A-Chassis for Articulated bus glitches out on Play

Help and Feedback Scripting Support
#1

You can write your topic however you want, but you need to answer these questions:

  1. What do you want to achieve? Keep it simple and clear!
    I want to edit an A-Chassis so I can use it on my articulated bus
  2. What is the issue? Include screenshots / videos if possible!
    The rear part glitches out when I hit play
  3. What solutions have you tried so far? Did you look for solutions on the Developer Hub?
    I have tried to edit the “Initialize” script, moving the VehicleSeat (the black part above the wheels), none of it has worked
    After that, you should include more details if you have any. Try to make your topic as descriptive as possible, so that it’s easier for people to help you!

I want to make an articulated bus with an A-Chassis so I have edited the “Initialize” script. The front part works like it did before but the rear just glitches out whenever I hit “Play” or “Run” in Studio. I think it has something to do with the “Initialize” script.

This is the “Initialize” script:

--[[
		___      _______                _     
	   / _ |____/ ___/ /  ___ ____ ___ (_)__ 
	  / __ /___/ /__/ _ \/ _ `(_-<(_-</ (_-<
	 /_/ |_|   \___/_//_/\_,_/___/___/_/___/
 						SecondLogic @ Inspare
]]

--[[START]]

_BuildVersion = require(script.Parent.README)

--[[Weld functions]]

local JS = game:GetService("JointsService")
local PGS_ON = workspace:PGSIsEnabled()

function MakeWeld(x,y,type,s) 
	if type==nil then type="Weld" end
	local W=Instance.new(type,JS) 
	W.Part0=x W.Part1=y 
	W.C0=x.CFrame:inverse()*x.CFrame 
	W.C1=y.CFrame:inverse()*x.CFrame 
	if type=="Motor" and s~=nil then 
		W.MaxVelocity=s 
	end 
	return W	
end

function ModelWeld(a,b) 
	if a:IsA("BasePart") then 
		MakeWeld(b,a,"Weld") 
	elseif a:IsA("Model") then 
		for i,v in pairs(a:GetChildren()) do 
			ModelWeld(v,b) 
		end 
	end 
end

function UnAnchor(a) 
	if a:IsA("BasePart") then a.Anchored=false  end for i,v in pairs(a:GetChildren()) do UnAnchor(v) end 
end



--[[Initialize]]

script.Parent:WaitForChild("A-Chassis Interface")
script.Parent:WaitForChild("Plugins")
script.Parent:WaitForChild("README")

local car=script.Parent.Parent
local _Tune=require(script.Parent)

wait(_Tune.LoadDelay)

--Weight Scaling
local weightScaling = _Tune.WeightScaling
if not workspace:PGSIsEnabled() then
	weightScaling = _Tune.LegacyScaling
end

local Drive=car.Wheels:GetChildren()
local Drive2=car.Misc.Wheels:GetChildren()

--Remove Existing Mass
function DReduce(p)
	for i,v in pairs(p:GetChildren())do
		if v:IsA("BasePart") then
			if v.CustomPhysicalProperties == nil then v.CustomPhysicalProperties = PhysicalProperties.new(v.Material) end
			v.CustomPhysicalProperties = PhysicalProperties.new(
				0,
				v.CustomPhysicalProperties.Friction,
				v.CustomPhysicalProperties.Elasticity,
				v.CustomPhysicalProperties.FrictionWeight,
				v.CustomPhysicalProperties.ElasticityWeight
			)
		end
		DReduce(v)
	end
end
DReduce(car)



--[[Wheel Configuration]]	

--Store Reference Orientation Function
function getParts(model,t,a)
	for i,v in pairs(model:GetChildren()) do
		if v:IsA("BasePart") then table.insert(t,{v,a.CFrame:toObjectSpace(v.CFrame)})
		elseif v:IsA("Model") then getParts(v,t,a)
		end
	end
end

--PGS/Legacy
local fDensity = _Tune.FWheelDensity
local rDensity = _Tune.RWheelDensity
if not PGS_ON then
	fDensity = _Tune.FWLgcyDensity
	rDensity = _Tune.RWLgcyDensity
end

local fDistX=_Tune.FWsBoneLen*math.cos(math.rad(_Tune.FWsBoneAngle))
local fDistY=_Tune.FWsBoneLen*math.sin(math.rad(_Tune.FWsBoneAngle))
local rDistX=_Tune.RWsBoneLen*math.cos(math.rad(_Tune.RWsBoneAngle))
local rDistY=_Tune.RWsBoneLen*math.sin(math.rad(_Tune.RWsBoneAngle))

local fSLX=_Tune.FSusLength*math.cos(math.rad(_Tune.FSusAngle))
local fSLY=_Tune.FSusLength*math.sin(math.rad(_Tune.FSusAngle))
local rSLX=_Tune.RSusLength*math.cos(math.rad(_Tune.RSusAngle))
local rSLY=_Tune.RSusLength*math.sin(math.rad(_Tune.RSusAngle))

for _,v in pairs(Drive) do
	--Apply Wheel Density
	if v.Name=="FL" or v.Name=="FR" or v.Name=="F" then
		if v:IsA("BasePart") then
			if v.CustomPhysicalProperties == nil then v.CustomPhysicalProperties = PhysicalProperties.new(v.Material) end
			v.CustomPhysicalProperties = PhysicalProperties.new(
				fDensity,
				v.CustomPhysicalProperties.Friction,
				v.CustomPhysicalProperties.Elasticity,
				v.CustomPhysicalProperties.FrictionWeight,
				v.CustomPhysicalProperties.ElasticityWeight
			)
		end
	else
		if v:IsA("BasePart") then
			if v.CustomPhysicalProperties == nil then v.CustomPhysicalProperties = PhysicalProperties.new(v.Material) end
			v.CustomPhysicalProperties = PhysicalProperties.new(
				rDensity,
				v.CustomPhysicalProperties.Friction,
				v.CustomPhysicalProperties.Elasticity,
				v.CustomPhysicalProperties.FrictionWeight,
				v.CustomPhysicalProperties.ElasticityWeight
			)
		end		
	end

	--Resurface Wheels
	for _,a in pairs({"Top","Bottom","Left","Right","Front","Back"}) do
		v[a.."Surface"]=Enum.SurfaceType.SmoothNoOutlines
	end

	--Store Axle-Anchored/Suspension-Anchored Part Orientation
	local WParts = {}

	local tPos = v.Position-car.DriveSeat.Position
	if v.Name=="FL" or v.Name=="RL" then
		v.CFrame = car.DriveSeat.CFrame*CFrame.Angles(math.rad(90),0,math.rad(90))
	else
		v.CFrame = car.DriveSeat.CFrame*CFrame.Angles(math.rad(90),0,math.rad(-90))
	end
	v.CFrame = v.CFrame+tPos

	if v:FindFirstChild("Parts")~=nil then
		getParts(v.Parts,WParts,v)
	end
	if v:FindFirstChild("Fixed")~=nil then
		getParts(v.Fixed,WParts,v)
	end

	--Align Wheels
	if v.Name=="FL" or v.Name=="FR" then
		v.CFrame = v.CFrame*CFrame.Angles(math.rad(_Tune.FCamber),0,0)
		if v.Name=="FL" then v.CFrame = v.CFrame*CFrame.Angles(0,math.rad(-_Tune.FCaster),0) end
		if v.Name=="FR" then v.CFrame = v.CFrame*CFrame.Angles(0,math.rad(_Tune.FCaster),0) end
		if v.Name=="FL" then
			v.CFrame = v.CFrame*CFrame.Angles(0,0,math.rad(_Tune.FToe))
		else
			v.CFrame = v.CFrame*CFrame.Angles(0,0,math.rad(-_Tune.FToe))
		end
	elseif v.Name=="RL" or v.Name=="RR" then
		v.CFrame = v.CFrame*CFrame.Angles(math.rad(_Tune.RCamber),0,0)
		if v.Name=="RL" then
			v.CFrame = v.CFrame*CFrame.Angles(0,0,math.rad(_Tune.RToe))
		else
			v.CFrame = v.CFrame*CFrame.Angles(0,0,math.rad(-_Tune.RToe))
		end
	end

	--Re-orient Axle-Anchored/Suspension-Anchored Parts
	for _,a in pairs(WParts) do
		a[1].CFrame=v.CFrame:toWorldSpace(a[2])
	end



	--[[Chassis Assembly]]
	--Create Steering Axle
	local arm=Instance.new("Part",v)
	arm.Name="Arm"
	arm.Anchored=true
	arm.CanCollide=false
	arm.FormFactor=Enum.FormFactor.Custom
	arm.Size=Vector3.new(_Tune.AxleSize,_Tune.AxleSize,_Tune.AxleSize)
	arm.CFrame=(v.CFrame*CFrame.new(0,_Tune.StAxisOffset,0))*CFrame.Angles(-math.pi/2,-math.pi/2,0)
	arm.CustomPhysicalProperties = PhysicalProperties.new(_Tune.AxleDensity,0,0,100,100)
	arm.TopSurface=Enum.SurfaceType.Smooth
	arm.BottomSurface=Enum.SurfaceType.Smooth
	arm.Transparency=1

	--Create Wheel Spindle
	local base=arm:Clone()
	base.Parent=v
	base.Name="Base"
	base.CFrame=base.CFrame*CFrame.new(0,_Tune.AxleSize,0)
	base.BottomSurface=Enum.SurfaceType.Hinge

	--Create Steering Anchor
	local axle=arm:Clone()
	axle.Parent=v
	axle.Name="Axle"
	axle.CFrame=CFrame.new(v.Position-((v.CFrame*CFrame.Angles(math.pi/2,0,0)).lookVector*((v.Size.x/2)+(axle.Size.x/2))),v.Position)*CFrame.Angles(0,math.pi,0)
	axle.BackSurface=Enum.SurfaceType.Hinge

	if v.Name=="F" or v.Name=="R" then
		local axle2=arm:Clone()
		axle2.Parent=v
		axle2.Name="Axle"
		axle2.CFrame=CFrame.new(v.Position+((v.CFrame*CFrame.Angles(math.pi/2,0,0)).lookVector*((v.Size.x/2)+(axle2.Size.x/2))),v.Position)*CFrame.Angles(0,math.pi,0)
		axle2.BackSurface=Enum.SurfaceType.Hinge
		MakeWeld(arm,axle2)
	end

	--Create Suspension
	if PGS_ON and _Tune.SusEnabled then			
		local sa=arm:Clone()
		sa.Parent=v
		sa.Name="#SA"
		if v.Name == "FL" or v.Name=="FR" or v.Name =="F" then
			local aOff = _Tune.FAnchorOffset
			sa.CFrame=v.CFrame*CFrame.new(_Tune.AxleSize/2,-fDistX,-fDistY)*CFrame.new(aOff[3],aOff[1],-aOff[2])*CFrame.Angles(-math.pi/2,-math.pi/2,0)
		else
			local aOff = _Tune.RAnchorOffset
			sa.CFrame=v.CFrame*CFrame.new(_Tune.AxleSize/2,-rDistX,-rDistY)*CFrame.new(aOff[3],aOff[1],-aOff[2])*CFrame.Angles(-math.pi/2,-math.pi/2,0)
		end

		local sb=sa:Clone()
		sb.Parent=v
		sb.Name="#SB"
		sb.CFrame=sa.CFrame*CFrame.new(0,0,_Tune.AxleSize)

		sb.FrontSurface=Enum.SurfaceType.Hinge	

		local g = Instance.new("BodyGyro",sb)
		g.Name = "Stabilizer"
		g.MaxTorque = Vector3.new(0,0,1)
		g.P = 0

		local sf1 = Instance.new("Attachment",sa)
		sf1.Name = "SAtt"

		local sf2 = sf1:Clone()
		sf2.Parent = sb


		if v.Name == "FL" or v.Name == "FR" or v.Name == "F" then
			sf1.Position = Vector3.new(fDistX-fSLX,-fDistY+fSLY,_Tune.AxleSize/2)
			sf2.Position = Vector3.new(fDistX,-fDistY,-_Tune.AxleSize/2)
		elseif v.Name == "RL" or v.Name=="RR" or v.Name == "R" then
			sf1.Position = Vector3.new(rDistX-rSLX,-rDistY+rSLY,_Tune.AxleSize/2)
			sf2.Position = Vector3.new(rDistX,-rDistY,-_Tune.AxleSize/2)
		end

		sb:MakeJoints()

		local sp = Instance.new("SpringConstraint",v)
		sp.Name = "Spring"
		sp.Attachment0 = sf1
		sp.Attachment1 = sf2
		sp.LimitsEnabled = true

		sp.Visible=_Tune.SusVisible
		sp.Radius=_Tune.SusRadius
		sp.Thickness=_Tune.SusThickness
		sp.Color=BrickColor.new(_Tune.SusColor)
		sp.Coils=_Tune.SusCoilCount

		if v.Name == "FL" or v.Name=="FR" or v.Name =="F" then
			g.D = _Tune.FAntiRoll
			sp.Damping = _Tune.FSusDamping
			sp.Stiffness = _Tune.FSusStiffness
			sp.FreeLength = _Tune.FSusLength+_Tune.FPreCompress
			sp.MaxLength = _Tune.FSusLength+_Tune.FExtensionLim
			sp.MinLength = _Tune.FSusLength-_Tune.FCompressLim
		else
			g.D = _Tune.RAntiRoll
			sp.Damping = _Tune.RSusDamping
			sp.Stiffness = _Tune.RSusStiffness
			sp.FreeLength = _Tune.RSusLength+_Tune.RPreCompress
			sp.MaxLength = _Tune.RSusLength+_Tune.RExtensionLim
			sp.MinLength = _Tune.RSusLength-_Tune.RCompressLim
		end

		MakeWeld(car.DriveSeat,sa)
		MakeWeld(sb,base)
	else
		MakeWeld(car.DriveSeat,base)
	end

	--Lock Rear Steering Axle
	if v.Name == "RL" or v.Name == "RR" or v.Name=="R" then
		MakeWeld(base,axle)
	end

	--Weld Assembly
	if v.Parent.Name == "RL" or v.Parent.Name == "RR" or v.Name=="R" then
		MakeWeld(car.DriveSeat,arm)
	end

	MakeWeld(arm,axle)

	arm:MakeJoints()
	axle:MakeJoints()

	--Weld Miscelaneous Parts
	if v:FindFirstChild("SuspensionFixed")~=nil then
		ModelWeld(v.SuspensionFixed,car.DriveSeat)
	end
	if v:FindFirstChild("WheelFixed")~=nil then
		ModelWeld(v.WheelFixed,axle)
	end
	if v:FindFirstChild("Fixed")~=nil then
		ModelWeld(v.Fixed,arm)
	end

	--Weld Wheel Parts
	if v:FindFirstChild("Parts")~=nil then
		ModelWeld(v.Parts,v)
	end

	--Add Steering Gyro
	if v:FindFirstChild("Steer") then
		v:FindFirstChild("Steer"):Destroy()
	end

	if v.Name=="FL" or v.Name=="FR" or v.Name=="F" then
		local steer=Instance.new("BodyGyro",arm)
		steer.Name="Steer"
		steer.P=_Tune.SteerP
		steer.D=_Tune.SteerD
		steer.MaxTorque=Vector3.new(0,_Tune.SteerMaxTorque,0)
		steer.cframe=v.CFrame*CFrame.Angles(0,-math.pi/2,0)
	end

	--Add Stabilization Gyro
	local gyro=Instance.new("BodyGyro",v)
	gyro.Name="Stabilizer"
	gyro.MaxTorque=Vector3.new(1,0,1)
	gyro.P=0
	if v.Name=="FL" or v.Name=="FR"  or v.Name=="F" then
		gyro.D=_Tune.FGyroDamp
	else
		gyro.D=_Tune.RGyroDamp
	end

	--Add Rotational BodyMover
	local AV=Instance.new("BodyAngularVelocity",v)
	AV.Name="#AV"
	AV.angularvelocity=Vector3.new(0,0,0)
	AV.maxTorque=Vector3.new(_Tune.PBrakeForce,0,_Tune.PBrakeForce)
	AV.P=1e9
end


for _,v in pairs(Drive2) do
	if v.Name=="RRL" or v.Name=="RRR"then
		if v:IsA("BasePart") then
			if v.CustomPhysicalProperties == nil then v.CustomPhysicalProperties = PhysicalProperties.new(v.Material) end
			v.CustomPhysicalProperties = PhysicalProperties.new(
				rDensity,
				v.CustomPhysicalProperties.Friction,
				v.CustomPhysicalProperties.Elasticity,
				v.CustomPhysicalProperties.FrictionWeight,
				v.CustomPhysicalProperties.ElasticityWeight
			)
		end		
	end
	--Resurface Wheels
	for _,a in pairs({"Top","Bottom","Left","Right","Front","Back"}) do
		v[a.."Surface"]=Enum.SurfaceType.SmoothNoOutlines
	end
	
	--Store Axle-Anchored/Suspension-Anchored Part Orientation
	local WParts = {}

	local tPos = v.Position-car.Misc.Body.VehicleSeat.Position
	if v.Name=="FL" or v.Name=="RL" then
		v.CFrame = car.Misc.Body.VehicleSeat.CFrame*CFrame.Angles(math.rad(90),0,math.rad(90))
	else
		v.CFrame = car.Misc.Body.VehicleSeat.CFrame*CFrame.Angles(math.rad(90),0,math.rad(-90))
	end
	v.CFrame = v.CFrame+tPos

	if v:FindFirstChild("Parts")~=nil then
		getParts(v.Parts,WParts,v)
	end
	if v:FindFirstChild("Fixed")~=nil then
		getParts(v.Fixed,WParts,v)
	end
	--Align Wheels
	if v.Name=="FL" or v.Name=="FR" then
		v.CFrame = v.CFrame*CFrame.Angles(math.rad(_Tune.FCamber),0,0)
		if v.Name=="FL" then
			v.CFrame = v.CFrame*CFrame.Angles(0,0,math.rad(_Tune.FToe))
		else
			v.CFrame = v.CFrame*CFrame.Angles(0,0,math.rad(-_Tune.FToe))
		end
	elseif v.Name=="RL" or v.Name=="RR" then
		v.CFrame = v.CFrame*CFrame.Angles(math.rad(_Tune.RCamber),0,0)
		if v.Name=="RL" then
			v.CFrame = v.CFrame*CFrame.Angles(0,0,math.rad(_Tune.RToe))
		else
			v.CFrame = v.CFrame*CFrame.Angles(0,0,math.rad(-_Tune.RToe))
		end
	end

	--Re-orient Axle-Anchored/Suspension-Anchored Parts
	for _,a in pairs(WParts) do
		a[1].CFrame=v.CFrame:toWorldSpace(a[2])
	end



	--[[Chassis Assembly]]
	--Create Steering Axle
	local arm=Instance.new("Part",v)
	arm.Name="Arm"
	arm.Anchored=true
	arm.CanCollide=false
	arm.FormFactor=Enum.FormFactor.Custom
	arm.Size=Vector3.new(_Tune.AxleSize,_Tune.AxleSize,_Tune.AxleSize)
	arm.CFrame=(v.CFrame*CFrame.new(0,_Tune.StAxisOffset,0))*CFrame.Angles(-math.pi/2,-math.pi/2,0)
	arm.CustomPhysicalProperties = PhysicalProperties.new(_Tune.AxleDensity,0,0,100,100)
	arm.TopSurface=Enum.SurfaceType.Smooth
	arm.BottomSurface=Enum.SurfaceType.Smooth
	arm.Transparency=1

	--Create Wheel Spindle
	local base=arm:Clone()
	base.Parent=v
	base.Name="Base"
	base.CFrame=base.CFrame*CFrame.new(0,_Tune.AxleSize,0)
	base.BottomSurface=Enum.SurfaceType.Hinge

	--Create Steering Anchor
	local axle=arm:Clone()
	axle.Parent=v
	axle.Name="Axle"
	axle.CFrame=CFrame.new(v.Position-((v.CFrame*CFrame.Angles(math.pi/2,0,0)).lookVector*((v.Size.x/2)+(axle.Size.x/2))),v.Position)*CFrame.Angles(0,math.pi,0)
	axle.BackSurface=Enum.SurfaceType.Hinge
	
	if v.Name=="F" or v.Name=="R" then
		local axle2=arm:Clone()
		axle2.Parent=v
		axle2.Name="Axle"
		axle2.CFrame=CFrame.new(v.Position+((v.CFrame*CFrame.Angles(math.pi/2,0,0)).lookVector*((v.Size.x/2)+(axle2.Size.x/2))),v.Position)*CFrame.Angles(0,math.pi,0)
		axle2.BackSurface=Enum.SurfaceType.Hinge
		MakeWeld(arm,axle2)
	end

	--Create Suspension
	if PGS_ON and _Tune.SusEnabled then			
		local sa=arm:Clone()
		sa.Parent=v
		sa.Name="#SA"
		if v.Name == "FL" or v.Name=="FR" or v.Name =="F" then
			local aOff = _Tune.FAnchorOffset
			sa.CFrame=v.CFrame*CFrame.new(_Tune.AxleSize/2,-fDistX,-fDistY)*CFrame.new(aOff[3],aOff[1],-aOff[2])*CFrame.Angles(-math.pi/2,-math.pi/2,0)
		else
			local aOff = _Tune.RAnchorOffset
			sa.CFrame=v.CFrame*CFrame.new(_Tune.AxleSize/2,-rDistX,-rDistY)*CFrame.new(aOff[3],aOff[1],-aOff[2])*CFrame.Angles(-math.pi/2,-math.pi/2,0)
		end
		
		local sb=sa:Clone()
		sb.Parent=v
		sb.Name="#SB"
		sb.CFrame=sa.CFrame*CFrame.new(0,0,_Tune.AxleSize)

		sb.FrontSurface=Enum.SurfaceType.Hinge	

		local g = Instance.new("BodyGyro",sb)
		g.Name = "Stabilizer"
		g.MaxTorque = Vector3.new(0,0,1)
		g.P = 0

		local sf1 = Instance.new("Attachment",sa)
		sf1.Name = "SAtt"

		local sf2 = sf1:Clone()
		sf2.Parent = sb


		if v.Name == "FL" or v.Name == "FR" or v.Name == "F" then
			sf1.Position = Vector3.new(fDistX-fSLX,-fDistY+fSLY,_Tune.AxleSize/2)
			sf2.Position = Vector3.new(fDistX,-fDistY,-_Tune.AxleSize/2)
		elseif v.Name == "RL" or v.Name=="RR" or v.Name == "R" then
			sf1.Position = Vector3.new(rDistX-rSLX,-rDistY+rSLY,_Tune.AxleSize/2)
			sf2.Position = Vector3.new(rDistX,-rDistY,-_Tune.AxleSize/2)
		end
		
		sb:MakeJoints()

		local sp = Instance.new("SpringConstraint",v)
		sp.Name = "Spring"
		sp.Attachment0 = sf1
		sp.Attachment1 = sf2
		sp.LimitsEnabled = true

		sp.Visible=_Tune.SusVisible
		sp.Radius=_Tune.SusRadius
		sp.Thickness=_Tune.SusThickness
		sp.Color=BrickColor.new(_Tune.SusColor)
		sp.Coils=_Tune.SusCoilCount
		
		if v.Name == "FL" or v.Name=="FR" or v.Name =="F" then
			g.D = _Tune.FAntiRoll
			sp.Damping = _Tune.FSusDamping
			sp.Stiffness = _Tune.FSusStiffness
			sp.FreeLength = _Tune.FSusLength+_Tune.FPreCompress
			sp.MaxLength = _Tune.FSusLength+_Tune.FExtensionLim
			sp.MinLength = _Tune.FSusLength-_Tune.FCompressLim
		else
			g.D = _Tune.RAntiRoll
			sp.Damping = _Tune.RSusDamping
			sp.Stiffness = _Tune.RSusStiffness
			sp.FreeLength = _Tune.RSusLength+_Tune.RPreCompress
			sp.MaxLength = _Tune.RSusLength+_Tune.RExtensionLim
			sp.MinLength = _Tune.RSusLength-_Tune.RCompressLim
		end
		
		MakeWeld(car.Misc.Body.VehicleSeat,sa)
		MakeWeld(sb,base)
	else
		MakeWeld(car.Misc.Body.VehicleSeat,base)
	end

	--Lock Rear Steering Axle
	if v.Name == "RL" or v.Name == "RR" or v.Name=="R" then
		MakeWeld(base,axle)
	end

	--Weld Assembly
	if v.Parent.Name == "RL" or v.Parent.Name == "RR" or v.Name=="R" then
		MakeWeld(car.Misc.Body.VehicleSeat,arm)
	end

	MakeWeld(arm,axle)

	arm:MakeJoints()
	axle:MakeJoints()

	--Weld Miscelaneous Parts
	if v:FindFirstChild("SuspensionFixed")~=nil then
		ModelWeld(v.SuspensionFixed,car.Misc.Body.VehicleSeat)
	end
	if v:FindFirstChild("WheelFixed")~=nil then
		ModelWeld(v.WheelFixed,axle)
	end
	if v:FindFirstChild("Fixed")~=nil then
		ModelWeld(v.Fixed,arm)
	end

	--Weld Wheel Parts
	if v:FindFirstChild("Parts")~=nil then
		ModelWeld(v.Parts,v)
	end

	--Add Steering Gyro
	if v:FindFirstChild("Steer") then
		v:FindFirstChild("Steer"):Destroy()
	end

	if v.Name=="FL" or v.Name=="FR" or v.Name=="F" then
		local steer=Instance.new("BodyGyro",arm)
		steer.Name="Steer"
		steer.P=_Tune.SteerP
		steer.D=_Tune.SteerD
		steer.MaxTorque=Vector3.new(0,_Tune.SteerMaxTorque,0)
		steer.cframe=v.CFrame*CFrame.Angles(0,-math.pi/2,0)
	end

	--Add Stabilization Gyro
	local gyro=Instance.new("BodyGyro",v)
	gyro.Name="Stabilizer"
	gyro.MaxTorque=Vector3.new(1,0,1)
	gyro.P=0
	if v.Name=="FL" or v.Name=="FR"  or v.Name=="F" then
		gyro.D=_Tune.FGyroDamp
	else
		gyro.D=_Tune.RGyroDamp
	end

	--Add Rotational BodyMover
	local AV=Instance.new("BodyAngularVelocity",v)
	AV.Name="#AV"
	AV.angularvelocity=Vector3.new(0,0,0)
	AV.maxTorque=Vector3.new(_Tune.PBrakeForce,0,_Tune.PBrakeForce)
	AV.P=1e9
end

--[[Vehicle Weight]]	
--Determine Current Mass
local mass=0

function getMass(p)
	for i,v in pairs(p:GetChildren())do
		if v:IsA("BasePart") then
			mass=mass+v:GetMass()
		end
		getMass(v)
	end	
end
getMass(car)

--Apply Vehicle Weight
if mass<_Tune.Weight*weightScaling then
	--Calculate Weight Distribution
	local centerF = Vector3.new()
	local centerR = Vector3.new()
	local countF = 0
	local countR = 0

	for i,v in pairs(Drive) do
		if v.Name=="FL" or v.Name=="FR" or v.Name=="F" then
			centerF = centerF+v.CFrame.p
			countF = countF+1
		else
			centerR = centerR+v.CFrame.p
			countR = countR+1
		end
	end
	centerF = centerF/countF
	centerR = centerR/countR
	local center = centerR:Lerp(centerF, _Tune.WeightDist/100)  

	--Create Weight Brick
	local weightB = Instance.new("Part",car.Body)
	weightB.Name = "#Weight"
	weightB.Anchored = true
	weightB.CanCollide = false
	weightB.BrickColor = BrickColor.new("Really black")
	weightB.TopSurface = Enum.SurfaceType.Smooth
	weightB.BottomSurface = Enum.SurfaceType.Smooth
	if _Tune.WBVisible then
		weightB.Transparency = .75			
	else
		weightB.Transparency = 1			
	end
	weightB.Size = Vector3.new(_Tune.WeightBSize[1],_Tune.WeightBSize[2],_Tune.WeightBSize[3])
	weightB.CustomPhysicalProperties = PhysicalProperties.new(((_Tune.Weight*weightScaling)-mass)/(weightB.Size.x*weightB.Size.y*weightB.Size.z),0,0,0,0)
	weightB.CFrame=(car.Misc.Body.VehicleSeat.CFrame-car.Misc.Body.VehicleSeat.Position+center)*CFrame.new(0,_Tune.CGHeight,0)
else
	--Existing Weight Is Too Massive
	warn( "\n\t [AC".._BuildVersion.."]: Mass too high for specified weight."
		.."\n\t    Target Mass:\t"..(math.ceil(_Tune.Weight*weightScaling*100)/100)
		.."\n\t    Current Mass:\t"..(math.ceil(mass*100)/100)
		.."\n\t Reduce part size or axle density to achieve desired weight.")
end

local flipG = Instance.new("BodyGyro",car.DriveSeat)
flipG.Name = "Flip"
flipG.D = 0
flipG.MaxTorque = Vector3.new(0,0,0)
flipG.P = 0




--[[Finalize Chassis]]	
--Misc Weld
wait()
for i,v in pairs(script:GetChildren()) do
	if v:IsA("ModuleScript") then
		require(v)
	end
end

--Weld Body
wait()
ModelWeld(car.Body,car.DriveSeat)

--Unanchor
wait()	
UnAnchor(car)

--[[Manage Plugins]]

script.Parent["A-Chassis Interface"].Car.Value=car
for i,v in pairs(script.Parent.Plugins:GetChildren()) do
	for _,a in pairs(v:GetChildren()) do
		if a:IsA("RemoteEvent") or a:IsA("RemoteFunction") then 
			a.Parent=car
			for _,b in pairs(a:GetChildren()) do
				if b:IsA("Script") then b.Disabled=false end
			end	
		end
	end
	v.Parent = script.Parent["A-Chassis Interface"]
end
script.Parent.Plugins:Destroy()



--[[Remove Character Weight]]
--Get Seats
local Seats = {}
function getSeats(p)
	for i,v in pairs(p:GetChildren()) do
		if v:IsA("VehicleSeat") or v:IsA("Seat") then
			local seat = {}
			seat.Seat = v
			seat.Parts = {}
			table.insert(Seats,seat)
		end
		getSeats(v)
	end	
end
getSeats(car)

--Store Physical Properties/Remove Mass Function
function getPProperties(mod,t)
	for i,v in pairs(mod:GetChildren()) do
		if v:IsA("BasePart") then
			if v.CustomPhysicalProperties == nil then v.CustomPhysicalProperties = PhysicalProperties.new(v.Material) end
			table.insert(t,{v,v.CustomPhysicalProperties})
			v.CustomPhysicalProperties = PhysicalProperties.new(
				0,
				v.CustomPhysicalProperties.Friction,
				v.CustomPhysicalProperties.Elasticity,
				v.CustomPhysicalProperties.FrictionWeight,
				v.CustomPhysicalProperties.ElasticityWeight
			)
		end
		getPProperties(v,t)
	end			
end

--Apply Seat Handler
for i,v in pairs(Seats) do
	--Sit Handler
	v.Seat.ChildAdded:connect(function(child)
		if child.Name=="SeatWeld" and child:IsA("Weld") and child.Part1~=nil and child.Part1.Parent ~= workspace and not child.Part1.Parent:IsDescendantOf(car) then
			v.Parts = {}
			getPProperties(child.Part1.Parent,v.Parts)
		end
	end)

	--Leave Handler
	v.Seat.ChildRemoved:connect(function(child)
		if child.Name=="SeatWeld" and child:IsA("Weld") then
			for i,v in pairs(v.Parts) do
				if v[1]~=nil and v[2]~=nil and v[1]:IsDescendantOf(workspace) then
					v[1].CustomPhysicalProperties = v[2]
				end
			end
			v.Parts = {}
		end
	end)
end



--[[Driver Handling]]

--Driver Sit	
car.DriveSeat.ChildAdded:connect(function(child)
	if child.Name=="SeatWeld" and child:IsA("Weld") and game.Players:GetPlayerFromCharacter(child.Part1.Parent)~=nil then
		--Distribute Client Interface
		local p=game.Players:GetPlayerFromCharacter(child.Part1.Parent)
		car.DriveSeat:SetNetworkOwner(p)
		local g=script.Parent["A-Chassis Interface"]:Clone()
		g.Parent=p.PlayerGui
	end
end)

--Driver Leave
car.DriveSeat.ChildRemoved:connect(function(child)
	if child.Name=="SeatWeld" and child:IsA("Weld") then
		--Remove Flip Force
		if car.DriveSeat:FindFirstChild("Flip")~=nil then
			car.DriveSeat.Flip.MaxTorque = Vector3.new()
		end

		--Remove Wheel Force
		for i,v in pairs(car.Wheels:GetChildren()) do
			if v:FindFirstChild("#AV")~=nil then
				if v["#AV"]:IsA("BodyAngularVelocity") then
					if v["#AV"].AngularVelocity.Magnitude>0 then
						v["#AV"].AngularVelocity = Vector3.new()
						v["#AV"].MaxTorque = Vector3.new()
					end
				else
					if v["#AV"].AngularVelocity>0 then
						v["#AV"].AngularVelocity = 0
						v["#AV"].MotorMaxTorque = 0
					end
				end
			end
		end
	end
end)

--[END]]

Please do not ask people to write entire scripts or design entire systems for you. If you can’t answer the three questions above, you should probably pick a different category.

#2

Are you sure it’s an A-chassis issue?
If you have an articulated bus then the rear wheels should be physically attached to the main body with a Constraint. Whether you use a HingeConstraint (which wouldn’t allow the bus to bend up and down, only sideways) or a BallSocketConstraint (pivots/rotates in all axes) or a UniversalConstraint (pivots in the left/right and up/down axis, but won’t rotate so if you are on an uneven banked surface the bus articulation wouldn’t twist) is up to you.
The trailing axle shouldn’t be driven because that would likely cause movement issues. It should basically be a trailer. Since the A-chassis has suspension built in it would be good, but you could even create suspension using Constraints as well.