Rear end spins out to the left.

[Detroit Bill]

Let's just say the old expression there is no such thing as a dumb question does not apply here. I have read back hundreds of pages in several sections and this is one of the most sarcastic boards I have ever seen and I have participated in many diverse boards. There are more post that do not apply in any way to the subject then I have ever seen anywhere.

[patrickt]

Originally Posted by Detroit Bill

Let's just say the old expression there is no such thing as a dumb question does not apply here. I have read back hundreds of pages in several sections and this is one of the most sarcastic boards I have ever seen and I have participated in many diverse boards. There are more post that do not apply in any way to the subject then I have ever seen anywhere.

Absolutely correct. And one of the reasons for that is that we have an unusually diverse membership... everything from blue collar mechanics to neurosurgeons... and nobody gets a free pass.

[RET_COP]

Nice-- Now depending how your rear twists based on the bushing material and flex points, angle the pinion down from the trans rear flange angle so that under hard acceleration the pinion flange and the trans flange are plumb with each other.
Scale the car with driver !!!!

[Detroit Bill]

Originally Posted by patrickt

Absolutely correct. And one of the reasons for that is that we have an unusually diverse membership... everything from blue collar mechanics to neurosurgeons... and nobody gets a free pass.

I see that. Very welcoming.

[Cashburn]

Incredibly more sarcastic comment completely erased...

[Cashburn]

Originally Posted by cycleguy55

Patrickt: Perhaps I took Detroit Bill's comment differently than you did.

Cashburn posted '9" ', with the 'smiley' indicating 'sarcasm'. I took that as his questioning why someone would have a 9" Ford rear end in their car, especially when he has a Backdraft with an IRS.

My perspective on Detroit Bill's comment was he was merely challenging Cashburn to do more than take a 'cheap shot' and explain his concerns or issues with a 9" live axle. Perhaps, as a purchaser of a car with an IRS, he'd like an informed opinion from someone who has one.

Just my $0.02.

Are you kidding? I don't have 1 Backdraft with IRS, I have hundreds!

9" best drag axle ever, come on, someone really wants to debate this. Let's get out of JV and play some Varsity.

[patrickt]

Originally Posted by Cashburn

Incredibly more sarcastic comment completely erased...

Damn, I love a really sarcastic comment.

[Cashburn]

Originally Posted by Detroit Bill

Let's just say the old expression there is no such thing as a dumb question does not apply here. I have read back hundreds of pages in several sections and this is one of the most sarcastic boards I have ever seen and I have participated in many diverse boards. There are more post that do not apply in any way to the subject then I have ever seen anywhere.

Ehhh... I'll put it back. You've got a way with hyperbole.

[Tommy]

Let me get this straight. Are you guys saying the hyperbolic sarcasm is more to blame for the clockwise rotation than the Coriolis effect? ..... I learn something new every day.

[vector1]

Naw, hyperbole is where you turn the thing around so it slides the other direction. Before this thing gets rolling we need to figure out who is making the aluminum bodies...

[mikeinatlanta]

At the risk of dragging a thread back on topic.

landmass:
I gather from your posts that this car is used on the strip, street, and track. With the multiple uses of the car (and even without), making changes without first knowing exactly where you are starting from is not a wise move. Your first step needs to be a complete four wheel alignment so that you can be confident where each wheel is located, and where it is pointed. This should include a corner weighting, pinion angle, and verifying shock valving on a shock dyno. The alignment figures you use are irrelevant as they are only a baseline. Once you know where you are starting, you need to mark your components and establish a setup log to record the effect of every change you make.

Unless you complete the above, not a person on this earth can accurately help you with setup advice. Someone may get lucky, but it will be luck.

Now, back to the regularly scheduled sarcasm.

[landmass]

Thanks, all of you, for your comments. I'm still confused as to why the size of the rear end would matter. It is a Ford 9" rear end with a Detroit Eaton Truetrac installed. I went to the track the other night, and during the burnout, the car stood still for about one second before going slightly to the right. When I look looked at the GoPro video, it showed that I jerk the wheel about 6 inches to the left under the pressure of the launch. I think this is what started the rear going to the right. But, then I was thinking how could that cause that when the car was sitting still - no forward movement for the turn to come into play - right? Would a turn of the steering wheel cause that when the car is NOT moving forward? I could hold the steering wheel much lower, so the force of launch wouldn't jerk the wheel to the left, but more straight back...

[RET_COP]

In the first post the rear drifted left during the burnout, now it drifts right, what changes if any were made.
Holding the steering wheel at 8 o'clock will lock your arm.
Are you using a line lock. Locked front tires will keep the car from drifting, if both tires do not lock evenly the car will drift.
How does it respond at launch with some traction

[landmass]

The panhard bar was centered(it was off about 1/4")to the frame. Now it is off about 1/16" - every time we lower the car and jacked it back up, the measurement changed slightly. This require several cycles before settling on 1/16"(which I am happy with for now). Also, we changed out one heim joint on the driver's side trailing arm bar, then verified that both trailing arms were of equal length from inside of rear mounting bracket to the frame point of connection. The pinion angle was then set. I had done the adjustments myself a couple of days prior to my ex-drag racer mechanic friend, but we rechecked and adjusted everything again at his shop. I haven't driven the car a lot since the repair due to the cold weather. But, when it warms up a bit, I'll do a couple of test burn outs and see what happens - both with and without the brake line lock. Thanks for the 8 o'clock tip - I'll try it for sure. Yes, I used the new line lock my very last race, the one described in my previous post. That's why I was surprised that the car drifted right when standing still - until I saw the GoPro video. How does it respond at launch with some traction you ask? I have a track photo that shows both front tires about 4 inches off the ground at launch - and with drag radials. I tried to attach the photo to this message, hope it works

[RET_COP]

If the car is launching straight and level ( the photo looks great by the way) through the first shift then you don't have a problem with the rear. Just make sure the line lock is locking both front tires evenly. Have someone take a video of the burnout and watch the front tires.
What rpm are you leaving at , and are you slipping the clutch?
How about some engine details!!!
Your track allows you to race without a cage?
ET. MPH !!!??

[mikeinatlanta]

Outstanding photo.

[Detroit Bill]

Originally Posted by RET_COP

If the car is launching straight and level ( the photo looks great by the way) through the first shift then you don't have a problem with the rear. Just make sure the line lock is locking both front tires evenly. Have someone take a video of the burnout and watch the front tires.
What rpm are you leaving at , and are you slipping the clutch?
How about some engine details!!!
Your track allows you to race without a cage?
ET. MPH !!!??

+1 I'd like to hear some details.

[landmass]

Thanks for the like on the picture The car goes straight, unless I spin out. I don't recall what I launched at because I'm relatively new at this and was very nervous during the launch, but I think it was about 4500 rpm. The tires spun for a split second, I let off the gas just a touch, and the tires grabbed - causing this little wheelie. I've been unable to duplicate it since. I now make all my launches at 3K rpm(soft starts), have 60 foot times between 1.5 and 1.6 seconds, with ET's running 11.4 - 11.5 at 119 to 120 mph. My best time was 11.3 at 121 mph with a short time of 1.5 with a 5 speed T5 tranny. I installed the line lock to try to improve my tire warm up, and have only used it once. Once I get the tires warmed up, I will move my launch RPM up to 3500 or 4000, or mayby higher if it doesn't spin out. I did video the front tires(with the line lock activated) once with the GoPro and one of the tires did not lock solid, then when I videod it again, the other tire did not lock, so I will be working on that problem. The race track officials said if I ever go below 11 secs, I will have to install a 5-point roll cage, which I can never do, as I want to keep the car "street" looking, and not dedicate it to the race track. It is my daily driver during good weather. Right now, they are OK with helmet, neck brace, 5-point restraint, arm restraints, and flame retardent jacket. But, if I break 11 seconds, my racing will be over due to the 5-point roll cage requirement.

[vector1]

I would check to make sure everything is square. You can find details in any stock car book, etc. I would use plumb bombs and find the centerline of the chassis or at least the center of the front of the chassis, then drop a line off each rear hub with jack stands under the axle, make sure the arms from the center front point and each rear tire are equal, you can also use this to adjust the rear end left to right in relation to the centerline of the rear of the chassis. With everything square on the car and in your mind you can move on to other possibilities. If you take it to an alignment shop they will do the thrust line off the front uprights or suspension when they check caster. Your choice on how you want to do it.

If the weights are adjusted for road racing as you say, I'm assuming you are referring to cross weights being 50/50. To get the cross weights equal the left and right rear tires are not going to be equal in weight, you can make them equal, but then when the front comes off the ground things change and you have to account for your ass. I'm not a drag racer so don't know if this comes into play, but I would check to see if everything is centered as described, that will prob fix a lot of questionable.

Nice pic btw.

[landmass]

Vector1 - thanks for the advice and I will check with my mechanic on the issue of the centerline. I know the machine is not perfect, and to get it so would take a lot of work from people with different opinions. Right now, I think I'm close to where I want to be - to track straight ahead when spinning out. I may take a short break from this to think about it and do more research into the matter. And yes, the cross weights were adjusted to 50/50,(I had this done to road race at Palm Beach International) and it doesn't seem to have negatively affected the streetability or drag racing. I did seem to notice that the one drag race I did after the adjustment that the car was stiffer, and didn't jerk around near as bad as before. I've had guys at the track tell me the car was really moving around when I shifted(prior to this adjustment). My next trip to the drags will be Feb 1rst and I'll learn more then. I know that all of this is extremely complex and I have a lot of learning to do. Thank you for the advice...