So today on my drive home my 68 cougar 302 4v j code cougar had problems. I speedily left a stoplight and at the point the car normally lurches forward into second gear it did nothing. i pulled over to the side of the road. None of the gears worked except reverse on my automatic transmission. the idle didnt sound normal. it sounded slower and would quiet down and pulse strangely. My transmission wont work except reverse, what is wrong!? it sounds like there might be a vac. leak on the transmission modulator… but could that really cause none of my gears to work? all of my gears are basically working as neutral right now. please help 
Torque converter gone bad, possibly?
First thing to check is the vacuum line to the modulator. Second thing is the fluid level. Let us know what you find.
I battled issues with mine after rebuilding it. I had the piston that the modulator drives installed backwards. It had 1st and 2nd though you had to shift into those gears manually. When you put it in “D” after getting it going in 2nd, the engine would race, like it was in neutral.
Try that and see if it will at least go froward and let us know.
Transmission hasnt ever been touched, only 130,000 original miles, 1 2 and D would do nothing. The engine didnt race when in any of those either. The idle sounded pretty pathetic “in gear” and in park.
The common denominator for all forward gears is the forward clutch pack. The modulator could cause that, but I am not sure to what extent. The pulsing sounds like the fluid could be low and the pump is pumping for a while, then sucking air, then pumping for a while, etc.
I would start with getting a helper and making sure the linkage under the car is all working correctly, checking fluid levels, then pull the pan and make sure the filter/pickup hasn’t become clogged or something along those lines.
So, if it isn’t modulator issues, you may have had some debris make a valve in the valve body hang up making the forward clutch not apply, or the orings in the forward clutch may have let go and it won’t apply.
Or there could be some other very simple solution that I am overlooking.
When I said my engine raced, it was because I was giving it gas, and the trans still wouldn’t engage. It wouldn’t rev up on its own.
Here is the order of operation:
1st gear: Forward clutch applied, one way clutch holding while accelerating, free wheeling while decelerating with car in “D”. When car is in “1”, low reverse band applied as well for engine braking when decelerating.
2nd gear: Forward clutch applied, intermediate band applied
3rd gear: Forward clutch applied, high/reverse/direct clutch applied (basically input and output shafts locked together for 1:1 ratio)
Reverse: High/reverse/direct clutch applied, low/reverse band applied
i couldnt figure out what was wrong so i had it rebuilt.
Did ‘they’ tell you what they found???
unfortunately no.