Rearend Question

[7uptruckracer]

Well we can agree his biggest change will be the pinion height so the Jbar will be different. That's going to be the most critical. I assume people want no binds in engine and midplate mounting that stuff cracks enough at the midplate mounts as it is.

[Fraley Racing Ent.]

It has to do with the direction of force (downward pressure) applied to tire when the pinion gear tries to climb the ring gear. TorqueOn a 9" rear, or any conventional style axle, there is more pressure applied to the LR wheel on acceleration.Which is why on an open rear end, you punch the throttle to accelerate in a straight line, the RR wheel spins, even though motor torque tries to twist chassis and plant RR, it still unloads the RR tire.that is why a lot of drag racers add their battery to the right rear corner of their vehicle.On a qc, the pinion is on the back side of the axle, and on the opposite side of ring gear, so the torque applied when pinion tries to climb the ring gear more pressure is applied to the RR wheel.It has nothing to do with lockers, or spools.It has to do with torque, and the directional forces in which items react when power, or rotation is applied.That is why you have to add a bit of wedge to compensate, typically I add about 25lbs on a 4 link car.Just my opinion.

thank you for stating this.... I am glad some can agree with me on this.... I have had customers with modified's including my own modified have issues with changing to a quickchange.... my own personal car after changing to a quick change has a ton more right rear drive and it mad the car hike up the entire rear instead of just the left rear. we had to change a lot to make the car drivable.

[Wheelman33]

I have a car built by a "big nut" and the set up sheet says 20-30# more LR with a quick change.

[JustAddDirt]

leeracing40.
driveshaft and thru-shaft do not matter, it is were the pinion contacts the ring gear, and the torque applied at that point, which makes the rotation forces that effects wheel weight.

7uptruckracer
sounds like you might need more ridged mounting of engine. If you are cracking and breaking stuff in the motor mount area might be other problems. Sounds like chassis builder needs to use something other than muffler tube, or thin wall elecktra-weld tubing...say DOM ,or moly.
I have never had any problems with anything binding, cracking or flexing anything including the powercoat in the motor mount area.

[7uptruckracer]

We get cracks in the ears that you attach your midplate to every now and then. We run Chrome Moly Tig chassis. Most manufacturers will not heat treat your chassis unless you ask and we have never bought them brand spankin new always a year or two old. I guess you don't find Rocket Chassis to be of good quality muffler tubing. Super Lates can twist up a good chassis.

[JustAddDirt]

yes late models can do that as much as the RF hits the track.
Rocket welds a flat tab on there don't they?
I think a tab with ears on it would be better in that application.
Rockets are moly, but are not tig welded, they are mig welded, just with correct wire.
(unless he has changed his welding processes) or something special was ordered.

[xxxmod]

Any difference you feel would probably be because the 9 inch and the quick change
use different length axles.

[7uptruckracer]

I'm sure that has some bearing, I know the QC and 9" Pinions are oriented differently as far as how it makes contact and left to right and front to back wise. I know the QC can absorb more torque and HP because your running it thought that intermediate shaft. I'd just count it all as a shove mount it all at the same points redo your Jbar height and see what your bottom feels and adjust from there, dirt is never the same any time its out anyways

[4coil]

Thanks folks for the valuable info..........................A lot of goodstuff here!

[el paso mod 19]

If a 6.0 gear was perfect for 9", what ratio do I run in QC? I've been told they're not the same.

[JustAddDirt]

I would start with a 6.03

[not clamped up]

I would start with a 6.03

JustAddDirt gives some of the best advice I see on here,I just wanna add to me alot of people have ended up with the 411 Ring and pinion in there quick change.If so you need to add 40 points to the gear you ran in the 9 inch.

[el paso mod 19]

Thanks to both of you.

[1Blacksheep]

9" drives off the LR
QC drives off the RR
have to add a smidge more wedge to compensate
Pinion is about 2" lower on QC. generally you have to move back of motor down a bit to correct driveshaft angle.

Agree completely . The balance we try to tune into a car has been a little harder to hit the sweet spot with the QC for this reason. There is more than one reason this JAD Cat wins a lot of races.