My transmission goes into neutral when I come to a traffic light or stop sign 90% of the time. I press the gas to go and goes into gear. I can put the shifter to neutral position and back to drive and it's fine. No other issues occur while driving, shifting is smooth. Any info would greatly be appreciated.

 

did you check the fluid level? how many miles on your rig? has the trans been serviced?

 

Fluid is fine. 191,000, not recetly

 

Does it have the large 4R100
Or the smaller 4477W
Easy to tell the larger trans has a massive rectangle shaped pan
And the smaller one is a square with 2 sides diagonal

 

All Lightnings had the 4R100.

I think either your internal filter is loose, or the forward clutch is damaged.

 

I agree with mark
Either the filter came loose or fwd drum issue .
Excessive clearance , cracked apply piston or possable input shaft ring wear or inner stator damage . Best bet is too pan and check filter . If it is down don't forget to remove the old orange metal clad seal for the filter . It will be up in the pump cover . Install new filter with seal on filter inlet . We use assembly lube but you can use ATF . Don't bang it up with hand . Work it up , little wiggle . We have seen do it your sellers crack the filter where the neck meets the body .
Good luck .
Let me know .
Ohh use Mercon 5 . I highly recommend motorcraft . Don't fall for the universal bs