more common failure points - the aluminum case is subject to distortion under extreme load, the ring and pinion is undersized, etc. My failure mode was always ring gear teeth, I would either pull a few right off, or one time I even managed to crack one, but not break it. Sounded awful!

The 9 inch is heavy, and undoubtedly one of the least efficient rear end setups you could run with it's substantially more aggressive hypoid offset - but that is all a trade off worth making for incredible strength and reliability. It was costly to purchase, but I'm hoping it should be the last rear end I ever buy, and only need to come out if I want to make gear changes.

I have a good read on our website about more conventional rear gear options for these cars. The bottom line is simple, there really isn't much of a reason to NOT go 4.10s. They are more likely to be noisy than a factory gear ratio, even when properly setup - simply put they move the audible resonant frequency down to a speed where you can more easily hear it. Your stock 3.45s might be noisy, but at a speed higher than you typically drive at. Aggressive differential and rear subframe bushings also can help transfer noise into the cabin more easily.

This is hard for a lot of people to wrap their head around, but the shorter first gear actually makes it easier to use at the drag strip, as it requires less clutch slip. Stock cars with 3.45s, especially once they have a tire with good traction, require a big clutch slip on the launch, or they will bog. They also need more RPM on the launch to better overcome that smaller ratio. 4.10s (or more in my case) really help shorten up the length of the clutch slip. Now, it's true, on street tires, if the car has enough power to overwhelm the tires with the factory ratio, it's going to be even easier to do so with 4.10s. I don't blame the gear ratio for that, I blame the tire, because with good traction a 4.10 can hook well on the street. It ultimately depends on what you want from the car, but 4.10s were one of my favorite mods on my car - they were great with bolt ons, and cammed setups. The 4.63s are more fun still!

Sorry, information overload! I have had some slow mornings this week - as evidenced by all this posting.

I finally got through all the knowledge.
I have to admit that you have a pretty mad frog
That car really oozes respect.



But what surprised me the most was that I had basically been using the car wrong all the time.
Never in my life would I have thought to loosen the clutch a little when starting in to the lights to avoid a sudden jerk.
I've always kept the idle higher before start and the clutch fully disengaged.


I'll have to try it somewhere this summer.
I don't think I will use all the modifications you described, but I really like a few of them and will definitely do them in the future.


The 2010 SS Camaro has launch control after double pressing the traction control button right...?
Could he be used as a beginner assistant nanny? ...for the initial determination of correctly high revolutions.


Thank you for a very interesting experience

[The Flash]

Originally Posted by acammer

I've had aluminum sub-frame bushings for years. No issues.

The subframe bushing is the key to the whole rear end. Nothing else you do as far as control arms, toe rods, trailing arms, and even diff bushings is worth a lot until you control what they are mounted to - the sub-frame. Like a few have said, the inserts are ok, the poly is good (plenty for most), and the solid aluminum is the ultimate solution. One of the best things I did on my car was the now discontinued Pegasus solid subframe bushings.

As far as axles - those cheap parts store axles are far weaker than the OEM axles. Once you kill a stock axle, you'll keep killing those parts store ones in a hurry. Getting hard to get the genuine GM ones anymore. It's pricey, but something from G-Force is your best path forward to a long term, reliable solution.

[The Flash]

Originally Posted by acutron42

I would highly recommend watching Andrew Cammer's videos on youtube. He has put countless hours into explaining proper techniques with these cars. These GPI guys are pushing the limits of these cars & getting great results as InFiD3ViL pointed out. Ryan's 8.55 pass with a stock bottom end is another great video.

Most Impressive!!!

[FasNuf]

Great video. I didn't know you could log clutch pedal position % in HPT.

[1JEWLDSSRS]

Originally Posted by acammer

I've had aluminum sub-frame bushings for years. No issues.

The subframe bushing is the key to the whole rear end. Nothing else you do as far as control arms, toe rods, trailing arms, and even diff bushings is worth a lot until you control what they are mounted to - the sub-frame. Like a few have said, the inserts are ok, the poly is good (plenty for most), and the solid aluminum is the ultimate solution. One of the best things I did on my car was the now discontinued Pegasus solid subframe bushings.

As far as axles - those cheap parts store axles are far weaker than the OEM axles. Once you kill a stock axle, you'll keep killing those parts store ones in a hurry. Getting hard to get the genuine GM ones anymore. It's pricey, but something from G-Force is your best path forward to a long term, reliable solution.

^^^ Great info here, as always. One of the best mods I have done to my suspension was the Pegasus solid aluminum cradle mounts per advice from JDP Motorsports when I chatted with Jordan about wheel hop and just getting more power to the road. Man what a night and day difference in how "solid" the rear end is now at putting the power to the ground, No more wheel hop, and the rest of my suspension is STILL stock, except for the Pfadt 1.25 springs.No issues to date.