docraymund
Full Access Members
It is due to residual transmission fluid in the clutch packs. It is not a cause for concern. Just apply the service brake before starting.
lurches forward when first started
- Thread starter whitelightning99
- Start date
Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.
ParadiseComputer
Member
May be failing neutral safety switch on transmission. Not sure though.
stamp11127
Full Access Members
I'm not one for throwing parts at a problem but after searching the net of others with that issue only one person was able to remedy the problem with a fluid change and Lucas trans additive. The others didn't have a solution. If the Lucas is acting as a friction modifier then that would make sense.
How many miles are on the trans and fluid?
Your call on adding it in with a fluid change.
How many miles are on the trans and fluid?
Your call on adding it in with a fluid change.
drewactual
Full Access Members
gents, this issue is a non-issue.
transmissions, while IN GEAR and idling are pre-loaded- meaning all the planetary and sun gears are pressing into position awaiting the release of the brakes. well sht..... this is gonna get winded, but it may help some of y'all:
if you can imagine a bucket of water and a person holding a paddle with intent to stir that water you have the general idea of fluid coupling. when the person starts stirring all the water starts flowing in the direction the person is stirring it.... the paddle represents the engines crankshaft.... the water is the transmission fluid in the torque converter, and the bucket is the torque converter housing.
imagine now there is a finned wheel in the bottom of the bucket with a sealed shaft that extends through the base of the bucket. when the input shaft (the paddle) is fired up by the engine (the person stirring) something has to give, or the engine won't be able to turn the paddle- meaning the engine (person) will stall (quit turning) or something will break.
imagine that doesn't happen, and the paddle turns freely in the bucket... in about one and a half turns the water in the bucket is starting to swirl in the direction intended- and the fins on the wheel/plate in the bottom of the bucket start to spin in tune with it. that is fluid coupling. the other side of that finned wheel/plate has a shaft on it which is the output shaft that feeds your input shaft which is what makes your transmission spin...
at rest the juice in the torque converter and transmissions are just that- at rest... still....
when the spinning begins, and fluid coupling happens (even though it is encountering resistance from the brakes being engaged) slack is removed from the spaces between the teeth on the sun an planetary gears (and other items of black magic present in an automatic transmission) throughout the transmission- and that which is represented as a lunge forward. that is all.
there are different types of stalls when discussing torque converters- the most common one is the speed the engine turns before the fluid coupling has the power to overcome sitting still- the point where it engages. I don't know what the OE stall speed is on these things, but I can say on the 09 superduty pushing the 5r110w transmission is varies depending on how much power torque management is scripted to deliver to the transmission- i'm thinking the stall speed is fairly low, like in the 1500~1800 range at the highest, which allows the transmission to engage quickly instead of suggesting the engine reach a higher RPM (where a 'built' for racing engine encounters the bottom of it's designed torque curve).... so.... when a person fires the truck up first thing in the morning it encounters a resting NOT 'preloaded' transmission and drive line (slack present in the gearing), and what does a cold mod engines PCM instruct it to do? a: deliver more fuel/run a higher RPM to get things going.... this is a higher rpm than you'd encounter on a warm start, and it's enough to 'preload' the transmission and almost enough to overcome the brake stall speed.
shorthand: slack in the gears, fluid coupling, higher initial idle speed on cold engine = lunge. not a problem.
transmissions, while IN GEAR and idling are pre-loaded- meaning all the planetary and sun gears are pressing into position awaiting the release of the brakes. well sht..... this is gonna get winded, but it may help some of y'all:
if you can imagine a bucket of water and a person holding a paddle with intent to stir that water you have the general idea of fluid coupling. when the person starts stirring all the water starts flowing in the direction the person is stirring it.... the paddle represents the engines crankshaft.... the water is the transmission fluid in the torque converter, and the bucket is the torque converter housing.
imagine now there is a finned wheel in the bottom of the bucket with a sealed shaft that extends through the base of the bucket. when the input shaft (the paddle) is fired up by the engine (the person stirring) something has to give, or the engine won't be able to turn the paddle- meaning the engine (person) will stall (quit turning) or something will break.
imagine that doesn't happen, and the paddle turns freely in the bucket... in about one and a half turns the water in the bucket is starting to swirl in the direction intended- and the fins on the wheel/plate in the bottom of the bucket start to spin in tune with it. that is fluid coupling. the other side of that finned wheel/plate has a shaft on it which is the output shaft that feeds your input shaft which is what makes your transmission spin...
at rest the juice in the torque converter and transmissions are just that- at rest... still....
when the spinning begins, and fluid coupling happens (even though it is encountering resistance from the brakes being engaged) slack is removed from the spaces between the teeth on the sun an planetary gears (and other items of black magic present in an automatic transmission) throughout the transmission- and that which is represented as a lunge forward. that is all.
there are different types of stalls when discussing torque converters- the most common one is the speed the engine turns before the fluid coupling has the power to overcome sitting still- the point where it engages. I don't know what the OE stall speed is on these things, but I can say on the 09 superduty pushing the 5r110w transmission is varies depending on how much power torque management is scripted to deliver to the transmission- i'm thinking the stall speed is fairly low, like in the 1500~1800 range at the highest, which allows the transmission to engage quickly instead of suggesting the engine reach a higher RPM (where a 'built' for racing engine encounters the bottom of it's designed torque curve).... so.... when a person fires the truck up first thing in the morning it encounters a resting NOT 'preloaded' transmission and drive line (slack present in the gearing), and what does a cold mod engines PCM instruct it to do? a: deliver more fuel/run a higher RPM to get things going.... this is a higher rpm than you'd encounter on a warm start, and it's enough to 'preload' the transmission and almost enough to overcome the brake stall speed.
shorthand: slack in the gears, fluid coupling, higher initial idle speed on cold engine = lunge. not a problem.
stamp11127
Full Access Members
Read post 1 then the correction in post 3. Trans is in park. Even though the tc is partially coupled the remainder of the driveline should be disengaged. None of the automatic trans I've had do the lurching forward. So to myself and others, it is an issue that shouldn't occur but we can live with.
I still would like to know the age and condition of his trans fluid.
I still would like to know the age and condition of his trans fluid.
drewactual
Full Access Members
aye.... that changes things...
parking sprag.
to the OP: have you ever ran the tire into a curb or something similar and put it in park without taking your foot off the brake and letting it rest before doing so? if you did, taking it OUT of park is a chore and seems like you're about to break something.... and you are... you're park sprag. I wager it's damage, and i further wager if you drop the pan you'll find a chunk off of it laying there.
Similar threads
Latest posts
-
2006 EB Rear HVAC Inoperable / Fuse, Relay, Resistor Good- Latest: 2006Overlander
-
-
Staff online
-
GriffinAdministrator